Fix: thread exit vs futex wait/wakeup race

[lttng-tools.git] / src / bin / lttng-relayd / main.c

/*
 * 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,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#define _LGPL_SOURCE
#include <getopt.h>
#include <grp.h>
#include <limits.h>
#include <pthread.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/mount.h>
#include <sys/resource.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <inttypes.h>
#include <urcu/futex.h>
#include <urcu/uatomic.h>
#include <unistd.h>
#include <fcntl.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/sessiond-comm.h>
#include <common/sessiond-comm/inet.h>
#include <common/sessiond-comm/relayd.h>
#include <common/uri.h>
#include <common/utils.h>
#include <common/config/session-config.h>
#include <urcu/rculist.h>

#include "cmd.h"
#include "ctf-trace.h"
#include "index.h"
#include "utils.h"
#include "lttng-relayd.h"
#include "live.h"
#include "health-relayd.h"
#include "testpoint.h"
#include "viewer-stream.h"
#include "session.h"
#include "stream.h"
#include "connection.h"
#include "tracefile-array.h"

/* command line options */
char *opt_output_path;
static int opt_daemon, opt_background;

/*
 * We need to wait for listener and live listener threads, as well as
 * health check thread, before being ready to signal readiness.
 */
#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

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. */

static struct lttng_uri *control_uri;
static struct lttng_uri *data_uri;
static struct lttng_uri *live_uri;

const char *progname;

const char *tracing_group_name = DEFAULT_TRACING_GROUP;
static int tracing_group_name_override;

const char * const config_section_name = "relayd";

/*
 * Quit pipe for all threads. This permits a single cancellation point
 * for all threads when receiving an event on the pipe.
 */
int thread_quit_pipe[2] = { -1, -1 };

/*
 * This pipe is used to inform the worker thread that a command is queued and
 * ready to be processed.
 */
static int relay_conn_pipe[2] = { -1, -1 };

/* Shared between threads */
static int dispatch_thread_exit;

static pthread_t listener_thread;
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;

/*
 * Relay command queue.
 *
 * The relay_thread_listener and relay_thread_dispatcher communicate with this
 * queue.
 */
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;

/* Global relay stream hash table. */
struct lttng_ht *relay_streams_ht;

/* Global relay viewer stream hash table. */
struct lttng_ht *viewer_streams_ht;

/* Global relay sessions hash table. */
struct lttng_ht *sessions_ht;

/* Relayd health monitoring */
struct health_app *health_relayd;

static struct option long_options[] = {
        { "control-port", 1, 0, 'C', },
        { "data-port", 1, 0, 'D', },
        { "live-port", 1, 0, 'L', },
        { "daemonize", 0, 0, 'd', },
        { "background", 0, 0, 'b', },
        { "group", 1, 0, 'g', },
        { "help", 0, 0, 'h', },
        { "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", "version" };

/*
 * Take an option from the getopt output and set it in the right variable to be
 * used later.
 *
 * Return 0 on success else a negative value.
 */
static int set_option(int opt, const char *arg, const char *optname)
{
        int ret;

        switch (opt) {
        case 0:
                fprintf(stderr, "option %s", optname);
                if (arg) {
                        fprintf(stderr, " with arg %s\n", arg);
                }
                break;
        case 'C':
                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':
                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':
                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':
                opt_daemon = 1;
                break;
        case 'b':
                opt_background = 1;
                break;
        case 'g':
                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;
                }
                break;
        case 'h':
                ret = utils_show_man_page(8, "lttng-relayd");
                if (ret) {
                        ERR("Cannot view man page lttng-relayd(8)");
                        perror("exec");
                }
                exit(EXIT_FAILURE);
        case 'V':
                fprintf(stdout, "%s\n", VERSION);
                exit(EXIT_SUCCESS);
        case 'o':
                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':
                /* Verbose level can increase using multiple -v */
                if (arg) {
                        lttng_opt_verbose = config_parse_value(arg);
                } else {
                        /* Only 3 level of verbosity (-vvv). */
                        if (lttng_opt_verbose < 3) {
                                lttng_opt_verbose += 1;
                        }
                }
                break;
        default:
                /* Unknown option or other error.
                 * Error is printed by getopt, just return */
                ret = -1;
                goto end;
        }

        /* All good. */
        ret = 0;

end:
        return ret;
}

/*
 * config_entry_handler_cb used to handle options read from a config file.
 * 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)
{
        int ret = 0, i;

        if (!entry || !entry->name || !entry->value) {
                ret = -EINVAL;
                goto end;
        }

        /* Check if the option is to be ignored */
        for (i = 0; i < sizeof(config_ignore_options) / sizeof(char *); i++) {
                if (!strcmp(entry->name, config_ignore_options[i])) {
                        goto end;
                }
        }

        for (i = 0; i < (sizeof(long_options) / sizeof(struct option)) - 1; i++) {
                /* Ignore if entry name is not fully matched. */
                if (strcmp(entry->name, long_options[i].name)) {
                        continue;
                }

                /*
                 * 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);
                        if (ret <= 0) {
                                if (ret) {
                                        WARN("Invalid configuration value \"%s\" for option %s",
                                                        entry->value, entry->name);
                                }
                                /* False, skip boolean config option. */
                                goto end;
                        }
                }

                ret = set_option(long_options[i].val, entry->value, entry->name);
                goto end;
        }

        WARN("Unrecognized option \"%s\" in daemon configuration file.",
                        entry->name);

end:
        return ret;
}

static int set_options(int argc, char **argv)
{
        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;

        optstring = utils_generate_optstring(long_options,
                        sizeof(long_options) / sizeof(struct option));
        if (!optstring) {
                retval = -ENOMEM;
                goto exit;
        }

