relayd: keep track of prev_index_seq in relayd_stream
[lttng-tools.git] / src / bin / lttng-relayd / main.c
index 78974af4c545f417e748efc9dc265b2ec197522d..92f9a5600ac28b7280dcea9f1041b7725b13b748 100644 (file)
@@ -2,6 +2,7 @@
  * Copyright (C) 2012 - Julien Desfossez <jdesfossez@efficios.com>
  *                      David Goulet <dgoulet@efficios.com>
  *               2013 - Jérémie Galarneau <jeremie.galarneau@efficios.com>
+ *               2015 - Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License, version 2 only,
@@ -17,7 +18,6 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
 #define _LGPL_SOURCE
 #include <getopt.h>
 #include <grp.h>
 #include <urcu/uatomic.h>
 #include <unistd.h>
 #include <fcntl.h>
-#include <config.h>
 
 #include <lttng/lttng.h>
 #include <common/common.h>
 #include <common/compat/poll.h>
 #include <common/compat/socket.h>
 #include <common/compat/endian.h>
+#include <common/compat/getenv.h>
 #include <common/defaults.h>
 #include <common/daemonize.h>
 #include <common/futex.h>
 #include <common/sessiond-comm/relayd.h>
 #include <common/uri.h>
 #include <common/utils.h>
-#include <common/config/config.h>
+#include <common/align.h>
+#include <common/config/session-config.h>
+#include <common/dynamic-buffer.h>
+#include <common/buffer-view.h>
+#include <urcu/rculist.h>
 
 #include "cmd.h"
 #include "ctf-trace.h"
 #include "session.h"
 #include "stream.h"
 #include "connection.h"
+#include "tracefile-array.h"
+#include "tcp_keep_alive.h"
+
+static const char *help_msg =
+#ifdef LTTNG_EMBED_HELP
+#include <lttng-relayd.8.h>
+#else
+NULL
+#endif
+;
+
+enum relay_connection_status {
+       RELAY_CONNECTION_STATUS_OK,
+       /* An error occured while processing an event on the connection. */
+       RELAY_CONNECTION_STATUS_ERROR,
+       /* Connection closed/shutdown cleanly. */
+       RELAY_CONNECTION_STATUS_CLOSED,
+};
 
 /* command line options */
 char *opt_output_path;
@@ -79,6 +101,11 @@ static int opt_daemon, opt_background;
  */
 #define NR_LTTNG_RELAY_READY   3
 static int lttng_relay_ready = NR_LTTNG_RELAY_READY;
+
+/* Size of receive buffer. */
+#define RECV_DATA_BUFFER_SIZE          65536
+#define FILE_COPY_BUFFER_SIZE          65536
+
 static int recv_child_signal;  /* Set to 1 when a SIGUSR1 signal is received. */
 static pid_t child_ppid;       /* Internal parent PID use with daemonize. */
 
@@ -113,6 +140,11 @@ static pthread_t dispatcher_thread;
 static pthread_t worker_thread;
 static pthread_t health_thread;
 
+/*
+ * last_relay_stream_id_lock protects last_relay_stream_id increment
+ * atomicity on 32-bit architectures.
+ */
+static pthread_mutex_t last_relay_stream_id_lock = PTHREAD_MUTEX_INITIALIZER;
 static uint64_t last_relay_stream_id;
 
 /*
@@ -123,22 +155,14 @@ static uint64_t last_relay_stream_id;
  */
 static struct relay_conn_queue relay_conn_queue;
 
-/* buffer allocated at startup, used to store the trace data */
-static char *data_buffer;
-static unsigned int data_buffer_size;
-
-/* We need those values for the file/dir creation. */
-static uid_t relayd_uid;
-static gid_t relayd_gid;
-
 /* Global relay stream hash table. */
 struct lttng_ht *relay_streams_ht;
 
 /* Global relay viewer stream hash table. */
 struct lttng_ht *viewer_streams_ht;
 
-/* Global hash table that stores relay index object. */
-struct lttng_ht *indexes_ht;
+/* Global relay sessions hash table. */
+struct lttng_ht *sessions_ht;
 
 /* Relayd health monitoring */
 struct health_app *health_relayd;
@@ -154,29 +178,11 @@ static struct option long_options[] = {
        { "output", 1, 0, 'o', },
        { "verbose", 0, 0, 'v', },
        { "config", 1, 0, 'f' },
+       { "version", 0, 0, 'V' },
        { NULL, 0, 0, 0, },
 };
 
-static const char *config_ignore_options[] = { "help", "config" };
-
-/*
- * usage function on stderr
- */
-static
-void usage(void)
-{
-       fprintf(stderr, "Usage: %s OPTIONS\n\nOptions:\n", progname);
-       fprintf(stderr, "  -h, --help                Display this usage.\n");
-       fprintf(stderr, "  -d, --daemonize           Start as a daemon.\n");
-       fprintf(stderr, "  -b, --background          Start as a daemon, keeping console open.\n");
-       fprintf(stderr, "  -C, --control-port URL    Control port listening.\n");
-       fprintf(stderr, "  -D, --data-port URL       Data port listening.\n");
-       fprintf(stderr, "  -L, --live-port URL       Live view port listening.\n");
-       fprintf(stderr, "  -o, --output PATH         Output path for traces. Must use an absolute path.\n");
-       fprintf(stderr, "  -v, --verbose             Verbose mode. Activate DBG() macro.\n");
-       fprintf(stderr, "  -g, --group NAME          Specify the tracing group name. (default: tracing)\n");
-       fprintf(stderr, "  -f  --config              Load daemon configuration file\n");
-}
+static const char *config_ignore_options[] = { "help", "config", "version" };
 
 /*
  * Take an option from the getopt output and set it in the right variable to be
@@ -184,8 +190,7 @@ void usage(void)
  *
  * Return 0 on success else a negative value.
  */
-static
-int set_option(int opt, const char *arg, const char *optname)
+static int set_option(int opt, const char *arg, const char *optname)
 {
        int ret;
 
@@ -197,33 +202,48 @@ int set_option(int opt, const char *arg, const char *optname)
                }
                break;
        case 'C':
-               ret = uri_parse(arg, &control_uri);
-               if (ret < 0) {
-                       ERR("Invalid control URI specified");
-                       goto end;
-               }
-               if (control_uri->port == 0) {
-                       control_uri->port = DEFAULT_NETWORK_CONTROL_PORT;
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-C, --control-port");
+               } else {
+                       ret = uri_parse(arg, &control_uri);
+                       if (ret < 0) {
+                               ERR("Invalid control URI specified");
+                               goto end;
+                       }
+                       if (control_uri->port == 0) {
+                               control_uri->port = DEFAULT_NETWORK_CONTROL_PORT;
+                       }
                }
                break;
        case 'D':
-               ret = uri_parse(arg, &data_uri);
-               if (ret < 0) {
-                       ERR("Invalid data URI specified");
-                       goto end;
-               }
-               if (data_uri->port == 0) {
-                       data_uri->port = DEFAULT_NETWORK_DATA_PORT;
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-D, -data-port");
+               } else {
+                       ret = uri_parse(arg, &data_uri);
+                       if (ret < 0) {
+                               ERR("Invalid data URI specified");
+                               goto end;
+                       }
+                       if (data_uri->port == 0) {
+                               data_uri->port = DEFAULT_NETWORK_DATA_PORT;
+                       }
                }
                break;
        case 'L':
-               ret = uri_parse(arg, &live_uri);
-               if (ret < 0) {
-                       ERR("Invalid live URI specified");
-                       goto end;
-               }
-               if (live_uri->port == 0) {
-                       live_uri->port = DEFAULT_NETWORK_VIEWER_PORT;
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-L, -live-port");
+               } else {
+                       ret = uri_parse(arg, &live_uri);
+                       if (ret < 0) {
+                               ERR("Invalid live URI specified");
+                               goto end;
+                       }
+                       if (live_uri->port == 0) {
+                               live_uri->port = DEFAULT_NETWORK_VIEWER_PORT;
+                       }
                }
                break;
        case 'd':
@@ -233,23 +253,40 @@ int set_option(int opt, const char *arg, const char *optname)
                opt_background = 1;
                break;
        case 'g':
-               tracing_group_name = strdup(arg);
-               if (tracing_group_name == NULL) {
-                       ret = -errno;
-                       PERROR("strdup");
-                       goto end;
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-g, --group");
+               } else {
+                       tracing_group_name = strdup(arg);
+                       if (tracing_group_name == NULL) {
+                               ret = -errno;
+                               PERROR("strdup");
+                               goto end;
+                       }
+                       tracing_group_name_override = 1;
                }
-               tracing_group_name_override = 1;
                break;
        case 'h':
-               usage();
+               ret = utils_show_help(8, "lttng-relayd", help_msg);
+               if (ret) {
+                       ERR("Cannot show --help for `lttng-relayd`");
+                       perror("exec");
+               }
                exit(EXIT_FAILURE);
+       case 'V':
+               fprintf(stdout, "%s\n", VERSION);
+               exit(EXIT_SUCCESS);
        case 'o':
-               ret = asprintf(&opt_output_path, "%s", arg);
-               if (ret < 0) {
-                       ret = -errno;
-                       PERROR("asprintf opt_output_path");
-                       goto end;
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-o, --output");
+               } else {
+                       ret = asprintf(&opt_output_path, "%s", arg);
+                       if (ret < 0) {
+                               ret = -errno;
+                               PERROR("asprintf opt_output_path");
+                               goto end;
+                       }
                }
                break;
        case 'v':
@@ -279,11 +316,10 @@ end:
 
 /*
  * config_entry_handler_cb used to handle options read from a config file.
- * See config_entry_handler_cb comment in common/config/config.h for the
+ * See config_entry_handler_cb comment in common/config/session-config.h for the
  * return value conventions.
  */
-static
-int config_entry_handler(const struct config_entry *entry, void *unused)
+static int config_entry_handler(const struct config_entry *entry, void *unused)
 {
        int ret = 0, i;
 
@@ -306,9 +342,9 @@ int config_entry_handler(const struct config_entry *entry, void *unused)
                }
 
                /*
-                * If the option takes no argument on the command line, we have to
-                * check if the value is "true". We support non-zero numeric values,
-                * true, on and yes.
+                * If the option takes no argument on the command line,
+                * we have to check if the value is "true". We support
+                * non-zero numeric values, true, on and yes.
                 */
                if (!long_options[i].has_arg) {
                        ret = config_parse_value(entry->value);
@@ -333,10 +369,9 @@ end:
        return ret;
 }
 
-static
-int set_options(int argc, char **argv)
+static int set_options(int argc, char **argv)
 {
-       int c, ret = 0, option_index = 0;
+       int c, ret = 0, option_index = 0, retval = 0;
        int orig_optopt = optopt, orig_optind = optind;
        char *default_address, *optstring;
        const char *config_path = NULL;
@@ -344,7 +379,7 @@ int set_options(int argc, char **argv)
        optstring = utils_generate_optstring(long_options,
                        sizeof(long_options) / sizeof(struct option));
        if (!optstring) {
-               ret = -ENOMEM;
+               retval = -ENOMEM;
                goto exit;
        }
 
@@ -353,15 +388,20 @@ int set_options(int argc, char **argv)
        while ((c = getopt_long(argc, argv, optstring, long_options,
                                        &option_index)) != -1) {
                if (c == '?') {
-                       ret = -EINVAL;
+                       retval = -EINVAL;
                        goto exit;
                } else if (c != 'f') {
                        continue;
                }
 
-               config_path = utils_expand_path(optarg);
-               if (!config_path) {
-                       ERR("Failed to resolve path: %s", optarg);
+               if (lttng_is_setuid_setgid()) {
+                       WARN("Getting '%s' argument from setuid/setgid binary refused for security reasons.",
+                               "-f, --config");
+               } else {
+                       config_path = utils_expand_path(optarg);
+                       if (!config_path) {
+                               ERR("Failed to resolve path: %s", optarg);
+                       }
                }
        }
 
@@ -370,8 +410,8 @@ int set_options(int argc, char **argv)
        if (ret) {
                if (ret > 0) {
                        ERR("Invalid configuration option at line %i", ret);
-                       ret = -1;
                }
+               retval = -1;
                goto exit;
        }
 
@@ -386,6 +426,7 @@ int set_options(int argc, char **argv)
 
                ret = set_option(c, optarg, long_options[option_index].name);
                if (ret < 0) {
+                       retval = -1;
                        goto exit;
                }
        }
@@ -397,6 +438,7 @@ int set_options(int argc, char **argv)
                        DEFAULT_NETWORK_CONTROL_PORT);
                if (ret < 0) {
                        PERROR("asprintf default data address");
+                       retval = -1;
                        goto exit;
                }
 
@@ -404,6 +446,7 @@ int set_options(int argc, char **argv)
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid control URI specified");
+                       retval = -1;
                        goto exit;
                }
        }
@@ -413,6 +456,7 @@ int set_options(int argc, char **argv)
                        DEFAULT_NETWORK_DATA_PORT);
                if (ret < 0) {
                        PERROR("asprintf default data address");
+                       retval = -1;
                        goto exit;
                }
 
@@ -420,6 +464,7 @@ int set_options(int argc, char **argv)
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid data URI specified");
+                       retval = -1;
                        goto exit;
                }
        }
@@ -429,6 +474,7 @@ int set_options(int argc, char **argv)
                        DEFAULT_NETWORK_VIEWER_PORT);
                if (ret < 0) {
                        PERROR("asprintf default viewer control address");
+                       retval = -1;
                        goto exit;
                }
 
@@ -436,23 +482,43 @@ int set_options(int argc, char **argv)
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid viewer control URI specified");
+                       retval = -1;
                        goto exit;
                }
        }
 
 exit:
        free(optstring);
-       return ret;
+       return retval;
+}
+
+static void print_global_objects(void)
+{
+       rcu_register_thread();
+
+       print_viewer_streams();
+       print_relay_streams();
+       print_sessions();
+
+       rcu_unregister_thread();
 }
 
 /*
  * Cleanup the daemon
  */
-static
-void cleanup(void)
+static void relayd_cleanup(void)
 {
+       print_global_objects();
+
        DBG("Cleaning up");
 
+       if (viewer_streams_ht)
+               lttng_ht_destroy(viewer_streams_ht);
+       if (relay_streams_ht)
+               lttng_ht_destroy(relay_streams_ht);
+       if (sessions_ht)
+               lttng_ht_destroy(sessions_ht);
+
        /* free the dynamically allocated opt_output_path */
        free(opt_output_path);
 
@@ -471,49 +537,61 @@ void cleanup(void)
 /*
  * Write to writable pipe used to notify a thread.
  */
-static
-int notify_thread_pipe(int wpipe)
+static int notify_thread_pipe(int wpipe)
 {
        ssize_t ret;
 
        ret = lttng_write(wpipe, "!", 1);
        if (ret < 1) {
                PERROR("write poll pipe");
+               goto end;
        }
-
+       ret = 0;
+end:
        return ret;
 }
 
-static void notify_health_quit_pipe(int *pipe)
+static int notify_health_quit_pipe(int *pipe)
 {
        ssize_t ret;
 
        ret = lttng_write(pipe[1], "4", 1);
        if (ret < 1) {
                PERROR("write relay health quit");
+               goto end;
        }
+       ret = 0;
+end:
+       return ret;
 }
 
 /*
- * Stop all threads by closing the thread quit pipe.
+ * Stop all relayd and relayd-live threads.
  */
-static
-void stop_threads(void)
+int lttng_relay_stop_threads(void)
 {
-       int ret;
+       int retval = 0;
 
        /* Stopping all threads */
        DBG("Terminating all threads");
-       ret = notify_thread_pipe(thread_quit_pipe[1]);
-       if (ret < 0) {
+       if (notify_thread_pipe(thread_quit_pipe[1])) {
                ERR("write error on thread quit pipe");
+               retval = -1;
        }
 
-       notify_health_quit_pipe(health_quit_pipe);
+       if (notify_health_quit_pipe(health_quit_pipe)) {
+               ERR("write error on health quit pipe");
+       }
 
        /* Dispatch thread */
        CMM_STORE_SHARED(dispatch_thread_exit, 1);
        futex_nto1_wake(&relay_conn_queue.futex);
+
+       if (relayd_live_stop()) {
+               ERR("Error stopping live threads");
+               retval = -1;
+       }
+       return retval;
 }
 
 /*
@@ -522,20 +600,20 @@ void stop_threads(void)
  * Simply stop all worker threads, leaving main() return gracefully after
  * joining all threads and calling cleanup().
  */
-static
-void sighandler(int sig)
+static void sighandler(int sig)
 {
        switch (sig) {
-       case SIGPIPE:
-               DBG("SIGPIPE caught");
-               return;
        case SIGINT:
                DBG("SIGINT caught");
-               stop_threads();
+               if (lttng_relay_stop_threads()) {
+                       ERR("Error stopping threads");
+               }
                break;
        case SIGTERM:
                DBG("SIGTERM caught");
-               stop_threads();
+               if (lttng_relay_stop_threads()) {
+                       ERR("Error stopping threads");
+               }
                break;
        case SIGUSR1:
                CMM_STORE_SHARED(recv_child_signal, 1);
@@ -549,8 +627,7 @@ void sighandler(int sig)
  * Setup signal handler for :
  *             SIGINT, SIGTERM, SIGPIPE
  */
-static
-int set_signal_handler(void)
+static int set_signal_handler(void)
 {
        int ret = 0;
        struct sigaction sa;
@@ -561,9 +638,10 @@ int set_signal_handler(void)
                return ret;
        }
 
-       sa.sa_handler = sighandler;
        sa.sa_mask = sigset;
        sa.sa_flags = 0;
+
+       sa.sa_handler = sighandler;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
@@ -574,12 +652,13 @@ int set_signal_handler(void)
                return ret;
        }
 
-       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
+       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }
 
