Fix concurrency issues while overwriting tracefiles in live
[lttng-tools.git] / src / bin / lttng-relayd / main.c
index ba97ab3d78a05bd2cec21c564b8ce4ca6bf35262..70a1948c328cc690e39e4add4d67f4a2a8f2fe44 100644 (file)
@@ -57,6 +57,7 @@
 #include "utils.h"
 #include "lttng-relayd.h"
 #include "live.h"
+#include "health-relayd.h"
 
 /* command line options */
 char *opt_output_path;
@@ -67,6 +68,8 @@ static struct lttng_uri *live_uri;
 
 const char *progname;
 
+const char *tracing_group_name = DEFAULT_TRACING_GROUP;
+
 /*
  * Quit pipe for all threads. This permits a single cancellation point
  * for all threads when receiving an event on the pipe.
@@ -85,6 +88,7 @@ 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;
 
 static uint64_t last_relay_stream_id;
 static uint64_t last_relay_session_id;
@@ -101,9 +105,6 @@ static struct relay_cmd_queue relay_cmd_queue;
 static char *data_buffer;
 static unsigned int data_buffer_size;
 
-/* Global hash table that stores relay index object. */
-static struct lttng_ht *indexes_ht;
-
 /* We need those values for the file/dir creation. */
 static uid_t relayd_uid;
 static gid_t relayd_gid;
@@ -111,6 +112,15 @@ static gid_t relayd_gid;
 /* Global relay stream hash table. */
 struct lttng_ht *relay_streams_ht;
 
+/* Global relay viewer stream hash table. */
+struct lttng_ht *viewer_streams_ht;
+
+/* Global hash table that stores relay index object. */
+struct lttng_ht *indexes_ht;
+
+/* Relayd health monitoring */
+struct health_app *health_relayd;
+
 /*
  * usage function on stderr
  */
@@ -124,6 +134,7 @@ void usage(void)
        fprintf(stderr, "  -D, --data-port URL       Data port listening.\n");
        fprintf(stderr, "  -o, --output PATH         Output path for traces. Must use an absolute path.\n");
        fprintf(stderr, "  -v, --verbose             Verbose mode. Activate DBG() macro.\n");
+       fprintf(stderr, "  -g, --group NAME          Specify the tracing group name. (default: tracing)\n");
 }
 
 static
@@ -137,6 +148,7 @@ int parse_args(int argc, char **argv)
                { "control-port", 1, 0, 'C', },
                { "data-port", 1, 0, 'D', },
                { "daemonize", 0, 0, 'd', },
+               { "group", 1, 0, 'g', },
                { "help", 0, 0, 'h', },
                { "output", 1, 0, 'o', },
                { "verbose", 0, 0, 'v', },
@@ -145,7 +157,7 @@ int parse_args(int argc, char **argv)
 
        while (1) {
                int option_index = 0;
-               c = getopt_long(argc, argv, "dhv" "C:D:o:",
+               c = getopt_long(argc, argv, "dhv" "C:D:o:g:",
                                long_options, &option_index);
                if (c == -1) {
                        break;
@@ -181,6 +193,9 @@ int parse_args(int argc, char **argv)
                case 'd':
                        opt_daemon = 1;
                        break;
+               case 'g':
+                       tracing_group_name = optarg;
+                       break;
                case 'h':
                        usage();
                        exit(EXIT_FAILURE);
@@ -278,18 +293,26 @@ void cleanup(void)
 static
 int notify_thread_pipe(int wpipe)
 {
-       int ret;
+       ssize_t ret;
 
-       do {
-               ret = write(wpipe, "!", 1);
-       } while (ret < 0 && errno == EINTR);
-       if (ret < 0 || ret != 1) {
+       ret = lttng_write(wpipe, "!", 1);
+       if (ret < 1) {
                PERROR("write poll pipe");
        }
 
        return ret;
 }
 
+static void notify_health_quit_pipe(int *pipe)
+{
+       ssize_t ret;
+
+       ret = lttng_write(pipe[1], "4", 1);
+       if (ret < 1) {
+               PERROR("write relay health quit");
+       }
+}
+
 /*
  * Stop all threads by closing the thread quit pipe.
  */
@@ -305,6 +328,8 @@ void stop_threads(void)
                ERR("write error on thread quit pipe");
        }
 
