Fix: remove unused session id map
[lttng-tools.git] / src / common / consumer.c
index e7d51078e64b9b5209d4e8208a61a25d9e0bef38..27dfe32b8592487e6c5e881604a650085240f536 100644 (file)
@@ -1,20 +1,20 @@
 /*
  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ *               2012 - David Goulet <dgoulet@efficios.com>
  *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; only version 2
- * of the License.
+ * 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.
+ * 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., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ * 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 _GNU_SOURCE
 #include <sys/socket.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <inttypes.h>
 
 #include <common/common.h>
+#include <common/utils.h>
+#include <common/compat/poll.h>
 #include <common/kernel-ctl/kernel-ctl.h>
+#include <common/sessiond-comm/relayd.h>
 #include <common/sessiond-comm/sessiond-comm.h>
 #include <common/kernel-consumer/kernel-consumer.h>
+#include <common/relayd/relayd.h>
 #include <common/ust-consumer/ust-consumer.h>
 
 #include "consumer.h"
@@ -42,35 +47,58 @@ struct lttng_consumer_global_data consumer_data = {
        .type = LTTNG_CONSUMER_UNKNOWN,
 };
 
-/* timeout parameter, to control the polling thread grace period. */
-int consumer_poll_timeout = -1;
-
 /*
  * Flag to inform the polling thread to quit when all fd hung up. Updated by
  * the consumer_thread_receive_fds when it notices that all fds has hung up.
  * Also updated by the signal handler (consumer_should_exit()). Read by the
  * polling threads.
  */
-volatile int consumer_quit = 0;
+volatile int consumer_quit;
+
+/*
+ * Global hash table containing respectively metadata and data streams. The
+ * stream element in this ht should only be updated by the metadata poll thread
+ * for the metadata and the data poll thread for the data.
+ */
+static struct lttng_ht *metadata_ht;
+static struct lttng_ht *data_ht;
+
+/*
+ * Notify a thread pipe to poll back again. This usually means that some global
+ * state has changed so we just send back the thread in a poll wait call.
+ */
+static void notify_thread_pipe(int wpipe)
+{
+       int ret;
+
+       do {
+               struct lttng_consumer_stream *null_stream = NULL;
+
+               ret = write(wpipe, &null_stream, sizeof(null_stream));
+       } while (ret < 0 && errno == EINTR);
+}
 
 /*
  * Find a stream. The consumer_data.lock must be locked during this
  * call.
  */
-static struct lttng_consumer_stream *consumer_find_stream(int key)
+static struct lttng_consumer_stream *consumer_find_stream(int key,
+               struct lttng_ht *ht)
 {
        struct lttng_ht_iter iter;
        struct lttng_ht_node_ulong *node;
        struct lttng_consumer_stream *stream = NULL;
 
+       assert(ht);
+
        /* Negative keys are lookup failures */
-       if (key < 0)
+       if (key < 0) {
                return NULL;
+       }
 
        rcu_read_lock();
 
-       lttng_ht_lookup(consumer_data.stream_ht, (void *)((unsigned long) key),
-                       &iter);
+       lttng_ht_lookup(ht, (void *)((unsigned long) key), &iter);
        node = lttng_ht_iter_get_node_ulong(&iter);
        if (node != NULL) {
                stream = caa_container_of(node, struct lttng_consumer_stream, node);
@@ -81,15 +109,30 @@ static struct lttng_consumer_stream *consumer_find_stream(int key)
        return stream;
 }
 
-static void consumer_steal_stream_key(int key)
+void consumer_steal_stream_key(int key, struct lttng_ht *ht)
 {
        struct lttng_consumer_stream *stream;
 
-       stream = consumer_find_stream(key);
-       if (stream)
+       rcu_read_lock();
+       stream = consumer_find_stream(key, ht);
+       if (stream) {
                stream->key = -1;
+               /*
+                * We don't want the lookup to match, but we still need
+                * to iterate on this stream when iterating over the hash table. Just
+                * change the node key.
+                */
+               stream->node.key = -1;
+       }
+       rcu_read_unlock();
 }
 
+/*
+ * Return a channel object for the given key.
+ *
+ * RCU read side lock MUST be acquired before calling this function and
+ * protects the channel ptr.
+ */
 static struct lttng_consumer_channel *consumer_find_channel(int key)
 {
        struct lttng_ht_iter iter;
@@ -97,10 +140,9 @@ static struct lttng_consumer_channel *consumer_find_channel(int key)
        struct lttng_consumer_channel *channel = NULL;
 
        /* Negative keys are lookup failures */
-       if (key < 0)
+       if (key < 0) {
                return NULL;
-
-       rcu_read_lock();
+       }
 
        lttng_ht_lookup(consumer_data.channel_ht, (void *)((unsigned long) key),
                        &iter);
@@ -109,8 +151,6 @@ static struct lttng_consumer_channel *consumer_find_channel(int key)
                channel = caa_container_of(node, struct lttng_consumer_channel, node);
        }
 
-       rcu_read_unlock();
-
        return channel;
 }
 
@@ -118,29 +158,228 @@ static void consumer_steal_channel_key(int key)
 {
        struct lttng_consumer_channel *channel;
 
+       rcu_read_lock();
        channel = consumer_find_channel(key);
-       if (channel)
+       if (channel) {
                channel->key = -1;
+               /*
+                * We don't want the lookup to match, but we still need
+                * to iterate on this channel when iterating over the hash table. Just
+                * change the node key.
+                */
+               channel->node.key = -1;
+       }
+       rcu_read_unlock();
+}
+
+static
+void consumer_free_stream(struct rcu_head *head)
+{
+       struct lttng_ht_node_ulong *node =
+               caa_container_of(head, struct lttng_ht_node_ulong, head);
+       struct lttng_consumer_stream *stream =
+               caa_container_of(node, struct lttng_consumer_stream, node);
+
+       free(stream);
+}
+
+/*
+ * RCU protected relayd socket pair free.
+ */
+static void consumer_rcu_free_relayd(struct rcu_head *head)
+{
+       struct lttng_ht_node_ulong *node =
+               caa_container_of(head, struct lttng_ht_node_ulong, head);
+       struct consumer_relayd_sock_pair *relayd =
+               caa_container_of(node, struct consumer_relayd_sock_pair, node);
+
+       /*
+        * Close all sockets. This is done in the call RCU since we don't want the
+        * socket fds to be reassigned thus potentially creating bad state of the
+        * relayd object.
+        *
+        * We do not have to lock the control socket mutex here since at this stage
+        * there is no one referencing to this relayd object.
+        */
+       (void) relayd_close(&relayd->control_sock);
+       (void) relayd_close(&relayd->data_sock);
+
+       free(relayd);
+}
+
+/*
+ * Destroy and free relayd socket pair object.
+ *
+ * This function MUST be called with the consumer_data lock acquired.
+ */
+static void destroy_relayd(struct consumer_relayd_sock_pair *relayd)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+
+       if (relayd == NULL) {
+               return;
+       }
+
+       DBG("Consumer destroy and close relayd socket pair");
+
+       iter.iter.node = &relayd->node.node;
+       ret = lttng_ht_del(consumer_data.relayd_ht, &iter);
+       if (ret != 0) {
+               /* We assume the relayd is being or is destroyed */
+               return;
+       }
+
+       /* RCU free() call */
+       call_rcu(&relayd->node.head, consumer_rcu_free_relayd);
+}
+
+/*
+ * Iterate over the relayd hash table and destroy each element. Finally,
+ * destroy the whole hash table.
+ */
+static void cleanup_relayd_ht(void)
+{
+       struct lttng_ht_iter iter;
+       struct consumer_relayd_sock_pair *relayd;
+
+       rcu_read_lock();
+
+       cds_lfht_for_each_entry(consumer_data.relayd_ht->ht, &iter.iter, relayd,
+                       node.node) {
+               destroy_relayd(relayd);
+       }
+
+       lttng_ht_destroy(consumer_data.relayd_ht);
+
+       rcu_read_unlock();
+}
+
+/*
+ * Update the end point status of all streams having the given network sequence
+ * index (relayd index).
+ *
+ * It's atomically set without having the stream mutex locked which is fine
+ * because we handle the write/read race with a pipe wakeup for each thread.
+ */
+static void update_endpoint_status_by_netidx(int net_seq_idx,
+               enum consumer_endpoint_status status)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer set delete flag on stream by idx %d", net_seq_idx);
+
+       rcu_read_lock();
+
+       /* Let's begin with metadata */
+       cds_lfht_for_each_entry(metadata_ht->ht, &iter.iter, stream, node.node) {
+               if (stream->net_seq_idx == net_seq_idx) {
+                       uatomic_set(&stream->endpoint_status, status);
+                       DBG("Delete flag set to metadata stream %d", stream->wait_fd);
+               }
+       }
+
+       /* Follow up by the data streams */
+       cds_lfht_for_each_entry(data_ht->ht, &iter.iter, stream, node.node) {
+               if (stream->net_seq_idx == net_seq_idx) {
+                       uatomic_set(&stream->endpoint_status, status);
+                       DBG("Delete flag set to data stream %d", stream->wait_fd);
+               }
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Cleanup a relayd object by flagging every associated streams for deletion,
+ * destroying the object meaning removing it from the relayd hash table,
+ * closing the sockets and freeing the memory in a RCU call.
+ *
+ * If a local data context is available, notify the threads that the streams'
+ * state have changed.
+ */
+static void cleanup_relayd(struct consumer_relayd_sock_pair *relayd,
+               struct lttng_consumer_local_data *ctx)
+{
+       int netidx;
+
+       assert(relayd);
+
+       DBG("Cleaning up relayd sockets");
+
+       /* Save the net sequence index before destroying the object */
+       netidx = relayd->net_seq_idx;
+
+       /*
+        * Delete the relayd from the relayd hash table, close the sockets and free
+        * the object in a RCU call.
+        */
+       destroy_relayd(relayd);
+
+       /* Set inactive endpoint to all streams */
+       update_endpoint_status_by_netidx(netidx, CONSUMER_ENDPOINT_INACTIVE);
+
+       /*
+        * With a local data context, notify the threads that the streams' state
+        * have changed. The write() action on the pipe acts as an "implicit"
+        * memory barrier ordering the updates of the end point status from the
+        * read of this status which happens AFTER receiving this notify.
+        */
+       if (ctx) {
+               notify_thread_pipe(ctx->consumer_data_pipe[1]);
+               notify_thread_pipe(ctx->consumer_metadata_pipe[1]);
+       }
+}
+
+/*
+ * Flag a relayd socket pair for destruction. Destroy it if the refcount
+ * reaches zero.
+ *
+ * RCU read side lock MUST be aquired before calling this function.
+ */
+void consumer_flag_relayd_for_destroy(struct consumer_relayd_sock_pair *relayd)
+{
+       assert(relayd);
+
+       /* Set destroy flag for this object */
+       uatomic_set(&relayd->destroy_flag, 1);
+
+       /* Destroy the relayd if refcount is 0 */
+       if (uatomic_read(&relayd->refcount) == 0) {
+               destroy_relayd(relayd);
+       }
 }
 
 /*
  * Remove a stream from the global list protected by a mutex. This
  * function is also responsible for freeing its data structures.
  */
-void consumer_del_stream(struct lttng_consumer_stream *stream)
+void consumer_del_stream(struct lttng_consumer_stream *stream,
+               struct lttng_ht *ht)
 {
        int ret;
        struct lttng_ht_iter iter;
        struct lttng_consumer_channel *free_chan = NULL;
+       struct consumer_relayd_sock_pair *relayd;
+
+       assert(stream);
+
+       DBG("Consumer del stream %d", stream->wait_fd);
+
+       if (ht == NULL) {
+               /* Means the stream was allocated but not successfully added */
+               goto free_stream;
+       }
 
        pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
 
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
                if (stream->mmap_base != NULL) {
                        ret = munmap(stream->mmap_base, stream->mmap_len);
                        if (ret != 0) {
-                               perror("munmap");
+                               PERROR("munmap");
                        }
                }
                break;
@@ -155,23 +394,19 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
        }
 
        rcu_read_lock();
-
-       /* Get stream node from hash table */
-       lttng_ht_lookup(consumer_data.stream_ht,
-                       (void *)((unsigned long) stream->key), &iter);
-       /* Remove stream node from hash table */
-       ret = lttng_ht_del(consumer_data.stream_ht, &iter);
+       iter.iter.node = &stream->node.node;
+       ret = lttng_ht_del(ht, &iter);
        assert(!ret);
 