-       if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
+       sa.sa_handler = SIG_IGN;
+       if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }
@@ -604,8 +683,7 @@ void lttng_relay_notify_ready(void)
  *
  * Return -1 on error or 0 if all pipes are created.
  */
-static
-int init_thread_quit_pipe(void)
+static int init_thread_quit_pipe(void)
 {
        int ret;
 
@@ -617,8 +695,7 @@ int init_thread_quit_pipe(void)
 /*
  * Create a poll set with O_CLOEXEC and add the thread quit pipe to the set.
  */
-static
-int create_thread_poll_set(struct lttng_poll_event *events, int size)
+static int create_thread_poll_set(struct lttng_poll_event *events, int size)
 {
        int ret;
 
@@ -649,8 +726,7 @@ error:
  *
  * Return 1 if it was triggered else 0;
  */
-static
-int check_thread_quit_pipe(int fd, uint32_t events)
+static int check_thread_quit_pipe(int fd, uint32_t events)
 {
        if (fd == thread_quit_pipe[0] && (events & LPOLLIN)) {
                return 1;
@@ -662,8 +738,7 @@ int check_thread_quit_pipe(int fd, uint32_t events)
 /*
  * Create and init socket from uri.
  */
-static
-struct lttcomm_sock *relay_init_sock(struct lttng_uri *uri)
+static struct lttcomm_sock *relay_socket_create(struct lttng_uri *uri)
 {
        int ret;
        struct lttcomm_sock *sock = NULL;
@@ -682,6 +757,7 @@ struct lttcomm_sock *relay_init_sock(struct lttng_uri *uri)
 
        ret = sock->ops->bind(sock);
        if (ret < 0) {
+               PERROR("Failed to bind socket");
                goto error;
        }
 
@@ -700,64 +776,10 @@ error:
        return NULL;
 }
 
-/*
- * Return nonzero if stream needs to be closed.
- */
-static
-int close_stream_check(struct relay_stream *stream)
-{
-       if (stream->close_flag && stream->prev_seq == stream->last_net_seq_num) {
-               /*
-                * We are about to close the stream so set the data pending flag to 1
-                * which will make the end data pending command skip the stream which
-                * is now closed and ready. Note that after proceeding to a file close,
-                * the written file is ready for reading.
-                */
-               stream->data_pending_check_done = 1;
-               return 1;
-       }
-       return 0;
-}
-
-static void try_close_stream(struct relay_session *session,
-               struct relay_stream *stream)
-{
-       int ret;
-       struct ctf_trace *ctf_trace;
-
-       assert(session);
-       assert(stream);
-
-       if (!close_stream_check(stream)) {
-               /* Can't close it, not ready for that. */
-               goto end;
-       }
-
-       ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
-                       stream->path_name);
-       assert(ctf_trace);
-
-       pthread_mutex_lock(&session->viewer_ready_lock);
-       ctf_trace->invalid_flag = 1;
-       pthread_mutex_unlock(&session->viewer_ready_lock);
-
-       ret = stream_close(session, stream);
-       if (ret || session->snapshot) {
-               /* Already close thus the ctf trace is being or has been destroyed. */
-               goto end;
-       }
-
-       ctf_trace_try_destroy(session, ctf_trace);
-
-end:
-       return;
-}
-
 /*
  * This thread manages the listening for new connections on the network
  */
-static
-void *relay_thread_listener(void *data)
+static void *relay_thread_listener(void *data)
 {
        int i, ret, pollfd, err = -1;
        uint32_t revents, nb_fd;
@@ -770,18 +792,19 @@ void *relay_thread_listener(void *data)
 
        health_code_update();
 
-       control_sock = relay_init_sock(control_uri);
+       control_sock = relay_socket_create(control_uri);
        if (!control_sock) {
                goto error_sock_control;
        }
 
-       data_sock = relay_init_sock(data_uri);
+       data_sock = relay_socket_create(data_uri);
        if (!data_sock) {
                goto error_sock_relay;
        }
 
        /*
-        * Pass 3 as size here for the thread quit pipe, control and data socket.
+        * Pass 3 as size here for the thread quit pipe, control and
+        * data socket.
         */
        ret = create_thread_poll_set(&events, 3);
        if (ret < 0) {
@@ -835,6 +858,14 @@ restart:
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);
 
+                       if (!revents) {
+                               /*
+                                * No activity for this FD (poll
+                                * implementation).
+                                */
+                               continue;
+                       }
+
                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
@@ -842,38 +873,32 @@ restart:
                                goto exit;
                        }
 
-                       if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
-                               ERR("socket poll error");
-                               goto error;
-                       } else if (revents & LPOLLIN) {
+                       if (revents & LPOLLIN) {
                                /*
-                                * Get allocated in this thread, enqueued to a global queue,
-                                * dequeued and freed in the worker thread.
+                                * A new connection is requested, therefore a
+                                * sessiond/consumerd connection is allocated in
+                                * this thread, enqueued to a global queue and
+                                * dequeued (and freed) in the worker thread.
                                 */
                                int val = 1;
                                struct relay_connection *new_conn;
                                struct lttcomm_sock *newsock;
-
-                               new_conn = connection_create();
-                               if (!new_conn) {
-                                       goto error;
-                               }
+                               enum connection_type type;
 
                                if (pollfd == data_sock->fd) {
-                                       new_conn->type = RELAY_DATA;
+                                       type = RELAY_DATA;
                                        newsock = data_sock->ops->accept(data_sock);
                                        DBG("Relay data connection accepted, socket %d",
                                                        newsock->fd);
                                } else {
                                        assert(pollfd == control_sock->fd);
-                                       new_conn->type = RELAY_CONTROL;
+                                       type = RELAY_CONTROL;
                                        newsock = control_sock->ops->accept(control_sock);
                                        DBG("Relay control connection accepted, socket %d",
                                                        newsock->fd);
                                }
                                if (!newsock) {
                                        PERROR("accepting sock");
-                                       connection_free(new_conn);
                                        goto error;
                                }
 
@@ -882,20 +907,39 @@ restart:
                                if (ret < 0) {
                                        PERROR("setsockopt inet");
                                        lttcomm_destroy_sock(newsock);
-                                       connection_free(new_conn);
                                        goto error;
                                }
-                               new_conn->sock = newsock;
+
+                               ret = socket_apply_keep_alive_config(newsock->fd);
+                               if (ret < 0) {
+                                       ERR("Failed to apply TCP keep-alive configuration on socket (%i)",
+                                                       newsock->fd);
+                                       lttcomm_destroy_sock(newsock);
+                                       goto error;
+                               }
+
+                               new_conn = connection_create(newsock, type);
+                               if (!new_conn) {
+                                       lttcomm_destroy_sock(newsock);
+                                       goto error;
+                               }
 
                                /* Enqueue request for the dispatcher thread. */
                                cds_wfcq_enqueue(&relay_conn_queue.head, &relay_conn_queue.tail,
                                                 &new_conn->qnode);
 
                                /*
-                                * Wake the dispatch queue futex. Implicit memory barrier with
-                                * the exchange in cds_wfcq_enqueue.
+                                * Wake the dispatch queue futex.
+                                * Implicit memory barrier with the
+                                * exchange in cds_wfcq_enqueue.
                                 */
                                futex_nto1_wake(&relay_conn_queue.futex);
+                       } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
+                               ERR("socket poll error");
+                               goto error;
+                       } else {
+                               ERR("Unexpected poll events %u for sock %d", revents, pollfd);
+                               goto error;
                        }
                }
        }
@@ -928,15 +972,14 @@ error_sock_control:
        }
        health_unregister(health_relayd);
        DBG("Relay listener thread cleanup complete");
-       stop_threads();
+       lttng_relay_stop_threads();
        return NULL;
 }
 
 /*
  * This thread manages the dispatching of the requests to worker threads
  */
-static
-void *relay_thread_dispatcher(void *data)
+static void *relay_thread_dispatcher(void *data)
 {
        int err = -1;
        ssize_t ret;
@@ -953,12 +996,16 @@ void *relay_thread_dispatcher(void *data)
 
        health_code_update();
 
-       while (!CMM_LOAD_SHARED(dispatch_thread_exit)) {
+       for (;;) {
                health_code_update();
 
                /* Atomically prepare the queue futex */
                futex_nto1_prepare(&relay_conn_queue.futex);
 
+               if (CMM_LOAD_SHARED(dispatch_thread_exit)) {
+                       break;
+               }
+
                do {
                        health_code_update();
 
@@ -975,14 +1022,15 @@ void *relay_thread_dispatcher(void *data)
                        DBG("Dispatching request waiting on sock %d", new_conn->sock->fd);
 
                        /*
-                        * Inform worker thread of the new request. This call is blocking
-                        * so we can be assured that the data will be read at some point in
-                        * time or wait to the end of the world :)
+                        * Inform worker thread of the new request. This
+                        * call is blocking so we can be assured that
+                        * the data will be read at some point in time
+                        * or wait to the end of the world :)
                         */
                        ret = lttng_write(relay_conn_pipe[1], &new_conn, sizeof(new_conn));
                        if (ret < 0) {
                                PERROR("write connection pipe");
-                               connection_destroy(new_conn);
+                               connection_put(new_conn);
                                goto error;
                        }
                } while (node != NULL);
@@ -1004,76 +1052,35 @@ error_testpoint:
        }
        health_unregister(health_relayd);
        DBG("Dispatch thread dying");
-       stop_threads();
+       lttng_relay_stop_threads();
        return NULL;
 }
 
-static void try_close_streams(struct relay_session *session)
-{
-       struct ctf_trace *ctf_trace;
-       struct lttng_ht_iter iter;
-
-       assert(session);
-
-       pthread_mutex_lock(&session->viewer_ready_lock);
-       rcu_read_lock();
-       cds_lfht_for_each_entry(session->ctf_traces_ht->ht, &iter.iter, ctf_trace,
-                       node.node) {
-               struct relay_stream *stream;
-
-               /* Close streams. */
-               cds_list_for_each_entry(stream, &ctf_trace->stream_list, trace_list) {
-                       stream_close(session, stream);
-               }
-
-               ctf_trace->invalid_flag = 1;
-               ctf_trace_try_destroy(session, ctf_trace);
-       }
-       rcu_read_unlock();
-       pthread_mutex_unlock(&session->viewer_ready_lock);
-}
-
 /*
- * Try to destroy a session within a connection.
+ * Set index data from the control port to a given index object.
  */
-static void destroy_session(struct relay_session *session,
-               struct lttng_ht *sessions_ht)
+static int set_index_control_data(struct relay_index *index,
+               struct lttcomm_relayd_index *data,
+               struct relay_connection *conn)
 {
-       assert(session);
-       assert(sessions_ht);
-
-       /* Indicate that this session can be destroyed from now on. */
-       session->close_flag = 1;
-
-       try_close_streams(session);
+       struct ctf_packet_index index_data;
 
        /*
-        * This will try to delete and destroy the session if no viewer is attached
-        * to it meaning the refcount is down to zero.
+        * The index on disk is encoded in big endian.
         */
-       session_try_destroy(sessions_ht, session);
-}
+       index_data.packet_size = htobe64(data->packet_size);
+       index_data.content_size = htobe64(data->content_size);
+       index_data.timestamp_begin = htobe64(data->timestamp_begin);
+       index_data.timestamp_end = htobe64(data->timestamp_end);
+       index_data.events_discarded = htobe64(data->events_discarded);
+       index_data.stream_id = htobe64(data->stream_id);
 
-/*
- * Copy index data from the control port to a given index object.
- */
-static void copy_index_control_data(struct relay_index *index,
-               struct lttcomm_relayd_index *data)
-{
-       assert(index);
-       assert(data);
+       if (conn->minor >= 8) {
+               index->index_data.stream_instance_id = htobe64(data->stream_instance_id);
+               index->index_data.packet_seq_num = htobe64(data->packet_seq_num);
+       }
 
-       /*
-        * The index on disk is encoded in big endian, so we don't need to convert
-        * the data received on the network. The data_offset value is NEVER
-        * modified here and is updated by the data thread.
-        */
-       index->index_data.packet_size = data->packet_size;
-       index->index_data.content_size = data->content_size;
-       index->index_data.timestamp_begin = data->timestamp_begin;
-       index->index_data.timestamp_end = data->timestamp_end;
-       index->index_data.events_discarded = data->events_discarded;
-       index->index_data.stream_id = data->stream_id;
+       return relay_index_set_data(index, &index_data);
 }
 
 /*
@@ -1081,45 +1088,54 @@ static void copy_index_control_data(struct relay_index *index,
  *
  * On success, send back the session id or else return a negative value.
  */
-static
-int relay_create_session(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_create_session(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret = 0, send_ret;
+       int ret = 0;
+       ssize_t send_ret;
        struct relay_session *session;
        struct lttcomm_relayd_status_session reply;
+       char session_name[LTTNG_NAME_MAX];
+       char hostname[LTTNG_HOST_NAME_MAX];
+       uint32_t live_timer = 0;
+       bool snapshot = false;
 
-       assert(recv_hdr);
-       assert(conn);
+       memset(session_name, 0, LTTNG_NAME_MAX);
+       memset(hostname, 0, LTTNG_HOST_NAME_MAX);
 
        memset(&reply, 0, sizeof(reply));
 
-       session = session_create();
+       if (conn->minor < 4) {
+               /* From 2.1 to 2.3 */
+               ret = 0;
+       } else if (conn->minor >= 4 && conn->minor < 11) {
+               /* From 2.4 to 2.10 */
+               ret = cmd_create_session_2_4(payload, session_name,
+                       hostname, &live_timer, &snapshot);
+       } else {
+               /* From 2.11 to ... */
+               ret = cmd_create_session_2_11(payload, session_name,
+                       hostname, &live_timer, &snapshot);
+       }
+
+       if (ret < 0) {
+               goto send_reply;
+       }
+
+       session = session_create(session_name, hostname, live_timer,
+                       snapshot, conn->major, conn->minor);
        if (!session) {
                ret = -1;
-               goto error;
+               goto send_reply;
        }
-       session->minor = conn->minor;
-       session->major = conn->major;
-       conn->session_id = session->id;
+       assert(!conn->session);
        conn->session = session;
+       DBG("Created session %" PRIu64, session->id);
 
        reply.session_id = htobe64(session->id);
 
-       switch (conn->minor) {
-       case 1:
-       case 2:
-       case 3:
-               break;
-       case 4: /* LTTng sessiond 2.4 */
-       default:
-               ret = cmd_create_session_2_4(conn, session);
-       }
-
-       lttng_ht_add_unique_u64(conn->sessions_ht, &session->session_n);
-       DBG("Created session %" PRIu64, session->id);
-
-error:
+send_reply:
        if (ret < 0) {
                reply.ret_code = htobe32(LTTNG_ERR_FATAL);
        } else {
@@ -1127,9 +1143,10 @@ error:
        }
 
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relayd sending session id");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"create session\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
        return ret;
@@ -1139,181 +1156,131 @@ error:
  * When we have received all the streams and the metadata for a channel,
  * we make them visible to the viewer threads.
  */
-static
-void set_viewer_ready_flag(struct relay_connection *conn)
+static void publish_connection_local_streams(struct relay_connection *conn)
 {
-       struct relay_stream *stream, *tmp_stream;
+       struct relay_stream *stream;
+       struct relay_session *session = conn->session;
 
-       pthread_mutex_lock(&conn->session->viewer_ready_lock);
-       cds_list_for_each_entry_safe(stream, tmp_stream, &conn->recv_head,
-                       recv_list) {
-               stream->viewer_ready = 1;
-               cds_list_del(&stream->recv_list);
+       /*
+        * We publish all streams belonging to a session atomically wrt
+        * session lock.
+        */
+       pthread_mutex_lock(&session->lock);
+       rcu_read_lock();
+       cds_list_for_each_entry_rcu(stream, &session->recv_list,
+                       recv_node) {
+               stream_publish(stream);
        }
-       pthread_mutex_unlock(&conn->session->viewer_ready_lock);
-       return;
-}
-
-/*
- * Add a recv handle node to the connection recv list with the given stream
- * handle. A new node is allocated thus must be freed when the node is deleted
- * from the list.
- */
-static void queue_stream(struct relay_stream *stream,
-               struct relay_connection *conn)
-{
-       assert(conn);
-       assert(stream);
+       rcu_read_unlock();
 
-       cds_list_add(&stream->recv_list, &conn->recv_head);
+       /*
+        * Inform the viewer that there are new streams in the session.
+        */
+       if (session->viewer_attached) {
+               uatomic_set(&session->new_streams, 1);
+       }
+       pthread_mutex_unlock(&session->lock);
 }
 
 /*
  * relay_add_stream: allocate a new stream for a session
  */
-static
-int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_add_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct relay_stream *stream = NULL;
        struct lttcomm_relayd_status_stream reply;
-       struct ctf_trace *trace;
+       struct ctf_trace *trace = NULL;
+       uint64_t stream_handle = -1ULL;
+       char *path_name = NULL, *channel_name = NULL;
+       uint64_t tracefile_size = 0, tracefile_count = 0;
+       struct relay_stream_chunk_id stream_chunk_id = { 0 };
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to add a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       stream = zmalloc(sizeof(struct relay_stream));
-       if (stream == NULL) {
-               PERROR("relay stream zmalloc");
-               ret = -1;
-               goto end_no_session;
-       }
-
-       switch (conn->minor) {
-       case 1: /* LTTng sessiond 2.1 */
-               ret = cmd_recv_stream_2_1(conn, stream);
-               break;
-       case 2: /* LTTng sessiond 2.2 */
-       default:
-               ret = cmd_recv_stream_2_2(conn, stream);
-               break;
-       }
-       if (ret < 0) {
-               goto err_free_stream;
-       }
-
-       rcu_read_lock();
-       stream->stream_handle = ++last_relay_stream_id;
-       stream->prev_seq = -1ULL;
-       stream->session_id = session->id;
-       stream->index_fd = -1;
-       stream->read_index_fd = -1;
-       stream->ctf_stream_id = -1ULL;
-       lttng_ht_node_init_u64(&stream->node, stream->stream_handle);
-       pthread_mutex_init(&stream->lock, NULL);
-
-       ret = utils_mkdir_recursive(stream->path_name, S_IRWXU | S_IRWXG);
-       if (ret < 0) {
-               ERR("relay creating output directory");
-               goto end;
+       if (session->minor == 1) {
+               /* For 2.1 */
+               ret = cmd_recv_stream_2_1(payload, &path_name,
+                       &channel_name);
+       } else if (session->minor > 1 && session->minor < 11) {
+               /* From 2.2 to 2.10 */
+               ret = cmd_recv_stream_2_2(payload, &path_name,
+                       &channel_name, &tracefile_size, &tracefile_count);
+       } else {
+               /* From 2.11 to ... */
+               ret = cmd_recv_stream_2_11(payload, &path_name,
+                       &channel_name, &tracefile_size, &tracefile_count,
+                       &stream_chunk_id.value);
+               stream_chunk_id.is_set = true;
        }
 