+       notify_health_quit_pipe(health_quit_pipe);
+
        /* Dispatch thread */
        CMM_STORE_SHARED(dispatch_thread_exit, 1);
        futex_nto1_wake(&relay_cmd_queue.futex);
@@ -510,6 +535,10 @@ void *relay_thread_listener(void *data)
 
        DBG("[thread] Relay listener started");
 
+       health_register(health_relayd, HEALTH_RELAYD_TYPE_LISTENER);
+
+       health_code_update();
+
        control_sock = relay_init_sock(control_uri);
        if (!control_sock) {
                goto error_sock_control;
@@ -541,10 +570,14 @@ void *relay_thread_listener(void *data)
        }
 
        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.
@@ -559,6 +592,8 @@ restart:
 
                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);
@@ -653,8 +688,10 @@ error_sock_relay:
        lttcomm_destroy_sock(control_sock);
 error_sock_control:
        if (err) {
-               DBG("Thread exited with error");
+               health_error();
+               ERR("Health error occurred in %s", __func__);
        }
+       health_unregister(health_relayd);
        DBG("Relay listener thread cleanup complete");
        stop_threads();
        return NULL;
@@ -666,17 +703,26 @@ error_sock_control:
 static
 void *relay_thread_dispatcher(void *data)
 {
-       int ret;
+       int err = -1;
+       ssize_t ret;
        struct cds_wfq_node *node;
        struct relay_command *relay_cmd = NULL;
 
        DBG("[thread] Relay dispatcher started");
 
+       health_register(health_relayd, HEALTH_RELAYD_TYPE_DISPATCHER);
+
+       health_code_update();
+
        while (!CMM_LOAD_SHARED(dispatch_thread_exit)) {
+               health_code_update();
+
                /* Atomically prepare the queue futex */
                futex_nto1_prepare(&relay_cmd_queue.futex);
 
                do {
+                       health_code_update();
+
                        /* Dequeue commands */
                        node = cds_wfq_dequeue_blocking(&relay_cmd_queue.queue);
                        if (node == NULL) {
@@ -693,22 +739,30 @@ void *relay_thread_dispatcher(void *data)
                         * 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 :)
                         */
-                       do {
-                               ret = write(relay_cmd_pipe[1], relay_cmd,
-                                               sizeof(struct relay_command));
-                       } while (ret < 0 && errno == EINTR);
+                       ret = lttng_write(relay_cmd_pipe[1], relay_cmd,
+                                       sizeof(struct relay_command));
                        free(relay_cmd);
-                       if (ret < 0 || ret != sizeof(struct relay_command)) {
+                       if (ret < sizeof(struct relay_command)) {
                                PERROR("write cmd pipe");
                                goto error;
                        }
                } while (node != NULL);
 
                /* Futex wait on queue. Blocking call on futex() */
+               health_poll_entry();
                futex_nto1_wait(&relay_cmd_queue.futex);
+               health_poll_exit();
        }
 
+       /* Normal exit, no error */
+       err = 0;
+
 error:
+       if (err) {
+               health_error();
+               ERR("Health error occurred in %s", __func__);
+       }
+       health_unregister(health_relayd);
        DBG("Dispatch thread dying");
        stop_threads();
        return NULL;
@@ -761,15 +815,19 @@ void deferred_free_session(struct rcu_head *head)
        free(session);
 }
 
-static void close_stream(struct relay_stream *stream,
-               struct lttng_ht *viewer_streams_ht, struct lttng_ht *ctf_traces_ht)
+/*
+ * Close a given stream. The stream is freed using a call RCU.
+ *
+ * RCU read side lock MUST be acquired. If NO close_stream_check() was called
+ * BEFORE the stream lock MUST be acquired.
+ */
+static void destroy_stream(struct relay_stream *stream)
 {
        int delret;
        struct relay_viewer_stream *vstream;
        struct lttng_ht_iter iter;
 
        assert(stream);
-       assert(viewer_streams_ht);
 
        delret = close(stream->fd);
        if (delret < 0) {
@@ -783,8 +841,7 @@ static void close_stream(struct relay_stream *stream,
                }
        }
 
-       vstream = live_find_viewer_stream_by_id(stream->stream_handle,
-                       viewer_streams_ht);
+       vstream = live_find_viewer_stream_by_id(stream->stream_handle);
        if (vstream) {
                /*
                 * Set the last good value into the viewer stream. This is done
@@ -792,14 +849,20 @@ static void close_stream(struct relay_stream *stream,
                 * lookup failure on the live thread side of a stream indicates
                 * that the viewer stream index received value should be used.
                 */
+               pthread_mutex_lock(&stream->viewer_stream_rotation_lock);
                vstream->total_index_received = stream->total_index_received;
+               vstream->close_write_flag = 1;
+               pthread_mutex_unlock(&stream->viewer_stream_rotation_lock);
        }
 