        /* Check for the --config option */

        while ((c = getopt_long(argc, argv, optstring, long_options,
                                        &option_index)) != -1) {
                if (c == '?') {
                        retval = -EINVAL;
                        goto exit;
                } else if (c != 'f') {
                        continue;
                }

                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);
                        }
                }
        }

        ret = config_get_section_entries(config_path, config_section_name,
                        config_entry_handler, NULL);
        if (ret) {
                if (ret > 0) {
                        ERR("Invalid configuration option at line %i", ret);
                }
                retval = -1;
                goto exit;
        }

        /* Reset getopt's global state */
        optopt = orig_optopt;
        optind = orig_optind;
        while (1) {
                c = getopt_long(argc, argv, optstring, long_options, &option_index);
                if (c == -1) {
                        break;
                }

                ret = set_option(c, optarg, long_options[option_index].name);
                if (ret < 0) {
                        retval = -1;
                        goto exit;
                }
        }

        /* assign default values */
        if (control_uri == NULL) {
                ret = asprintf(&default_address,
                        "tcp://" DEFAULT_NETWORK_CONTROL_BIND_ADDRESS ":%d",
                        DEFAULT_NETWORK_CONTROL_PORT);
                if (ret < 0) {
                        PERROR("asprintf default data address");
                        retval = -1;
                        goto exit;
                }

                ret = uri_parse(default_address, &control_uri);
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid control URI specified");
                        retval = -1;
                        goto exit;
                }
        }
        if (data_uri == NULL) {
                ret = asprintf(&default_address,
                        "tcp://" DEFAULT_NETWORK_DATA_BIND_ADDRESS ":%d",
                        DEFAULT_NETWORK_DATA_PORT);
                if (ret < 0) {
                        PERROR("asprintf default data address");
                        retval = -1;
                        goto exit;
                }

                ret = uri_parse(default_address, &data_uri);
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid data URI specified");
                        retval = -1;
                        goto exit;
                }
        }
        if (live_uri == NULL) {
                ret = asprintf(&default_address,
                        "tcp://" DEFAULT_NETWORK_VIEWER_BIND_ADDRESS ":%d",
                        DEFAULT_NETWORK_VIEWER_PORT);
                if (ret < 0) {
                        PERROR("asprintf default viewer control address");
                        retval = -1;
                        goto exit;
                }

                ret = uri_parse(default_address, &live_uri);
                free(default_address);
                if (ret < 0) {
                        ERR("Invalid viewer control URI specified");
                        retval = -1;
                        goto exit;
                }
        }

exit:
        free(optstring);
        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 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);

        /* Close thread quit pipes */
        utils_close_pipe(thread_quit_pipe);

        uri_free(control_uri);
        uri_free(data_uri);
        /* Live URI is freed in the live thread. */

        if (tracing_group_name_override) {
                free((void *) tracing_group_name);
        }
}

/*
 * Write to writable pipe used to notify a thread.
 */
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 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 relayd and relayd-live threads.
 */
int lttng_relay_stop_threads(void)
{
        int retval = 0;

        /* Stopping all threads */
        DBG("Terminating all threads");
        if (notify_thread_pipe(thread_quit_pipe[1])) {
                ERR("write error on thread quit pipe");
                retval = -1;
        }

        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;
}

/*
 * Signal handler for the daemon
 *
 * Simply stop all worker threads, leaving main() return gracefully after
 * joining all threads and calling cleanup().
 */
static void sighandler(int sig)
{
        switch (sig) {
        case SIGINT:
                DBG("SIGINT caught");
                if (lttng_relay_stop_threads()) {
                        ERR("Error stopping threads");
                }
                break;
        case SIGTERM:
                DBG("SIGTERM caught");
                if (lttng_relay_stop_threads()) {
                        ERR("Error stopping threads");
                }
                break;
        case SIGUSR1:
                CMM_STORE_SHARED(recv_child_signal, 1);
                break;
        default:
                break;
        }
}

/*
 * Setup signal handler for :
 *              SIGINT, SIGTERM, SIGPIPE
 */
static int set_signal_handler(void)
{
        int ret = 0;
        struct sigaction sa;
        sigset_t sigset;

        if ((ret = sigemptyset(&sigset)) < 0) {
                PERROR("sigemptyset");
                return ret;
        }

        sa.sa_mask = sigset;
        sa.sa_flags = 0;

        sa.sa_handler = sighandler;
        if ((ret = sigaction(SIGTERM, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGINT, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        if ((ret = sigaction(SIGUSR1, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        sa.sa_handler = SIG_IGN;
        if ((ret = sigaction(SIGPIPE, &sa, NULL)) < 0) {
                PERROR("sigaction");
                return ret;
        }

        DBG("Signal handler set for SIGTERM, SIGUSR1, SIGPIPE and SIGINT");

        return ret;
}

void lttng_relay_notify_ready(void)
{
        /* Notify the parent of the fork() process that we are ready. */
        if (opt_daemon || opt_background) {
                if (uatomic_sub_return(&lttng_relay_ready, 1) == 0) {
                        kill(child_ppid, SIGUSR1);
                }
        }
}

/*
 * Init thread quit pipe.
 *
 * Return -1 on error or 0 if all pipes are created.
 */
static int init_thread_quit_pipe(void)
{
        int ret;

        ret = utils_create_pipe_cloexec(thread_quit_pipe);

        return ret;
}

/*
 * 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)
{
        int ret;

        if (events == NULL || size == 0) {
                ret = -1;
                goto error;
        }

        ret = lttng_poll_create(events, size, LTTNG_CLOEXEC);
        if (ret < 0) {
                goto error;
        }