+       /* Remove node session id from the consumer_data stream ht */
+       iter.iter.node = &stream->node_session_id.node;
+       ret = lttng_ht_del(consumer_data.stream_list_ht, &iter);
+       assert(!ret);
        rcu_read_unlock();
 
-       if (consumer_data.stream_count <= 0) {
-               goto end;
-       }
+       assert(consumer_data.stream_count > 0);
        consumer_data.stream_count--;
-       if (!stream) {
-               goto end;
-       }
+
        if (stream->out_fd >= 0) {
                ret = close(stream->out_fd);
                if (ret) {
@@ -190,25 +425,54 @@ void consumer_del_stream(struct lttng_consumer_stream *stream)
                        PERROR("close");
                }
        }
-       if (!--stream->chan->refcount)
+
+       /* Check and cleanup relayd */
+       rcu_read_lock();
+       relayd = consumer_find_relayd(stream->net_seq_idx);
+       if (relayd != NULL) {
+               uatomic_dec(&relayd->refcount);
+               assert(uatomic_read(&relayd->refcount) >= 0);
+
+               /* Closing streams requires to lock the control socket. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_send_close_stream(&relayd->control_sock,
+                               stream->relayd_stream_id,
+                               stream->next_net_seq_num - 1);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       DBG("Unable to close stream on the relayd. Continuing");
+                       /*
+                        * Continue here. There is nothing we can do for the relayd.
+                        * Chances are that the relayd has closed the socket so we just
+                        * continue cleaning up.
+                        */
+               }
+
+               /* Both conditions are met, we destroy the relayd. */
+               if (uatomic_read(&relayd->refcount) == 0 &&
+                               uatomic_read(&relayd->destroy_flag)) {
+                       destroy_relayd(relayd);
+               }
+       }
+       rcu_read_unlock();
+
+       uatomic_dec(&stream->chan->refcount);
+       if (!uatomic_read(&stream->chan->refcount)
+                       && !uatomic_read(&stream->chan->nb_init_streams)) {
                free_chan = stream->chan;
-       free(stream);
+       }
+
 end:
        consumer_data.need_update = 1;
+       pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
-       if (free_chan)
+       if (free_chan) {
                consumer_del_channel(free_chan);
-}
-
-static void consumer_del_stream_rcu(struct rcu_head *head)
-{
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
-       struct lttng_consumer_stream *stream =
-               caa_container_of(node, struct lttng_consumer_stream, node);
+       }
 
-       consumer_del_stream(stream);
+free_stream:
+       call_rcu(&stream->node.head, consumer_free_stream);
 }
 
 struct lttng_consumer_stream *consumer_allocate_stream(
@@ -219,22 +483,34 @@ struct lttng_consumer_stream *consumer_allocate_stream(
                enum lttng_event_output output,
                const char *path_name,
                uid_t uid,
-               gid_t gid)
+               gid_t gid,
+               int net_index,
+               int metadata_flag,
+               uint64_t session_id,
+               int *alloc_ret)
 {
        struct lttng_consumer_stream *stream;
-       int ret;
 
        stream = zmalloc(sizeof(*stream));
        if (stream == NULL) {
-               perror("malloc struct lttng_consumer_stream");
+               PERROR("malloc struct lttng_consumer_stream");
+               *alloc_ret = -ENOMEM;
                goto end;
        }
+
+       rcu_read_lock();
+
+       /*
+        * Get stream's channel reference. Needed when adding the stream to the
+        * global hash table.
+        */
        stream->chan = consumer_find_channel(channel_key);
        if (!stream->chan) {
-               perror("Unable to find channel key");
-               goto end;
+               *alloc_ret = -ENOENT;
+               ERR("Unable to find channel for stream %d", stream_key);
+               goto error;
        }
-       stream->chan->refcount++;
+
        stream->key = stream_key;
        stream->shm_fd = shm_fd;
        stream->wait_fd = wait_fd;
@@ -246,97 +522,277 @@ struct lttng_consumer_stream *consumer_allocate_stream(
        stream->output = output;
        stream->uid = uid;
        stream->gid = gid;
-       strncpy(stream->path_name, path_name, PATH_MAX - 1);
-       stream->path_name[PATH_MAX - 1] = '\0';
-       lttng_ht_node_init_ulong(&stream->node, stream->key);
+       stream->net_seq_idx = net_index;
+       stream->metadata_flag = metadata_flag;
+       stream->session_id = session_id;
+       strncpy(stream->path_name, path_name, sizeof(stream->path_name));
+       stream->path_name[sizeof(stream->path_name) - 1] = '\0';
+       pthread_mutex_init(&stream->lock, NULL);
 
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               stream->cpu = stream->chan->cpucount++;
-               ret = lttng_ustconsumer_allocate_stream(stream);
-               if (ret) {
-                       free(stream);
-                       return NULL;
-               }
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               goto end;
+       /*
+        * Index differently the metadata node because the thread is using an
+        * internal hash table to match streams in the metadata_ht to the epoll set
+        * file descriptor.
+        */
+       if (metadata_flag) {
+               lttng_ht_node_init_ulong(&stream->node, stream->wait_fd);
+       } else {
+               lttng_ht_node_init_ulong(&stream->node, stream->key);
        }
-       DBG("Allocated stream %s (key %d, shm_fd %d, wait_fd %d, mmap_len %llu, out_fd %d)",
-                       stream->path_name, stream->key,
-                       stream->shm_fd,
-                       stream->wait_fd,
-                       (unsigned long long) stream->mmap_len,
-                       stream->out_fd);
-end:
+
+       /* Init session id node with the stream session id */
+       lttng_ht_node_init_ulong(&stream->node_session_id, stream->session_id);
+
+       /*
+        * The cpu number is needed before using any ustctl_* actions. Ignored for
+        * the kernel so the value does not matter.
+        */
+       pthread_mutex_lock(&consumer_data.lock);
+       stream->cpu = stream->chan->cpucount++;
+       pthread_mutex_unlock(&consumer_data.lock);
+
+       DBG3("Allocated stream %s (key %d, shm_fd %d, wait_fd %d, mmap_len %llu,"
+                       " out_fd %d, net_seq_idx %d, session_id %" PRIu64,
+                       stream->path_name, stream->key, stream->shm_fd, stream->wait_fd,
+                       (unsigned long long) stream->mmap_len, stream->out_fd,
+                       stream->net_seq_idx, stream->session_id);
+
+       rcu_read_unlock();
        return stream;
+
+error:
+       rcu_read_unlock();
+       free(stream);
+end:
+       return NULL;
 }
 
 /*
  * Add a stream to the global list protected by a mutex.
  */
-int consumer_add_stream(struct lttng_consumer_stream *stream)
+static int consumer_add_stream(struct lttng_consumer_stream *stream,
+               struct lttng_ht *ht)
 {
        int ret = 0;
+       struct consumer_relayd_sock_pair *relayd;
+
+       assert(stream);
+       assert(ht);
+
+       DBG3("Adding consumer stream %d", stream->key);
 
        pthread_mutex_lock(&consumer_data.lock);
-       /* Steal stream identifier, for UST */
-       consumer_steal_stream_key(stream->key);
+       pthread_mutex_lock(&stream->lock);
        rcu_read_lock();
-       lttng_ht_add_unique_ulong(consumer_data.stream_ht, &stream->node);
-       rcu_read_unlock();
-       consumer_data.stream_count++;
-       consumer_data.need_update = 1;
 
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               /* Streams are in CPU number order (we rely on this) */
-               stream->cpu = stream->chan->nr_streams++;
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               goto end;
+       /* Steal stream identifier to avoid having streams with the same key */
+       consumer_steal_stream_key(stream->key, ht);
+
+       lttng_ht_add_unique_ulong(ht, &stream->node);
+
+       /*
+        * Add stream to the stream_list_ht of the consumer data. No need to steal
+        * the key since the HT does not use it and we allow to add redundant keys
+        * into this table.
+        */
+       lttng_ht_add_ulong(consumer_data.stream_list_ht, &stream->node_session_id);
+
+       /* Check and cleanup relayd */
+       relayd = consumer_find_relayd(stream->net_seq_idx);
+       if (relayd != NULL) {
+               uatomic_inc(&relayd->refcount);
        }
 
-end:
+       /* Update channel refcount once added without error(s). */
+       uatomic_inc(&stream->chan->refcount);
+
+       /*
+        * When nb_init_streams reaches 0, we don't need to trigger any action in
+        * terms of destroying the associated channel, because the action that
+        * causes the count to become 0 also causes a stream to be added. The
+        * channel deletion will thus be triggered by the following removal of this
+        * stream.
+        */
+       if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
+               uatomic_dec(&stream->chan->nb_init_streams);
+       }
+
+       /* Update consumer data once the node is inserted. */
+       consumer_data.stream_count++;
+       consumer_data.need_update = 1;
+
+       rcu_read_unlock();
+       pthread_mutex_unlock(&stream->lock);
        pthread_mutex_unlock(&consumer_data.lock);
+
        return ret;
 }
 
 /*
- * Update a stream according to what we just received.
+ * Add relayd socket to global consumer data hashtable. RCU read side lock MUST
+ * be acquired before calling this.
  */
-void consumer_change_stream_state(int stream_key,
-               enum lttng_consumer_stream_state state)
+static int add_relayd(struct consumer_relayd_sock_pair *relayd)
 {
-       struct lttng_consumer_stream *stream;
+       int ret = 0;
+       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_iter iter;
 
-       pthread_mutex_lock(&consumer_data.lock);
-       stream = consumer_find_stream(stream_key);
-       if (stream) {
-               stream->state = state;
+       if (relayd == NULL) {
+               ret = -1;
+               goto end;
        }
-       consumer_data.need_update = 1;
-       pthread_mutex_unlock(&consumer_data.lock);
+
+       lttng_ht_lookup(consumer_data.relayd_ht,
+                       (void *)((unsigned long) relayd->net_seq_idx), &iter);
+       node = lttng_ht_iter_get_node_ulong(&iter);
+       if (node != NULL) {
+               /* Relayd already exist. Ignore the insertion */
+               goto end;
+       }
+       lttng_ht_add_unique_ulong(consumer_data.relayd_ht, &relayd->node);
+
+end:
+       return ret;
 }
 