+       /* Cleanup index of that stream. */
+       relay_index_destroy_by_stream_id(stream->stream_handle);
+
        iter.iter.node = &stream->stream_n.node;
        delret = lttng_ht_del(relay_streams_ht, &iter);
        assert(!delret);
        iter.iter.node = &stream->ctf_trace_node.node;
-       delret = lttng_ht_del(ctf_traces_ht, &iter);
+       delret = lttng_ht_del(stream->ctf_traces_ht, &iter);
        assert(!delret);
        call_rcu(&stream->rcu_node, deferred_free_stream);
        DBG("Closed tracefile %d from close stream", stream->fd);
@@ -827,29 +890,22 @@ void relay_delete_session(struct relay_command *cmd,
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_streams_ht->ht, &iter.iter, node, node) {
                node = lttng_ht_iter_get_node_ulong(&iter);
-               if (node) {
-                       stream = caa_container_of(node,
-                                       struct relay_stream, stream_n);
-                       if (stream->session == cmd->session) {
-                               ret = close(stream->fd);
-                               if (ret < 0) {
-                                       PERROR("close stream fd on delete session");
-                               }
-                               ret = lttng_ht_del(relay_streams_ht, &iter);
-                               assert(!ret);
-                               call_rcu(&stream->rcu_node,
-                                       deferred_free_stream);
-                       }
-                       /* Cleanup index of that stream. */
-                       relay_index_destroy_by_stream_id(stream->stream_handle,
-                                       indexes_ht);
+               if (!node) {
+                       continue;
+               }
+               stream = caa_container_of(node, struct relay_stream, stream_n);
+               if (stream->session == cmd->session) {
+                       destroy_stream(stream);
+                       cmd->session->stream_count--;
+                       assert(cmd->session->stream_count >= 0);
                }
        }
+
+       /* Make this session not visible anymore. */
        iter.iter.node = &cmd->session->session_n.node;
        ret = lttng_ht_del(sessions_ht, &iter);
        assert(!ret);
-       call_rcu(&cmd->session->rcu_node,
-                       deferred_free_session);
+       call_rcu(&cmd->session->rcu_node, deferred_free_session);
        rcu_read_unlock();
 }
 
@@ -903,6 +959,8 @@ int relay_create_session(struct lttcomm_relayd_hdr *recv_hdr,
 
        session->id = ++last_relay_session_id;
        session->sock = cmd->sock;
+       session->minor = cmd->minor;
+       session->major = cmd->major;
        cmd->session = session;
 
        reply.session_id = htobe64(session->id);
@@ -1027,6 +1085,7 @@ int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
                stream->ctf_trace->metadata_stream = stream;
        }
        ctf_trace_assign(cmd->ctf_traces_ht, stream);
+       stream->ctf_traces_ht = cmd->ctf_traces_ht;
 
        lttng_ht_node_init_ulong(&stream->stream_n,
                        (unsigned long) stream->stream_handle);
@@ -1035,6 +1094,7 @@ int relay_add_stream(struct lttcomm_relayd_hdr *recv_hdr,
 
        lttng_ht_node_init_str(&stream->ctf_trace_node, stream->path_name);
        lttng_ht_add_str(cmd->ctf_traces_ht, &stream->ctf_trace_node);
+       session->stream_count++;
 
        DBG("Relay new stream added %s with ID %" PRIu64, stream->channel_name,
                        stream->stream_handle);
@@ -1073,7 +1133,7 @@ err_free_stream:
  */
 static
 int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_command *cmd, struct lttng_ht *viewer_streams_ht)
+               struct relay_command *cmd)
 {
        int ret, send_ret;
        struct relay_session *session = cmd->session;
@@ -1111,9 +1171,11 @@ int relay_close_stream(struct lttcomm_relayd_hdr *recv_hdr,
 
        stream->last_net_seq_num = be64toh(stream_info.last_net_seq_num);
        stream->close_flag = 1;
+       session->stream_count--;
+       assert(session->stream_count >= 0);
 
        if (close_stream_check(stream)) {
-               close_stream(stream, viewer_streams_ht, cmd->ctf_traces_ht);
+               destroy_stream(stream);
        }
 
 end_unlock:
@@ -1184,7 +1246,7 @@ int relay_start(struct lttcomm_relayd_hdr *recv_hdr,
  */
 static int write_padding_to_file(int fd, uint32_t size)
 {
-       int ret = 0;
+       ssize_t ret = 0;
        char *zeros;
 
        if (size == 0) {
@@ -1198,10 +1260,8 @@ static int write_padding_to_file(int fd, uint32_t size)
                goto end;
        }
 