        /* Add quit pipe */
        ret = lttng_poll_add(events, thread_quit_pipe[0], LPOLLIN | LPOLLERR);
        if (ret < 0) {
                goto error;
        }

        return 0;

error:
        return ret;
}

/*
 * Check if the thread quit pipe was triggered.
 *
 * Return 1 if it was triggered else 0;
 */
static int check_thread_quit_pipe(int fd, uint32_t events)
{
        if (fd == thread_quit_pipe[0] && (events & LPOLLIN)) {
                return 1;
        }

        return 0;
}

/*
 * Create and init socket from uri.
 */
static struct lttcomm_sock *relay_socket_create(struct lttng_uri *uri)
{
        int ret;
        struct lttcomm_sock *sock = NULL;

        sock = lttcomm_alloc_sock_from_uri(uri);
        if (sock == NULL) {
                ERR("Allocating socket");
                goto error;
        }

        ret = lttcomm_create_sock(sock);
        if (ret < 0) {
                goto error;
        }
        DBG("Listening on sock %d", sock->fd);

        ret = sock->ops->bind(sock);
        if (ret < 0) {
                goto error;
        }

        ret = sock->ops->listen(sock, -1);
        if (ret < 0) {
                goto error;

        }

        return sock;

error:
        if (sock) {
                lttcomm_destroy_sock(sock);
        }
        return NULL;
}

/*
 * This thread manages the listening for new connections on the network
 */
static void *relay_thread_listener(void *data)
{
        int i, ret, pollfd, err = -1;
        uint32_t revents, nb_fd;
        struct lttng_poll_event events;
        struct lttcomm_sock *control_sock, *data_sock;

        DBG("[thread] Relay listener started");

        health_register(health_relayd, HEALTH_RELAYD_TYPE_LISTENER);

        health_code_update();

        control_sock = relay_socket_create(control_uri);
        if (!control_sock) {
                goto error_sock_control;
        }

        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.
         */
        ret = create_thread_poll_set(&events, 3);
        if (ret < 0) {
                goto error_create_poll;
        }

        /* Add the control socket */
        ret = lttng_poll_add(&events, control_sock->fd, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error_poll_add;
        }

        /* Add the data socket */
        ret = lttng_poll_add(&events, data_sock->fd, LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error_poll_add;
        }

        lttng_relay_notify_ready();

        if (testpoint(relayd_thread_listener)) {
                goto error_testpoint;
        }

        while (1) {
                health_code_update();

                DBG("Listener accepting connections");

restart:
                health_poll_entry();
                ret = lttng_poll_wait(&events, -1);
                health_poll_exit();
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }

                nb_fd = ret;

                DBG("Relay new connection received");
                for (i = 0; i < nb_fd; i++) {
                        health_code_update();

                        /* Fetch once the poll data */
                        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) {
                                err = 0;
                                goto exit;
                        }

                        if (revents & LPOLLIN) {
                                /*
                                 * 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;
                                enum connection_type type;

                                if (pollfd == data_sock->fd) {
                                        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);
                                        type = RELAY_CONTROL;
                                        newsock = control_sock->ops->accept(control_sock);
                                        DBG("Relay control connection accepted, socket %d",
                                                        newsock->fd);
                                }
                                if (!newsock) {
                                        PERROR("accepting sock");
                                        goto error;
                                }

                                ret = setsockopt(newsock->fd, SOL_SOCKET, SO_REUSEADDR, &val,
                                                sizeof(val));
                                if (ret < 0) {
                                        PERROR("setsockopt inet");
                                        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.
                                 */
                                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;
                        }
                }
        }

exit:
error:
error_poll_add:
error_testpoint:
        lttng_poll_clean(&events);
error_create_poll:
        if (data_sock->fd >= 0) {
                ret = data_sock->ops->close(data_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        lttcomm_destroy_sock(data_sock);
error_sock_relay:
        if (control_sock->fd >= 0) {
                ret = control_sock->ops->close(control_sock);
                if (ret) {
                        PERROR("close");
                }
        }
        lttcomm_destroy_sock(control_sock);
error_sock_control:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister(health_relayd);
        DBG("Relay listener thread cleanup complete");
        lttng_relay_stop_threads();
        return NULL;
}

/*
 * This thread manages the dispatching of the requests to worker threads
 */
static void *relay_thread_dispatcher(void *data)
{
        int err = -1;
        ssize_t ret;
        struct cds_wfcq_node *node;
        struct relay_connection *new_conn = NULL;

        DBG("[thread] Relay dispatcher started");

        health_register(health_relayd, HEALTH_RELAYD_TYPE_DISPATCHER);

        if (testpoint(relayd_thread_dispatcher)) {
                goto error_testpoint;
        }

        health_code_update();

        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();

                        /* Dequeue commands */
                        node = cds_wfcq_dequeue_blocking(&relay_conn_queue.head,
                                                         &relay_conn_queue.tail);
                        if (node == NULL) {
                                DBG("Woken up but nothing in the relay command queue");
                                /* Continue thread execution */
                                break;
                        }
                        new_conn = caa_container_of(node, struct relay_connection, qnode);

                        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 :)
                         */
                        ret = lttng_write(relay_conn_pipe[1], &new_conn, sizeof(new_conn));
                        if (ret < 0) {
                                PERROR("write connection pipe");
                                connection_put(new_conn);
                                goto error;
                        }
                } while (node != NULL);

                /* Futex wait on queue. Blocking call on futex() */
                health_poll_entry();
                futex_nto1_wait(&relay_conn_queue.futex);
                health_poll_exit();
        }

        /* Normal exit, no error */
        err = 0;

error:
error_testpoint:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister(health_relayd);
        DBG("Dispatch thread dying");
        lttng_relay_stop_threads();
        return NULL;
}

/*
 * Set index data from the control port to a given index object.
 */
static int set_index_control_data(struct relay_index *index,
                struct lttcomm_relayd_index *data,
                struct relay_connection *conn)
{
        struct ctf_packet_index index_data;