 /*
- * Remove a channel from the global list protected by a mutex. This
- * function is also responsible for freeing its data structures.
+ * Allocate and return a consumer relayd socket.
  */
-void consumer_del_channel(struct lttng_consumer_channel *channel)
+struct consumer_relayd_sock_pair *consumer_allocate_relayd_sock_pair(
+               int net_seq_idx)
 {
-       int ret;
-       struct lttng_ht_iter iter;
+       struct consumer_relayd_sock_pair *obj = NULL;
+
+       /* Negative net sequence index is a failure */
+       if (net_seq_idx < 0) {
+               goto error;
+       }
+
+       obj = zmalloc(sizeof(struct consumer_relayd_sock_pair));
+       if (obj == NULL) {
+               PERROR("zmalloc relayd sock");
+               goto error;
+       }
+
+       obj->net_seq_idx = net_seq_idx;
+       obj->refcount = 0;
+       obj->destroy_flag = 0;
+       lttng_ht_node_init_ulong(&obj->node, obj->net_seq_idx);
+       pthread_mutex_init(&obj->ctrl_sock_mutex, NULL);
+
+error:
+       return obj;
+}
+
+/*
+ * Find a relayd socket pair in the global consumer data.
+ *
+ * Return the object if found else NULL.
+ * RCU read-side lock must be held across this call and while using the
+ * returned object.
+ */
+struct consumer_relayd_sock_pair *consumer_find_relayd(int key)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_ulong *node;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+
+       /* Negative keys are lookup failures */
+       if (key < 0) {
+               goto error;
+       }
+
+       lttng_ht_lookup(consumer_data.relayd_ht, (void *)((unsigned long) key),
+                       &iter);
+       node = lttng_ht_iter_get_node_ulong(&iter);
+       if (node != NULL) {
+               relayd = caa_container_of(node, struct consumer_relayd_sock_pair, node);
+       }
+
+error:
+       return relayd;
+}
+
+/*
+ * Handle stream for relayd transmission if the stream applies for network
+ * streaming where the net sequence index is set.
+ *
+ * Return destination file descriptor or negative value on error.
+ */
+static int write_relayd_stream_header(struct lttng_consumer_stream *stream,
+               size_t data_size, unsigned long padding,
+               struct consumer_relayd_sock_pair *relayd)
+{
+       int outfd = -1, ret;
+       struct lttcomm_relayd_data_hdr data_hdr;
+
+       /* Safety net */
+       assert(stream);
+       assert(relayd);
+
+       /* Reset data header */
+       memset(&data_hdr, 0, sizeof(data_hdr));
+
+       if (stream->metadata_flag) {
+               /* Caller MUST acquire the relayd control socket lock */
+               ret = relayd_send_metadata(&relayd->control_sock, data_size);
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /* Metadata are always sent on the control socket. */
+               outfd = relayd->control_sock.fd;
+       } else {
+               /* Set header with stream information */
+               data_hdr.stream_id = htobe64(stream->relayd_stream_id);
+               data_hdr.data_size = htobe32(data_size);
+               data_hdr.padding_size = htobe32(padding);
+               /*
+                * Note that net_seq_num below is assigned with the *current* value of
+                * next_net_seq_num and only after that the next_net_seq_num will be
+                * increment. This is why when issuing a command on the relayd using
+                * this next value, 1 should always be substracted in order to compare
+                * the last seen sequence number on the relayd side to the last sent.
+                */
+               data_hdr.net_seq_num = htobe64(stream->next_net_seq_num++);
+               /* Other fields are zeroed previously */
+
+               ret = relayd_send_data_hdr(&relayd->data_sock, &data_hdr,
+                               sizeof(data_hdr));
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /* Set to go on data socket */
+               outfd = relayd->data_sock.fd;
+       }
+
+error:
+       return outfd;
+}
+
+static
+void consumer_free_channel(struct rcu_head *head)
+{
+       struct lttng_ht_node_ulong *node =
+               caa_container_of(head, struct lttng_ht_node_ulong, head);
+       struct lttng_consumer_channel *channel =
+               caa_container_of(node, struct lttng_consumer_channel, node);
+
+       free(channel);
+}
+
+/*
+ * Remove a channel from the global list protected by a mutex. This
+ * function is also responsible for freeing its data structures.
+ */
+void consumer_del_channel(struct lttng_consumer_channel *channel)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+
+       DBG("Consumer delete channel key %d", channel->key);
 
        pthread_mutex_lock(&consumer_data.lock);
 
@@ -354,18 +810,15 @@ void consumer_del_channel(struct lttng_consumer_channel *channel)
        }
 
        rcu_read_lock();
-
-       lttng_ht_lookup(consumer_data.channel_ht,
-                       (void *)((unsigned long) channel->key), &iter);
+       iter.iter.node = &channel->node.node;
        ret = lttng_ht_del(consumer_data.channel_ht, &iter);
        assert(!ret);
-
        rcu_read_unlock();
 
        if (channel->mmap_base != NULL) {
                ret = munmap(channel->mmap_base, channel->mmap_len);
                if (ret != 0) {
-                       perror("munmap");
+                       PERROR("munmap");
                }
        }
        if (channel->wait_fd >= 0 && !channel->wait_fd_is_copy) {
@@ -380,33 +833,25 @@ void consumer_del_channel(struct lttng_consumer_channel *channel)
                        PERROR("close");
                }
        }
-       free(channel);
+
+       call_rcu(&channel->node.head, consumer_free_channel);
 end:
        pthread_mutex_unlock(&consumer_data.lock);
 }
 
-static void consumer_del_channel_rcu(struct rcu_head *head)
-{
-       struct lttng_ht_node_ulong *node =
-               caa_container_of(head, struct lttng_ht_node_ulong, head);
-       struct lttng_consumer_channel *channel=
-               caa_container_of(node, struct lttng_consumer_channel, node);
-
-       consumer_del_channel(channel);
-}
-
 struct lttng_consumer_channel *consumer_allocate_channel(
                int channel_key,
                int shm_fd, int wait_fd,
                uint64_t mmap_len,
-               uint64_t max_sb_size)
+               uint64_t max_sb_size,
+               unsigned int nb_init_streams)
 {
        struct lttng_consumer_channel *channel;
        int ret;
 
        channel = zmalloc(sizeof(*channel));
        if (channel == NULL) {
-               perror("malloc struct lttng_consumer_channel");
+               PERROR("malloc struct lttng_consumer_channel");
                goto end;
        }
        channel->key = channel_key;
@@ -415,7 +860,7 @@ struct lttng_consumer_channel *consumer_allocate_channel(
        channel->mmap_len = mmap_len;
        channel->max_sb_size = max_sb_size;
        channel->refcount = 0;
-       channel->nr_streams = 0;
+       channel->nb_init_streams = nb_init_streams;
        lttng_ht_node_init_ulong(&channel->node, channel->key);
 
        switch (consumer_data.type) {
@@ -437,9 +882,7 @@ struct lttng_consumer_channel *consumer_allocate_channel(
                goto end;
        }
        DBG("Allocated channel (key %d, shm_fd %d, wait_fd %d, mmap_len %llu, max_sb_size %llu)",
-                       channel->key,
-                       channel->shm_fd,
-                       channel->wait_fd,
+                       channel->key, channel->shm_fd, channel->wait_fd,
                        (unsigned long long) channel->mmap_len,
                        (unsigned long long) channel->max_sb_size);
 end:
@@ -451,13 +894,28 @@ end:
  */
 int consumer_add_channel(struct lttng_consumer_channel *channel)
 {
+       struct lttng_ht_node_ulong *node;
+       struct lttng_ht_iter iter;
+
        pthread_mutex_lock(&consumer_data.lock);
        /* Steal channel identifier, for UST */
        consumer_steal_channel_key(channel->key);
        rcu_read_lock();
+
+       lttng_ht_lookup(consumer_data.channel_ht,
+                       (void *)((unsigned long) channel->key), &iter);
+       node = lttng_ht_iter_get_node_ulong(&iter);
+       if (node != NULL) {
+               /* Channel already exist. Ignore the insertion */
+               goto end;
+       }
+
        lttng_ht_add_unique_ulong(consumer_data.channel_ht, &channel->node);
+
+end:
        rcu_read_unlock();
        pthread_mutex_unlock(&consumer_data.lock);
+
        return 0;
 }
 
@@ -468,18 +926,28 @@ int consumer_add_channel(struct lttng_consumer_channel *channel)
  *
  * Returns the number of fds in the structures.
  */
-int consumer_update_poll_array(
+static int consumer_update_poll_array(
                struct lttng_consumer_local_data *ctx, struct pollfd **pollfd,
-               struct lttng_consumer_stream **local_stream)
+               struct lttng_consumer_stream **local_stream, struct lttng_ht *ht)
 {
        int i = 0;
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;
 
        DBG("Updating poll fd array");
-       cds_lfht_for_each_entry(consumer_data.stream_ht->ht, &iter.iter, stream,
-                       node.node) {
-               if (stream->state != LTTNG_CONSUMER_ACTIVE_STREAM) {
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Only active streams with an active end point can be added to the
+                * poll set and local stream storage of the thread.
+                *
+                * There is a potential race here for endpoint_status to be updated
+                * just after the check. However, this is OK since the stream(s) will
+                * be deleted once the thread is notified that the end point state has
+                * changed where this function will be called back again.
+                */
+               if (stream->state != LTTNG_CONSUMER_ACTIVE_STREAM ||
+                               stream->endpoint_status == CONSUMER_ENDPOINT_INACTIVE) {
                        continue;
                }
                DBG("Active FD %d", stream->wait_fd);
@@ -488,13 +956,14 @@ int consumer_update_poll_array(
                local_stream[i] = stream;
                i++;
        }
+       rcu_read_unlock();
 
        /*
-        * Insert the consumer_poll_pipe at the end of the array and don't
+        * Insert the consumer_data_pipe at the end of the array and don't
         * increment i so nb_fd is the number of real FD.
         */
-       (*pollfd)[i].fd = ctx->consumer_poll_pipe[0];
-       (*pollfd)[i].events = POLLIN;
+       (*pollfd)[i].fd = ctx->consumer_data_pipe[0];
+       (*pollfd)[i].events = POLLIN | POLLPRI;
        return i;
 }
 
@@ -515,10 +984,10 @@ restart:
                if (errno == EINTR) {
                        goto restart;
                }
-               perror("Poll error");
+               PERROR("Poll error");
                goto exit;
        }
-       if (consumer_sockpoll[0].revents == POLLIN) {
+       if (consumer_sockpoll[0].revents & (POLLIN | POLLPRI)) {
                DBG("consumer_should_quit wake up");
                goto exit;
        }
@@ -540,7 +1009,6 @@ void lttng_consumer_set_error_sock(
 /*
  * Set the command socket path.
  */
-
 void lttng_consumer_set_command_sock_path(
                struct lttng_consumer_local_data *ctx, char *sock)
 {
@@ -563,36 +1031,35 @@ int lttng_consumer_send_error(
 }
 
 /*
- * Close all the tracefiles and stream fds, should be called when all instances
- * are destroyed.
+ * Close all the tracefiles and stream fds and MUST be called when all
+ * instances are destroyed i.e. when all threads were joined and are ended.
  */
 void lttng_consumer_cleanup(void)
 {
-       int ret;
        struct lttng_ht_iter iter;
        struct lttng_ht_node_ulong *node;
 
        rcu_read_lock();
 
-       /*
-        * close all outfd. Called when there are no more threads running (after
-        * joining on the threads), no need to protect list iteration with mutex.
-        */
-       cds_lfht_for_each_entry(consumer_data.stream_ht->ht, &iter.iter, node,
-                       node) {
-               ret = lttng_ht_del(consumer_data.stream_ht, &iter);
-               assert(!ret);
-               call_rcu(&node->head, consumer_del_stream_rcu);
-       }
-
        cds_lfht_for_each_entry(consumer_data.channel_ht->ht, &iter.iter, node,
                        node) {
-               ret = lttng_ht_del(consumer_data.channel_ht, &iter);
-               assert(!ret);
-               call_rcu(&node->head, consumer_del_channel_rcu);
+               struct lttng_consumer_channel *channel =
+                       caa_container_of(node, struct lttng_consumer_channel, node);
+               consumer_del_channel(channel);
        }
 
        rcu_read_unlock();
+
+       lttng_ht_destroy(consumer_data.channel_ht);
+
+       cleanup_relayd_ht();
+
+       /*
+        * This HT contains streams that are freed by either the metadata thread or
+        * the data thread so we do *nothing* on the hash table and simply destroy
+        * it.
+        */
+       lttng_ht_destroy(consumer_data.stream_list_ht);
 }
 
 /*
@@ -602,14 +1069,18 @@ void lttng_consumer_should_exit(struct lttng_consumer_local_data *ctx)
 {
        int ret;
        consumer_quit = 1;
-       ret = write(ctx->consumer_should_quit[1], "4", 1);
-       if (ret < 0) {
-               perror("write consumer quit");
+       do {
+               ret = write(ctx->consumer_should_quit[1], "4", 1);
+       } while (ret < 0 && errno == EINTR);
+       if (ret < 0 || ret != 1) {
+               PERROR("write consumer quit");
        }
+
+       DBG("Consumer flag that it should quit");
 }
 