-       do {
-               ret = write(fd, zeros, size);
-       } while (ret < 0 && errno == EINTR);
-       if (ret < 0 || ret != size) {
+       ret = lttng_write(fd, zeros, size);
+       if (ret < size) {
                PERROR("write padding to file");
        }
 
@@ -1219,6 +1279,7 @@ int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
                struct relay_command *cmd)
 {
        int ret = htobe32(LTTNG_OK);
+       ssize_t size_ret;
        struct relay_session *session = cmd->session;
        struct lttcomm_relayd_metadata_payload *metadata_struct;
        struct relay_stream *metadata_stream;
@@ -1275,11 +1336,9 @@ int relay_recv_metadata(struct lttcomm_relayd_hdr *recv_hdr,
                goto end_unlock;
        }
 
-       do {
-               ret = write(metadata_stream->fd, metadata_struct->payload,
-                               payload_size);
-       } while (ret < 0 && errno == EINTR);
-       if (ret < 0 || ret != payload_size) {
+       size_ret = lttng_write(metadata_stream->fd, metadata_struct->payload,
+                       payload_size);
+       if (size_ret < payload_size) {
                ERR("Relay error writing metadata on file");
                ret = -1;
                goto end_unlock;
@@ -1652,7 +1711,7 @@ end_no_session:
  */
 static
 int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
-               struct relay_command *cmd, struct lttng_ht *indexes_ht)
+               struct relay_command *cmd)
 {
        int ret, send_ret, index_created = 0;
        struct relay_session *session = cmd->session;
@@ -1663,7 +1722,6 @@ int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
        uint64_t net_seq_num;
 
        assert(cmd);
-       assert(indexes_ht);
 
        DBG("Relay receiving index");
 
@@ -1711,7 +1769,7 @@ int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
                stream->beacon_ts_end = -1ULL;
        }
 
-       index = relay_index_find(stream->stream_handle, net_seq_num, indexes_ht);
+       index = relay_index_find(stream->stream_handle, net_seq_num);
        if (!index) {
                /* A successful creation will add the object to the HT. */
                index = relay_index_create(stream->stream_handle, net_seq_num);
@@ -1729,7 +1787,7 @@ int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
                 * already exist, destroy back the index created, set the data in this
                 * object and write it on disk.
                 */
-               relay_index_add(index, indexes_ht, &wr_index);
+               relay_index_add(index, &wr_index);
                if (wr_index) {
                        copy_index_control_data(wr_index, &index_info);
                        free(index);
@@ -1752,7 +1810,7 @@ int relay_recv_index(struct lttcomm_relayd_hdr *recv_hdr,
                        stream->index_fd = ret;
                }
 
-               ret = relay_index_write(wr_index->fd, wr_index, indexes_ht);
+               ret = relay_index_write(wr_index->fd, wr_index);
                if (ret < 0) {
                        goto end_rcu_unlock;
                }
@@ -1803,7 +1861,7 @@ int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
                ret = relay_send_version(recv_hdr, cmd, ctx->sessions_ht);
                break;
        case RELAYD_CLOSE_STREAM:
-               ret = relay_close_stream(recv_hdr, cmd, ctx->viewer_streams_ht);
+               ret = relay_close_stream(recv_hdr, cmd);
                break;
        case RELAYD_DATA_PENDING:
                ret = relay_data_pending(recv_hdr, cmd);
@@ -1818,7 +1876,7 @@ int relay_process_control(struct lttcomm_relayd_hdr *recv_hdr,
                ret = relay_end_data_pending(recv_hdr, cmd);
                break;
        case RELAYD_SEND_INDEX:
-               ret = relay_recv_index(recv_hdr, cmd, indexes_ht);
+               ret = relay_recv_index(recv_hdr, cmd);
                break;
        case RELAYD_UPDATE_SYNC_INFO:
        default:
@@ -1832,18 +1890,99 @@ end:
        return ret;
 }
 