        /*
         * 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_data.packet_size = data->packet_size;
        index_data.content_size = data->content_size;
        index_data.timestamp_begin = data->timestamp_begin;
        index_data.timestamp_end = data->timestamp_end;
        index_data.events_discarded = data->events_discarded;
        index_data.stream_id = data->stream_id;

        if (conn->minor >= 8) {
                index->index_data.stream_instance_id = data->stream_instance_id;
                index->index_data.packet_seq_num = data->packet_seq_num;
        }

        return relay_index_set_data(index, &index_data);
}

/*
 * Handle the RELAYD_CREATE_SESSION command.
 *
 * 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)
{
        int ret = 0, 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;

        memset(session_name, 0, LTTNG_NAME_MAX);
        memset(hostname, 0, LTTNG_HOST_NAME_MAX);

        memset(&reply, 0, sizeof(reply));

        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_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 send_reply;
        }
        assert(!conn->session);
        conn->session = session;
        DBG("Created session %" PRIu64, session->id);

        reply.session_id = htobe64(session->id);

send_reply:
        if (ret < 0) {
                reply.ret_code = htobe32(LTTNG_ERR_FATAL);
        } else {
                reply.ret_code = htobe32(LTTNG_OK);
        }

        send_ret = conn->sock->ops->sendmsg(conn->sock, &reply, sizeof(reply), 0);
        if (send_ret < 0) {
                ERR("Relayd sending session id");
                ret = send_ret;
        }

        return ret;
}

/*
 * When we have received all the streams and the metadata for a channel,
 * we make them visible to the viewer threads.
 */
static void publish_connection_local_streams(struct relay_connection *conn)
{
        struct relay_stream *stream;
        struct relay_session *session = conn->session;

        /*
         * 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);
        }
        rcu_read_unlock();

        /*
         * 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)
{
        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 = NULL;
        uint64_t stream_handle = -1ULL;
        char *path_name = NULL, *channel_name = NULL;
        uint64_t tracefile_size = 0, tracefile_count = 0;

        if (!session || conn->version_check_done == 0) {
                ERR("Trying to add a stream before version check");
                ret = -1;
                goto end_no_session;
        }

        switch (session->minor) {
        case 1: /* LTTng sessiond 2.1. Allocates path_name and channel_name. */
                ret = cmd_recv_stream_2_1(conn, &path_name,
                        &channel_name);
                break;
        case 2: /* LTTng sessiond 2.2. Allocates path_name and channel_name. */
        default:
                ret = cmd_recv_stream_2_2(conn, &path_name,
                        &channel_name, &tracefile_size, &tracefile_count);
                break;
        }
        if (ret < 0) {
                goto send_reply;
        }

        trace = ctf_trace_get_by_path_or_create(session, path_name);
        if (!trace) {
                goto send_reply;
        }
        /* This stream here has one reference on the trace. */

        pthread_mutex_lock(&last_relay_stream_id_lock);
        stream_handle = ++last_relay_stream_id;
        pthread_mutex_unlock(&last_relay_stream_id_lock);

        /* We pass ownership of path_name and channel_name. */
        stream = stream_create(trace, stream_handle, path_name,
                        channel_name, tracefile_size, tracefile_count);
        path_name = NULL;
        channel_name = NULL;

        /*
         * Streams are the owners of their trace. Reference to trace is
         * kept within stream_create().
         */
        ctf_trace_put(trace);

send_reply:
        memset(&reply, 0, sizeof(reply));
        reply.handle = htobe64(stream_handle);
        if (!stream) {
                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_status_stream), 0);
        if (send_ret < 0) {
                ERR("Relay sending stream id");
                ret = (int) send_ret;
        }

end_no_session:
        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)
{
        int ret, send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_close_stream stream_info;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;

        DBG("Close stream received");

        if (!session || conn->version_check_done == 0) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        stream = stream_get_by_id(be64toh(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 = be64toh(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);

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 < 0) {
                ERR("Relay sending stream id");
                ret = send_ret;
        }

end_no_session:
        return ret;
}

/*
 * relay_reset_metadata: reset a metadata stream
 */
static
int relay_reset_metadata(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret, 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 == 0) {
                ERR("Trying to reset a metadata stream before version check");
                ret = -1;
                goto end_no_session;
        }

        ret = conn->sock->ops->recvmsg(conn->sock, &stream_info,
                        sizeof(struct lttcomm_relayd_reset_metadata), 0);
        if (ret < sizeof(struct lttcomm_relayd_reset_metadata)) {
                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 reset_metadata struct "
                                        "size : %d", ret);
                }
                ret = -1;
                goto end_no_session;
        }
        DBG("Update metadata to version %" PRIu64, be64toh(stream_info.version));

        /* Unsupported for live sessions for now. */
        if (session->live_timer != 0) {
                ret = -1;
                goto end;
        }

        stream = stream_get_by_id(be64toh(stream_info.stream_id));
        if (!stream) {
                ret = -1;
                goto end;
        }
        pthread_mutex_lock(&stream->lock);
        if (!stream->is_metadata) {
                ret = -1;
                goto end_unlock;
        }

        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:
        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 < 0) {
                ERR("Relay sending reset metadata reply");
                ret = send_ret;
        }

end_no_session:
        return ret;
}

/*
 * relay_unknown_command: send -1 if received unknown command
 */
static void relay_unknown_command(struct relay_connection *conn)
{
        struct lttcomm_relayd_generic_reply reply;
        int 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");
        }
}

/*
 * 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)
{
        int ret = htobe32(LTTNG_OK);
        struct lttcomm_relayd_generic_reply reply;
        struct relay_session *session = conn->session;

        if (!session) {
                DBG("Trying to start the streaming without a session established");
                ret = htobe32(LTTNG_ERR_UNK);
        }