-void lttng_consumer_sync_trace_file(
-               struct lttng_consumer_stream *stream, off_t orig_offset)
+void lttng_consumer_sync_trace_file(struct lttng_consumer_stream *stream,
+               off_t orig_offset)
 {
        int outfd = stream->out_fd;
 
@@ -676,7 +1147,7 @@ struct lttng_consumer_local_data *lttng_consumer_create(
 
        ctx = zmalloc(sizeof(struct lttng_consumer_local_data));
        if (ctx == NULL) {
-               perror("allocating context");
+               PERROR("allocating context");
                goto error;
        }
 
@@ -687,27 +1158,54 @@ struct lttng_consumer_local_data *lttng_consumer_create(
        ctx->on_recv_stream = recv_stream;
        ctx->on_update_stream = update_stream;
 
-       ret = pipe(ctx->consumer_poll_pipe);
+       ret = pipe(ctx->consumer_data_pipe);
        if (ret < 0) {
-               perror("Error creating poll pipe");
+               PERROR("Error creating poll pipe");
                goto error_poll_pipe;
        }
 
+       /* set read end of the pipe to non-blocking */
+       ret = fcntl(ctx->consumer_data_pipe[0], F_SETFL, O_NONBLOCK);
+       if (ret < 0) {
+               PERROR("fcntl O_NONBLOCK");
+               goto error_poll_fcntl;
+       }
+
+       /* set write end of the pipe to non-blocking */
+       ret = fcntl(ctx->consumer_data_pipe[1], F_SETFL, O_NONBLOCK);
+       if (ret < 0) {
+               PERROR("fcntl O_NONBLOCK");
+               goto error_poll_fcntl;
+       }
+
        ret = pipe(ctx->consumer_should_quit);
        if (ret < 0) {
-               perror("Error creating recv pipe");
+               PERROR("Error creating recv pipe");
                goto error_quit_pipe;
        }
 
        ret = pipe(ctx->consumer_thread_pipe);
        if (ret < 0) {
-               perror("Error creating thread pipe");
+               PERROR("Error creating thread pipe");
                goto error_thread_pipe;
        }
 
-       return ctx;
+       ret = utils_create_pipe(ctx->consumer_metadata_pipe);
+       if (ret < 0) {
+               goto error_metadata_pipe;
+       }
+
+       ret = utils_create_pipe(ctx->consumer_splice_metadata_pipe);
+       if (ret < 0) {
+               goto error_splice_pipe;
+       }
 
+       return ctx;
 
+error_splice_pipe:
+       utils_close_pipe(ctx->consumer_metadata_pipe);
+error_metadata_pipe:
+       utils_close_pipe(ctx->consumer_thread_pipe);
 error_thread_pipe:
        for (i = 0; i < 2; i++) {
                int err;
@@ -717,11 +1215,12 @@ error_thread_pipe:
                        PERROR("close");
                }
        }
+error_poll_fcntl:
 error_quit_pipe:
        for (i = 0; i < 2; i++) {
                int err;
 
-               err = close(ctx->consumer_poll_pipe[i]);
+               err = close(ctx->consumer_data_pipe[i]);
                if (err) {
                        PERROR("close");
                }
@@ -739,6 +1238,8 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
 {
        int ret;
 
+       DBG("Consumer destroying it. Closing everything.");
+
        ret = close(ctx->consumer_error_socket);
        if (ret) {
                PERROR("close");
@@ -751,11 +1252,11 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
        if (ret) {
                PERROR("close");
        }
-       ret = close(ctx->consumer_poll_pipe[0]);
+       ret = close(ctx->consumer_data_pipe[0]);
        if (ret) {
                PERROR("close");
        }
-       ret = close(ctx->consumer_poll_pipe[1]);
+       ret = close(ctx->consumer_data_pipe[1]);
        if (ret) {
                PERROR("close");
        }
@@ -767,54 +1268,422 @@ void lttng_consumer_destroy(struct lttng_consumer_local_data *ctx)
        if (ret) {
                PERROR("close");
        }
+       utils_close_pipe(ctx->consumer_splice_metadata_pipe);
+
        unlink(ctx->consumer_command_sock_path);
        free(ctx);
 }
 
 /*
- * Mmap the ring buffer, read it and write the data to the tracefile.
+ * Write the metadata stream id on the specified file descriptor.
+ */
+static int write_relayd_metadata_id(int fd,
+               struct lttng_consumer_stream *stream,
+               struct consumer_relayd_sock_pair *relayd,
+               unsigned long padding)
+{
+       int ret;
+       struct lttcomm_relayd_metadata_payload hdr;
+
+       hdr.stream_id = htobe64(stream->relayd_stream_id);
+       hdr.padding_size = htobe32(padding);
+       do {
+               ret = write(fd, (void *) &hdr, sizeof(hdr));
+       } while (ret < 0 && errno == EINTR);
+       if (ret < 0 || ret != sizeof(hdr)) {
+               /*
+                * This error means that the fd's end is closed so ignore the perror
+                * not to clubber the error output since this can happen in a normal
+                * code path.
+                */
+               if (errno != EPIPE) {
+                       PERROR("write metadata stream id");
+               }
+               DBG3("Consumer failed to write relayd metadata id (errno: %d)", errno);
+               /*
+                * Set ret to a negative value because if ret != sizeof(hdr), we don't
+                * handle writting the missing part so report that as an error and
+                * don't lie to the caller.
+                */
+               ret = -1;
+               goto end;
+       }
+       DBG("Metadata stream id %" PRIu64 " with padding %lu written before data",
+                       stream->relayd_stream_id, padding);
+
+end:
+       return ret;
+}
+
+/*
+ * Mmap the ring buffer, read it and write the data to the tracefile. This is a
+ * core function for writing trace buffers to either the local filesystem or
+ * the network.
+ *
+ * It must be called with the stream lock held.
+ *
+ * Careful review MUST be put if any changes occur!
  *
  * Returns the number of bytes written
  */
 ssize_t lttng_consumer_on_read_subbuffer_mmap(
                struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream, unsigned long len)
+               struct lttng_consumer_stream *stream, unsigned long len,
+               unsigned long padding)
 {
+       unsigned long mmap_offset;
+       ssize_t ret = 0, written = 0;
+       off_t orig_offset = stream->out_fd_offset;
+       /* Default is on the disk */
+       int outfd = stream->out_fd;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       unsigned int relayd_hang_up = 0;
+
+       /* RCU lock for the relayd pointer */
+       rcu_read_lock();
+
+       /* Flag that the current stream if set for network streaming. */
+       if (stream->net_seq_idx != -1) {
+               relayd = consumer_find_relayd(stream->net_seq_idx);
+               if (relayd == NULL) {
+                       goto end;
+               }
+       }
+
+       /* get the offset inside the fd to mmap */
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_on_read_subbuffer_mmap(ctx, stream, len);
+               ret = kernctl_get_mmap_read_offset(stream->wait_fd, &mmap_offset);
+               break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_on_read_subbuffer_mmap(ctx, stream, len);
+               ret = lttng_ustctl_get_mmap_read_offset(stream->chan->handle,
+                               stream->buf, &mmap_offset);
+               break;
        default:
                ERR("Unknown consumer_data type");
                assert(0);
        }
+       if (ret != 0) {
+               errno = -ret;
+               PERROR("tracer ctl get_mmap_read_offset");
+               written = ret;
+               goto end;
+       }
 
-       return 0;
+       /* Handle stream on the relayd if the output is on the network */
+       if (relayd) {
+               unsigned long netlen = len;
+
+               /*
+                * Lock the control socket for the complete duration of the function
+                * since from this point on we will use the socket.
+                */
+               if (stream->metadata_flag) {
+                       /* Metadata requires the control socket. */
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+                       netlen += sizeof(struct lttcomm_relayd_metadata_payload);
+               }
+
+               ret = write_relayd_stream_header(stream, netlen, padding, relayd);
+               if (ret >= 0) {
+                       /* Use the returned socket. */
+                       outfd = ret;
+
+                       /* Write metadata stream id before payload */
+                       if (stream->metadata_flag) {
+                               ret = write_relayd_metadata_id(outfd, stream, relayd, padding);
+                               if (ret < 0) {
+                                       written = ret;
+                                       /* Socket operation failed. We consider the relayd dead */
+                                       if (ret == -EPIPE || ret == -EINVAL) {
+                                               relayd_hang_up = 1;
+                                               goto write_error;
+                                       }
+                                       goto end;
+                               }
+                       }
+               } else {
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (ret == -EPIPE || ret == -EINVAL) {
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
+                       /* Else, use the default set before which is the filesystem. */
+               }
+       } else {
+               /* No streaming, we have to set the len with the full padding */
+               len += padding;
+       }
+
+       while (len > 0) {
+               do {
+                       ret = write(outfd, stream->mmap_base + mmap_offset, len);
+               } while (ret < 0 && errno == EINTR);
+               DBG("Consumer mmap write() ret %zd (len %lu)", ret, len);
+               if (ret < 0) {
+                       /*
+                        * This is possible if the fd is closed on the other side (outfd)
+                        * or any write problem. It can be verbose a bit for a normal
+                        * execution if for instance the relayd is stopped abruptly. This
+                        * can happen so set this to a DBG statement.
+                        */
+                       DBG("Error in file write mmap");
+                       if (written == 0) {
+                               written = ret;
+                       }
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (errno == EPIPE || errno == EINVAL) {
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
+                       goto end;
+               } else if (ret > len) {
+                       PERROR("Error in file write (ret %zd > len %lu)", ret, len);
+                       written += ret;
+                       goto end;
+               } else {
+                       len -= ret;
+                       mmap_offset += ret;
+               }
+
+               /* This call is useless on a socket so better save a syscall. */
+               if (!relayd) {
+                       /* This won't block, but will start writeout asynchronously */
+                       lttng_sync_file_range(outfd, stream->out_fd_offset, ret,
+                                       SYNC_FILE_RANGE_WRITE);
+                       stream->out_fd_offset += ret;
+               }
+               written += ret;
+       }
+       lttng_consumer_sync_trace_file(stream, orig_offset);
+
+write_error:
+       /*
+        * This is a special case that the relayd has closed its socket. Let's
+        * cleanup the relayd object and all associated streams.
+        */
+       if (relayd && relayd_hang_up) {
+               cleanup_relayd(relayd, ctx);
+       }
+
+end:
+       /* Unlock only if ctrl socket used */
+       if (relayd && stream->metadata_flag) {
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+       }
+
+       rcu_read_unlock();
+       return written;
 }
 
 /*
  * Splice the data from the ring buffer to the tracefile.
  *
+ * It must be called with the stream lock held.
+ *
  * Returns the number of bytes spliced.
  */
 ssize_t lttng_consumer_on_read_subbuffer_splice(
                struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream, unsigned long len)
+               struct lttng_consumer_stream *stream, unsigned long len,
+               unsigned long padding)
 {
+       ssize_t ret = 0, written = 0, ret_splice = 0;
+       loff_t offset = 0;
+       off_t orig_offset = stream->out_fd_offset;
+       int fd = stream->wait_fd;
+       /* Default is on the disk */
+       int outfd = stream->out_fd;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       int *splice_pipe;
+       unsigned int relayd_hang_up = 0;
+
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_on_read_subbuffer_splice(ctx, stream, len);
+               break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
+               /* Not supported for user space tracing */
                return -ENOSYS;
        default:
                ERR("Unknown consumer_data type");
                assert(0);
-               return -ENOSYS;
        }
 