-       /*
-        * No need to use run_as API here because whatever we receives, the relayd
-        * uses its own credentials for the stream files.
-        */
-       ret = utils_create_stream_file(stream->path_name, stream->channel_name,
-                       stream->tracefile_size, 0, relayd_uid, relayd_gid, NULL);
        if (ret < 0) {
-               ERR("Create output file");
-               goto end;
-       }
-       stream->fd = ret;
-       if (stream->tracefile_size) {
-               DBG("Tracefile %s/%s_0 created", stream->path_name, stream->channel_name);
-       } else {
-               DBG("Tracefile %s/%s created", stream->path_name, stream->channel_name);
+               goto send_reply;
        }
 
-       trace = ctf_trace_find_by_path(session->ctf_traces_ht, stream->path_name);
+       trace = ctf_trace_get_by_path_or_create(session, path_name);
        if (!trace) {
-               trace = ctf_trace_create(stream->path_name);
-               if (!trace) {
-                       ret = -1;
-                       goto end;
-               }
-               ctf_trace_add(session->ctf_traces_ht, trace);
+               goto send_reply;
        }
-       ctf_trace_get_ref(trace);
+       /* This stream here has one reference on the trace. */
 
-       if (!strncmp(stream->channel_name, DEFAULT_METADATA_NAME, NAME_MAX)) {
-               stream->metadata_flag = 1;
-               /* Assign quick reference to the metadata stream in the trace. */
-               trace->metadata_stream = stream;
-       }
+       pthread_mutex_lock(&last_relay_stream_id_lock);
+       stream_handle = ++last_relay_stream_id;
+       pthread_mutex_unlock(&last_relay_stream_id_lock);
 
-       /*
-        * Add the stream in the recv list of the connection. Once the end stream
-        * message is received, this list is emptied and streams are set with the
-        * viewer ready flag.
-        */
-       queue_stream(stream, conn);
+       /* We pass ownership of path_name and channel_name. */
+       stream = stream_create(trace, stream_handle, path_name,
+               channel_name, tracefile_size, tracefile_count,
+               &stream_chunk_id);
+       path_name = NULL;
+       channel_name = NULL;
 
        /*
-        * Both in the ctf_trace object and the global stream ht since the data
-        * side of the relayd does not have the concept of session.
+        * Streams are the owners of their trace. Reference to trace is
+        * kept within stream_create().
         */
-       lttng_ht_add_unique_u64(relay_streams_ht, &stream->node);
-       cds_list_add_tail(&stream->trace_list, &trace->stream_list);
-
-       session->stream_count++;
+       ctf_trace_put(trace);
 
-       DBG("Relay new stream added %s with ID %" PRIu64, stream->channel_name,
-                       stream->stream_handle);
-
-end:
+send_reply:
        memset(&reply, 0, sizeof(reply));
-       reply.handle = htobe64(stream->stream_handle);
-       /* send the session id to the client or a negative return code on error */
-       if (ret < 0) {
+       reply.handle = htobe64(stream_handle);
+       if (!stream) {
                reply.ret_code = htobe32(LTTNG_ERR_UNK);
-               /* stream was not properly added to the ht, so free it */
-               free(stream);
        } else {
                reply.ret_code = htobe32(LTTNG_OK);
        }
 
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_status_stream), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending stream id");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"add stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
-       rcu_read_unlock();
 
 end_no_session:
-       return ret;
-
-err_free_stream:
-       free(stream->path_name);
-       free(stream->channel_name);
-       free(stream);
+       free(path_name);
+       free(channel_name);
        return ret;
 }
 
 /*
  * relay_close_stream: close a specific stream
  */
-static
-int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_close_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_close_stream stream_info;
        struct lttcomm_relayd_generic_reply reply;
@@ -1321,43 +1288,151 @@ int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
 
        DBG("Close stream received");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &stream_info,
-                       sizeof(struct lttcomm_relayd_close_stream), 0);
-       if (ret < sizeof(struct lttcomm_relayd_close_stream)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid add_stream struct size : %d", ret);
+       if (payload->size < sizeof(stream_info)) {
+               ERR("Unexpected payload size in \"relay_close_stream\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(stream_info), payload->size);
+               ret = -1;
+               goto end_no_session;
+       }
+       memcpy(&stream_info, payload->data, sizeof(stream_info));
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.last_net_seq_num = be64toh(stream_info.last_net_seq_num);
+
+       stream = stream_get_by_id(stream_info.stream_id);
+       if (!stream) {
+               ret = -1;
+               goto end;
+       }
+
+       /*
+        * Set last_net_seq_num before the close flag. Required by data
+        * pending check.
+        */
+       pthread_mutex_lock(&stream->lock);
+       stream->last_net_seq_num = stream_info.last_net_seq_num;
+       pthread_mutex_unlock(&stream->lock);
+
+       /*
+        * This is one of the conditions which may trigger a stream close
+        * with the others being:
+        *     1) A close command is received for a stream
+        *     2) The control connection owning the stream is closed
+        *     3) We have received all of the stream's data _after_ a close
+        *        request.
+        */
+       try_stream_close(stream);
+       if (stream->is_metadata) {
+               struct relay_viewer_stream *vstream;
+
+               vstream = viewer_stream_get_by_id(stream->stream_handle);
+               if (vstream) {
+                       if (vstream->metadata_sent == stream->metadata_received) {
+                               /*
+                                * Since all the metadata has been sent to the
+                                * viewer and that we have a request to close
+                                * its stream, we can safely teardown the
+                                * corresponding metadata viewer stream.
+                                */
+                               viewer_stream_put(vstream);
+                       }
+                       /* Put local reference. */
+                       viewer_stream_put(vstream);
                }
+       }
+       stream_put(stream);
+       ret = 0;
+
+end:
+       memset(&reply, 0, sizeof(reply));
+       if (ret < 0) {
+               reply.ret_code = htobe32(LTTNG_ERR_UNK);
+       } else {
+               reply.ret_code = htobe32(LTTNG_OK);
+       }
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(struct lttcomm_relayd_generic_reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"close stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_session:
+       return ret;
+}
+
+/*
+ * relay_reset_metadata: reset a metadata stream
+ */
+static
+int relay_reset_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret;
+       ssize_t send_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_reset_metadata stream_info;
+       struct lttcomm_relayd_generic_reply reply;
+       struct relay_stream *stream;
+
+       DBG("Reset metadata received");
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to reset a metadata stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       rcu_read_lock();
-       stream = stream_find_by_id(relay_streams_ht,
-                       be64toh(stream_info.stream_id));
+       if (payload->size < sizeof(stream_info)) {
+               ERR("Unexpected payload size in \"relay_reset_metadata\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(stream_info), payload->size);
+               ret = -1;
+               goto end_no_session;
+       }
+       memcpy(&stream_info, payload->data, sizeof(stream_info));
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.version = be64toh(stream_info.version);
+
+       DBG("Update metadata to version %" PRIu64, stream_info.version);
+
+       /* Unsupported for live sessions for now. */
+       if (session->live_timer != 0) {
+               ret = -1;
+               goto end;
+       }
+
+       stream = stream_get_by_id(stream_info.stream_id);
        if (!stream) {
+               ret = -1;
+               goto end;
+       }
+       pthread_mutex_lock(&stream->lock);
+       if (!stream->is_metadata) {
                ret = -1;
                goto end_unlock;
        }
 
-       stream->last_net_seq_num = be64toh(stream_info.last_net_seq_num);
-       stream->close_flag = 1;
-       session->stream_count--;
-
-       /* Check if we can close it or else the data will do it. */
-       try_close_stream(session, stream);
+       ret = utils_rotate_stream_file(stream->path_name, stream->channel_name,
+                       0, 0, -1, -1, stream->stream_fd->fd, NULL,
+                       &stream->stream_fd->fd);
+       if (ret < 0) {
+               ERR("Failed to rotate metadata file %s of channel %s",
+                               stream->path_name, stream->channel_name);
+               goto end_unlock;
+       }
 
 end_unlock:
-       rcu_read_unlock();
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
 
+end:
        memset(&reply, 0, sizeof(reply));
        if (ret < 0) {
                reply.ret_code = htobe32(LTTNG_ERR_UNK);
@@ -1366,9 +1441,10 @@ end_unlock:
        }
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
                        sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending stream id");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"reset metadata\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1378,18 +1454,16 @@ end_no_session:
 /*
  * relay_unknown_command: send -1 if received unknown command
  */
-static
-void relay_unknown_command(struct relay_connection *conn)
+static void relay_unknown_command(struct relay_connection *conn)
 {
        struct lttcomm_relayd_generic_reply reply;
-       int ret;
+       ssize_t send_ret;
 
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_ERR_UNK);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (ret < 0) {
-               ERR("Relay sending unknown command");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < sizeof(reply)) {
+               ERR("Failed to send \"unknown command\" command reply (ret = %zd)", send_ret);
        }
 }
 
@@ -1397,11 +1471,12 @@ void relay_unknown_command(struct relay_connection *conn)
  * relay_start: send an acknowledgment to the client to tell if we are
  * ready to receive data. We are ready if a session is established.
  */
-static
-int relay_start(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_start(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret = htobe32(LTTNG_OK);
+       int ret = 0;
+       ssize_t send_ret;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_session *session = conn->session;
 
@@ -1411,11 +1486,13 @@ int relay_start(struct lttcomm_relayd_hdr *recv_hdr,
        }
 
        memset(&reply, 0, sizeof(reply));
-       reply.ret_code = ret;
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_generic_reply), 0);
-       if (ret < 0) {
-               ERR("Relay sending start ack");
+       reply.ret_code = htobe32(LTTNG_OK);
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"relay_start\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
        return ret;
@@ -1452,95 +1529,321 @@ end:
 }
 
 /*
- * relay_recv_metadata: receive the metada for the session.
+ * Close the current index file if it is open, and create a new one.
+ *
+ * Return 0 on success, -1 on error.
  */
 static
-int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+int create_rotate_index_file(struct relay_stream *stream)
 {
-       int ret = htobe32(LTTNG_OK);
-       ssize_t size_ret;
-       struct relay_session *session = conn->session;
-       struct lttcomm_relayd_metadata_payload *metadata_struct;
-       struct relay_stream *metadata_stream;
-       uint64_t data_size, payload_size;
-       struct ctf_trace *ctf_trace;
+       int ret;
+       uint32_t major, minor;
+
+       /* Put ref on previous index_file. */
+       if (stream->index_file) {
+               lttng_index_file_put(stream->index_file);
+               stream->index_file = NULL;
+       }
+       major = stream->trace->session->major;
+       minor = stream->trace->session->minor;
+       stream->index_file = lttng_index_file_create(stream->path_name,
+                       stream->channel_name,
+                       -1, -1, stream->tracefile_size,
+                       tracefile_array_get_file_index_head(stream->tfa),
+                       lttng_to_index_major(major, minor),
+                       lttng_to_index_minor(major, minor));
+       if (!stream->index_file) {
+               ret = -1;
+               goto end;
+       }
 
-       if (!session) {
-               ERR("Metadata sent before version check");
+       ret = 0;
+
+end:
+       return ret;
+}
+
+static
+int do_rotate_stream(struct relay_stream *stream)
+{
+       int ret;
+
+       /* Perform the stream rotation. */
+       ret = utils_rotate_stream_file(stream->path_name,
+                       stream->channel_name, stream->tracefile_size,
+                       stream->tracefile_count, -1,
+                       -1, stream->stream_fd->fd,
+                       NULL, &stream->stream_fd->fd);
+       if (ret < 0) {
+               ERR("Rotating stream output file");
+               goto end;
+       }
+       stream->tracefile_size_current = 0;
+
+       /* Rotate also the index if the stream is not a metadata stream. */
+       if (!stream->is_metadata) {
+               ret = create_rotate_index_file(stream);
+               if (ret < 0) {
+                       ERR("Failed to rotate index file");
+                       goto end;
+               }
+       }
+
+       stream->rotate_at_seq_num = -1ULL;
+       stream->pos_after_last_complete_data_index = 0;
+
+end:
+       return ret;
+}
+
+/*
+ * If too much data has been written in a tracefile before we received the
+ * rotation command, we have to move the excess data to the new tracefile and
+ * perform the rotation. This can happen because the control and data
+ * connections are separate, the indexes as well as the commands arrive from
+ * the control connection and we have no control over the order so we could be
+ * in a situation where too much data has been received on the data connection
+ * before the rotation command on the control connection arrives. We don't need
+ * to update the index because its order is guaranteed with the rotation
+ * command message.
+ */
+static
+int rotate_truncate_stream(struct relay_stream *stream)
+{
+       int ret, new_fd;
+       off_t lseek_ret;
+       uint64_t diff, pos = 0;
+       char buf[FILE_COPY_BUFFER_SIZE];
+
+       assert(!stream->is_metadata);
+
+       assert(stream->tracefile_size_current >
+                       stream->pos_after_last_complete_data_index);
+       diff = stream->tracefile_size_current -
+                       stream->pos_after_last_complete_data_index;
+
+       /* Create the new tracefile. */
+       new_fd = utils_create_stream_file(stream->path_name,
+                       stream->channel_name,
+                       stream->tracefile_size, stream->tracefile_count,
+                       /* uid */ -1, /* gid */ -1, /* suffix */ NULL);
+       if (new_fd < 0) {
+               ERR("Failed to create new stream file at path %s for channel %s",
+                               stream->path_name, stream->channel_name);
                ret = -1;
                goto end;
        }
 
-       data_size = payload_size = be64toh(recv_hdr->data_size);
-       if (data_size < sizeof(struct lttcomm_relayd_metadata_payload)) {
-               ERR("Incorrect data size");
+       /*
+        * Rewind the current tracefile to the position at which the rotation
+        * should have occured.
+        */
+       lseek_ret = lseek(stream->stream_fd->fd,
+                       stream->pos_after_last_complete_data_index, SEEK_SET);
+       if (lseek_ret < 0) {
+               PERROR("seek truncate stream");
                ret = -1;
                goto end;
        }
-       payload_size -= sizeof(struct lttcomm_relayd_metadata_payload);
 
-       if (data_buffer_size < data_size) {
-               /* In case the realloc fails, we can free the memory */
-               char *tmp_data_ptr;
+       /* Move data from the old file to the new file. */
+       while (pos < diff) {
+               uint64_t count, bytes_left;
+               ssize_t io_ret;
+
+               bytes_left = diff - pos;
+               count = bytes_left > sizeof(buf) ? sizeof(buf) : bytes_left;
+               assert(count <= SIZE_MAX);
 
-               tmp_data_ptr = realloc(data_buffer, data_size);
-               if (!tmp_data_ptr) {
-                       ERR("Allocating data buffer");
-                       free(data_buffer);
+               io_ret = lttng_read(stream->stream_fd->fd, buf, count);
+               if (io_ret < (ssize_t) count) {
+                       char error_string[256];
+
+                       snprintf(error_string, sizeof(error_string),
+                                       "Failed to read %" PRIu64 " bytes from fd %i in rotate_truncate_stream(), returned %zi",
+                                       count, stream->stream_fd->fd, io_ret);
+                       if (io_ret == -1) {
+                               PERROR("%s", error_string);
+                       } else {
+                               ERR("%s", error_string);
+                       }
                        ret = -1;
                        goto end;
                }
-               data_buffer = tmp_data_ptr;
-               data_buffer_size = data_size;
-       }
-       memset(data_buffer, 0, data_size);
-       DBG2("Relay receiving metadata, waiting for %" PRIu64 " bytes", data_size);
-       ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, data_size, 0);
-       if (ret < 0 || ret != data_size) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive the whole metadata");
+
+               io_ret = lttng_write(new_fd, buf, count);
+               if (io_ret < (ssize_t) count) {
+                       char error_string[256];
+
+                       snprintf(error_string, sizeof(error_string),
+                                       "Failed to write %" PRIu64 " bytes from fd %i in rotate_truncate_stream(), returned %zi",
+                                       count, new_fd, io_ret);
+                       if (io_ret == -1) {
+                               PERROR("%s", error_string);
+                       } else {
+                               ERR("%s", error_string);
+                       }
+                       ret = -1;
+                       goto end;
+               }
+
+               pos += count;
+       }
+
+       /* Truncate the file to get rid of the excess data. */
+       ret = ftruncate(stream->stream_fd->fd,
+                       stream->pos_after_last_complete_data_index);
+       if (ret) {
+               PERROR("ftruncate");
+               goto end;
+       }
+
+       ret = close(stream->stream_fd->fd);
+       if (ret < 0) {
+               PERROR("Closing tracefile");
+               goto end;
+       }
+
+       ret = create_rotate_index_file(stream);
+       if (ret < 0) {
+               ERR("Rotate stream index file");
+               goto end;
+       }
+
+       /*
+        * Update the offset and FD of all the eventual indexes created by the
+        * data connection before the rotation command arrived.
+        */
+       ret = relay_index_switch_all_files(stream);
+       if (ret < 0) {
+               ERR("Failed to rotate index file");
+               goto end;
+       }
+
+       stream->stream_fd->fd = new_fd;
+       stream->tracefile_size_current = diff;
+       stream->pos_after_last_complete_data_index = 0;
+       stream->rotate_at_seq_num = -1ULL;
+
+       ret = 0;
+
+end:
+       return ret;
+}
+
+/*
+ * Check if a stream should perform a rotation (for session rotation).
+ * Must be called with the stream lock held.
+ *
+ * Return 0 on success, a negative value on error.
+ */
+static
+int try_rotate_stream(struct relay_stream *stream)
+{
+       int ret = 0;
+
+       /* No rotation expected. */
+       if (stream->rotate_at_seq_num == -1ULL) {
+               goto end;
+       }
+
+       if (stream->prev_seq < stream->rotate_at_seq_num ||
+                       stream->prev_seq == -1ULL) {
+               DBG("Stream %" PRIu64 " no yet ready for rotation",
+                               stream->stream_handle);
+               goto end;
+       } else if (stream->prev_seq > stream->rotate_at_seq_num) {
+               DBG("Rotation after too much data has been written in tracefile "
+                               "for stream %" PRIu64 ", need to truncate before "
+                               "rotating", stream->stream_handle);
+               ret = rotate_truncate_stream(stream);
+               if (ret) {
+                       ERR("Failed to truncate stream");
+                       goto end;
                }
+       } else {
+               /* stream->prev_seq == stream->rotate_at_seq_num */
+               DBG("Stream %" PRIu64 " ready for rotation",
+                               stream->stream_handle);
+               ret = do_rotate_stream(stream);
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * relay_recv_metadata: receive the metadata for the session.
+ */
+static int relay_recv_metadata(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret = 0;
+       ssize_t size_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_metadata_payload metadata_payload_header;
+       struct relay_stream *metadata_stream;
+       uint64_t metadata_payload_size;
+
+       if (!session) {
+               ERR("Metadata sent before version check");
                ret = -1;
                goto end;
        }
-       metadata_struct = (struct lttcomm_relayd_metadata_payload *) data_buffer;
 