        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");
        }

        return ret;
}

/*
 * Append padding to the file pointed by the file descriptor fd.
 */
static int write_padding_to_file(int fd, uint32_t size)
{
        ssize_t ret = 0;
        char *zeros;

        if (size == 0) {
                goto end;
        }

        zeros = zmalloc(size);
        if (zeros == NULL) {
                PERROR("zmalloc zeros for padding");
                ret = -1;
                goto end;
        }

        ret = lttng_write(fd, zeros, size);
        if (ret < size) {
                PERROR("write padding to file");
        }

        free(zeros);

end:
        return ret;
}

/*
 * relay_recv_metadata: receive the metadata for the session.
 */
static int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret = 0;
        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;

        if (!session) {
                ERR("Metadata sent before version check");
                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");
                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;

                tmp_data_ptr = realloc(data_buffer, data_size);
                if (!tmp_data_ptr) {
                        ERR("Allocating data buffer");
                        free(data_buffer);
                        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);
        size_ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, data_size, 0);
        if (size_ret < 0 || size_ret != data_size) {
                if (size_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");
                }
                ret = -1;
                goto end;
        }
        metadata_struct = (struct lttcomm_relayd_metadata_payload *) data_buffer;

        metadata_stream = stream_get_by_id(be64toh(metadata_struct->stream_id));
        if (!metadata_stream) {
                ret = -1;
                goto end;
        }

        pthread_mutex_lock(&metadata_stream->lock);

        size_ret = lttng_write(metadata_stream->stream_fd->fd, metadata_struct->payload,
                        payload_size);
        if (size_ret < payload_size) {
                ERR("Relay error writing metadata on file");
                ret = -1;
                goto end_put;
        }

        size_ret = write_padding_to_file(metadata_stream->stream_fd->fd,
                        be32toh(metadata_struct->padding_size));
        if (size_ret < 0) {
                goto end_put;
        }

        metadata_stream->metadata_received +=
                payload_size + be32toh(metadata_struct->padding_size);
        DBG2("Relay metadata written. Updated metadata_received %" PRIu64,
                metadata_stream->metadata_received);

end_put:
        pthread_mutex_unlock(&metadata_stream->lock);
        stream_put(metadata_stream);
end:
        return ret;
}

/*
 * relay_send_version: send relayd version number
 */
static int relay_send_version(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret;
        struct lttcomm_relayd_version reply, msg;

        conn->version_check_done = 1;

        /* 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.");
                }
                ret = -1;
                goto end;
        }

        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)) {
                DBG("Incompatible major versions (%u vs %u), deleting session",
                                reply.major, be32toh(msg.major));
                connection_put(conn);
                ret = 0;
                goto end;
        }

        conn->major = reply.major;
        /* We adapt to the lowest compatible version */
        if (reply.minor <= be32toh(msg.minor)) {
                conn->minor = reply.minor;
        } else {
                conn->minor = be32toh(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");
        }

        DBG("Version check done using protocol %u.%u", conn->major,
                        conn->minor);

end:
        return ret;
}

/*
 * 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)
{
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_data_pending msg;
        struct lttcomm_relayd_generic_reply reply;
        struct relay_stream *stream;
        int ret;
        uint64_t last_net_seq_num, stream_id;

        DBG("Data pending command received");

        if (!session || conn->version_check_done == 0) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        stream_id = be64toh(msg.stream_id);
        last_net_seq_num = be64toh(msg.last_net_seq_num);

        stream = stream_get_by_id(stream_id);
        if (stream == NULL) {
                ret = -1;
                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);

        /* Avoid wrapping issue */
        if (((int64_t) (stream->prev_seq - last_net_seq_num)) >= 0) {
                /* Data has in fact been written and is NOT pending */
                ret = 0;
        } else {
                /* Data still being streamed thus pending */
                ret = 1;
        }

        stream->data_pending_check_done = true;
        pthread_mutex_unlock(&stream->lock);

        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");
        }

end_no_session:
        return ret;
}

/*
 * 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.
 */
static int relay_quiescent_control(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret;
        uint64_t stream_id;
        struct relay_stream *stream;
        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) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        stream_id = be64toh(msg.stream_id);
        stream = stream_get_by_id(stream_id);
        if (!stream) {
                goto reply;
        }
        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, 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");
        }

end_no_session:
        return ret;
}

/*
 * 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)
{
        int 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) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        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.
         */
        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->id == 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();

        memset(&reply, 0, sizeof(reply));
        /* 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");
        }

end_no_session:
        return ret;
}

/*
 * 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)
{
        int 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;

        DBG("End data pending command");

        if (!conn->session || conn->version_check_done == 0) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        session_id = be64toh(msg.session_id);

        /*
         * 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_get(stream)) {
                        continue;
                }
                if (stream->trace->session->id != 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();

        memset(&reply, 0, sizeof(reply));
        /* 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");
        }

end_no_session:
        return ret;
}

/*
 * Receive an index for a specific stream.
 *
 * Return 0 on success else a negative value.
 */
static int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret, send_ret;
        struct relay_session *session = conn->session;
        struct lttcomm_relayd_index index_info;
        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) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }

        msg_len = lttcomm_relayd_index_len(
                        lttng_to_index_major(conn->major, conn->minor),
                        lttng_to_index_minor(conn->major, conn->minor));
        ret = conn->sock->ops->recvmsg(conn->sock, &index_info,
                        msg_len, 0);
        if (ret < msg_len) {
                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);
                }
                ret = -1;
                goto end_no_session;
        }

        net_seq_num = be64toh(index_info.net_seq_num);

        stream = stream_get_by_id(be64toh(index_info.relay_stream_id));
        if (!stream) {
                ERR("stream_get_by_id not found");
                ret = -1;
                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);