+/*
+ * Handle index for a data stream.
+ *
+ * RCU read side lock MUST be acquired.
+ *
+ * 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, index_created = 0;
+       uint64_t stream_id, data_offset;
+       struct relay_index *index, *wr_index = NULL;
+
+       assert(stream);
+
+       stream_id = stream->stream_handle;
+       /* Get data offset because we are about to update the index. */
+       data_offset = htobe64(stream->tracefile_size_current);
+
+       /*
+        * Lookup for an existing index for that stream id/sequence number. If on
+        * exists, the control thread already received the data for it thus we need
+        * to write it on disk.
+        */
+       index = relay_index_find(stream_id, net_seq_num);
+       if (!index) {
+               /* A successful creation will add the object to the HT. */
+               index = relay_index_create(stream_id, net_seq_num);
+               if (!index) {
+                       ret = -1;
+                       goto error;
+               }
+               index_created = 1;
+       }
+
+       if (rotate_index || stream->index_fd < 0) {
+               index->to_close_fd = stream->index_fd;
+               ret = index_create_file(stream->path_name, stream->channel_name,
+                               relayd_uid, relayd_gid, stream->tracefile_size,
+                               stream->tracefile_count_current);
+               if (ret < 0) {
+                       /* This will close the stream's index fd if one. */
+                       relay_index_free_safe(index);
+                       goto error;
+               }
+               stream->index_fd = ret;
+       }
+       index->fd = stream->index_fd;
+       index->index_data.offset = data_offset;
+
+       if (index_created) {
+               /*
+                * Try to add the relay index object to the hash table. If an object
+                * already exist, destroy back the index created and set the data.
+                */
+               relay_index_add(index, &wr_index);
+               if (wr_index) {
+                       /* Copy back data from the created index. */
+                       wr_index->fd = index->fd;
+                       wr_index->to_close_fd = index->to_close_fd;
+                       wr_index->index_data.offset = data_offset;
+                       free(index);
+               }
+       } else {
+               /* The index already exists so write it on disk. */
+               wr_index = index;
+       }
+
+       /* Do we have a writable ready index to write on disk. */
+       if (wr_index) {
+               ret = relay_index_write(wr_index->fd, wr_index);
+               if (ret < 0) {
+                       goto error;
+               }
+               stream->total_index_received++;
+       }
+
+error:
+       return ret;
+}
+
 /*
  * relay_process_data: Process the data received on the data socket
  */
 static
-int relay_process_data(struct relay_command *cmd,
-               struct lttng_ht *indexes_ht, struct lttng_ht *viewer_streams_ht)
+int relay_process_data(struct relay_command *cmd)
 {
-       int ret = 0, rotate_index = 0, index_created = 0;
+       int ret = 0, rotate_index = 0;
+       ssize_t size_ret;
        struct relay_stream *stream;
-       struct relay_index *index, *wr_index = NULL;
        struct lttcomm_relayd_data_hdr data_hdr;
-       uint64_t stream_id, data_offset;
+       uint64_t stream_id;
        uint64_t net_seq_num;
        uint32_t data_size;
 
@@ -1903,10 +2042,54 @@ int relay_process_data(struct relay_command *cmd,
        if (stream->tracefile_size > 0 &&
                        (stream->tracefile_size_current + data_size) >
                        stream->tracefile_size) {
+               struct relay_viewer_stream *vstream;
+               uint64_t new_id;
+
+               new_id = (stream->tracefile_count_current + 1) %
+                       stream->tracefile_count;
+               /*
+                * When we wrap-around back to 0, we start overwriting old
+                * trace data.
+                */
+               if (!stream->tracefile_overwrite && new_id == 0) {
+                       stream->tracefile_overwrite = 1;
+               }
+               pthread_mutex_lock(&stream->viewer_stream_rotation_lock);
+               if (stream->tracefile_overwrite) {
+                       stream->oldest_tracefile_id =
+                               (stream->oldest_tracefile_id + 1) %
+                               stream->tracefile_count;
+               }
+               vstream = live_find_viewer_stream_by_id(stream->stream_handle);
+               if (vstream) {
+                       /*
+                        * The viewer is reading a file about to be
+                        * overwritten. Close the FDs it is
+                        * currently using and let it handle the fault.
+                        */
+                       if (vstream->tracefile_count_current == new_id) {
+                               pthread_mutex_lock(&vstream->overwrite_lock);
+                               vstream->abort_flag = 1;
+                               pthread_mutex_unlock(&vstream->overwrite_lock);
+                               DBG("Streaming side setting abort_flag on stream %s_%lu\n",
+                                               stream->channel_name, new_id);
+                       } else if (vstream->tracefile_count_current ==
+                                       stream->tracefile_count_current) {
+                               /*
+                                * The reader and writer were in the
+                                * same trace file, inform the viewer
+                                * that no new index will ever be added
+                                * to this file.
+                                */
+                               vstream->close_write_flag = 1;
+                       }
+               }
                ret = utils_rotate_stream_file(stream->path_name, stream->channel_name,
                                stream->tracefile_size, stream->tracefile_count,
                                relayd_uid, relayd_gid, stream->fd,
                                &(stream->tracefile_count_current), &stream->fd);
+               stream->total_index_received = 0;
+               pthread_mutex_unlock(&stream->viewer_stream_rotation_lock);
                if (ret < 0) {
                        ERR("Rotating stream output file");
                        goto end_rcu_unlock;
@@ -1916,81 +2099,20 @@ int relay_process_data(struct relay_command *cmd,
                rotate_index = 1;
        }
 