-       rcu_read_lock();
-       metadata_stream = stream_find_by_id(relay_streams_ht,
-                       be64toh(metadata_struct->stream_id));
+       if (recv_hdr->data_size < sizeof(struct lttcomm_relayd_metadata_payload)) {
+               ERR("Incorrect data size");
+               ret = -1;
+               goto end;
+       }
+       metadata_payload_size = recv_hdr->data_size -
+                       sizeof(struct lttcomm_relayd_metadata_payload);
+
+       memcpy(&metadata_payload_header, payload->data,
+                       sizeof(metadata_payload_header));
+       metadata_payload_header.stream_id = be64toh(
+                       metadata_payload_header.stream_id);
+       metadata_payload_header.padding_size = be32toh(
+                       metadata_payload_header.padding_size);
+
+       metadata_stream = stream_get_by_id(metadata_payload_header.stream_id);
        if (!metadata_stream) {
                ret = -1;
-               goto end_unlock;
+               goto end;
        }
 
-       size_ret = lttng_write(metadata_stream->fd, metadata_struct->payload,
-                       payload_size);
-       if (size_ret < payload_size) {
+       pthread_mutex_lock(&metadata_stream->lock);
+
+       size_ret = lttng_write(metadata_stream->stream_fd->fd,
+                       payload->data + sizeof(metadata_payload_header),
+                       metadata_payload_size);
+       if (size_ret < metadata_payload_size) {
                ERR("Relay error writing metadata on file");
                ret = -1;
-               goto end_unlock;
+               goto end_put;
        }
 
-       ret = write_padding_to_file(metadata_stream->fd,
-                       be32toh(metadata_struct->padding_size));
-       if (ret < 0) {
-               goto end_unlock;
+       size_ret = write_padding_to_file(metadata_stream->stream_fd->fd,
+                       metadata_payload_header.padding_size);
+       if (size_ret < (int64_t) metadata_payload_header.padding_size) {
+               ret = -1;
+               goto end_put;
        }
 
-       ctf_trace = ctf_trace_find_by_path(session->ctf_traces_ht,
-                       metadata_stream->path_name);
-       assert(ctf_trace);
-       ctf_trace->metadata_received +=
-               payload_size + be32toh(metadata_struct->padding_size);
+       metadata_stream->metadata_received +=
+               metadata_payload_size + metadata_payload_header.padding_size;
+       DBG2("Relay metadata written. Updated metadata_received %" PRIu64,
+               metadata_stream->metadata_received);
 
-       DBG2("Relay metadata written");
+       ret = try_rotate_stream(metadata_stream);
+       if (ret < 0) {
+               goto end_put;
+       }
 
-end_unlock:
-       rcu_read_unlock();
+end_put:
+       pthread_mutex_unlock(&metadata_stream->lock);
+       stream_put(metadata_stream);
 end:
        return ret;
 }
@@ -1548,57 +1851,64 @@ end:
 /*
  * relay_send_version: send relayd version number
  */
-static
-int relay_send_version(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_send_version(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttcomm_relayd_version reply, msg;
+       bool compatible = true;
 
-       assert(conn);
-
-       conn->version_check_done = 1;
+       conn->version_check_done = true;
 
        /* Get version from the other side. */
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < 0 || ret != sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay failed to receive the version values.");
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_send_version\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end;
        }
 
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.major = be32toh(msg.major);
+       msg.minor = be32toh(msg.minor);
+
        memset(&reply, 0, sizeof(reply));
        reply.major = RELAYD_VERSION_COMM_MAJOR;
        reply.minor = RELAYD_VERSION_COMM_MINOR;
 
        /* Major versions must be the same */
-       if (reply.major != be32toh(msg.major)) {
+       if (reply.major != msg.major) {
                DBG("Incompatible major versions (%u vs %u), deleting session",
-                               reply.major, be32toh(msg.major));
-               destroy_session(conn->session, conn->sessions_ht);
-               ret = 0;
-               goto end;
+                               reply.major, msg.major);
+               compatible = false;
        }
 
        conn->major = reply.major;
        /* We adapt to the lowest compatible version */
-       if (reply.minor <= be32toh(msg.minor)) {
+       if (reply.minor <= msg.minor) {
                conn->minor = reply.minor;
        } else {
-               conn->minor = be32toh(msg.minor);
+               conn->minor = msg.minor;
        }
 
        reply.major = htobe32(reply.major);
        reply.minor = htobe32(reply.minor);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply,
-                       sizeof(struct lttcomm_relayd_version), 0);
-       if (ret < 0) {
-               ERR("Relay sending version");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"send version\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+               goto end;
+       } else {
+               ret = 0;
+       }
+
+       if (!compatible) {
+               ret = -1;
+               goto end;
        }
 
        DBG("Version check done using protocol %u.%u", conn->major,
@@ -1611,54 +1921,49 @@ end:
 /*
  * Check for data pending for a given stream id from the session daemon.
  */
-static
-int relay_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
+       ssize_t send_ret;
        int ret;
-       uint64_t last_net_seq_num, stream_id;
 
        DBG("Data pending command received");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid data_pending struct size : %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.stream_id = be64toh(msg.stream_id);
+       msg.last_net_seq_num = be64toh(msg.last_net_seq_num);
 
-       stream_id = be64toh(msg.stream_id);
-       last_net_seq_num = be64toh(msg.last_net_seq_num);
-
-       rcu_read_lock();
-       stream = stream_find_by_id(relay_streams_ht, stream_id);
+       stream = stream_get_by_id(msg.stream_id);
        if (stream == NULL) {
                ret = -1;
-               goto end_unlock;
+               goto end;
        }
 
+       pthread_mutex_lock(&stream->lock);
+
        DBG("Data pending for stream id %" PRIu64 " prev_seq %" PRIu64
-                       " and last_seq %" PRIu64, stream_id, stream->prev_seq,
-                       last_net_seq_num);
+                       " and last_seq %" PRIu64, msg.stream_id,
+                       stream->prev_seq, msg.last_net_seq_num);
 
        /* Avoid wrapping issue */
-       if (((int64_t) (stream->prev_seq - last_net_seq_num)) >= 0) {
+       if (((int64_t) (stream->prev_seq - msg.last_net_seq_num)) >= 0) {
                /* Data has in fact been written and is NOT pending */
                ret = 0;
        } else {
@@ -1666,17 +1971,19 @@ int relay_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
                ret = 1;
        }
 
-       /* Pending check is now done. */
-       stream->data_pending_check_done = 1;
+       stream->data_pending_check_done = true;
+       pthread_mutex_unlock(&stream->lock);
 
-end_unlock:
-       rcu_read_unlock();
+       stream_put(stream);
+end:
 
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(ret);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay data pending ret code failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"data pending\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -1686,61 +1993,58 @@ end_no_session:
 /*
  * Wait for the control socket to reach a quiescent state.
  *
- * Note that for now, when receiving this command from the session daemon, this
- * means that every subsequent commands or data received on the control socket
- * has been handled. So, this is why we simply return OK here.
+ * Note that for now, when receiving this command from the session
+ * daemon, this means that every subsequent commands or data received on
+ * the control socket has been handled. So, this is why we simply return
+ * OK here.
  */
-static
-int relay_quiescent_control(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_quiescent_control(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
-       uint64_t stream_id;
+       ssize_t send_ret;
        struct relay_stream *stream;
-       struct lttng_ht_iter iter;
        struct lttcomm_relayd_quiescent_control msg;
        struct lttcomm_relayd_generic_reply reply;
 
        DBG("Checking quiescent state on control socket");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid begin data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_quiescent_control\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.stream_id = be64toh(msg.stream_id);
 
-       stream_id = be64toh(msg.stream_id);
-
-       rcu_read_lock();
-       cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, stream,
-                       node.node) {
-               if (stream->stream_handle == stream_id) {
-                       stream->data_pending_check_done = 1;
-                       DBG("Relay quiescent control pending flag set to %" PRIu64,
-                                       stream_id);
-                       break;
-               }
+       stream = stream_get_by_id(msg.stream_id);
+       if (!stream) {
+               goto reply;
        }
-       rcu_read_unlock();
+       pthread_mutex_lock(&stream->lock);
+       stream->data_pending_check_done = true;
+       pthread_mutex_unlock(&stream->lock);
 
+       DBG("Relay quiescent control pending flag set to %" PRIu64, msg.stream_id);
+       stream_put(stream);
+reply:
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_OK);
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay data quiescent control ret code failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"quiescent control\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1748,62 +2052,63 @@ end_no_session:
 }
 
 /*
- * Initialize a data pending command. This means that a client is about to ask
- * for data pending for each stream he/she holds. Simply iterate over all
- * streams of a session and set the data_pending_check_done flag.
+ * Initialize a data pending command. This means that a consumer is about
+ * to ask for data pending for each stream it holds. Simply iterate over
+ * all streams of a session and set the data_pending_check_done flag.
  *
  * This command returns to the client a LTTNG_OK code.
  */
-static
-int relay_begin_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_begin_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttng_ht_iter iter;
        struct lttcomm_relayd_begin_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t session_id;
 
        assert(recv_hdr);
        assert(conn);
 
        DBG("Init streams for data pending");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid begin data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_begin_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
-
-       session_id = be64toh(msg.session_id);
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.session_id = be64toh(msg.session_id);
 
        /*
-        * Iterate over all streams to set the begin data pending flag. For now, the
-        * streams are indexed by stream handle so we have to iterate over all
-        * streams to find the one associated with the right session_id.
+        * Iterate over all streams to set the begin data pending flag.
+        * For now, the streams are indexed by stream handle so we have
+        * to iterate over all streams to find the one associated with
+        * the right session_id.
         */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, stream,
                        node.node) {
-               if (stream->session_id == session_id) {
-                       stream->data_pending_check_done = 0;
+               if (!stream_get(stream)) {
+                       continue;
+               }
+               if (stream->trace->session->id == msg.session_id) {
+                       pthread_mutex_lock(&stream->lock);
+                       stream->data_pending_check_done = false;
+                       pthread_mutex_unlock(&stream->lock);
                        DBG("Set begin data pending flag to stream %" PRIu64,
                                        stream->stream_handle);
                }
+               stream_put(stream);
        }
        rcu_read_unlock();
 
@@ -1811,9 +2116,13 @@ int relay_begin_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
        /* All good, send back reply. */
        reply.ret_code = htobe32(LTTNG_OK);
 
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay begin data pending send reply failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"begin data pending\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1821,63 +2130,70 @@ end_no_session:
 }
 
 /*
- * End data pending command. This will check, for a given session id, if each
- * stream associated with it has its data_pending_check_done flag set. If not,
- * this means that the client lost track of the stream but the data is still
- * being streamed on our side. In this case, we inform the client that data is
- * inflight.
+ * End data pending command. This will check, for a given session id, if
+ * each stream associated with it has its data_pending_check_done flag
+ * set. If not, this means that the client lost track of the stream but
+ * the data is still being streamed on our side. In this case, we inform
+ * the client that data is in flight.
  *
  * Return to the client if there is data in flight or not with a ret_code.
  */
-static
-int relay_end_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_end_data_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
        int ret;
+       ssize_t send_ret;
        struct lttng_ht_iter iter;
        struct lttcomm_relayd_end_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t session_id;
        uint32_t is_data_inflight = 0;
 
-       assert(recv_hdr);
-       assert(conn);
-
        DBG("End data pending command");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to check for data before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &msg, sizeof(msg), 0);
-       if (ret < sizeof(msg)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid end data_pending struct size: %d",
-                                       ret);
-               }
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_end_data_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&msg, payload->data, sizeof(msg));
+       msg.session_id = be64toh(msg.session_id);
 
-       session_id = be64toh(msg.session_id);
-
-       /* Iterate over all streams to see if the begin data pending flag is set. */
+       /*
+        * Iterate over all streams to see if the begin data pending
+        * flag is set.
+        */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, stream,
                        node.node) {
-               if (stream->session_id == session_id &&
-                               !stream->data_pending_check_done && !stream->terminated_flag) {
-                       is_data_inflight = 1;
-                       DBG("Data is still in flight for stream %" PRIu64,
-                                       stream->stream_handle);
-                       break;
+               if (!stream_get(stream)) {
+                       continue;
+               }
+               if (stream->trace->session->id != msg.session_id) {
+                       stream_put(stream);
+                       continue;
+               }
+               pthread_mutex_lock(&stream->lock);
+               if (!stream->data_pending_check_done) {
+                       if (!stream->closed || !(((int64_t) (stream->prev_seq - stream->last_net_seq_num)) >= 0)) {
+                               is_data_inflight = 1;
+                               DBG("Data is still in flight for stream %" PRIu64,
+                                               stream->stream_handle);
+                               pthread_mutex_unlock(&stream->lock);
+                               stream_put(stream);
+                               break;
+                       }
                }
+               pthread_mutex_unlock(&stream->lock);
+               stream_put(stream);
        }
        rcu_read_unlock();
 
@@ -1885,9 +2201,13 @@ int relay_end_data_pending(struct lttcomm_relayd_hdr *recv_hdr,
        /* All good, send back reply. */
        reply.ret_code = htobe32(is_data_inflight);
 
-       ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (ret < 0) {
-               ERR("Relay end data pending send reply failed");
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"end data pending\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
+       } else {
+               ret = 0;
        }
 
 end_no_session:
@@ -1899,113 +2219,121 @@ end_no_session:
  *
  * Return 0 on success else a negative value.
  */
-static
-int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_recv_index(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret, index_created = 0;
+       int ret;
+       ssize_t send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_index index_info;
-       struct relay_index *index, *wr_index = NULL;
+       struct relay_index *index;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
-       uint64_t net_seq_num;
+       size_t msg_len;
 
        assert(conn);
 
        DBG("Relay receiving index");
 
-       if (!session || conn->version_check_done == 0) {
+       if (!session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &index_info,
-                       sizeof(index_info), 0);
-       if (ret < sizeof(index_info)) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Relay didn't receive valid index struct size : %d", ret);
-               }
+       msg_len = lttcomm_relayd_index_len(
+                       lttng_to_index_major(conn->major, conn->minor),
+                       lttng_to_index_minor(conn->major, conn->minor));
+       if (payload->size < msg_len) {
+               ERR("Unexpected payload size in \"relay_recv_index\": expected >= %zu bytes, got %zu bytes",
+                               msg_len, payload->size);
                ret = -1;
                goto end_no_session;
        }
+       memcpy(&index_info, payload->data, msg_len);
+       index_info.relay_stream_id = be64toh(index_info.relay_stream_id);
+       index_info.net_seq_num = be64toh(index_info.net_seq_num);
+       index_info.packet_size = be64toh(index_info.packet_size);
+       index_info.content_size = be64toh(index_info.content_size);
+       index_info.timestamp_begin = be64toh(index_info.timestamp_begin);
+       index_info.timestamp_end = be64toh(index_info.timestamp_end);
+       index_info.events_discarded = be64toh(index_info.events_discarded);
+       index_info.stream_id = be64toh(index_info.stream_id);
 
-       net_seq_num = be64toh(index_info.net_seq_num);
+       if (conn->minor >= 8) {
+               index_info.stream_instance_id =
+                               be64toh(index_info.stream_instance_id);
+               index_info.packet_seq_num = be64toh(index_info.packet_seq_num);
+       }
 
-       rcu_read_lock();
-       stream = stream_find_by_id(relay_streams_ht,
-                       be64toh(index_info.relay_stream_id));
+       stream = stream_get_by_id(index_info.relay_stream_id);
        if (!stream) {
+               ERR("stream_get_by_id not found");
                ret = -1;
-               goto end_rcu_unlock;
+               goto end;
        }
+       pthread_mutex_lock(&stream->lock);
 