                /*
                 * Only flag a stream inactive when it has already
                 * received data and no indexes are in flight.
                 */
                if (stream->index_received_seqcount > 0
                                && stream->indexes_in_flight == 0) {
                        stream->beacon_ts_end =
                                be64toh(index_info.timestamp_end);
                }
                ret = 0;
                goto end_stream_put;
        } else {
                stream->beacon_ts_end = -1ULL;
        }

        if (stream->ctf_stream_id == -1ULL) {
                stream->ctf_stream_id = be64toh(index_info.stream_id);
        }
        index = relay_index_get_by_id_or_create(stream, 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++;
        } else if (ret > 0) {
                /* no flush. */
                ret = 0;
        } else {
                ERR("relay_index_try_flush error %d", ret);
                relay_index_put(index);
                ret = -1;
        }

end_stream_put:
        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(reply), 0);
        if (send_ret < 0) {
                ERR("Relay sending close index id reply");
                ret = send_ret;
        }

end_no_session:
        return ret;
}

/*
 * Receive the streams_sent message.
 *
 * Return 0 on success else a negative value.
 */
static int relay_streams_sent(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret, send_ret;
        struct lttcomm_relayd_generic_reply reply;

        assert(conn);

        DBG("Relay receiving streams_sent");

        if (!conn->session || conn->version_check_done == 0) {
                ERR("Trying to close a stream before version check");
                ret = -1;
                goto end_no_session;
        }

        /*
         * Publish every pending stream in the connection recv list which are
         * now ready to be used by the viewer.
         */
        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;
        } else {
                /* Success. */
                ret = 0;
        }

end_no_session:
        return ret;
}

/*
 * Process the commands received on the control socket
 */
static int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_connection *conn)
{
        int ret = 0;

        switch (be32toh(recv_hdr->cmd)) {
        case RELAYD_CREATE_SESSION:
                ret = relay_create_session(recv_hdr, conn);
                break;
        case RELAYD_ADD_STREAM:
                ret = relay_add_stream(recv_hdr, conn);
                break;
        case RELAYD_START_DATA:
                ret = relay_start(recv_hdr, conn);
                break;
        case RELAYD_SEND_METADATA:
                ret = relay_recv_metadata(recv_hdr, conn);
                break;
        case RELAYD_VERSION:
                ret = relay_send_version(recv_hdr, conn);
                break;
        case RELAYD_CLOSE_STREAM:
                ret = relay_close_stream(recv_hdr, conn);
                break;
        case RELAYD_DATA_PENDING:
                ret = relay_data_pending(recv_hdr, conn);
                break;
        case RELAYD_QUIESCENT_CONTROL:
                ret = relay_quiescent_control(recv_hdr, conn);
                break;
        case RELAYD_BEGIN_DATA_PENDING:
                ret = relay_begin_data_pending(recv_hdr, conn);
                break;
        case RELAYD_END_DATA_PENDING:
                ret = relay_end_data_pending(recv_hdr, conn);
                break;
        case RELAYD_SEND_INDEX:
                ret = relay_recv_index(recv_hdr, conn);
                break;
        case RELAYD_STREAMS_SENT:
                ret = relay_streams_sent(recv_hdr, conn);
                break;
        case RELAYD_RESET_METADATA:
                ret = relay_reset_metadata(recv_hdr, conn);
                break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
                ERR("Received unknown command (%u)", be32toh(recv_hdr->cmd));
                relay_unknown_command(conn);
                ret = -1;
                goto end;
        }

end:
        return ret;
}

/*
 * Handle index for a data stream.
 *
 * 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)
{
        int ret = 0;
        uint64_t data_offset;
        struct relay_index *index;

        /* 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 it exists, the control thread has already received the
         * data for it, thus we need to write it to disk.
         */
        index = relay_index_get_by_id_or_create(stream, net_seq_num);
        if (!index) {
                ret = -1;
                goto end;
        }

        if (rotate_index || !stream->index_file) {
                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;
                        /* Put self-ref for this index due to error. */
                        relay_index_put(index);
                        index = NULL;
                        goto end;
                }
        }

        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;
        }

        ret = relay_index_try_flush(index);
        if (ret == 0) {
                tracefile_array_commit_seq(stream->tfa);
                stream->index_received_seqcount++;
        } else if (ret > 0) {
                /* No flush. */
                ret = 0;
        } else {
                /* Put self-ref for this index due to error. */
                relay_index_put(index);
                index = NULL;
                ret = -1;
        }
end:
        return ret;
}

/*
 * relay_process_data: Process the data received on the data socket
 */
static int relay_process_data(struct relay_connection *conn)
{
        int ret = 0, rotate_index = 0;
        ssize_t size_ret;
        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;
        bool new_stream = false, close_requested = false;
        size_t chunk_size = RECV_DATA_BUFFER_SIZE;
        size_t recv_off = 0;
        char data_buffer[chunk_size];

        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 = -1;
                goto end;
        }

        stream_id = be64toh(data_hdr.stream_id);
        stream = stream_get_by_id(stream_id);
        if (!stream) {
                ERR("relay_process_data: Cannot find stream %" PRIu64, stream_id);
                ret = -1;
                goto end;
        }
        session = stream->trace->session;
        data_size = be32toh(data_hdr.data_size);

        net_seq_num = be64toh(data_hdr.net_seq_num);

        DBG3("Receiving data of size %u for stream id %" PRIu64 " seqnum %" PRIu64,
                data_size, stream_id, net_seq_num);

        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) {
                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("Rotating stream output file");
                        goto end_stream_unlock;
                }
                /*
                 * Reset current size because we just performed a stream
                 * rotation.
                 */
                stream->tracefile_size_current = 0;
                rotate_index = 1;
        }