-       /* Get data offset because we are about to update the index. */
-       data_offset = htobe64(stream->tracefile_size_current);
-
        /*
-        * Lookup for an existing index for that stream id/sequence number. If on
-        * exists, the control thread already received the data for it thus we need
-        * to write it on disk.
+        * Index are handled in protocol version 2.4 and above. Also, snapshot and
+        * index are NOT supported.
         */
-       index = relay_index_find(stream_id, net_seq_num, indexes_ht);
-       if (!index) {
-               /* A successful creation will add the object to the HT. */
-               index = relay_index_create(stream->stream_handle, net_seq_num);
-               if (!index) {
-                       goto end_rcu_unlock;
-               }
-               index_created = 1;
-       }
-
-       if (rotate_index || stream->index_fd < 0) {
-               index->to_close_fd = stream->index_fd;
-               ret = index_create_file(stream->path_name, stream->channel_name,
-                               relayd_uid, relayd_gid, stream->tracefile_size,
-                               stream->tracefile_count_current);
-               if (ret < 0) {
-                       /* This will close the stream's index fd if one. */
-                       relay_index_free_safe(index);
-                       goto end_rcu_unlock;
-               }
-               stream->index_fd = ret;
-       }
-       index->fd = stream->index_fd;
-       index->index_data.offset = data_offset;
-
-       if (index_created) {
-               /*
-                * Try to add the relay index object to the hash table. If an object
-                * already exist, destroy back the index created and set the data.
-                */
-               relay_index_add(index, indexes_ht, &wr_index);
-               if (wr_index) {
-                       /* Copy back data from the created index. */
-                       wr_index->fd = index->fd;
-                       wr_index->to_close_fd = index->to_close_fd;
-                       wr_index->index_data.offset = data_offset;
-                       free(index);
-               }
-       } else {
-               /* The index already exists so write it on disk. */
-               wr_index = index;
-       }
-
-       /* Do we have a writable ready index to write on disk. */
-       if (wr_index) {
-               /* Starting at 2.4, create the index file if none available. */
-               if (cmd->minor >= 4 && stream->index_fd < 0) {
-                       ret = index_create_file(stream->path_name, stream->channel_name,
-                                       relayd_uid, relayd_gid, stream->tracefile_size,
-                                       stream->tracefile_count_current);
-                       if (ret < 0) {
-                               goto end_rcu_unlock;
-                       }
-                       stream->index_fd = ret;
-               }
-
-               ret = relay_index_write(wr_index->fd, wr_index, indexes_ht);
+       if (stream->session->minor >= 4 && !stream->session->snapshot) {
+               ret = handle_index_data(stream, net_seq_num, rotate_index);
                if (ret < 0) {
                        goto end_rcu_unlock;
                }
-               stream->total_index_received++;
        }
 
-       do {
-               ret = write(stream->fd, data_buffer, data_size);
-       } while (ret < 0 && errno == EINTR);
-       if (ret < 0 || ret != data_size) {
+       /* Write data to stream output fd. */
+       size_ret = lttng_write(stream->fd, data_buffer, data_size);
+       if (size_ret < data_size) {
                ERR("Relay error writing data to file");
                ret = -1;
                goto end_rcu_unlock;
@@ -2009,7 +2131,7 @@ int relay_process_data(struct relay_command *cmd,
 