+       /* RCU lock for the relayd pointer */
+       rcu_read_lock();
+
+       /* Flag that the current stream if set for network streaming. */
+       if (stream->net_seq_idx != -1) {
+               relayd = consumer_find_relayd(stream->net_seq_idx);
+               if (relayd == NULL) {
+                       goto end;
+               }
+       }
+
+       /*
+        * Choose right pipe for splice. Metadata and trace data are handled by
+        * different threads hence the use of two pipes in order not to race or
+        * corrupt the written data.
+        */
+       if (stream->metadata_flag) {
+               splice_pipe = ctx->consumer_splice_metadata_pipe;
+       } else {
+               splice_pipe = ctx->consumer_thread_pipe;
+       }
+
+       /* Write metadata stream id before payload */
+       if (relayd) {
+               int total_len = len;
+
+               if (stream->metadata_flag) {
+                       /*
+                        * Lock the control socket for the complete duration of the function
+                        * since from this point on we will use the socket.
+                        */
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+
+                       ret = write_relayd_metadata_id(splice_pipe[1], stream, relayd,
+                                       padding);
+                       if (ret < 0) {
+                               written = ret;
+                               /* Socket operation failed. We consider the relayd dead */
+                               if (ret == -EBADF) {
+                                       WARN("Remote relayd disconnected. Stopping");
+                                       relayd_hang_up = 1;
+                                       goto write_error;
+                               }
+                               goto end;
+                       }
+
+                       total_len += sizeof(struct lttcomm_relayd_metadata_payload);
+               }
+
+               ret = write_relayd_stream_header(stream, total_len, padding, relayd);
+               if (ret >= 0) {
+                       /* Use the returned socket. */
+                       outfd = ret;
+               } else {
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (ret == -EBADF) {
+                               WARN("Remote relayd disconnected. Stopping");
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
+                       goto end;
+               }
+       } else {
+               /* No streaming, we have to set the len with the full padding */
+               len += padding;
+       }
+
+       while (len > 0) {
+               DBG("splice chan to pipe offset %lu of len %lu (fd : %d, pipe: %d)",
+                               (unsigned long)offset, len, fd, splice_pipe[1]);
+               ret_splice = splice(fd, &offset, splice_pipe[1], NULL, len,
+                               SPLICE_F_MOVE | SPLICE_F_MORE);
+               DBG("splice chan to pipe, ret %zd", ret_splice);
+               if (ret_splice < 0) {
+                       PERROR("Error in relay splice");
+                       if (written == 0) {
+                               written = ret_splice;
+                       }
+                       ret = errno;
+                       goto splice_error;
+               }
+
+               /* Handle stream on the relayd if the output is on the network */
+               if (relayd) {
+                       if (stream->metadata_flag) {
+                               size_t metadata_payload_size =
+                                       sizeof(struct lttcomm_relayd_metadata_payload);
+
+                               /* Update counter to fit the spliced data */
+                               ret_splice += metadata_payload_size;
+                               len += metadata_payload_size;
+                               /*
+                                * We do this so the return value can match the len passed as
+                                * argument to this function.
+                                */
+                               written -= metadata_payload_size;
+                       }
+               }
+
+               /* Splice data out */
+               ret_splice = splice(splice_pipe[0], NULL, outfd, NULL,
+                               ret_splice, SPLICE_F_MOVE | SPLICE_F_MORE);
+               DBG("Consumer splice pipe to file, ret %zd", ret_splice);
+               if (ret_splice < 0) {
+                       PERROR("Error in file splice");
+                       if (written == 0) {
+                               written = ret_splice;
+                       }
+                       /* Socket operation failed. We consider the relayd dead */
+                       if (errno == EBADF || errno == EPIPE) {
+                               WARN("Remote relayd disconnected. Stopping");
+                               relayd_hang_up = 1;
+                               goto write_error;
+                       }
+                       ret = errno;
+                       goto splice_error;
+               } else if (ret_splice > len) {
+                       errno = EINVAL;
+                       PERROR("Wrote more data than requested %zd (len: %lu)",
+                                       ret_splice, len);
+                       written += ret_splice;
+                       ret = errno;
+                       goto splice_error;
+               }
+               len -= ret_splice;
+
+               /* This call is useless on a socket so better save a syscall. */
+               if (!relayd) {
+                       /* This won't block, but will start writeout asynchronously */
+                       lttng_sync_file_range(outfd, stream->out_fd_offset, ret_splice,
+                                       SYNC_FILE_RANGE_WRITE);
+                       stream->out_fd_offset += ret_splice;
+               }
+               written += ret_splice;
+       }
+       lttng_consumer_sync_trace_file(stream, orig_offset);
+
+       ret = ret_splice;
+
+       goto end;
+
+write_error:
+       /*
+        * This is a special case that the relayd has closed its socket. Let's
+        * cleanup the relayd object and all associated streams.
+        */
+       if (relayd && relayd_hang_up) {
+               cleanup_relayd(relayd, ctx);
+               /* Skip splice error so the consumer does not fail */
+               goto end;
+       }
+
+splice_error:
+       /* send the appropriate error description to sessiond */
+       switch (ret) {
+       case EINVAL:
+               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_SPLICE_EINVAL);
+               break;
+       case ENOMEM:
+               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_SPLICE_ENOMEM);
+               break;
+       case ESPIPE:
+               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_SPLICE_ESPIPE);
+               break;
+       }
+
+end:
+       if (relayd && stream->metadata_flag) {
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+       }
+
+       rcu_read_unlock();
+       return written;
 }
 
 /*
@@ -837,65 +1706,569 @@ int lttng_consumer_take_snapshot(struct lttng_consumer_local_data *ctx,
                return -ENOSYS;
        }
 