        /*
         * Index are handled in protocol version 2.4 and above. Also,
         * snapshot and index are NOT supported.
         */
        if (session->minor >= 4 && !session->snapshot) {
                ret = handle_index_data(stream, net_seq_num, rotate_index);
                if (ret < 0) {
                        ERR("handle_index_data: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
                                        stream->stream_handle, net_seq_num, ret);
                        goto end_stream_unlock;
                }
        }

        for (recv_off = 0; recv_off < data_size; recv_off += chunk_size) {
                size_t recv_size = min(data_size - recv_off, chunk_size);

                ret = conn->sock->ops->recvmsg(conn->sock, data_buffer, recv_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);
                        } else {
                                ERR("Socket %d error %d", conn->sock->fd, ret);
                        }
                        ret = -1;
                        goto end_stream_unlock;
                }

                /* Write data to stream output fd. */
                size_ret = lttng_write(stream->stream_fd->fd, data_buffer,
                                recv_size);
                if (size_ret < recv_size) {
                        ERR("Relay error writing data to file");
                        ret = -1;
                        goto end_stream_unlock;
                }

                DBG2("Relay wrote %zd bytes to tracefile for stream id %" PRIu64,
                                size_ret, stream->stream_handle);
        }

        ret = write_padding_to_file(stream->stream_fd->fd,
                        be32toh(data_hdr.padding_size));
        if (ret < 0) {
                ERR("write_padding_to_file: fail stream %" PRIu64 " net_seq_num %" PRIu64 " ret %d",
                                stream->stream_handle, net_seq_num, ret);
                goto end_stream_unlock;
        }
        stream->tracefile_size_current +=
                        data_size + be32toh(data_hdr.padding_size);
        if (stream->prev_seq == -1ULL) {
                new_stream = true;
        }

        stream->prev_seq = net_seq_num;

end_stream_unlock:
        close_requested = stream->close_requested;
        pthread_mutex_unlock(&stream->lock);
        if (close_requested) {
                try_stream_close(stream);
        }

        if (new_stream) {
                pthread_mutex_lock(&session->lock);
                uatomic_set(&session->new_streams, 1);
                pthread_mutex_unlock(&session->lock);
        }
        stream_put(stream);
end:
        return ret;
}

static void cleanup_connection_pollfd(struct lttng_poll_event *events, int pollfd)
{
        int ret;

        (void) lttng_poll_del(events, pollfd);

        ret = close(pollfd);
        if (ret < 0) {
                ERR("Closing pollfd %d", pollfd);
        }
}

static void relay_thread_close_connection(struct lttng_poll_event *events,
                int pollfd, struct relay_connection *conn)
{
        const char *type_str;

        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";
        }
        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)
{
        int ret, err = -1, last_seen_data_fd = -1;
        uint32_t nb_fd;
        struct lttng_poll_event events;
        struct lttng_ht *relay_connections_ht;
        struct lttng_ht_iter iter;
        struct lttcomm_relayd_hdr recv_hdr;
        struct relay_connection *destroy_conn = NULL;

        DBG("[thread] Relay worker started");

        rcu_register_thread();

        health_register(health_relayd, HEALTH_RELAYD_TYPE_WORKER);

        if (testpoint(relayd_thread_worker)) {
                goto error_testpoint;
        }

        health_code_update();

        /* table of connections indexed on socket */
        relay_connections_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        if (!relay_connections_ht) {
                goto relay_connections_ht_error;
        }

        ret = create_thread_poll_set(&events, 2);
        if (ret < 0) {
                goto error_poll_create;
        }

        ret = lttng_poll_add(&events, relay_conn_pipe[0], LPOLLIN | LPOLLRDHUP);
        if (ret < 0) {
                goto error;
        }

restart:
        while (1) {
                int idx = -1, i, seen_control = 0, last_notdel_data_fd = -1;

                health_code_update();

                /* Infinite blocking call, waiting for transmission */
                DBG3("Relayd worker thread polling...");
                health_poll_entry();
                ret = lttng_poll_wait(&events, -1);
                health_poll_exit();
                if (ret < 0) {
                        /*
                         * Restart interrupted system call.
                         */
                        if (errno == EINTR) {
                                goto restart;
                        }
                        goto error;
                }

                nb_fd = ret;

                /*
                 * 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 */
                        uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                        int pollfd = LTTNG_POLL_GETFD(&events, i);

                        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) {
                                err = 0;
                                goto exit;
                        }

                        /* Inspect the relay conn pipe for new connection */
                        if (pollfd == relay_conn_pipe[0]) {
                                if (revents & LPOLLIN) {
                                        struct relay_connection *conn;

                                        ret = lttng_read(relay_conn_pipe[0], &conn, sizeof(conn));
                                        if (ret < 0) {
                                                goto error;
                                        }
                                        lttng_poll_add(&events, conn->sock->fd,
                                                        LPOLLIN | LPOLLRDHUP);
                                        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 {
                                struct relay_connection *ctrl_conn;

                                ctrl_conn = connection_get_by_sock(relay_connections_ht, pollfd);
                                /* If not found, there is a synchronization issue. */
                                assert(ctrl_conn);

                                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
                                                 * this first loop.
                                                 */
                                                last_notdel_data_fd = pollfd;
                                        }
                                        goto put_ctrl_connection;
                                }
                                assert(ctrl_conn->type == RELAY_CONTROL);

                                if (revents & LPOLLIN) {
                                        ret = ctrl_conn->sock->ops->recvmsg(ctrl_conn->sock,
                                                        &recv_hdr, sizeof(recv_hdr), 0);
                                        if (ret <= 0) {
                                                /* Connection closed */
                                                relay_thread_close_connection(&events, pollfd,
                                                                ctrl_conn);
                                        } else {
                                                ret = relay_process_control(&recv_hdr, ctrl_conn);
                                                if (ret < 0) {
                                                        /* Clear the session on error. */
                                                        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("Unexpected poll events %u for control sock %d",
                                                        revents, pollfd);
                                        connection_put(ctrl_conn);
                                        goto error;
                                }
                        put_ctrl_connection:
                                connection_put(ctrl_conn);
                        }
                }