        /* Check if we need to close the FD */
        if (close_stream_check(stream)) {
-               close_stream(stream, viewer_streams_ht, cmd->ctf_traces_ht);
+               destroy_stream(stream);
        }
 
 end_rcu_unlock:
@@ -2036,24 +2158,30 @@ int relay_add_connection(int fd, struct lttng_poll_event *events,
                struct lttng_ht *relay_connections_ht)
 {
        struct relay_command *relay_connection;
-       int ret;
+       ssize_t ret;
 
        relay_connection = zmalloc(sizeof(struct relay_command));
        if (relay_connection == NULL) {
                PERROR("Relay command zmalloc");
                goto error;
        }
-       do {
-               ret = read(fd, relay_connection, sizeof(struct relay_command));
-       } while (ret < 0 && errno == EINTR);
-       if (ret < 0 || ret < sizeof(struct relay_command)) {
+       ret = lttng_read(fd, relay_connection, sizeof(struct relay_command));
+       if (ret < sizeof(struct relay_command)) {
                PERROR("read relay cmd pipe");
                goto error_read;
        }
 
-       relay_connection->ctf_traces_ht = lttng_ht_new(0, LTTNG_HT_TYPE_STRING);
-       if (!relay_connection->ctf_traces_ht) {
-               goto error_read;
+       /*
+        * Only used by the control side and the reference is copied inside each
+        * stream from that connection. Thus a destroy HT must be done after every
+        * stream has been destroyed.
+        */
+       if (relay_connection->type == RELAY_CONTROL) {
+               relay_connection->ctf_traces_ht = lttng_ht_new(0,
+                               LTTNG_HT_TYPE_STRING);
+               if (!relay_connection->ctf_traces_ht) {
+                       goto error_read;
+               }
        }
 
        lttng_ht_node_init_ulong(&relay_connection->sock_n,
@@ -2078,7 +2206,6 @@ void deferred_free_connection(struct rcu_head *head)
        struct relay_command *relay_connection =
                caa_container_of(head, struct relay_command, rcu_node);
 
-       lttng_ht_destroy(relay_connection->ctf_traces_ht);
        lttcomm_destroy_sock(relay_connection->sock);
        free(relay_connection);
 }
@@ -2092,12 +2219,13 @@ void relay_del_connection(struct lttng_ht *relay_connections_ht,
 
        ret = lttng_ht_del(relay_connections_ht, iter);
        assert(!ret);
+
        if (relay_connection->type == RELAY_CONTROL) {
                relay_delete_session(relay_connection, sessions_ht);
+               lttng_ht_destroy(relay_connection->ctf_traces_ht);
        }
 
-       call_rcu(&relay_connection->rcu_node,
-               deferred_free_connection);
+       call_rcu(&relay_connection->rcu_node, deferred_free_connection);
 }
 
 /*
@@ -2121,6 +2249,10 @@ void *relay_thread_worker(void *data)
 
        rcu_register_thread();
 
+       health_register(health_relayd, HEALTH_RELAYD_TYPE_WORKER);
+
+       health_code_update();
+
        /* table of connections indexed on socket */
        relay_connections_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        if (!relay_connections_ht) {
@@ -2147,9 +2279,13 @@ 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.
@@ -2172,6 +2308,8 @@ restart:
                        uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                        int pollfd = LTTNG_POLL_GETFD(&events, i);
 
+                       health_code_update();
+
                        /* Thread quit pipe has been closed. Killing thread. */
                        ret = check_thread_quit_pipe(pollfd, revents);
                        if (ret) {
@@ -2274,6 +2412,9 @@ restart:
                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;
@@ -2287,6 +2428,8 @@ restart:
                        uint32_t revents = LTTNG_POLL_GETEV(&events, i);
                        int pollfd = LTTNG_POLL_GETFD(&events, i);
 
+                       health_code_update();
+
                        /* Skip the command pipe. It's handled in the first loop. */
                        if (pollfd == relay_cmd_pipe[0]) {
                                continue;
@@ -2311,8 +2454,7 @@ restart:
                                                continue;
                                        }
 
-                                       ret = relay_process_data(relay_connection, indexes_ht,
-                                                       relay_ctx->viewer_streams_ht);
+                                       ret = relay_process_data(relay_connection);
                                        /* connection closed */
                                        if (ret < 0) {
                                                relay_cleanup_poll_connection(&events, pollfd);
@@ -2337,6 +2479,9 @@ restart:
                last_seen_data_fd = -1;
        }
 