-}
+}
+
+/*
+ * Get the produced position
+ *
+ * Returns 0 on success, < 0 on error
+ */
+int lttng_consumer_get_produced_snapshot(
+               struct lttng_consumer_local_data *ctx,
+               struct lttng_consumer_stream *stream,
+               unsigned long *pos)
+{
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               return lttng_kconsumer_get_produced_snapshot(ctx, stream, pos);
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               return lttng_ustconsumer_get_produced_snapshot(ctx, stream, pos);
+       default:
+               ERR("Unknown consumer_data type");
+               assert(0);
+               return -ENOSYS;
+       }
+}
+
+int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
+               int sock, struct pollfd *consumer_sockpoll)
+{
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               return lttng_kconsumer_recv_cmd(ctx, sock, consumer_sockpoll);
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               return lttng_ustconsumer_recv_cmd(ctx, sock, consumer_sockpoll);
+       default:
+               ERR("Unknown consumer_data type");
+               assert(0);
+               return -ENOSYS;
+       }
+}
+
+/*
+ * Iterate over all streams of the hashtable and free them properly.
+ *
+ * WARNING: *MUST* be used with data stream only.
+ */
+static void destroy_data_stream_ht(struct lttng_ht *ht)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       if (ht == NULL) {
+               return;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Ignore return value since we are currently cleaning up so any error
+                * can't be handled.
+                */
+               (void) consumer_del_stream(stream, ht);
+       }
+       rcu_read_unlock();
+
+       lttng_ht_destroy(ht);
+}
+
+/*
+ * Iterate over all streams of the hashtable and free them properly.
+ *
+ * XXX: Should not be only for metadata stream or else use an other name.
+ */
+static void destroy_stream_ht(struct lttng_ht *ht)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       if (ht == NULL) {
+               return;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(ht->ht, &iter.iter, stream, node.node) {
+               /*
+                * Ignore return value since we are currently cleaning up so any error
+                * can't be handled.
+                */
+               (void) consumer_del_metadata_stream(stream, ht);
+       }
+       rcu_read_unlock();
+
+       lttng_ht_destroy(ht);
+}
+
+/*
+ * Clean up a metadata stream and free its memory.
+ */
+void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
+               struct lttng_ht *ht)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_channel *free_chan = NULL;
+       struct consumer_relayd_sock_pair *relayd;
+
+       assert(stream);
+       /*
+        * This call should NEVER receive regular stream. It must always be
+        * metadata stream and this is crucial for data structure synchronization.
+        */
+       assert(stream->metadata_flag);
+
+       DBG3("Consumer delete metadata stream %d", stream->wait_fd);
+
+       if (ht == NULL) {
+               /* Means the stream was allocated but not successfully added */
+               goto free_stream;
+       }
+
+       pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
+
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               if (stream->mmap_base != NULL) {
+                       ret = munmap(stream->mmap_base, stream->mmap_len);
+                       if (ret != 0) {
+                               PERROR("munmap metadata stream");
+                       }
+               }
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               lttng_ustconsumer_del_stream(stream);
+               break;
+       default:
+               ERR("Unknown consumer_data type");
+               assert(0);
+               goto end;
+       }
+
+       rcu_read_lock();
+       iter.iter.node = &stream->node.node;
+       ret = lttng_ht_del(ht, &iter);
+       assert(!ret);
+
+       /* Remove node session id from the consumer_data stream ht */
+       iter.iter.node = &stream->node_session_id.node;
+       ret = lttng_ht_del(consumer_data.stream_list_ht, &iter);
+       assert(!ret);
+       rcu_read_unlock();
+
+       if (stream->out_fd >= 0) {
+               ret = close(stream->out_fd);
+               if (ret) {
+                       PERROR("close");
+               }
+       }
+
+       if (stream->wait_fd >= 0 && !stream->wait_fd_is_copy) {
+               ret = close(stream->wait_fd);
+               if (ret) {
+                       PERROR("close");
+               }
+       }
+
+       if (stream->shm_fd >= 0 && stream->wait_fd != stream->shm_fd) {
+               ret = close(stream->shm_fd);
+               if (ret) {
+                       PERROR("close");
+               }
+       }
+
+       /* Check and cleanup relayd */
+       rcu_read_lock();
+       relayd = consumer_find_relayd(stream->net_seq_idx);
+       if (relayd != NULL) {
+               uatomic_dec(&relayd->refcount);
+               assert(uatomic_read(&relayd->refcount) >= 0);
+
+               /* Closing streams requires to lock the control socket. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_send_close_stream(&relayd->control_sock,
+                               stream->relayd_stream_id, stream->next_net_seq_num - 1);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       DBG("Unable to close stream on the relayd. Continuing");
+                       /*
+                        * Continue here. There is nothing we can do for the relayd.
+                        * Chances are that the relayd has closed the socket so we just
+                        * continue cleaning up.
+                        */
+               }
+
+               /* Both conditions are met, we destroy the relayd. */
+               if (uatomic_read(&relayd->refcount) == 0 &&
+                               uatomic_read(&relayd->destroy_flag)) {
+                       destroy_relayd(relayd);
+               }
+       }
+       rcu_read_unlock();
+
+       /* Atomically decrement channel refcount since other threads can use it. */
+       uatomic_dec(&stream->chan->refcount);
+       if (!uatomic_read(&stream->chan->refcount)
+                       && !uatomic_read(&stream->chan->nb_init_streams)) {
+               /* Go for channel deletion! */
+               free_chan = stream->chan;
+       }
+
+end:
+       pthread_mutex_unlock(&stream->lock);
+       pthread_mutex_unlock(&consumer_data.lock);
+
+       if (free_chan) {
+               consumer_del_channel(free_chan);
+       }
+
+free_stream:
+       call_rcu(&stream->node.head, consumer_free_stream);
+}
+
+/*
+ * Action done with the metadata stream when adding it to the consumer internal
+ * data structures to handle it.
+ */
+static int consumer_add_metadata_stream(struct lttng_consumer_stream *stream,
+               struct lttng_ht *ht)
+{
+       int ret = 0;
+       struct consumer_relayd_sock_pair *relayd;
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_ulong *node;
+
+       assert(stream);
+       assert(ht);
+
+       DBG3("Adding metadata stream %d to hash table", stream->wait_fd);
+
+       pthread_mutex_lock(&consumer_data.lock);
+       pthread_mutex_lock(&stream->lock);
+
+       /*
+        * From here, refcounts are updated so be _careful_ when returning an error
+        * after this point.
+        */
+
+       rcu_read_lock();
+
+       /*
+        * Lookup the stream just to make sure it does not exist in our internal
+        * state. This should NEVER happen.
+        */
+       lttng_ht_lookup(ht, (void *)((unsigned long) stream->wait_fd), &iter);
+       node = lttng_ht_iter_get_node_ulong(&iter);
+       assert(!node);
+
+       /* Find relayd and, if one is found, increment refcount. */
+       relayd = consumer_find_relayd(stream->net_seq_idx);
+       if (relayd != NULL) {
+               uatomic_inc(&relayd->refcount);
+       }
+
+       /* Update channel refcount once added without error(s). */
+       uatomic_inc(&stream->chan->refcount);
+
+       /*
+        * When nb_init_streams reaches 0, we don't need to trigger any action in
+        * terms of destroying the associated channel, because the action that
+        * causes the count to become 0 also causes a stream to be added. The
+        * channel deletion will thus be triggered by the following removal of this
+        * stream.
+        */
+       if (uatomic_read(&stream->chan->nb_init_streams) > 0) {
+               uatomic_dec(&stream->chan->nb_init_streams);
+       }
+
+       lttng_ht_add_unique_ulong(ht, &stream->node);
+
+       /*
+        * Add stream to the stream_list_ht of the consumer data. No need to steal
+        * the key since the HT does not use it and we allow to add redundant keys
+        * into this table.
+        */
+       lttng_ht_add_ulong(consumer_data.stream_list_ht, &stream->node_session_id);
+
+       rcu_read_unlock();
+
+       pthread_mutex_unlock(&stream->lock);
+       pthread_mutex_unlock(&consumer_data.lock);
+       return ret;
+}
+
+/*
+ * Delete data stream that are flagged for deletion (endpoint_status).
+ */
+static void validate_endpoint_status_data_stream(void)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer delete flagged data stream");
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(data_ht->ht, &iter.iter, stream, node.node) {
+               /* Validate delete flag of the stream */
+               if (stream->endpoint_status == CONSUMER_ENDPOINT_ACTIVE) {
+                       continue;
+               }
+               /* Delete it right now */
+               consumer_del_stream(stream, data_ht);
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Delete metadata stream that are flagged for deletion (endpoint_status).
+ */
+static void validate_endpoint_status_metadata_stream(
+               struct lttng_poll_event *pollset)
+{
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_stream *stream;
+
+       DBG("Consumer delete flagged metadata stream");
+
+       assert(pollset);
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry(metadata_ht->ht, &iter.iter, stream, node.node) {
+               /* Validate delete flag of the stream */
+               if (stream->endpoint_status == CONSUMER_ENDPOINT_ACTIVE) {
+                       continue;
+               }
+               /*
+                * Remove from pollset so the metadata thread can continue without
+                * blocking on a deleted stream.
+                */
+               lttng_poll_del(pollset, stream->wait_fd);
+
+               /* Delete it right now */
+               consumer_del_metadata_stream(stream, metadata_ht);
+       }
+       rcu_read_unlock();
+}
+
+/*
+ * Thread polls on metadata file descriptor and write them on disk or on the
+ * network.
+ */
+void *consumer_thread_metadata_poll(void *data)
+{
+       int ret, i, pollfd;
+       uint32_t revents, nb_fd;
+       struct lttng_consumer_stream *stream = NULL;
+       struct lttng_ht_iter iter;
+       struct lttng_ht_node_ulong *node;
+       struct lttng_poll_event events;
+       struct lttng_consumer_local_data *ctx = data;
+       ssize_t len;
+
+       rcu_register_thread();
+
+       metadata_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       if (!metadata_ht) {
+               /* ENOMEM at this point. Better to bail out. */
+               goto error;
+       }
+
+       DBG("Thread metadata poll started");
+
+       /* Size is set to 1 for the consumer_metadata pipe */
+       ret = lttng_poll_create(&events, 2, LTTNG_CLOEXEC);
+       if (ret < 0) {
+               ERR("Poll set creation failed");
+               goto end;
+       }
+
+       ret = lttng_poll_add(&events, ctx->consumer_metadata_pipe[0], LPOLLIN);
+       if (ret < 0) {
+               goto end;
+       }
+
+       /* Main loop */
+       DBG("Metadata main loop started");
+
+       while (1) {
+               /* Only the metadata pipe is set */
+               if (LTTNG_POLL_GETNB(&events) == 0 && consumer_quit == 1) {
+                       goto end;
+               }
+
+restart:
+               DBG("Metadata poll wait with %d fd(s)", LTTNG_POLL_GETNB(&events));
+               ret = lttng_poll_wait(&events, -1);
+               DBG("Metadata event catched in thread");
+               if (ret < 0) {
+                       if (errno == EINTR) {
+                               ERR("Poll EINTR catched");
+                               goto restart;
+                       }
+                       goto error;
+               }
+
+               nb_fd = ret;
+
+               /* From here, the event is a metadata wait fd */
+               for (i = 0; i < nb_fd; i++) {
+                       revents = LTTNG_POLL_GETEV(&events, i);
+                       pollfd = LTTNG_POLL_GETFD(&events, i);
+
+                       /* Just don't waste time if no returned events for the fd */
+                       if (!revents) {
+                               continue;
+                       }
+
+                       if (pollfd == ctx->consumer_metadata_pipe[0]) {
+                               if (revents & (LPOLLERR | LPOLLHUP )) {
+                                       DBG("Metadata thread pipe hung up");
+                                       /*
+                                        * Remove the pipe from the poll set and continue the loop
+                                        * since their might be data to consume.
+                                        */
+                                       lttng_poll_del(&events, ctx->consumer_metadata_pipe[0]);
+                                       ret = close(ctx->consumer_metadata_pipe[0]);
+                                       if (ret < 0) {
+                                               PERROR("close metadata pipe");
+                                       }
+                                       continue;
+                               } else if (revents & LPOLLIN) {
+                                       do {
+                                               /* Get the stream pointer received */
+                                               ret = read(pollfd, &stream, sizeof(stream));
+                                       } while (ret < 0 && errno == EINTR);
+                                       if (ret < 0 ||
+                                                       ret < sizeof(struct lttng_consumer_stream *)) {
+                                               PERROR("read metadata stream");
+                                               /*
+                                                * Let's continue here and hope we can still work
+                                                * without stopping the consumer. XXX: Should we?
+                                                */
+                                               continue;
+                                       }
+
+                                       /* A NULL stream means that the state has changed. */
+                                       if (stream == NULL) {
+                                               /* Check for deleted streams. */
+                                               validate_endpoint_status_metadata_stream(&events);
+                                               continue;
+                                       }
+
+                                       DBG("Adding metadata stream %d to poll set",
+                                                       stream->wait_fd);
+
+                                       ret = consumer_add_metadata_stream(stream, metadata_ht);
+                                       if (ret) {
+                                               ERR("Unable to add metadata stream");
+                                               /* Stream was not setup properly. Continuing. */
+                                               consumer_del_metadata_stream(stream, NULL);
+                                               continue;
+                                       }
+
+                                       /* Add metadata stream to the global poll events list */
+                                       lttng_poll_add(&events, stream->wait_fd,
+                                                       LPOLLIN | LPOLLPRI);
+                               }
+
+                               /* Handle other stream */
+                               continue;
+                       }
 
-/*
- * Get the produced position
- *
- * Returns 0 on success, < 0 on error
- */
-int lttng_consumer_get_produced_snapshot(
-               struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream,
-               unsigned long *pos)
-{
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_get_produced_snapshot(ctx, stream, pos);
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_get_produced_snapshot(ctx, stream, pos);
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               return -ENOSYS;
-       }
-}
+                       rcu_read_lock();
+                       lttng_ht_lookup(metadata_ht, (void *)((unsigned long) pollfd),
+                                       &iter);
+                       node = lttng_ht_iter_get_node_ulong(&iter);
+                       assert(node);
+
+                       stream = caa_container_of(node, struct lttng_consumer_stream,
+                                       node);
+
+                       /* Check for error event */
+                       if (revents & (LPOLLERR | LPOLLHUP)) {
+                               DBG("Metadata fd %d is hup|err.", pollfd);
+                               if (!stream->hangup_flush_done
+                                               && (consumer_data.type == LTTNG_CONSUMER32_UST
+                                                       || consumer_data.type == LTTNG_CONSUMER64_UST)) {
+                                       DBG("Attempting to flush and consume the UST buffers");
+                                       lttng_ustconsumer_on_stream_hangup(stream);
+
+                                       /* We just flushed the stream now read it. */
+                                       do {
+                                               len = ctx->on_buffer_ready(stream, ctx);
+                                               /*
+                                                * We don't check the return value here since if we get
+                                                * a negative len, it means an error occured thus we
+                                                * simply remove it from the poll set and free the
+                                                * stream.
+                                                */
+                                       } while (len > 0);
+                               }
 
-int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
-               int sock, struct pollfd *consumer_sockpoll)
-{
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_recv_cmd(ctx, sock, consumer_sockpoll);
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_recv_cmd(ctx, sock, consumer_sockpoll);
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               return -ENOSYS;
+                               lttng_poll_del(&events, stream->wait_fd);
+                               /*
+                                * This call update the channel states, closes file descriptors
+                                * and securely free the stream.
+                                */
+                               consumer_del_metadata_stream(stream, metadata_ht);
+                       } else if (revents & (LPOLLIN | LPOLLPRI)) {
+                               /* Get the data out of the metadata file descriptor */
+                               DBG("Metadata available on fd %d", pollfd);
+                               assert(stream->wait_fd == pollfd);
+
+                               len = ctx->on_buffer_ready(stream, ctx);
+                               /* It's ok to have an unavailable sub-buffer */
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean up stream from consumer and free it. */
+                                       lttng_poll_del(&events, stream->wait_fd);
+                                       consumer_del_metadata_stream(stream, metadata_ht);
+                               } else if (len > 0) {
+                                       stream->data_read = 1;
+                               }
+                       }
+
+                       /* Release RCU lock for the stream looked up */
+                       rcu_read_unlock();
+               }
        }
+
+error:
+end:
+       DBG("Metadata poll thread exiting");
+       lttng_poll_clean(&events);
+
+       destroy_stream_ht(metadata_ht);
+
+       rcu_unregister_thread();
+       return NULL;
 }
 
 /*
  * This thread polls the fds in the set to consume the data and write
  * it to tracefile if necessary.
  */
-void *lttng_consumer_thread_poll_fds(void *data)
+void *consumer_thread_data_poll(void *data)
 {
        int num_rdy, num_hup, high_prio, ret, i;
        struct pollfd *pollfd = NULL;
        /* local view of the streams */
-       struct lttng_consumer_stream **local_stream = NULL;
+       struct lttng_consumer_stream **local_stream = NULL, *new_stream = NULL;
        /* local view of consumer_data.fds_count */
        int nb_fd = 0;
-       char tmp;
-       int tmp2;
        struct lttng_consumer_local_data *ctx = data;
+       ssize_t len;
 
        rcu_register_thread();
 
+       data_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       if (data_ht == NULL) {
+               /* ENOMEM at this point. Better to bail out. */
+               goto end;
+       }
+
        local_stream = zmalloc(sizeof(struct lttng_consumer_stream));
 
        while (1) {
@@ -917,26 +2290,27 @@ void *lttng_consumer_thread_poll_fds(void *data)
                                local_stream = NULL;
                        }
 
-                       /* allocate for all fds + 1 for the consumer_poll_pipe */
+                       /* allocate for all fds + 1 for the consumer_data_pipe */
                        pollfd = zmalloc((consumer_data.stream_count + 1) * sizeof(struct pollfd));
                        if (pollfd == NULL) {
-                               perror("pollfd malloc");
+                               PERROR("pollfd malloc");
                                pthread_mutex_unlock(&consumer_data.lock);
                                goto end;
                        }
 