        /* Live beacon handling */
        if (index_info.packet_size == 0) {
-               DBG("Received live beacon for stream %" PRIu64, stream->stream_handle);
+               DBG("Received live beacon for stream %" PRIu64,
+                               stream->stream_handle);
 
                /*
-                * Only flag a stream inactive when it has already received data
-                * and no indexes are in flight.
+                * Only flag a stream inactive when it has already
+                * received data and no indexes are in flight.
                 */
-               if (stream->total_index_received > 0 && stream->indexes_in_flight == 0) {
-                       stream->beacon_ts_end = be64toh(index_info.timestamp_end);
+               if (stream->index_received_seqcount > 0
+                               && stream->indexes_in_flight == 0) {
+                       stream->beacon_ts_end = index_info.timestamp_end;
                }
                ret = 0;
-               goto end_rcu_unlock;
+               goto end_stream_put;
        } else {
                stream->beacon_ts_end = -1ULL;
        }
 
-       index = relay_index_find(stream->stream_handle, net_seq_num);
-       if (!index) {
-               /* A successful creation will add the object to the HT. */
-               index = relay_index_create(stream->stream_handle, net_seq_num);
-               if (!index) {
-                       goto end_rcu_unlock;
-               }
-               index_created = 1;
-               stream->indexes_in_flight++;
-       }
-
-       copy_index_control_data(index, &index_info);
        if (stream->ctf_stream_id == -1ULL) {
-               stream->ctf_stream_id = be64toh(index_info.stream_id);
+               stream->ctf_stream_id = index_info.stream_id;
        }
-
-       if (index_created) {
+       index = relay_index_get_by_id_or_create(stream, index_info.net_seq_num);
+       if (!index) {
+               ret = -1;
+               ERR("relay_index_get_by_id_or_create index NULL");
+               goto end_stream_put;
+       }
+       if (set_index_control_data(index, &index_info, conn)) {
+               ERR("set_index_control_data error");
+               relay_index_put(index);
+               ret = -1;
+               goto end_stream_put;
+       }
+       ret = relay_index_try_flush(index);
+       if (ret == 0) {
+               tracefile_array_commit_seq(stream->tfa);
+               stream->index_received_seqcount++;
+               stream->pos_after_last_complete_data_index += index->total_size;
+               stream->prev_index_seq = index_info.net_seq_num;
+       } else if (ret > 0) {
+               /* no flush. */
+               ret = 0;
+       } else {
                /*
-                * Try to add the relay index object to the hash table. If an object
-                * already exist, destroy back the index created, set the data in this
-                * object and write it on disk.
+                * ret < 0
+                *
+                * relay_index_try_flush is responsible for the self-reference
+                * put of the index object on error.
                 */
-               relay_index_add(index, &wr_index);
-               if (wr_index) {
-                       copy_index_control_data(wr_index, &index_info);
-                       free(index);
-               }
-       } else {
-               /* The index already exists so write it on disk. */
-               wr_index = index;
+               ERR("relay_index_try_flush error %d", ret);
+               ret = -1;
        }
 
-       /* Do we have a writable ready index to write on disk. */
-       if (wr_index) {
-               ret = relay_index_write(wr_index->fd, wr_index);
-               if (ret < 0) {
-                       goto end_rcu_unlock;
-               }
-               stream->total_index_received++;
-               stream->indexes_in_flight--;
-               assert(stream->indexes_in_flight >= 0);
-       }
+end_stream_put:
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
 
-end_rcu_unlock:
-       rcu_read_unlock();
+end:
 
        memset(&reply, 0, sizeof(reply));
        if (ret < 0) {
@@ -2014,9 +2342,9 @@ end_rcu_unlock:
                reply.ret_code = htobe32(LTTNG_OK);
        }
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending close index id reply");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"recv index\" command reply (ret = %zd)", send_ret);
+               ret = -1;
        }
 
 end_no_session:
@@ -2028,42 +2356,37 @@ end_no_session:
  *
  * Return 0 on success else a negative value.
  */
-static
-int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+static int relay_streams_sent(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
-       int ret, send_ret;
+       int ret;
+       ssize_t send_ret;
        struct lttcomm_relayd_generic_reply reply;
 
        assert(conn);
 
        DBG("Relay receiving streams_sent");
 
-       if (!conn->session || conn->version_check_done == 0) {
+       if (!conn->session || !conn->version_check_done) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }
 
        /*
-        * Flag every pending stream in the connection recv list that they are
-        * ready to be used by the viewer.
+        * Publish every pending stream in the connection recv list which are
+        * now ready to be used by the viewer.
         */
-       set_viewer_ready_flag(conn);
-
-       /*
-        * Inform the viewer that there are new streams in the session.
-        */
-       if (conn->session->viewer_refcount) {
-               uatomic_set(&conn->session->new_streams, 1);
-       }
+       publish_connection_local_streams(conn);
 
        memset(&reply, 0, sizeof(reply));
        reply.ret_code = htobe32(LTTNG_OK);
        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
-       if (send_ret < 0) {
-               ERR("Relay sending sent_stream reply");
-               ret = send_ret;
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"streams sent\" command reply (ret = %zd)",
+                       send_ret);
+               ret = -1;
        } else {
                /* Success. */
                ret = 0;
@@ -2074,54 +2397,575 @@ end_no_session:
 }
 
 /*
- * Process the commands received on the control socket
+ * relay_rotate_session_stream: rotate a stream to a new tracefile for the session
+ * rotation feature (not the tracefile rotation feature).
+ */
+static int relay_rotate_session_stream(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret;
+       ssize_t send_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_rotate_stream stream_info;
+       struct lttcomm_relayd_generic_reply reply;
+       struct relay_stream *stream;
+       size_t header_len;
+       size_t path_len;
+       struct lttng_buffer_view new_path_view;
+
+       DBG("Rotate stream received");
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to rotate a stream before version check");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               ERR("Unsupported feature before 2.11");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       header_len = sizeof(struct lttcomm_relayd_rotate_stream);
+
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_rotate_session_stream\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       memcpy(&stream_info, payload->data, header_len);
+
+       /* Convert to host */
+       stream_info.pathname_length = be32toh(stream_info.pathname_length);
+       stream_info.stream_id = be64toh(stream_info.stream_id);
+       stream_info.new_chunk_id = be64toh(stream_info.new_chunk_id);
+       stream_info.rotate_at_seq_num = be64toh(stream_info.rotate_at_seq_num);
+
+       path_len = stream_info.pathname_length;
+       if (payload->size < header_len + path_len) {
+               ERR("Unexpected payload size in \"relay_rotate_session_stream\" including path: expected >= %zu bytes, got %zu bytes",
+                               header_len + path_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }       
+       
+       /* Ensure it fits in local filename length. */
+       if (path_len >= LTTNG_PATH_MAX) {
+               ret = -ENAMETOOLONG;
+               ERR("Length of relay_rotate_session_stream command's path name (%zu bytes) exceeds the maximal allowed length of %i bytes",
+                               path_len, LTTNG_PATH_MAX);
+               goto end;
+       }
+
+       new_path_view = lttng_buffer_view_from_view(payload, header_len,
+                       stream_info.pathname_length);
+
+       stream = stream_get_by_id(stream_info.stream_id);
+       if (!stream) {
+               ret = -1;
+               goto end;
+       }
+
+       pthread_mutex_lock(&stream->lock);
+
+       /*
+        * Update the trace path (just the folder, the stream name does not
+        * change).
+        */
+       free(stream->path_name);
+       stream->path_name = create_output_path(new_path_view.data);
+       if (!stream->path_name) {
+               ERR("Failed to create a new output path");
+               ret = -1;
+               goto end_stream_unlock;
+       }
+       ret = utils_mkdir_recursive(stream->path_name, S_IRWXU | S_IRWXG,
+                       -1, -1);
+       if (ret < 0) {
+               ERR("relay creating output directory");
+               ret = -1;
+               goto end_stream_unlock;
+       }
+
+       assert(stream->current_chunk_id.is_set);
+       stream->current_chunk_id.value = stream_info.new_chunk_id;
+
+       if (stream->is_metadata) {
+               /*
+                * The metadata stream is sent only over the control connection
+                * so we know we have all the data to perform the stream
+                * rotation.
+                */
+               ret = do_rotate_stream(stream);
+       } else {
+               stream->rotate_at_seq_num = stream_info.rotate_at_seq_num;
+               ret = try_rotate_stream(stream);
+       }
+       if (ret < 0) {
+               goto end_stream_unlock;
+       }
+
+end_stream_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
+end:
+       memset(&reply, 0, sizeof(reply));
+       if (ret < 0) {
+               reply.ret_code = htobe32(LTTNG_ERR_UNK);
+       } else {
+               reply.ret_code = htobe32(LTTNG_OK);
+       }
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(struct lttcomm_relayd_generic_reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"rotate session stream\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_reply:
+       return ret;
+}
+
+/*
+ * relay_mkdir: Create a folder on the disk.
+ */
+static int relay_mkdir(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_mkdir path_info_header;
+       struct lttcomm_relayd_generic_reply reply;
+       char *path = NULL;
+       size_t header_len;
+       ssize_t send_ret;
+       struct lttng_buffer_view path_view;
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to create a directory before version check");
+               ret = -1;
+               goto end_no_session;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               /*
+                * This client is not supposed to use this command since
+                * it predates its introduction.
+                */
+               ERR("relay_mkdir command is unsupported before LTTng 2.11");
+               ret = -1;
+               goto end_no_session;
+       }
+
+       header_len = sizeof(path_info_header);
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_mkdir\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_session;
+       }
+
+       memcpy(&path_info_header, payload->data, header_len);
+
+       path_info_header.length = be32toh(path_info_header.length);
+
+       if (payload->size < header_len + path_info_header.length) {
+               ERR("Unexpected payload size in \"relay_mkdir\" including path: expected >= %zu bytes, got %zu bytes",
+                               header_len + path_info_header.length, payload->size);
+               ret = -1;
+               goto end_no_session;
+       }
+
+       /* Ensure that it fits in local path length. */
+       if (path_info_header.length >= LTTNG_PATH_MAX) {
+               ret = -ENAMETOOLONG;
+               ERR("Path name argument of mkdir command (%" PRIu32 " bytes) exceeds the maximal length allowed (%d bytes)",
+                               path_info_header.length, LTTNG_PATH_MAX);
+               goto end;
+       }
+
+       path_view = lttng_buffer_view_from_view(payload, header_len,
+                       path_info_header.length);
+
+       path = create_output_path(path_view.data);
+       if (!path) {
+               ERR("Failed to create output path");
+               ret = -1;
+               goto end;
+       }
+
+       ret = utils_mkdir_recursive(path, S_IRWXU | S_IRWXG, -1, -1);
+       if (ret < 0) {
+               ERR("relay creating output directory");
+               goto end;
+       }
+
+       ret = 0;
+
+end:
+       memset(&reply, 0, sizeof(reply));
+       if (ret < 0) {
+               reply.ret_code = htobe32(LTTNG_ERR_UNK);
+       } else {
+               reply.ret_code = htobe32(LTTNG_OK);
+       }
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"mkdir\" command reply (ret = %zd)", send_ret);
+               ret = -1;
+       }
+
+end_no_session:
+       free(path);
+       return ret;
+}
+
+static int validate_rotate_rename_path_length(const char *path_type,
+               uint32_t path_length)
+{
+       int ret = 0;
+
+       if (path_length > LTTNG_PATH_MAX) {
+               ret = -ENAMETOOLONG;
+               ERR("rotate rename \"%s\" path name length (%" PRIu32 " bytes) exceeds the allowed size of %i bytes",
+                               path_type, path_length, LTTNG_PATH_MAX);
+       } else if (path_length == 0) {
+               ret = -EINVAL;
+               ERR("rotate rename \"%s\" path name has an illegal length of 0", path_type);
+       }
+       return ret;
+}
+
+/*
+ * relay_rotate_rename: rename the trace folder after a rotation is
+ * completed. We are not closing any fd here, just moving the folder, so it
+ * works even if data is still in-flight.
+ */
+static int relay_rotate_rename(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
+{
+       int ret;
+       ssize_t send_ret;
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_generic_reply reply;
+       struct lttcomm_relayd_rotate_rename header;
+       size_t header_len;
+       size_t received_paths_size;
+       char *complete_old_path = NULL, *complete_new_path = NULL;
+       struct lttng_buffer_view old_path_view;
+       struct lttng_buffer_view new_path_view;
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to rename a trace folder before version check");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               ERR("relay_rotate_rename command is unsupported before LTTng 2.11");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       header_len = sizeof(header);
+       if (payload->size < header_len) {
+               ERR("Unexpected payload size in \"relay_rotate_rename\": expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       memcpy(&header, payload->data, header_len);
+
+       header.old_path_length = be32toh(header.old_path_length);
+       header.new_path_length = be32toh(header.new_path_length);
+       received_paths_size = header.old_path_length + header.new_path_length;
+
+       if (payload->size < header_len + received_paths_size) {
+               ERR("Unexpected payload size in \"relay_rotate_rename\" including paths: expected >= %zu bytes, got %zu bytes",
+                               header_len, payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       /* Ensure the paths don't exceed their allowed size. */
+       ret = validate_rotate_rename_path_length("old", header.old_path_length);
+       if (ret) {
+               goto end;
+       }
+       ret = validate_rotate_rename_path_length("new", header.new_path_length);
+       if (ret) {
+               goto end;
+       }
+
+       old_path_view = lttng_buffer_view_from_view(payload, header_len,
+                       header.old_path_length);
+       new_path_view = lttng_buffer_view_from_view(payload,
+                       header_len + header.old_path_length,
+                       header.new_path_length);
+
+       /* Validate that both paths received are NULL terminated. */
+       if (old_path_view.data[old_path_view.size - 1] != '\0') {
+               ERR("relay_rotate_rename command's \"old\" path is invalid (not NULL terminated)");
+               ret = -1;
+               goto end;
+       }
+       if (new_path_view.data[new_path_view.size - 1] != '\0') {
+               ERR("relay_rotate_rename command's \"new\" path is invalid (not NULL terminated)");
+               ret = -1;
+               goto end;
+       }
+
+       complete_old_path = create_output_path(old_path_view.data);
+       if (!complete_old_path) {
+               ERR("Failed to build old output path in rotate_rename command");
+               ret = -1;
+               goto end;
+       }
+
+       complete_new_path = create_output_path(new_path_view.data);
+       if (!complete_new_path) {
+               ERR("Failed to build new output path in rotate_rename command");
+               ret = -1;
+               goto end;
+       }
+
+       ret = utils_mkdir_recursive(complete_new_path, S_IRWXU | S_IRWXG,
+                       -1, -1);
+       if (ret < 0) {
+               ERR("Failed to mkdir() rotate_rename's \"new\" output directory at \"%s\"",
+                               complete_new_path);
+               goto end;
+       }
+
+       /*
+        * If a domain has not yet created its channel, the domain-specific
+        * folder might not exist, but this is not an error.
+        */
+       ret = rename(complete_old_path, complete_new_path);
+       if (ret < 0 && errno != ENOENT) {
+               PERROR("Renaming chunk in rotate_rename command from \"%s\" to \"%s\"",
+                               complete_old_path, complete_new_path);
+               goto end;
+       }
+       ret = 0;
+
+end:
+       memset(&reply, 0, sizeof(reply));
+       if (ret < 0) {
+               reply.ret_code = htobe32(LTTNG_ERR_UNK);
+       } else {
+               reply.ret_code = htobe32(LTTNG_OK);
+       }
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < sizeof(reply)) {
+               ERR("Failed to send \"rotate rename\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_reply:
+       free(complete_old_path);
+       free(complete_new_path);
+       return ret;
+}
+
+/*
+ * Check if all the streams in the session have completed the last rotation.
+ * The chunk_id value is used to distinguish the cases where a stream was
+ * closed on the consumerd before the rotation started but it still active on
+ * the relayd, and the case where a stream appeared on the consumerd/relayd
+ * after the last rotation started (in that case, it is already writing in the
+ * new chunk folder).
  */
 static
-int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_connection *conn)
+int relay_rotate_pending(const struct lttcomm_relayd_hdr *recv_hdr,
+               struct relay_connection *conn,
+               const struct lttng_buffer_view *payload)
 {
+       struct relay_session *session = conn->session;
+       struct lttcomm_relayd_rotate_pending msg;
+       struct lttcomm_relayd_rotate_pending_reply reply;
+       struct lttng_ht_iter iter;
+       struct relay_stream *stream;
        int ret = 0;
+       ssize_t send_ret;
+       uint64_t chunk_id;
+        bool rotate_pending = false;
+
+       DBG("Rotate pending command received");
+
+       if (!session || !conn->version_check_done) {
+               ERR("Trying to check for data before version check");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (session->major == 2 && session->minor < 11) {
+               ERR("Unsupported feature before 2.11");
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       if (payload->size < sizeof(msg)) {
+               ERR("Unexpected payload size in \"relay_rotate_pending\": expected >= %zu bytes, got %zu bytes",
+                               sizeof(msg), payload->size);
+               ret = -1;
+               goto end_no_reply;
+       }
+
+       memcpy(&msg, payload->data, sizeof(msg));
 