                /*
                 * The last loop handled a control request, go back to poll to make
                 * sure we prioritise the control socket.
                 */
                if (seen_control) {
                        continue;
                }

                if (last_seen_data_fd >= 0) {
                        for (i = 0; i < nb_fd; i++) {
                                int pollfd = LTTNG_POLL_GETFD(&events, i);

                                health_code_update();

                                if (last_seen_data_fd == pollfd) {
                                        idx = i;
                                        break;
                                }
                        }
                }

                /* Process data connection. */
                for (i = idx + 1; i < nb_fd; i++) {
                        /* 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;
                        }

                        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) {
                                ret = relay_process_data(data_conn);
                                /* Connection closed */
                                if (ret < 0) {
                                        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;
                                }
                        } 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;
        }

        /* Normal exit, no error */
        ret = 0;

exit:
error:
        /* Cleanup reamaining connection object. */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter,
                        destroy_conn,
                        sock_n.node) {
                health_code_update();

                if (session_abort(destroy_conn->session)) {
                        assert(0);
                }

                /*
                 * 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:
        lttng_ht_destroy(relay_connections_ht);
relay_connections_ht_error:
        /* Close relay conn pipes */
        utils_close_pipe(relay_conn_pipe);
        if (err) {
                DBG("Thread exited with error");
        }
        DBG("Worker thread cleanup complete");
error_testpoint:
        if (err) {
                health_error();
                ERR("Health error occurred in %s", __func__);
        }
        health_unregister(health_relayd);
        rcu_unregister_thread();
        lttng_relay_stop_threads();
        return NULL;
}

/*
 * Create the relay command pipe to wake thread_manage_apps.
 * Closed in cleanup().
 */
static int create_relay_conn_pipe(void)
{
        int ret;

        ret = utils_create_pipe_cloexec(relay_conn_pipe);

        return ret;
}

/*
 * main
 */
int main(int argc, char **argv)
{
        int ret = 0, retval = 0;
        void *status;

        /* Parse arguments */
        progname = argv[0];
        if (set_options(argc, argv)) {
                retval = -1;
                goto exit_options;
        }

        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");
                        retval = -1;
                        goto exit_options;
                }

                ret = utils_mkdir_recursive(opt_output_path, S_IRWXU | S_IRWXG,
                                -1, -1);
                if (ret < 0) {
                        ERR("Unable to create %s", opt_output_path);
                        retval = -1;
                        goto exit_options;
                }
        }

        /* Daemonize */
        if (opt_daemon || opt_background) {
                int i;

                ret = lttng_daemonize(&child_ppid, &recv_child_signal,
                        !opt_background);
                if (ret < 0) {
                        retval = -1;
                        goto exit_options;
                }

                /*
                 * We are in the child. Make sure all other file
                 * descriptors are closed, in case we are called with
                 * more opened file descriptors than the standard ones.
                 */
                for (i = 3; i < sysconf(_SC_OPEN_MAX); i++) {
                        (void) close(i);
                }
        }

        /* 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;
        }

        /* Create thread quit pipe */
        if (init_thread_quit_pipe()) {
                retval = -1;
                goto exit_init_data;
        }

        /* Setup the thread apps communication pipe. */
        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);

        /* Initialize communication library */
        lttcomm_init();
        lttcomm_inet_init();

        /* tables of sessions indexed by session ID */
        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) {
                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) {
                retval = -1;
                goto exit_init_data;
        }

        ret = utils_create_pipe(health_quit_pipe);
        if (ret) {
                retval = -1;
                goto exit_health_quit_pipe;
        }

        /* Create thread to manage the client socket */
        ret = pthread_create(&health_thread, default_pthread_attr(),
                        thread_manage_health, (void *) NULL);
        if (ret) {
                errno = ret;
                PERROR("pthread_create health");
                retval = -1;
                goto exit_health_thread;
        }

        /* Setup the dispatcher thread */
        ret = pthread_create(&dispatcher_thread, default_pthread_attr(),
                        relay_thread_dispatcher, (void *) NULL);
        if (ret) {
                errno = ret;
                PERROR("pthread_create dispatcher");
                retval = -1;
                goto exit_dispatcher_thread;
        }

        /* Setup the worker thread */
        ret = pthread_create(&worker_thread, default_pthread_attr(),
                        relay_thread_worker, NULL);
        if (ret) {
                errno = ret;
                PERROR("pthread_create worker");
                retval = -1;
                goto exit_worker_thread;
        }

        /* Setup the listener thread */
        ret = pthread_create(&listener_thread, default_pthread_attr(),
                        relay_thread_listener, (void *) NULL);
        if (ret) {
                errno = ret;
                PERROR("pthread_create listener");
                retval = -1;
                goto exit_listener_thread;
        }

        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) {
                errno = ret;
                PERROR("pthread_join listener_thread");
                retval = -1;
        }

exit_listener_thread:
        ret = pthread_join(worker_thread, &status);
        if (ret) {
                errno = ret;
                PERROR("pthread_join worker_thread");
                retval = -1;
        }

exit_worker_thread:
        ret = pthread_join(dispatcher_thread, &status);
        if (ret) {
                errno = ret;
                PERROR("pthread_join dispatcher_thread");
                retval = -1;
        }
exit_dispatcher_thread:

        ret = pthread_join(health_thread, &status);
        if (ret) {
                errno = ret;
                PERROR("pthread_join health_thread");
                retval = -1;
        }
exit_health_thread:

        utils_close_pipe(health_quit_pipe);
exit_health_quit_pipe:

exit_init_data:
        health_app_destroy(health_relayd);
exit_health_app_create:
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();

        /* Ensure all prior call_rcu are done. */
        rcu_barrier();

        if (!retval) {
                exit(EXIT_SUCCESS);
        } else {
                exit(EXIT_FAILURE);
        }
}