-                       /* allocate for all fds + 1 for the consumer_poll_pipe */
+                       /* allocate for all fds + 1 for the consumer_data_pipe */
                        local_stream = zmalloc((consumer_data.stream_count + 1) *
                                        sizeof(struct lttng_consumer_stream));
                        if (local_stream == NULL) {
-                               perror("local_stream malloc");
+                               PERROR("local_stream malloc");
                                pthread_mutex_unlock(&consumer_data.lock);
                                goto end;
                        }
-                       ret = consumer_update_poll_array(ctx, &pollfd, local_stream);
+                       ret = consumer_update_poll_array(ctx, &pollfd, local_stream,
+                                       data_ht);
                        if (ret < 0) {
                                ERR("Error in allocating pollfd or local_outfds");
-                               lttng_consumer_send_error(ctx, CONSUMERD_POLL_ERROR);
+                               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_POLL_ERROR);
                                pthread_mutex_unlock(&consumer_data.lock);
                                goto end;
                        }
@@ -952,7 +2326,7 @@ void *lttng_consumer_thread_poll_fds(void *data)
                /* poll on the array of fds */
        restart:
                DBG("polling on %d fd", nb_fd + 1);
-               num_rdy = poll(pollfd, nb_fd + 1, consumer_poll_timeout);
+               num_rdy = poll(pollfd, nb_fd + 1, -1);
                DBG("poll num_rdy : %d", num_rdy);
                if (num_rdy == -1) {
                        /*
@@ -961,8 +2335,8 @@ void *lttng_consumer_thread_poll_fds(void *data)
                        if (errno == EINTR) {
                                goto restart;
                        }
-                       perror("Poll error");
-                       lttng_consumer_send_error(ctx, CONSUMERD_POLL_ERROR);
+                       PERROR("Poll error");
+                       lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_POLL_ERROR);
                        goto end;
                } else if (num_rdy == 0) {
                        DBG("Polling thread timed out");
@@ -970,31 +2344,64 @@ void *lttng_consumer_thread_poll_fds(void *data)
                }
 
                /*
-                * If the consumer_poll_pipe triggered poll go
-                * directly to the beginning of the loop to update the
-                * array. We want to prioritize array update over
-                * low-priority reads.
+                * If the consumer_data_pipe triggered poll go directly to the
+                * beginning of the loop to update the array. We want to prioritize
+                * array update over low-priority reads.
                 */
-               if (pollfd[nb_fd].revents & POLLIN) {
-                       DBG("consumer_poll_pipe wake up");
-                       tmp2 = read(ctx->consumer_poll_pipe[0], &tmp, 1);
-                       if (tmp2 < 0) {
-                               perror("read consumer poll");
+               if (pollfd[nb_fd].revents & (POLLIN | POLLPRI)) {
+                       size_t pipe_readlen;
+
+                       DBG("consumer_data_pipe wake up");
+                       /* Consume 1 byte of pipe data */
+                       do {
+                               pipe_readlen = read(ctx->consumer_data_pipe[0], &new_stream,
+                                               sizeof(new_stream));
+                       } while (pipe_readlen == -1 && errno == EINTR);
+                       if (pipe_readlen < 0) {
+                               PERROR("read consumer data pipe");
+                               /* Continue so we can at least handle the current stream(s). */
+                               continue;
+                       }
+
+                       /*
+                        * If the stream is NULL, just ignore it. It's also possible that
+                        * the sessiond poll thread changed the consumer_quit state and is
+                        * waking us up to test it.
+                        */
+                       if (new_stream == NULL) {
+                               validate_endpoint_status_data_stream();
+                               continue;
+                       }
+
+                       ret = consumer_add_stream(new_stream, data_ht);
+                       if (ret) {
+                               ERR("Consumer add stream %d failed. Continuing",
+                                               new_stream->key);
+                               /*
+                                * At this point, if the add_stream fails, it is not in the
+                                * hash table thus passing the NULL value here.
+                                */
+                               consumer_del_stream(new_stream, NULL);
                        }
+
+                       /* Continue to update the local streams and handle prio ones */
                        continue;
                }
 
                /* Take care of high priority channels first. */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if (pollfd[i].revents & POLLPRI) {
-                               ssize_t len;
-
                                DBG("Urgent read on fd %d", pollfd[i].fd);
                                high_prio = 1;
                                len = ctx->on_buffer_ready(local_stream[i], ctx);
                                /* it's ok to have an unavailable sub-buffer */
-                               if (len < 0 && len != -EAGAIN) {
-                                       goto end;
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean the stream and free it. */
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                } else if (len > 0) {
                                        local_stream[i]->data_read = 1;
                                }
@@ -1011,17 +2418,18 @@ void *lttng_consumer_thread_poll_fds(void *data)
 
                /* Take care of low priority channels. */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if ((pollfd[i].revents & POLLIN) ||
                                        local_stream[i]->hangup_flush_done) {
-                               ssize_t len;
-
-                               assert(!(pollfd[i].revents & POLLERR));
-                               assert(!(pollfd[i].revents & POLLNVAL));
                                DBG("Normal read on fd %d", pollfd[i].fd);
                                len = ctx->on_buffer_ready(local_stream[i], ctx);
                                /* it's ok to have an unavailable sub-buffer */
-                               if (len < 0 && len != -EAGAIN) {
-                                       goto end;
+                               if (len < 0 && len != -EAGAIN && len != -ENODATA) {
+                                       /* Clean the stream and free it. */
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                } else if (len > 0) {
                                        local_stream[i]->data_read = 1;
                                }
@@ -1030,12 +2438,15 @@ void *lttng_consumer_thread_poll_fds(void *data)
 
                /* Handle hangup and errors */
                for (i = 0; i < nb_fd; i++) {
+                       if (local_stream[i] == NULL) {
+                               continue;
+                       }
                        if (!local_stream[i]->hangup_flush_done
                                        && (pollfd[i].revents & (POLLHUP | POLLERR | POLLNVAL))
                                        && (consumer_data.type == LTTNG_CONSUMER32_UST
                                                || consumer_data.type == LTTNG_CONSUMER64_UST)) {
                                DBG("fd %d is hup|err|nval. Attempting flush and read.",
-                                       pollfd[i].fd);
+                                               pollfd[i].fd);
                                lttng_ustconsumer_on_stream_hangup(local_stream[i]);
                                /* Attempt read again, for the data we just flushed. */
                                local_stream[i]->data_read = 1;
@@ -1048,29 +2459,28 @@ void *lttng_consumer_thread_poll_fds(void *data)
                        if ((pollfd[i].revents & POLLHUP)) {
                                DBG("Polling fd %d tells it has hung up.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       rcu_read_lock();
-                                       consumer_del_stream_rcu(&local_stream[i]->node.head);
-                                       rcu_read_unlock();
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        } else if (pollfd[i].revents & POLLERR) {
                                ERR("Error returned in polling fd %d.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       rcu_read_lock();
-                                       consumer_del_stream_rcu(&local_stream[i]->node.head);
-                                       rcu_read_unlock();
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        } else if (pollfd[i].revents & POLLNVAL) {
                                ERR("Polling fd %d tells fd is not open.", pollfd[i].fd);
                                if (!local_stream[i]->data_read) {
-                                       rcu_read_lock();
-                                       consumer_del_stream_rcu(&local_stream[i]->node.head);
-                                       rcu_read_unlock();
+                                       consumer_del_stream(local_stream[i], data_ht);
+                                       local_stream[i] = NULL;
                                        num_hup++;
                                }
                        }
-                       local_stream[i]->data_read = 0;
+                       if (local_stream[i] != NULL) {
+                               local_stream[i]->data_read = 0;
+                       }
                }
        }
 end:
@@ -1083,6 +2493,22 @@ end:
                free(local_stream);
                local_stream = NULL;
        }
+
+       /*
+        * Close the write side of the pipe so epoll_wait() in
+        * consumer_thread_metadata_poll can catch it. The thread is monitoring the
+        * read side of the pipe. If we close them both, epoll_wait strangely does
+        * not return and could create a endless wait period if the pipe is the
+        * only tracked fd in the poll set. The thread will take care of closing
+        * the read side.
+        */
+       ret = close(ctx->consumer_metadata_pipe[1]);
+       if (ret < 0) {
+               PERROR("close data pipe");
+       }
+
+       destroy_data_stream_ht(data_ht);
+
        rcu_unregister_thread();
        return NULL;
 }
@@ -1091,9 +2517,9 @@ end:
  * This thread listens on the consumerd socket and receives the file
  * descriptors from the session daemon.
  */
-void *lttng_consumer_thread_receive_fds(void *data)
+void *consumer_thread_sessiond_poll(void *data)
 {
-       int sock, client_socket, ret;
+       int sock = -1, client_socket, ret;
        /*
         * structure to poll for incoming data on communication socket avoids
         * making blocking sockets.
@@ -1117,7 +2543,7 @@ void *lttng_consumer_thread_receive_fds(void *data)
        }
 
        DBG("Sending ready command to lttng-sessiond");
-       ret = lttng_consumer_send_error(ctx, CONSUMERD_COMMAND_SOCK_READY);
+       ret = lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_COMMAND_SOCK_READY);
        /* return < 0 on error, but == 0 is not fatal */
        if (ret < 0) {
                ERR("Error sending ready command to lttng-sessiond");
@@ -1126,7 +2552,7 @@ void *lttng_consumer_thread_receive_fds(void *data)
 
        ret = fcntl(client_socket, F_SETFL, O_NONBLOCK);
        if (ret < 0) {
-               perror("fcntl O_NONBLOCK");
+               PERROR("fcntl O_NONBLOCK");
                goto end;
        }
 
@@ -1143,16 +2569,23 @@ void *lttng_consumer_thread_receive_fds(void *data)
 
        /* Blocking call, waiting for transmission */
        sock = lttcomm_accept_unix_sock(client_socket);
-       if (sock <= 0) {
+       if (sock < 0) {
                WARN("On accept");
                goto end;
        }
        ret = fcntl(sock, F_SETFL, O_NONBLOCK);
        if (ret < 0) {
-               perror("fcntl O_NONBLOCK");
+               PERROR("fcntl O_NONBLOCK");
                goto end;
        }
 
+       /* This socket is not useful anymore. */
+       ret = close(client_socket);
+       if (ret < 0) {
+               PERROR("close client_socket");
+       }
+       client_socket = -1;
+
        /* update the polling structure to poll on the established socket */
        consumer_sockpoll[1].fd = sock;
        consumer_sockpoll[1].events = POLLIN | POLLPRI;
@@ -1167,8 +2600,12 @@ void *lttng_consumer_thread_receive_fds(void *data)
                        DBG("Received STOP command");
                        goto end;
                }
-               if (ret < 0) {
-                       ERR("Communication interrupted on command socket");
+               if (ret <= 0) {
+                       /*
+                        * This could simply be a session daemon quitting. Don't output
+                        * ERR() here.
+                        */
+                       DBG("Communication interrupted on command socket");
                        goto end;
                }
                if (consumer_quit) {
@@ -1187,17 +2624,25 @@ end:
        consumer_quit = 1;
 
        /*
-        * 2s of grace period, if no polling events occur during
-        * this period, the polling thread will exit even if there
-        * are still open FDs (should not happen, but safety mechanism).
+        * Notify the data poll thread to poll back again and test the
+        * consumer_quit state that we just set so to quit gracefully.
         */
-       consumer_poll_timeout = LTTNG_CONSUMER_POLL_TIMEOUT;
+       notify_thread_pipe(ctx->consumer_data_pipe[1]);
 