-       switch (be32toh(recv_hdr->cmd)) {
+       chunk_id = be64toh(msg.chunk_id);
+
+       DBG("Evaluating rotate pending for session \"%s\" and  chunk id %" PRIu64,
+                       session->session_name, chunk_id);
+
+       /*
+        * Iterate over all the streams in the session and check if they are
+        * still waiting for data to perform their rotation.
+        */
+       rcu_read_lock();
+       cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, stream,
+                       node.node) {
+               if (!stream_get(stream)) {
+                       continue;
+               }
+               if (stream->trace->session != session) {
+                       stream_put(stream);
+                       continue;
+               }
+               pthread_mutex_lock(&stream->lock);
+               if (stream->rotate_at_seq_num != -1ULL) {
+                       /* We have not yet performed the rotation. */
+                       rotate_pending = true;
+                       DBG("Stream %" PRIu64 " is still rotating",
+                                       stream->stream_handle);
+               } else if (stream->current_chunk_id.value < chunk_id) {
+                       /*
+                        * Stream closed on the consumer but still active on the
+                        * relay.
+                        */
+                       rotate_pending = true;
+                       DBG("Stream %" PRIu64 " did not exist on the consumer "
+                                       "when the last rotation started, but is"
+                                       "still waiting for data before getting"
+                                       "closed",
+                                       stream->stream_handle);
+               }
+               pthread_mutex_unlock(&stream->lock);
+               stream_put(stream);
+               if (rotate_pending) {
+                       goto send_reply;
+               }
+       }
+
+send_reply:
+       rcu_read_unlock();
+       memset(&reply, 0, sizeof(reply));
+       reply.generic.ret_code = htobe32((uint32_t) LTTNG_OK);
+       reply.is_pending = (uint8_t) !!rotate_pending;
+       send_ret = conn->sock->ops->sendmsg(conn->sock, &reply,
+                       sizeof(reply), 0);
+       if (send_ret < (ssize_t) sizeof(reply)) {
+               ERR("Failed to send \"rotate pending\" command reply (ret = %zd)",
+                               send_ret);
+               ret = -1;
+       }
+
+end_no_reply:
+       return ret;
+}
+
+#define DBG_CMD(cmd_name, conn) \
+               DBG3("Processing \"%s\" command for socket %i", cmd_name, conn->sock->fd);
+
+static int relay_process_control_command(struct relay_connection *conn,
+               const struct lttcomm_relayd_hdr *header,
+               const struct lttng_buffer_view *payload)
+{
+       int ret = 0;
+
+       switch (header->cmd) {
        case RELAYD_CREATE_SESSION:
-               ret = relay_create_session(recv_hdr, conn);
+               DBG_CMD("RELAYD_CREATE_SESSION", conn);
+               ret = relay_create_session(header, conn, payload);
                break;
        case RELAYD_ADD_STREAM:
-               ret = relay_add_stream(recv_hdr, conn);
+               DBG_CMD("RELAYD_ADD_STREAM", conn);
+               ret = relay_add_stream(header, conn, payload);
                break;
        case RELAYD_START_DATA:
-               ret = relay_start(recv_hdr, conn);
+               DBG_CMD("RELAYD_START_DATA", conn);
+               ret = relay_start(header, conn, payload);
                break;
        case RELAYD_SEND_METADATA:
-               ret = relay_recv_metadata(recv_hdr, conn);
+               DBG_CMD("RELAYD_SEND_METADATA", conn);
+               ret = relay_recv_metadata(header, conn, payload);
                break;
        case RELAYD_VERSION:
-               ret = relay_send_version(recv_hdr, conn);
+               DBG_CMD("RELAYD_VERSION", conn);
+               ret = relay_send_version(header, conn, payload);
                break;
        case RELAYD_CLOSE_STREAM:
-               ret = relay_close_stream(recv_hdr, conn);
+               DBG_CMD("RELAYD_CLOSE_STREAM", conn);
+               ret = relay_close_stream(header, conn, payload);
                break;
        case RELAYD_DATA_PENDING:
-               ret = relay_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_DATA_PENDING", conn);
+               ret = relay_data_pending(header, conn, payload);
                break;
        case RELAYD_QUIESCENT_CONTROL:
-               ret = relay_quiescent_control(recv_hdr, conn);
+               DBG_CMD("RELAYD_QUIESCENT_CONTROL", conn);
+               ret = relay_quiescent_control(header, conn, payload);
                break;
        case RELAYD_BEGIN_DATA_PENDING:
-               ret = relay_begin_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_BEGIN_DATA_PENDING", conn);
+               ret = relay_begin_data_pending(header, conn, payload);
                break;
        case RELAYD_END_DATA_PENDING:
-               ret = relay_end_data_pending(recv_hdr, conn);
+               DBG_CMD("RELAYD_END_DATA_PENDING", conn);
+               ret = relay_end_data_pending(header, conn, payload);
                break;
        case RELAYD_SEND_INDEX:
-               ret = relay_recv_index(recv_hdr, conn);
+               DBG_CMD("RELAYD_SEND_INDEX", conn);
+               ret = relay_recv_index(header, conn, payload);
                break;
        case RELAYD_STREAMS_SENT:
-               ret = relay_streams_sent(recv_hdr, conn);
+               DBG_CMD("RELAYD_STREAMS_SENT", conn);
+               ret = relay_streams_sent(header, conn, payload);
+               break;
+       case RELAYD_RESET_METADATA:
+               DBG_CMD("RELAYD_RESET_METADATA", conn);
+               ret = relay_reset_metadata(header, conn, payload);
+               break;
+       case RELAYD_ROTATE_STREAM:
+               DBG_CMD("RELAYD_ROTATE_STREAM", conn);
+               ret = relay_rotate_session_stream(header, conn, payload);
+               break;
+       case RELAYD_ROTATE_RENAME:
+               DBG_CMD("RELAYD_ROTATE_RENAME", conn);
+               ret = relay_rotate_rename(header, conn, payload);
+               break;
+       case RELAYD_ROTATE_PENDING:
+               DBG_CMD("RELAYD_ROTATE_PENDING", conn);
+               ret = relay_rotate_pending(header, conn, payload);
+               break;
+       case RELAYD_MKDIR:
+               DBG_CMD("RELAYD_MKDIR", conn);
+               ret = relay_mkdir(header, conn, payload);
                break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
-               ERR("Received unknown command (%u)", be32toh(recv_hdr->cmd));
+               ERR("Received unknown command (%u)", header->cmd);
                relay_unknown_command(conn);
                ret = -1;
                goto end;
@@ -2131,268 +2975,577 @@ end:
        return ret;
 }
 
+static enum relay_connection_status relay_process_control_receive_payload(
+               struct relay_connection *conn)
+{
+       int ret = 0;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct lttng_dynamic_buffer *reception_buffer =
+                       &conn->protocol.ctrl.reception_buffer;
+       struct ctrl_connection_state_receive_payload *state =
+                       &conn->protocol.ctrl.state.receive_payload;
+       struct lttng_buffer_view payload_view;
+
+       if (state->left_to_receive == 0) {
+               /* Short-circuit for payload-less commands. */
+               goto reception_complete;
+       }
+
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       reception_buffer->data + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive command payload on sock %d",
+                                       conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+               }
+               goto end;
+       } else if (ret == 0) {
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
+               goto end;
+       }
+
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
+
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of control connection protocol payload (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
+               goto end;
+       }
+
+reception_complete:
+       DBG("Done receiving control command payload: fd = %i, payload size = %" PRIu64 " bytes",
+                       conn->sock->fd, state->received);
+       /*
+        * The payload required to process the command has been received.
+        * A view to the reception buffer is forwarded to the various
+        * commands and the state of the control is reset on success.
+        *
+        * Commands are responsible for sending their reply to the peer.
+        */
+       payload_view = lttng_buffer_view_from_dynamic_buffer(reception_buffer,
+                       0, -1);
+       ret = relay_process_control_command(conn,
+                       &state->header, &payload_view);
+       if (ret < 0) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       ret = connection_reset_protocol_state(conn);
+       if (ret) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+       }
+end:
+       return status;
+}
+
+static enum relay_connection_status relay_process_control_receive_header(
+               struct relay_connection *conn)
+{
+       int ret = 0;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct lttcomm_relayd_hdr header;
+       struct lttng_dynamic_buffer *reception_buffer =
+                       &conn->protocol.ctrl.reception_buffer;
+       struct ctrl_connection_state_receive_header *state =
+                       &conn->protocol.ctrl.state.receive_header;
+
+       assert(state->left_to_receive != 0);
+
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       reception_buffer->data + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive control command header on sock %d",
+                                       conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+               }
+               goto end;
+       } else if (ret == 0) {
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
+               goto end;
+       }
+
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
+
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of control connection protocol header (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
+               goto end;
+       }
+
+       /* Transition to next state: receiving the command's payload. */
+       conn->protocol.ctrl.state_id =
+                       CTRL_CONNECTION_STATE_RECEIVE_PAYLOAD;
+       memcpy(&header, reception_buffer->data, sizeof(header));
+       header.circuit_id = be64toh(header.circuit_id);
+       header.data_size = be64toh(header.data_size);
+       header.cmd = be32toh(header.cmd);
+       header.cmd_version = be32toh(header.cmd_version);
+       memcpy(&conn->protocol.ctrl.state.receive_payload.header,
+                       &header, sizeof(header));
+
+       DBG("Done receiving control command header: fd = %i, cmd = %" PRIu32 ", cmd_version = %" PRIu32 ", payload size = %" PRIu64 " bytes",
+                       conn->sock->fd, header.cmd, header.cmd_version,
+                       header.data_size);
+
+       if (header.data_size > DEFAULT_NETWORK_RELAYD_CTRL_MAX_PAYLOAD_SIZE) {
+               ERR("Command header indicates a payload (%" PRIu64 " bytes) that exceeds the maximal payload size allowed on a control connection.",
+                               header.data_size);
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       conn->protocol.ctrl.state.receive_payload.left_to_receive =
+                       header.data_size;
+       conn->protocol.ctrl.state.receive_payload.received = 0;
+       ret = lttng_dynamic_buffer_set_size(reception_buffer,
+                       header.data_size);
+       if (ret) {
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       if (header.data_size == 0) {
+               /*
+                * Manually invoke the next state as the poll loop
+                * will not wake-up to allow us to proceed further.
+                */
+               status = relay_process_control_receive_payload(conn);
+       }
+end:
+       return status;
+}
+
+/*
+ * Process the commands received on the control socket
+ */
+static enum relay_connection_status relay_process_control(
+               struct relay_connection *conn)
+{
+       enum relay_connection_status status;
+
+       switch (conn->protocol.ctrl.state_id) {
+       case CTRL_CONNECTION_STATE_RECEIVE_HEADER:
+               status = relay_process_control_receive_header(conn);
+               break;
+       case CTRL_CONNECTION_STATE_RECEIVE_PAYLOAD:
+               status = relay_process_control_receive_payload(conn);
+               break;
+       default:
+               ERR("Unknown control connection protocol state encountered.");
+               abort();
+       }
+
+       return status;
+}
+
 /*
  * Handle index for a data stream.
  *
- * RCU read side lock MUST be acquired.
+ * Called with the stream lock held.
  *
  * Return 0 on success else a negative value.
  */
 static int handle_index_data(struct relay_stream *stream, uint64_t net_seq_num,
-               int rotate_index)
+               bool rotate_index, bool *flushed, uint64_t total_size)
 {
-       int ret = 0, index_created = 0;
-       uint64_t stream_id, data_offset;
-       struct relay_index *index, *wr_index = NULL;
-
-       assert(stream);
+       int ret = 0;
+       uint64_t data_offset;
+       struct relay_index *index;
 
-       stream_id = stream->stream_handle;
        /* Get data offset because we are about to update the index. */
        data_offset = htobe64(stream->tracefile_size_current);
 
+       DBG("handle_index_data: stream %" PRIu64 " net_seq_num %" PRIu64 " data offset %" PRIu64,
+                       stream->stream_handle, net_seq_num, stream->tracefile_size_current);
+
        /*
-        * Lookup for an existing index for that stream id/sequence number. If on
-        * exists, the control thread already received the data for it thus we need
-        * to write it on disk.
+        * Lookup for an existing index for that stream id/sequence
+        * number. If it exists, the control thread has already received the
+        * data for it, thus we need to write it to disk.
         */
-       index = relay_index_find(stream_id, net_seq_num);
+       index = relay_index_get_by_id_or_create(stream, net_seq_num);
        if (!index) {
-               /* A successful creation will add the object to the HT. */
-               index = relay_index_create(stream_id, net_seq_num);
-               if (!index) {
-                       ret = -1;
-                       goto error;
-               }
-               index_created = 1;
-               stream->indexes_in_flight++;
+               ret = -1;
+               goto end;
        }
 
-       if (rotate_index || stream->index_fd < 0) {
-               index->to_close_fd = stream->index_fd;
-               ret = index_create_file(stream->path_name, stream->channel_name,
-                               relayd_uid, relayd_gid, stream->tracefile_size,
-                               stream->tracefile_count_current);
+       if (rotate_index || !stream->index_file) {
+               ret = create_rotate_index_file(stream);
                if (ret < 0) {
-                       /* This will close the stream's index fd if one. */
-                       relay_index_free_safe(index);
-                       goto error;
+                       ERR("Failed to rotate index");
+                       /* Put self-ref for this index due to error. */
+                       relay_index_put(index);
+                       index = NULL;
+                       goto end;
                }
-               stream->index_fd = ret;
        }
-       index->fd = stream->index_fd;
-       index->index_data.offset = data_offset;
 
-       if (index_created) {
-               /*
-                * Try to add the relay index object to the hash table. If an object
-                * already exist, destroy back the index created and set the data.
-                */
-               relay_index_add(index, &wr_index);
-               if (wr_index) {
-                       /* Copy back data from the created index. */
-                       wr_index->fd = index->fd;
-                       wr_index->to_close_fd = index->to_close_fd;
-                       wr_index->index_data.offset = data_offset;
-                       free(index);
-               }
-       } else {
-               /* The index already exists so write it on disk. */
-               wr_index = index;
+       if (relay_index_set_file(index, stream->index_file, data_offset)) {
+               ret = -1;
+               /* Put self-ref for this index due to error. */
+               relay_index_put(index);
+               index = NULL;
+               goto end;
        }
 
-       /* Do we have a writable ready index to write on disk. */
-       if (wr_index) {
-               ret = relay_index_write(wr_index->fd, wr_index);
-               if (ret < 0) {
-                       goto error;
-               }
-               stream->total_index_received++;
-               stream->indexes_in_flight--;
-               assert(stream->indexes_in_flight >= 0);
+       ret = relay_index_try_flush(index);
+       if (ret == 0) {
+               tracefile_array_commit_seq(stream->tfa);
+               stream->index_received_seqcount++;
+               *flushed = true;
+       } else if (ret > 0) {
+               index->total_size = total_size;
+               /* No flush. */
+               ret = 0;
+       } else {
+               /*
+                * ret < 0
+                *
+                * relay_index_try_flush is responsible for the self-reference
+                * put of the index object on error.
+                */
+               ERR("relay_index_try_flush error %d", ret);
+               ret = -1;
        }
-
-error:
+end:
        return ret;
 }
 
-/*
- * relay_process_data: Process the data received on the data socket
- */
-static
-int relay_process_data(struct relay_connection *conn)
+static enum relay_connection_status relay_process_data_receive_header(
+               struct relay_connection *conn)
 {
-       int ret = 0, rotate_index = 0;
-       ssize_t size_ret;
+       int ret;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct data_connection_state_receive_header *state =
+                       &conn->protocol.data.state.receive_header;
+       struct lttcomm_relayd_data_hdr header;
        struct relay_stream *stream;
-       struct lttcomm_relayd_data_hdr data_hdr;
-       uint64_t stream_id;
-       uint64_t net_seq_num;
-       uint32_t data_size;
-       struct relay_session *session;
 
-       assert(conn);
+       assert(state->left_to_receive != 0);
 
-       ret = conn->sock->ops->recvmsg(conn->sock, &data_hdr,
-                       sizeof(struct lttcomm_relayd_data_hdr), 0);
-       if (ret <= 0) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               } else {
-                       ERR("Unable to receive data header on sock %d", conn->sock->fd);
+       ret = conn->sock->ops->recvmsg(conn->sock,
+                       state->header_reception_buffer + state->received,
+                       state->left_to_receive, MSG_DONTWAIT);
+       if (ret < 0) {
+               if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                       PERROR("Unable to receive data header on sock %d", conn->sock->fd);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
                }
-               ret = -1;
+               goto end;
+       } else if (ret == 0) {
+               /* Orderly shutdown. Not necessary to print an error. */
+               DBG("Socket %d performed an orderly shutdown (received EOF)", conn->sock->fd);
+               status = RELAY_CONNECTION_STATUS_CLOSED;
                goto end;
        }
 
-       stream_id = be64toh(data_hdr.stream_id);
+       assert(ret > 0);
+       assert(ret <= state->left_to_receive);
 
-       rcu_read_lock();
-       stream = stream_find_by_id(relay_streams_ht, stream_id);
-       if (!stream) {
-               ret = -1;
-               goto end_rcu_unlock;
+       state->left_to_receive -= ret;
+       state->received += ret;
+
+       if (state->left_to_receive > 0) {
+               /*
+                * Can't transition to the protocol's next state, wait to
+                * receive the rest of the header.
+                */
+               DBG3("Partial reception of data connection header (received %" PRIu64 " bytes, %" PRIu64 " bytes left to receive, fd = %i)",
+                               state->received, state->left_to_receive,
+                               conn->sock->fd);
+               goto end;
        }
 
-       session = session_find_by_id(conn->sessions_ht, stream->session_id);
-       assert(session);
+       /* Transition to next state: receiving the payload. */
+       conn->protocol.data.state_id = DATA_CONNECTION_STATE_RECEIVE_PAYLOAD;
 
-       data_size = be32toh(data_hdr.data_size);
-       if (data_buffer_size < data_size) {
-               char *tmp_data_ptr;
+       memcpy(&header, state->header_reception_buffer, sizeof(header));
+       header.circuit_id = be64toh(header.circuit_id);
+       header.stream_id = be64toh(header.stream_id);
+       header.data_size = be32toh(header.data_size);
+       header.net_seq_num = be64toh(header.net_seq_num);
+       header.padding_size = be32toh(header.padding_size);
+       memcpy(&conn->protocol.data.state.receive_payload.header, &header, sizeof(header));
 