+       /* Normal exit, no error */
+       ret = 0;
+
 exit:
 error:
        lttng_poll_clean(&events);
@@ -2344,6 +2489,8 @@ error:
        /* empty the hash table and free the memory */
        rcu_read_lock();
        cds_lfht_for_each_entry(relay_connections_ht->ht, &iter.iter, node, node) {
+               health_code_update();
+
                node = lttng_ht_iter_get_node_ulong(&iter);
                if (node) {
                        relay_connection = caa_container_of(node,
@@ -2352,15 +2499,9 @@ error:
                                        &iter, relay_connection, sessions_ht);
                }
        }
-error_poll_create:
-       {
-               struct relay_index *index;
-               cds_lfht_for_each_entry(indexes_ht->ht, &iter.iter, index, index_n.node) {
-                       relay_index_delete(index, indexes_ht);
-               }
-               lttng_ht_destroy(indexes_ht);
-       }
        rcu_read_unlock();
+error_poll_create:
+       lttng_ht_destroy(indexes_ht);
 indexes_ht_error:
        lttng_ht_destroy(relay_connections_ht);
 relay_connections_ht_error:
@@ -2371,8 +2512,13 @@ relay_connections_ht_error:
        }
        DBG("Worker thread cleanup complete");
        free(data_buffer);
-       stop_threads();
+       if (err) {
+               health_error();
+               ERR("Health error occurred in %s", __func__);
+       }
+       health_unregister(health_relayd);
        rcu_unregister_thread();
+       stop_threads();
        return NULL;
 }
 
@@ -2482,11 +2628,31 @@ int main(int argc, char **argv)
        }
 
        /* tables of streams indexed by stream ID */
-       relay_ctx->viewer_streams_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
-       if (!relay_ctx->viewer_streams_ht) {
+       viewer_streams_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!viewer_streams_ht) {
                goto exit_relay_ctx_viewer_streams;
        }
 
+       /* Initialize thread health monitoring */
+       health_relayd = health_app_create(NR_HEALTH_RELAYD_TYPES);
+       if (!health_relayd) {
+               PERROR("health_app_create error");
+               goto exit_health_app_create;
+       }
+
+       ret = utils_create_pipe(health_quit_pipe);
+       if (ret < 0) {
+               goto error_health_pipe;
+       }
+
+       /* Create thread to manage the client socket */
+       ret = pthread_create(&health_thread, NULL,
+                       thread_manage_health, (void *) NULL);
+       if (ret != 0) {
+               PERROR("pthread_create health");
+               goto health_error;
+       }
+
        /* Setup the dispatcher thread */
        ret = pthread_create(&dispatcher_thread, NULL,
                        relay_thread_dispatcher, (void *) NULL);
@@ -2511,32 +2677,53 @@ int main(int argc, char **argv)
                goto exit_listener;
        }
 
-       ret = live_start_threads(live_uri, relay_ctx);
+       ret = live_start_threads(live_uri, relay_ctx, thread_quit_pipe);
        if (ret != 0) {
                ERR("Starting live viewer threads");
+               goto exit_live;
        }
 
-exit_listener:
+exit_live:
        ret = pthread_join(listener_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }
 
-exit_worker:
+exit_listener:
        ret = pthread_join(worker_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }
 
-exit_dispatcher:
+exit_worker:
        ret = pthread_join(dispatcher_thread, &status);
        if (ret != 0) {
                PERROR("pthread_join");
                goto error;     /* join error, exit without cleanup */
        }
-       lttng_ht_destroy(relay_ctx->viewer_streams_ht);
+
+exit_dispatcher:
+       ret = pthread_join(health_thread, &status);
+       if (ret != 0) {
+               PERROR("pthread_join health thread");
+               goto error;     /* join error, exit without cleanup */
+       }
+
+       /*
+        * Stop live threads only after joining other threads.
+        */
+       live_stop_threads();
+
+health_error:
+       utils_close_pipe(health_quit_pipe);
+
+error_health_pipe:
+       health_app_destroy(health_relayd);
+
+exit_health_app_create:
+       lttng_ht_destroy(viewer_streams_ht);
 
 exit_relay_ctx_viewer_streams:
        lttng_ht_destroy(relay_streams_ht);
@@ -2548,7 +2735,6 @@ exit_relay_ctx_sessions:
        free(relay_ctx);
 
 exit:
-       live_stop_threads();
        cleanup();
        if (!ret) {
                exit(EXIT_SUCCESS);
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