-       /* wake up the polling thread */
-       ret = write(ctx->consumer_poll_pipe[1], "4", 1);
-       if (ret < 0) {
-               perror("poll pipe write");
+       /* Cleaning up possibly open sockets. */
+       if (sock >= 0) {
+               ret = close(sock);
+               if (ret < 0) {
+                       PERROR("close sock sessiond poll");
+               }
        }
+       if (client_socket >= 0) {
+               ret = close(sock);
+               if (ret < 0) {
+                       PERROR("close client_socket sessiond poll");
+               }
+       }
+
        rcu_unregister_thread();
        return NULL;
 }
@@ -1205,17 +2650,27 @@ end:
 ssize_t lttng_consumer_read_subbuffer(struct lttng_consumer_stream *stream,
                struct lttng_consumer_local_data *ctx)
 {
+       ssize_t ret;
+
+       pthread_mutex_lock(&stream->lock);
+
        switch (consumer_data.type) {
        case LTTNG_CONSUMER_KERNEL:
-               return lttng_kconsumer_read_subbuffer(stream, ctx);
+               ret = lttng_kconsumer_read_subbuffer(stream, ctx);
+               break;
        case LTTNG_CONSUMER32_UST:
        case LTTNG_CONSUMER64_UST:
-               return lttng_ustconsumer_read_subbuffer(stream, ctx);
+               ret = lttng_ustconsumer_read_subbuffer(stream, ctx);
+               break;
        default:
                ERR("Unknown consumer_data type");
                assert(0);
-               return -ENOSYS;
+               ret = -ENOSYS;
+               break;
        }
+
+       pthread_mutex_unlock(&stream->lock);
+       return ret;
 }
 
 int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream)
@@ -1238,7 +2693,361 @@ int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream)
  */
 void lttng_consumer_init(void)
 {
-       consumer_data.stream_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
        consumer_data.channel_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       consumer_data.relayd_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+       consumer_data.stream_list_ht = lttng_ht_new(0, LTTNG_HT_TYPE_ULONG);
+}
+
+/*
+ * Process the ADD_RELAYD command receive by a consumer.
+ *
+ * This will create a relayd socket pair and add it to the relayd hash table.
+ * The caller MUST acquire a RCU read side lock before calling it.
+ */
+int consumer_add_relayd_socket(int net_seq_idx, int sock_type,
+               struct lttng_consumer_local_data *ctx, int sock,
+               struct pollfd *consumer_sockpoll, struct lttcomm_sock *relayd_sock,
+               unsigned int sessiond_id)
+{
+       int fd = -1, ret = -1, relayd_created = 0;
+       enum lttng_error_code ret_code = LTTNG_OK;
+       struct consumer_relayd_sock_pair *relayd;
+
+       DBG("Consumer adding relayd socket (idx: %d)", net_seq_idx);
+
+       /* First send a status message before receiving the fds. */
+       ret = consumer_send_status_msg(sock, ret_code);
+       if (ret < 0) {
+               /* Somehow, the session daemon is not responding anymore. */
+               goto error;
+       }
+
+       /* Get relayd reference if exists. */
+       relayd = consumer_find_relayd(net_seq_idx);
+       if (relayd == NULL) {
+               /* Not found. Allocate one. */
+               relayd = consumer_allocate_relayd_sock_pair(net_seq_idx);
+               if (relayd == NULL) {
+                       lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_OUTFD_ERROR);
+                       ret = -1;
+                       goto error;
+               }
+               relayd->sessiond_session_id = (uint64_t) sessiond_id;
+               relayd_created = 1;
+       }
+
+       /* Poll on consumer socket. */
+       if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
+               ret = -EINTR;
+               goto error;
+       }
+
+       /* Get relayd socket from session daemon */
+       ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
+       if (ret != sizeof(fd)) {
+               lttng_consumer_send_error(ctx, LTTCOMM_CONSUMERD_ERROR_RECV_FD);
+               ret = -1;
+               fd = -1;        /* Just in case it gets set with an invalid value. */
+               goto error;
+       }
+
+       /* We have the fds without error. Send status back. */
+       ret = consumer_send_status_msg(sock, ret_code);
+       if (ret < 0) {
+               /* Somehow, the session daemon is not responding anymore. */
+               goto error;
+       }
+
+       /* Copy socket information and received FD */
+       switch (sock_type) {
+       case LTTNG_STREAM_CONTROL:
+               /* Copy received lttcomm socket */
+               lttcomm_copy_sock(&relayd->control_sock, relayd_sock);
+               ret = lttcomm_create_sock(&relayd->control_sock);
+               /* Immediately try to close the created socket if valid. */
+               if (relayd->control_sock.fd >= 0) {
+                       if (close(relayd->control_sock.fd)) {
+                               PERROR("close relayd control socket");
+                       }
+               }
+               /* Handle create_sock error. */
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /* Assign new file descriptor */
+               relayd->control_sock.fd = fd;
+
+               /*
+                * Create a session on the relayd and store the returned id. Lock the
+                * control socket mutex if the relayd was NOT created before.
+                */
+               if (!relayd_created) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               }
+               ret = relayd_create_session(&relayd->control_sock,
+                               &relayd->relayd_session_id);
+               if (!relayd_created) {
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               }
+               if (ret < 0) {
+                       goto error;
+               }
+
+               break;
+       case LTTNG_STREAM_DATA:
+               /* Copy received lttcomm socket */
+               lttcomm_copy_sock(&relayd->data_sock, relayd_sock);
+               ret = lttcomm_create_sock(&relayd->data_sock);
+               /* Immediately try to close the created socket if valid. */
+               if (relayd->data_sock.fd >= 0) {
+                       if (close(relayd->data_sock.fd)) {
+                               PERROR("close relayd data socket");
+                       }
+               }
+               /* Handle create_sock error. */
+               if (ret < 0) {
+                       goto error;
+               }
+
+               /* Assign new file descriptor */
+               relayd->data_sock.fd = fd;
+               break;
+       default:
+               ERR("Unknown relayd socket type (%d)", sock_type);
+               ret = -1;
+               goto error;
+       }
+
+       DBG("Consumer %s socket created successfully with net idx %d (fd: %d)",
+                       sock_type == LTTNG_STREAM_CONTROL ? "control" : "data",
+                       relayd->net_seq_idx, fd);
+
+       /*
+        * Add relayd socket pair to consumer data hashtable. If object already
+        * exists or on error, the function gracefully returns.
+        */
+       add_relayd(relayd);
+
+       /* All good! */
+       return 0;
+
+error:
+       /* Close received socket if valid. */
+       if (fd >= 0) {
+               if (close(fd)) {
+                       PERROR("close received socket");
+               }
+       }
+
+       if (relayd_created) {
+               /* We just want to cleanup. Ignore ret value. */
+               (void) relayd_close(&relayd->control_sock);
+               (void) relayd_close(&relayd->data_sock);
+               free(relayd);
+       }
+
+       return ret;
+}
+
+/*
+ * Try to lock the stream mutex.
+ *
+ * On success, 1 is returned else 0 indicating that the mutex is NOT lock.
+ */
+static int stream_try_lock(struct lttng_consumer_stream *stream)
+{
+       int ret;
+
+       assert(stream);
+
+       /*
+        * Try to lock the stream mutex. On failure, we know that the stream is
+        * being used else where hence there is data still being extracted.
+        */
+       ret = pthread_mutex_trylock(&stream->lock);
+       if (ret) {
+               /* For both EBUSY and EINVAL error, the mutex is NOT locked. */
+               ret = 0;
+               goto end;
+       }
+
+       ret = 1;
+
+end:
+       return ret;
+}
+
+/*
+ * Search for a relayd associated to the session id and return the reference.
+ *
+ * A rcu read side lock MUST be acquire before calling this function and locked
+ * until the relayd object is no longer necessary.
+ */
+static struct consumer_relayd_sock_pair *find_relayd_by_session_id(uint64_t id)
+{
+       struct lttng_ht_iter iter;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+
+       /* Iterate over all relayd since they are indexed by net_seq_idx. */
+       cds_lfht_for_each_entry(consumer_data.relayd_ht->ht, &iter.iter, relayd,
+                       node.node) {
+               /*
+                * Check by sessiond id which is unique here where the relayd session
+                * id might not be when having multiple relayd.
+                */
+               if (relayd->sessiond_session_id == id) {
+                       /* Found the relayd. There can be only one per id. */
+                       goto found;
+               }
+       }
+
+       return NULL;
+
+found:
+       return relayd;
+}
+
+/*
+ * Check if for a given session id there is still data needed to be extract
+ * from the buffers.
+ *
+ * Return 1 if data is pending or else 0 meaning ready to be read.
+ */
+int consumer_data_pending(uint64_t id)
+{
+       int ret;
+       struct lttng_ht_iter iter;
+       struct lttng_ht *ht;
+       struct lttng_consumer_stream *stream;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       int (*data_pending)(struct lttng_consumer_stream *);
+
+       DBG("Consumer data pending command on session id %" PRIu64, id);
+
+       rcu_read_lock();
+       pthread_mutex_lock(&consumer_data.lock);
+
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               data_pending = lttng_kconsumer_data_pending;
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               data_pending = lttng_ustconsumer_data_pending;
+               break;
+       default:
+               ERR("Unknown consumer data type");
+               assert(0);
+       }
+
+       /* Ease our life a bit */
+       ht = consumer_data.stream_list_ht;
+
+       relayd = find_relayd_by_session_id(id);
+       if (relayd) {
+               /* Send init command for data pending. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_begin_data_pending(&relayd->control_sock,
+                               relayd->relayd_session_id);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       /* Communication error thus the relayd so no data pending. */
+                       goto data_not_pending;
+               }
+       }
+
+       cds_lfht_for_each_entry_duplicate(ht->ht,
+                       ht->hash_fct((void *)((unsigned long) id), lttng_ht_seed),
+                       ht->match_fct, (void *)((unsigned long) id),
+                       &iter.iter, stream, node_session_id.node) {
+               /* If this call fails, the stream is being used hence data pending. */
+               ret = stream_try_lock(stream);
+               if (!ret) {
+                       goto data_pending;
+               }
+
+               /*
+                * A removed node from the hash table indicates that the stream has
+                * been deleted thus having a guarantee that the buffers are closed
+                * on the consumer side. However, data can still be transmitted
+                * over the network so don't skip the relayd check.
+                */
+               ret = cds_lfht_is_node_deleted(&stream->node.node);
+               if (!ret) {
+                       /* Check the stream if there is data in the buffers. */
+                       ret = data_pending(stream);
+                       if (ret == 1) {
+                               pthread_mutex_unlock(&stream->lock);
+                               goto data_pending;
+                       }
+               }
+
+               /* Relayd check */
+               if (relayd) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+                       if (stream->metadata_flag) {
+                               ret = relayd_quiescent_control(&relayd->control_sock,
+                                               stream->relayd_stream_id);
+                       } else {
+                               ret = relayd_data_pending(&relayd->control_sock,
+                                               stream->relayd_stream_id,
+                                               stream->next_net_seq_num - 1);
+                       }
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+                       if (ret == 1) {
+                               pthread_mutex_unlock(&stream->lock);
+                               goto data_pending;
+                       }
+               }
+               pthread_mutex_unlock(&stream->lock);
+       }
+
+       if (relayd) {
+               unsigned int is_data_inflight = 0;
+
+               /* Send init command for data pending. */
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_end_data_pending(&relayd->control_sock,
+                               relayd->relayd_session_id, &is_data_inflight);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       goto data_not_pending;
+               }
+               if (is_data_inflight) {
+                       goto data_pending;
+               }
+       }
+
+       /*
+        * Finding _no_ node in the hash table and no inflight data means that the
+        * stream(s) have been removed thus data is guaranteed to be available for
+        * analysis from the trace files.
+        */
+
+data_not_pending:
+       /* Data is available to be read by a viewer. */
+       pthread_mutex_unlock(&consumer_data.lock);
+       rcu_read_unlock();
+       return 0;
+
+data_pending:
+       /* Data is still being extracted from buffers. */
+       pthread_mutex_unlock(&consumer_data.lock);
+       rcu_read_unlock();
+       return 1;
 }
 
+/*
+ * Send a ret code status message to the sessiond daemon.
+ *
+ * Return the sendmsg() return value.
+ */
+int consumer_send_status_msg(int sock, int ret_code)
+{
+       struct lttcomm_consumer_status_msg msg;
+
+       msg.ret_code = ret_code;
+
+       return lttcomm_send_unix_sock(sock, &msg, sizeof(msg));
+}
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