-               tmp_data_ptr = realloc(data_buffer, data_size);
-               if (!tmp_data_ptr) {
-                       ERR("Allocating data buffer");
-                       free(data_buffer);
-                       ret = -1;
-                       goto end_rcu_unlock;
-               }
-               data_buffer = tmp_data_ptr;
-               data_buffer_size = data_size;
-       }
-       memset(data_buffer, 0, data_size);
+       conn->protocol.data.state.receive_payload.left_to_receive =
+                       header.data_size;
+       conn->protocol.data.state.receive_payload.received = 0;
+       conn->protocol.data.state.receive_payload.rotate_index = false;
 
-       net_seq_num = be64toh(data_hdr.net_seq_num);
+       DBG("Received data connection header on fd %i: circuit_id = %" PRIu64 ", stream_id = %" PRIu64 ", data_size = %" PRIu32 ", net_seq_num = %" PRIu64 ", padding_size = %" PRIu32,
+                       conn->sock->fd, header.circuit_id,
+                       header.stream_id, header.data_size,
+                       header.net_seq_num, header.padding_size);
 
-       DBG3("Receiving data of size %u for stream id %" PRIu64 " seqnum %" PRIu64,
-               data_size, stream_id, net_seq_num);
-       ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, data_size, 0);
-       if (ret <= 0) {
-               if (ret == 0) {
-                       /* Orderly shutdown. Not necessary to print an error. */
-                       DBG("Socket %d did an orderly shutdown", conn->sock->fd);
-               }
-               ret = -1;
-               goto end_rcu_unlock;
+       stream = stream_get_by_id(header.stream_id);
+       if (!stream) {
+               DBG("relay_process_data_receive_payload: Cannot find stream %" PRIu64,
+                               header.stream_id);
+               /* Protocol error. */
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
        }
 
+       pthread_mutex_lock(&stream->lock);
+
        /* Check if a rotation is needed. */
        if (stream->tracefile_size > 0 &&
-                       (stream->tracefile_size_current + data_size) >
+                       (stream->tracefile_size_current + header.data_size) >
                        stream->tracefile_size) {
-               struct relay_viewer_stream *vstream;
-               uint64_t new_id;
+               uint64_t old_id, new_id;
+
+               old_id = tracefile_array_get_file_index_head(stream->tfa);
+               tracefile_array_file_rotate(stream->tfa);
+
+               /* new_id is updated by utils_rotate_stream_file. */
+               new_id = old_id;
+
+               ret = utils_rotate_stream_file(stream->path_name,
+                               stream->channel_name, stream->tracefile_size,
+                               stream->tracefile_count, -1,
+                               -1, stream->stream_fd->fd,
+                               &new_id, &stream->stream_fd->fd);
+               if (ret < 0) {
+                       ERR("Failed to rotate stream output file");
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+                       goto end_stream_unlock;
+               }
 
-               new_id = (stream->tracefile_count_current + 1) %
-                       stream->tracefile_count;
                /*
-                * When we wrap-around back to 0, we start overwriting old
-                * trace data.
+                * Reset current size because we just performed a stream
+                * rotation.
                 */
-               if (!stream->tracefile_overwrite && new_id == 0) {
-                       stream->tracefile_overwrite = 1;
-               }
-               pthread_mutex_lock(&stream->viewer_stream_rotation_lock);
-               if (stream->tracefile_overwrite) {
-                       stream->oldest_tracefile_id =
-                               (stream->oldest_tracefile_id + 1) %
-                               stream->tracefile_count;
+               stream->tracefile_size_current = 0;
+               conn->protocol.data.state.receive_payload.rotate_index = true;
+       }
+
+end_stream_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       stream_put(stream);
+end:
+       return status;
+}
+
+static enum relay_connection_status relay_process_data_receive_payload(
+               struct relay_connection *conn)
+{
+       int ret;
+       enum relay_connection_status status = RELAY_CONNECTION_STATUS_OK;
+       struct relay_stream *stream;
+       struct data_connection_state_receive_payload *state =
+                       &conn->protocol.data.state.receive_payload;
+       const size_t chunk_size = RECV_DATA_BUFFER_SIZE;
+       char data_buffer[chunk_size];
+       bool partial_recv = false;
+       bool new_stream = false, close_requested = false, index_flushed = false;
+       uint64_t left_to_receive = state->left_to_receive;
+       struct relay_session *session;
+
+       DBG3("Receiving data for stream id %" PRIu64 " seqnum %" PRIu64 ", %" PRIu64" bytes received, %" PRIu64 " bytes left to receive",
+                       state->header.stream_id, state->header.net_seq_num,
+                       state->received, left_to_receive);
+
+       stream = stream_get_by_id(state->header.stream_id);
+       if (!stream) {
+               /* Protocol error. */
+               ERR("relay_process_data_receive_payload: cannot find stream %" PRIu64,
+                               state->header.stream_id);
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end;
+       }
+
+       pthread_mutex_lock(&stream->lock);
+       session = stream->trace->session;
+       if (!conn->session) {
+               ret = connection_set_session(conn, session);
+               if (ret) {
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+                       goto end_stream_unlock;
                }
-               vstream = viewer_stream_find_by_id(stream->stream_handle);
-               if (vstream) {
+       }
+
+       /*
+        * The size of the "chunk" received on any iteration is bounded by:
+        *   - the data left to receive,
+        *   - the data immediately available on the socket,
+        *   - the on-stack data buffer
+        */
+       while (left_to_receive > 0 && !partial_recv) {
+               ssize_t write_ret;
+               size_t recv_size = min(left_to_receive, chunk_size);
+
+               ret = conn->sock->ops->recvmsg(conn->sock, data_buffer,
+                               recv_size, MSG_DONTWAIT);
+               if (ret < 0) {
+                       if (errno != EAGAIN && errno != EWOULDBLOCK) {
+                               PERROR("Socket %d error", conn->sock->fd);
+                               status = RELAY_CONNECTION_STATUS_ERROR;
+                       }
+                       goto end_stream_unlock;
+               } else if (ret == 0) {
+                       /* No more data ready to be consumed on socket. */
+                       DBG3("No more data ready for consumption on data socket of stream id %" PRIu64,
+                                       state->header.stream_id);
+                       status = RELAY_CONNECTION_STATUS_CLOSED;
+                       break;
+               } else if (ret < (int) recv_size) {
                        /*
-                        * The viewer is reading a file about to be
-                        * overwritten. Close the FDs it is
-                        * currently using and let it handle the fault.
+                        * All the data available on the socket has been
+                        * consumed.
                         */
-                       if (vstream->tracefile_count_current == new_id) {
-                               pthread_mutex_lock(&vstream->overwrite_lock);
-                               vstream->abort_flag = 1;
-                               pthread_mutex_unlock(&vstream->overwrite_lock);
-                               DBG("Streaming side setting abort_flag on stream %s_%lu\n",
-                                               stream->channel_name, new_id);
-                       } else if (vstream->tracefile_count_current ==
-                                       stream->tracefile_count_current) {
-                               /*
-                                * The reader and writer were in the
-                                * same trace file, inform the viewer
-                                * that no new index will ever be added
-                                * to this file.
-                                */
-                               vstream->close_write_flag = 1;
-                       }
+                       partial_recv = true;
                }
-               ret = utils_rotate_stream_file(stream->path_name, stream->channel_name,
-                               stream->tracefile_size, stream->tracefile_count,
-                               relayd_uid, relayd_gid, stream->fd,
-                               &(stream->tracefile_count_current), &stream->fd);
-               stream->total_index_received = 0;
-               pthread_mutex_unlock(&stream->viewer_stream_rotation_lock);
-               if (ret < 0) {
-                       ERR("Rotating stream output file");
-                       goto end_rcu_unlock;
+
+               recv_size = ret;
+
+               /* Write data to stream output fd. */
+               write_ret = lttng_write(stream->stream_fd->fd, data_buffer,
+                               recv_size);
+               if (write_ret < (ssize_t) recv_size) {
+                       ERR("Relay error writing data to file");
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+                       goto end_stream_unlock;
                }
-               /* Reset current size because we just perform a stream rotation. */
-               stream->tracefile_size_current = 0;
-               rotate_index = 1;
+
+               left_to_receive -= recv_size;
+               state->received += recv_size;
+               state->left_to_receive = left_to_receive;
+
+               DBG2("Relay wrote %zd bytes to tracefile for stream id %" PRIu64,
+                               write_ret, stream->stream_handle);
        }
 
-       /*
-        * Index are handled in protocol version 2.4 and above. Also, snapshot and
-        * index are NOT supported.
-        */
+       if (state->left_to_receive > 0) {
+               /*
+                * Did not receive all the data expected, wait for more data to
+                * become available on the socket.
+                */
+               DBG3("Partial receive on data connection of stream id %" PRIu64 ", %" PRIu64 " bytes received, %" PRIu64 " bytes left to receive",
+                               state->header.stream_id, state->received,
+                               state->left_to_receive);
+               goto end_stream_unlock;
+       }
+
+       ret = write_padding_to_file(stream->stream_fd->fd,
+                       state->header.padding_size);
+       if ((int64_t) ret < (int64_t) state->header.padding_size) {
+               ERR("write_padding_to_file: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
+                               stream->stream_handle,
+                               state->header.net_seq_num, ret);
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end_stream_unlock;
+       }
+
+
        if (session->minor >= 4 && !session->snapshot) {
-               ret = handle_index_data(stream, net_seq_num, rotate_index);
+               ret = handle_index_data(stream, state->header.net_seq_num,
+                               state->rotate_index, &index_flushed, state->header.data_size + state->header.padding_size);
                if (ret < 0) {
-                       goto end_rcu_unlock;
+                       ERR("handle_index_data: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
+                                       stream->stream_handle,
+                                       state->header.net_seq_num, ret);
+                       status = RELAY_CONNECTION_STATUS_ERROR;
+                       goto end_stream_unlock;
                }
        }
 
-       /* Write data to stream output fd. */
-       size_ret = lttng_write(stream->fd, data_buffer, data_size);
-       if (size_ret < data_size) {
-               ERR("Relay error writing data to file");
-               ret = -1;
-               goto end_rcu_unlock;
+       stream->tracefile_size_current += state->header.data_size +
+                       state->header.padding_size;
+
+       if (stream->prev_seq == -1ULL) {
+               new_stream = true;
+       }
+       if (index_flushed) {
+               stream->pos_after_last_complete_data_index =
+                               stream->tracefile_size_current;
+               stream->prev_index_seq = state->header.net_seq_num;
        }
 
-       DBG2("Relay wrote %d bytes to tracefile for stream id %" PRIu64,
-                       ret, stream->stream_handle);
+       stream->prev_seq = state->header.net_seq_num;
+
+       /*
+        * Resetting the protocol state (to RECEIVE_HEADER) will trash the
+        * contents of *state which are aliased (union) to the same location as
+        * the new state. Don't use it beyond this point.
+        */
+       connection_reset_protocol_state(conn);
+       state = NULL;
 
-       ret = write_padding_to_file(stream->fd, be32toh(data_hdr.padding_size));
+       ret = try_rotate_stream(stream);
        if (ret < 0) {
-               goto end_rcu_unlock;
+               status = RELAY_CONNECTION_STATUS_ERROR;
+               goto end_stream_unlock;
        }
-       stream->tracefile_size_current += data_size + be32toh(data_hdr.padding_size);
 
-       stream->prev_seq = net_seq_num;
+end_stream_unlock:
+       close_requested = stream->close_requested;
+       pthread_mutex_unlock(&stream->lock);
+       if (close_requested && left_to_receive == 0) {
+               try_stream_close(stream);
+       }
 
-       try_close_stream(session, stream);
+       if (new_stream) {
+               pthread_mutex_lock(&session->lock);
+               uatomic_set(&session->new_streams, 1);
+               pthread_mutex_unlock(&session->lock);
+       }
 
-end_rcu_unlock:
-       rcu_read_unlock();
+       stream_put(stream);
 end:
-       return ret;
+       return status;
 }
 
-static
-void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
+/*
+ * relay_process_data: Process the data received on the data socket
+ */
+static enum relay_connection_status relay_process_data(
+               struct relay_connection *conn)
 {
-       int ret;
+       enum relay_connection_status status;
+
+       switch (conn->protocol.data.state_id) {
+       case DATA_CONNECTION_STATE_RECEIVE_HEADER:
+               status = relay_process_data_receive_header(conn);
+               break;
+       case DATA_CONNECTION_STATE_RECEIVE_PAYLOAD:
+               status = relay_process_data_receive_payload(conn);
+               break;
+       default:
+               ERR("Unexpected data connection communication state.");
+               abort();
+       }
 
-       assert(events);
+       return status;
+}
+
+static void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
+{
+       int ret;
 
        (void) lttng_poll_del(events, pollfd);
 
@@ -2402,38 +3555,43 @@ void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
        }
 }
 
-static void destroy_connection(struct lttng_ht *relay_connections_ht,
-               struct relay_connection *conn)
+static void relay_thread_close_connection(struct lttng_poll_event *events,
+               int pollfd, struct relay_connection *conn)
 {
-       assert(relay_connections_ht);
-       assert(conn);
+       const char *type_str;
 
-       connection_delete(relay_connections_ht, conn);
-
-       /* For the control socket, we try to destroy the session. */
-       if (conn->type == RELAY_CONTROL && conn->session) {
-               destroy_session(conn->session, conn->sessions_ht);
+       switch (conn->type) {
+       case RELAY_DATA:
+               type_str = "Data";
+               break;
+       case RELAY_CONTROL:
+               type_str = "Control";
+               break;
+       case RELAY_VIEWER_COMMAND:
+               type_str = "Viewer Command";
+               break;
+       case RELAY_VIEWER_NOTIFICATION:
+               type_str = "Viewer Notification";
+               break;
+       default:
+               type_str = "Unknown";
        }
-
-       connection_destroy(conn);
+       cleanup_connection_pollfd(events, pollfd);
+       connection_put(conn);
+       DBG("%s connection closed with %d", type_str, pollfd);
 }
 
 /*
  * This thread does the actual work
  */
-static
-void *relay_thread_worker(void *data)
+static void *relay_thread_worker(void *data)
 {
        int ret, err = -1, last_seen_data_fd = -1;
        uint32_t nb_fd;
-       struct relay_connection *conn;
        struct lttng_poll_event events;
        struct lttng_ht *relay_connections_ht;
        struct lttng_ht_iter iter;
-       struct lttcomm_relayd_hdr recv_hdr;
-       struct relay_local_data *relay_ctx = (struct relay_local_data *) data;
-       struct lttng_ht *sessions_ht = relay_ctx->sessions_ht;
-       struct relay_index *index;
+       struct relay_connection *destroy_conn = NULL;
 
        DBG("[thread] Relay worker started");
 
@@ -2453,12 +3611,6 @@ void *relay_thread_worker(void *data)
                goto relay_connections_ht_error;
        }
 
-       /* Tables of received indexes indexed by index handle and net_seq_num. */
-       indexes_ht = lttng_ht_new(0, LTTNG_HT_TYPE_TWO_U64);
-       if (!indexes_ht) {
-               goto indexes_ht_error;
-       }
-
        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll_create;
@@ -2493,9 +3645,9 @@ restart:
                nb_fd = ret;
 
                /*
-                * Process control. The control connection is prioritised so we don't
-                * starve it with high throughout put tracing data on the data
-                * connection.
+                * Process control. The control connection is
+                * prioritized so we don't starve it with high
+                * throughput tracing data on the data connection.
                 */
                for (i = 0; i < nb_fd; i++) {
                        /* Fetch once the poll data */
@@ -2504,6 +3656,14 @@ restart:
 
                        health_code_update();
 
+                       if (!revents) {
+                               /*
+                                * No activity for this FD (poll
+                                * implementation).
+                                */
+                               continue;
+                       }
+
                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
@@ -2513,56 +3673,33 @@ restart:
 
                        /* Inspect the relay conn pipe for new connection */
                        if (pollfd == relay_conn_pipe[0]) {
-                               if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
-                                       ERR("Relay connection pipe error");
-                                       goto error;
-                               } else if (revents & LPOLLIN) {
+                               if (revents & LPOLLIN) {
+                                       struct relay_connection *conn;
+
                                        ret = lttng_read(relay_conn_pipe[0], &conn, sizeof(conn));
                                        if (ret < 0) {
                                                goto error;
                                        }
-                                       conn->sessions_ht = sessions_ht;
-                                       connection_init(conn);
                                        lttng_poll_add(&events, conn->sock->fd,
                                                        LPOLLIN | LPOLLRDHUP);
-                                       rcu_read_lock();
-                                       lttng_ht_add_unique_ulong(relay_connections_ht,
-                                                       &conn->sock_n);
-                                       rcu_read_unlock();
+                                       connection_ht_add(relay_connections_ht, conn);
                                        DBG("Connection socket %d added", conn->sock->fd);
+                               } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
+                                       ERR("Relay connection pipe error");
+                                       goto error;
+                               } else {
+                                       ERR("Unexpected poll events %u for sock %d", revents, pollfd);
+                                       goto error;
                                }
                        } else {
-                               rcu_read_lock();
-                               conn = connection_find_by_sock(relay_connections_ht, pollfd);
+                               struct relay_connection *ctrl_conn;
+
+                               ctrl_conn = connection_get_by_sock(relay_connections_ht, pollfd);
                                /* If not found, there is a synchronization issue. */
-                               assert(conn);
+                               assert(ctrl_conn);
 
-                               if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
-                                       cleanup_connection_pollfd(&events, pollfd);
-                                       destroy_connection(relay_connections_ht, conn);
-                                       if (last_seen_data_fd == pollfd) {
-                                               last_seen_data_fd = last_notdel_data_fd;
-                                       }
-                               } else if (revents & LPOLLIN) {
-                                       if (conn->type == RELAY_CONTROL) {
-                                               ret = conn->sock->ops->recvmsg(conn->sock, &recv_hdr,
-                                                               sizeof(recv_hdr), 0);
-                                               if (ret <= 0) {
-                                                       /* Connection closed */
-                                                       cleanup_connection_pollfd(&events, pollfd);
-                                                       destroy_connection(relay_connections_ht, conn);
-                                                       DBG("Control connection closed with %d", pollfd);
-                                               } else {
-                                                       ret = relay_process_control(&recv_hdr, conn);
-                                                       if (ret < 0) {
-                                                               /* Clear the session on error. */
-                                                               cleanup_connection_pollfd(&events, pollfd);
-                                                               destroy_connection(relay_connections_ht, conn);
-                                                               DBG("Connection closed with %d", pollfd);
-                                                       }
-                                                       seen_control = 1;
-                                               }
-                                       } else {
+                               if (ctrl_conn->type == RELAY_DATA) {
+                                       if (revents & LPOLLIN) {
                                                /*
                                                 * Flag the last seen data fd not deleted. It will be
                                                 * used as the last seen fd if any fd gets deleted in
@@ -2570,10 +3707,55 @@ restart:
                                                 */
                                                last_notdel_data_fd = pollfd;
                                        }
+                                       goto put_ctrl_connection;
+                               }
+                               assert(ctrl_conn->type == RELAY_CONTROL);
+
+                               if (revents & LPOLLIN) {
+                                       enum relay_connection_status status;
+
+                                       status = relay_process_control(ctrl_conn);
+                                       if (status != RELAY_CONNECTION_STATUS_OK) {
+                                               /*
+                                                * On socket error flag the session as aborted to force
+                                                * the cleanup of its stream otherwise it can leak
+                                                * during the lifetime of the relayd.
+                                                *
+                                                * This prevents situations in which streams can be
+                                                * left opened because an index was received, the
+                                                * control connection is closed, and the data
+                                                * connection is closed (uncleanly) before the packet's
+                                                * data provided.
+                                                *
+                                                * Since the control connection encountered an error,
+                                                * it is okay to be conservative and close the
+                                                * session right now as we can't rely on the protocol
+                                                * being respected anymore.
+                                                */
+                                               if (status == RELAY_CONNECTION_STATUS_ERROR) {
+                                                       session_abort(ctrl_conn->session);
+                                               }
+
+                                               /* Clear the connection on error or close. */
+                                               relay_thread_close_connection(&events,
+                                                               pollfd,
+                                                               ctrl_conn);
+                                       }
+                                       seen_control = 1;
+                               } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
+                                       relay_thread_close_connection(&events,
+                                                       pollfd, ctrl_conn);
+                                       if (last_seen_data_fd == pollfd) {
+                                               last_seen_data_fd = last_notdel_data_fd;
+                                       }
                                } else {
-                                       ERR("Unknown poll events %u for sock %d", revents, pollfd);
+                                       ERR("Unexpected poll events %u for control sock %d",
+                                                       revents, pollfd);
+                                       connection_put(ctrl_conn);
+                                       goto error;
                                }
-                               rcu_read_unlock();
+                       put_ctrl_connection:
+                               connection_put(ctrl_conn);
                        }
                }
 
@@ -2603,48 +3785,77 @@ restart:
                        /* Fetch the poll data. */
                        uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                        int pollfd = LTTNG_POLL_GETFD(&events, i);
+                       struct relay_connection *data_conn;
 
                        health_code_update();
 
+                       if (!revents) {
+                               /* No activity for this FD (poll implementation). */
+                               continue;
+                       }
+
                        /* Skip the command pipe. It's handled in the first loop. */
                        if (pollfd == relay_conn_pipe[0]) {
                                continue;
                        }
 
-                       if (revents) {
-                               rcu_read_lock();
-                               conn = connection_find_by_sock(relay_connections_ht, pollfd);
-                               if (!conn) {
-                                       /* Skip it. Might be removed before. */
-                                       rcu_read_unlock();
-                                       continue;
-                               }
-
-                               if (revents & LPOLLIN) {
-                                       if (conn->type != RELAY_DATA) {
-                                               continue;
-                                       }
-
-                                       ret = relay_process_data(conn);
-                                       /* Connection closed */
-                                       if (ret < 0) {
-                                               cleanup_connection_pollfd(&events, pollfd);
-                                               destroy_connection(relay_connections_ht, conn);
-                                               DBG("Data connection closed with %d", pollfd);
-                                               /*
-                                                * Every goto restart call sets the last seen fd where
-                                                * here we don't really care since we gracefully
-                                                * continue the loop after the connection is deleted.
-                                                */
-                                       } else {
-                                               /* Keep last seen port. */
-                                               last_seen_data_fd = pollfd;
-                                               rcu_read_unlock();
-                                               goto restart;
+                       data_conn = connection_get_by_sock(relay_connections_ht, pollfd);
+                       if (!data_conn) {
+                               /* Skip it. Might be removed before. */
+                               continue;
+                       }
+                       if (data_conn->type == RELAY_CONTROL) {
+                               goto put_data_connection;
+                       }
+                       assert(data_conn->type == RELAY_DATA);
+
+                       if (revents & LPOLLIN) {
+                               enum relay_connection_status status;
+
+                               status = relay_process_data(data_conn);
+                               /* Connection closed or error. */
+                               if (status != RELAY_CONNECTION_STATUS_OK) {
+                                       /*
+                                        * On socket error flag the session as aborted to force
+                                        * the cleanup of its stream otherwise it can leak
+                                        * during the lifetime of the relayd.
+                                        *
+                                        * This prevents situations in which streams can be
+                                        * left opened because an index was received, the
+                                        * control connection is closed, and the data
+                                        * connection is closed (uncleanly) before the packet's
+                                        * data provided.
+                                        *
+                                        * Since the data connection encountered an error,
+                                        * it is okay to be conservative and close the
+                                        * session right now as we can't rely on the protocol
+                                        * being respected anymore.
+                                        */
+                                       if (status == RELAY_CONNECTION_STATUS_ERROR) {
+                                               session_abort(data_conn->session);
                                        }
+                                       relay_thread_close_connection(&events, pollfd,
+                                                       data_conn);
+                                       /*
+                                        * Every goto restart call sets the last seen fd where
+                                        * here we don't really care since we gracefully
+                                        * continue the loop after the connection is deleted.
+                                        */
+                               } else {
+                                       /* Keep last seen port. */
+                                       last_seen_data_fd = pollfd;
+                                       connection_put(data_conn);
+                                       goto restart;
                                }
-                               rcu_read_unlock();
+                       } else if (revents & (LPOLLERR | LPOLLHUP | LPOLLRDHUP)) {
+                               relay_thread_close_connection(&events, pollfd,
+                                               data_conn);
+                       } else {
+                               ERR("Unknown poll events %u for data sock %d",
+                                               revents, pollfd);
                        }
+               put_data_connection:
+                       connection_put(data_conn);
                }
                last_seen_data_fd = -1;
        }
@@ -2654,27 +3865,26 @@ restart:
 
 exit:
 error:
-       lttng_poll_clean(&events);
-
-       /* Cleanup reamaining connection object. */
+       /* Cleanup remaining connection object. */
        rcu_read_lock();
-       cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter, conn,
+       cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter,
+                       destroy_conn,
                        sock_n.node) {
                health_code_update();
-               destroy_connection(relay_connections_ht, conn);
+
+               session_abort(destroy_conn->session);
+
+               /*
+                * No need to grab another ref, because we own
+                * destroy_conn.
+                */
+               relay_thread_close_connection(&events, destroy_conn->sock->fd,
+                               destroy_conn);
        }
        rcu_read_unlock();
+
+       lttng_poll_clean(&events);
 error_poll_create:
-       rcu_read_lock();
-       cds_lfht_for_each_entry(indexes_ht->ht, &iter.iter, index,
-                       index_n.node) {
-               health_code_update();
-               relay_index_delete(index);
-               relay_index_free_safe(index);
-       }
-       rcu_read_unlock();
-       lttng_ht_destroy(indexes_ht);
-indexes_ht_error:
        lttng_ht_destroy(relay_connections_ht);
 relay_connections_ht_error:
        /* Close relay conn pipes */
@@ -2683,7 +3893,6 @@ relay_connections_ht_error:
                DBG("Thread exited with error");
        }
        DBG("Worker thread cleanup complete");
-       free(data_buffer);
 error_testpoint:
        if (err) {
                health_error();
@@ -2691,7 +3900,7 @@ error_testpoint:
        }
        health_unregister(health_relayd);
        rcu_unregister_thread();
-       stop_threads();
+       lttng_relay_stop_threads();
        return NULL;
 }
 
@@ -2713,31 +3922,35 @@ static int create_relay_conn_pipe(void)
  */
 int main(int argc, char **argv)
 {
-       int ret = 0;
+       int ret = 0, retval = 0;
        void *status;
-       struct relay_local_data *relay_ctx;
 
        /* Parse arguments */
        progname = argv[0];
-       if ((ret = set_options(argc, argv)) < 0) {
-               goto exit;
+       if (set_options(argc, argv)) {
+               retval = -1;
+               goto exit_options;
        }
 
-       if ((ret = set_signal_handler()) < 0) {
-               goto exit;
+       if (set_signal_handler()) {
+               retval = -1;
+               goto exit_options;
        }
 
        /* Try to create directory if -o, --output is specified. */
        if (opt_output_path) {
                if (*opt_output_path != '/') {
                        ERR("Please specify an absolute path for -o, --output PATH");
-                       goto exit;
+                       retval = -1;
+                       goto exit_options;
                }
 
-               ret = utils_mkdir_recursive(opt_output_path, S_IRWXU | S_IRWXG);
+               ret = utils_mkdir_recursive(opt_output_path, S_IRWXU | S_IRWXG,
+                               -1, -1);
                if (ret < 0) {
                        ERR("Unable to create %s", opt_output_path);
-                       goto exit;
+                       retval = -1;
+                       goto exit_options;
                }
        }
 
@@ -2748,7 +3961,8 @@ int main(int argc, char **argv)
                ret = lttng_daemonize(&child_ppid, &recv_child_signal,
                        !opt_background);
                if (ret < 0) {
-                       goto exit;
+                       retval = -1;
+                       goto exit_options;
                }
 
                /*
@@ -2761,170 +3975,171 @@ int main(int argc, char **argv)
                }
        }
 
-       /* Create thread quit pipe */
-       if ((ret = init_thread_quit_pipe()) < 0) {
-               goto error;
+       /* Initialize thread health monitoring */
+       health_relayd = health_app_create(NR_HEALTH_RELAYD_TYPES);
+       if (!health_relayd) {
+               PERROR("health_app_create error");
+               retval = -1;
+               goto exit_health_app_create;
        }
 
-       /* We need those values for the file/dir creation. */
-       relayd_uid = getuid();
-       relayd_gid = getgid();
-
-       /* Check if daemon is UID = 0 */
-       if (relayd_uid == 0) {
-               if (control_uri->port < 1024 || data_uri->port < 1024 || live_uri->port < 1024) {
-                       ERR("Need to be root to use ports < 1024");
-                       ret = -1;
-                       goto exit;
-               }
+       /* Create thread quit pipe */
+       if (init_thread_quit_pipe()) {
+               retval = -1;
+               goto exit_init_data;
        }
 
        /* Setup the thread apps communication pipe. */
-       if ((ret = create_relay_conn_pipe()) < 0) {
-               goto exit;
+       if (create_relay_conn_pipe()) {
+               retval = -1;
+               goto exit_init_data;
        }
 
        /* Init relay command queue. */
        cds_wfcq_init(&relay_conn_queue.head, &relay_conn_queue.tail);
 
-       /* Set up max poll set size */
-       lttng_poll_set_max_size();
-
        /* Initialize communication library */
        lttcomm_init();
        lttcomm_inet_init();
 
-       relay_ctx = zmalloc(sizeof(struct relay_local_data));
-       if (!relay_ctx) {
-               PERROR("relay_ctx");
-               goto exit;
-       }
-
        /* tables of sessions indexed by session ID */
-       relay_ctx->sessions_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
-       if (!relay_ctx->sessions_ht) {
-               goto exit_relay_ctx_sessions;
+       sessions_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!sessions_ht) {
+               retval = -1;
+               goto exit_init_data;
        }
 
        /* tables of streams indexed by stream ID */
        relay_streams_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
        if (!relay_streams_ht) {
-               goto exit_relay_ctx_streams;
+               retval = -1;
+               goto exit_init_data;
        }
 
        /* tables of streams indexed by stream ID */
        viewer_streams_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
        if (!viewer_streams_ht) {
-               goto exit_relay_ctx_viewer_streams;
-       }
-
-       /* Initialize thread health monitoring */
-       health_relayd = health_app_create(NR_HEALTH_RELAYD_TYPES);
-       if (!health_relayd) {
-               PERROR("health_app_create error");
-               goto exit_health_app_create;
+               retval = -1;
+               goto exit_init_data;
        }
 
        ret = utils_create_pipe(health_quit_pipe);
-       if (ret < 0) {
-               goto error_health_pipe;
+       if (ret) {
+               retval = -1;
+               goto exit_health_quit_pipe;
        }
 
        /* Create thread to manage the client socket */
-       ret = pthread_create(&health_thread, NULL,
+       ret = pthread_create(&health_thread, default_pthread_attr(),
                        thread_manage_health, (void *) NULL);
-       if (ret != 0) {
+       if (ret) {
+               errno = ret;
                PERROR("pthread_create health");
-               goto health_error;
+               retval = -1;
+               goto exit_health_thread;
        }
 
        /* Setup the dispatcher thread */
-       ret = pthread_create(&dispatcher_thread, NULL,
+       ret = pthread_create(&dispatcher_thread, default_pthread_attr(),
                        relay_thread_dispatcher, (void *) NULL);
-       if (ret != 0) {
+       if (ret) {
+               errno = ret;
                PERROR("pthread_create dispatcher");
-               goto exit_dispatcher;
+               retval = -1;
+               goto exit_dispatcher_thread;
        }
 
        /* Setup the worker thread */
-       ret = pthread_create(&worker_thread, NULL,
-                       relay_thread_worker, (void *) relay_ctx);
-       if (ret != 0) {
+       ret = pthread_create(&worker_thread, default_pthread_attr(),
+                       relay_thread_worker, NULL);
+       if (ret) {
+               errno = ret;
                PERROR("pthread_create worker");
-               goto exit_worker;
+               retval = -1;
+               goto exit_worker_thread;
        }
 
        /* Setup the listener thread */
-       ret = pthread_create(&listener_thread, NULL,
+       ret = pthread_create(&listener_thread, default_pthread_attr(),
                        relay_thread_listener, (void *) NULL);
-       if (ret != 0) {
+       if (ret) {
+               errno = ret;
                PERROR("pthread_create listener");
-               goto exit_listener;
+               retval = -1;
+               goto exit_listener_thread;
        }
 
-       ret = live_start_threads(live_uri, relay_ctx);
-       if (ret != 0) {
+       ret = relayd_live_create(live_uri);
+       if (ret) {
                ERR("Starting live viewer threads");
+               retval = -1;
                goto exit_live;
        }
 
+       /*
+        * This is where we start awaiting program completion (e.g. through
+        * signal that asks threads to teardown).
+        */
+
+       ret = relayd_live_join();
+       if (ret) {
+               retval = -1;
+       }
 exit_live:
+
        ret = pthread_join(listener_thread, &status);
-       if (ret != 0) {
-               PERROR("pthread_join");
-               goto error;     /* join error, exit without cleanup */
+       if (ret) {
+               errno = ret;
+               PERROR("pthread_join listener_thread");
+               retval = -1;
        }
 
-exit_listener:
+exit_listener_thread:
        ret = pthread_join(worker_thread, &status);
-       if (ret != 0) {
-               PERROR("pthread_join");
-               goto error;     /* join error, exit without cleanup */
+       if (ret) {
+               errno = ret;
+               PERROR("pthread_join worker_thread");
+               retval = -1;
        }
 
-exit_worker:
+exit_worker_thread:
        ret = pthread_join(dispatcher_thread, &status);
-       if (ret != 0) {
-               PERROR("pthread_join");
-               goto error;     /* join error, exit without cleanup */
+       if (ret) {
+               errno = ret;
+               PERROR("pthread_join dispatcher_thread");
+               retval = -1;
        }
+exit_dispatcher_thread:
 
-exit_dispatcher:
        ret = pthread_join(health_thread, &status);
-       if (ret != 0) {
-               PERROR("pthread_join health thread");
-               goto error;     /* join error, exit without cleanup */
+       if (ret) {
+               errno = ret;
+               PERROR("pthread_join health_thread");
+               retval = -1;
        }
+exit_health_thread:
 
-       /*
-        * Stop live threads only after joining other threads.
-        */
-       live_stop_threads();
-
-health_error:
        utils_close_pipe(health_quit_pipe);
+exit_health_quit_pipe:
 
-error_health_pipe:
+exit_init_data:
        health_app_destroy(health_relayd);
-
 exit_health_app_create:
-       lttng_ht_destroy(viewer_streams_ht);
-
-exit_relay_ctx_viewer_streams:
-       lttng_ht_destroy(relay_streams_ht);
-
-exit_relay_ctx_streams:
-       lttng_ht_destroy(relay_ctx->sessions_ht);
+exit_options:
+       /*
+        * Wait for all pending call_rcu work to complete before tearing
+        * down data structures. call_rcu worker may be trying to
+        * perform lookups in those structures.
+        */
+       rcu_barrier();
+       relayd_cleanup();
 
-exit_relay_ctx_sessions:
-       free(relay_ctx);
+       /* Ensure all prior call_rcu are done. */
+       rcu_barrier();
 
-exit:
-       cleanup();
-       if (!ret) {
+       if (!retval) {
                exit(EXIT_SUCCESS);
+       } else {
+               exit(EXIT_FAILURE);
        }
-
-error:
-       exit(EXIT_FAILURE);
 }
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