Clean-up: consumer: fix -Wshadow error in lttng_consumer_trace_chunk_exists
[lttng-tools.git] / src / common / consumer / consumer.c
index 3e991c8c71035f6ee9f43f768db27247209e8707..27a01bd7a4c162c83b92f8c5ff10386771f9dab9 100644 (file)
@@ -1,22 +1,13 @@
 /*
- * Copyright (C) 2011 Julien Desfossez <julien.desfossez@polymtl.ca>
- *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- *               2012 - David Goulet <dgoulet@efficios.com>
+ * Copyright (C) 2011 Julien Desfossez <julien.desfossez@polymtl.ca>
+ * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 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, version 2 only,
- * as published by the Free Software Foundation.
+ * SPDX-License-Identifier: GPL-2.0-only
  *
- * This program is distributed in the hope that it will be useful, but WITHOUT
- * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
- * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
- * more details.
- *
- * You should have received a copy of the GNU General Public License along
- * with this program; if not, write to the Free Software Foundation, Inc.,
- * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
+#include "common/index/ctf-index.h"
 #define _LGPL_SOURCE
 #include <assert.h>
 #include <poll.h>
@@ -33,6 +24,7 @@
 #include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
 #include <common/utils.h>
+#include <common/time.h>
 #include <common/compat/poll.h>
 #include <common/compat/endian.h>
 #include <common/index/index.h>
 #include <common/consumer/consumer-testpoint.h>
 #include <common/align.h>
 #include <common/consumer/consumer-metadata-cache.h>
+#include <common/trace-chunk.h>
+#include <common/trace-chunk-registry.h>
+#include <common/string-utils/format.h>
+#include <common/dynamic-array.h>
 
 struct lttng_consumer_global_data consumer_data = {
        .stream_count = 0,
@@ -86,6 +82,20 @@ int consumer_quit;
 static struct lttng_ht *metadata_ht;
 static struct lttng_ht *data_ht;
 
+static const char *get_consumer_domain(void)
+{
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               return DEFAULT_KERNEL_TRACE_DIR;
+       case LTTNG_CONSUMER64_UST:
+               /* Fall-through. */
+       case LTTNG_CONSUMER32_UST:
+               return DEFAULT_UST_TRACE_DIR;
+       default:
+               abort();
+       }
+}
+
 /*
  * Notify a thread lttng 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
@@ -323,6 +333,7 @@ static void free_relayd_rcu(struct rcu_head *head)
        (void) relayd_close(&relayd->control_sock);
        (void) relayd_close(&relayd->data_sock);
 
+       pthread_mutex_destroy(&relayd->ctrl_sock_mutex);
        free(relayd);
 }
 
@@ -357,7 +368,6 @@ void consumer_destroy_relayd(struct consumer_relayd_sock_pair *relayd)
  */
 void consumer_del_channel(struct lttng_consumer_channel *channel)
 {
-       int ret;
        struct lttng_ht_iter iter;
 
        DBG("Consumer delete channel key %" PRIu64, channel->key);
@@ -388,12 +398,25 @@ void consumer_del_channel(struct lttng_consumer_channel *channel)
                goto end;
        }
 
-       rcu_read_lock();
-       iter.iter.node = &channel->node.node;
-       ret = lttng_ht_del(consumer_data.channel_ht, &iter);
-       assert(!ret);
-       rcu_read_unlock();
+       lttng_trace_chunk_put(channel->trace_chunk);
+       channel->trace_chunk = NULL;
+
+       if (channel->is_published) {
+               int ret;
+
+               rcu_read_lock();
+               iter.iter.node = &channel->node.node;
+               ret = lttng_ht_del(consumer_data.channel_ht, &iter);
+               assert(!ret);
 
+               iter.iter.node = &channel->channels_by_session_id_ht_node.node;
+               ret = lttng_ht_del(consumer_data.channels_by_session_id_ht,
+                               &iter);
+               assert(!ret);
+               rcu_read_unlock();
+       }
+
+       channel->is_deleted = true;
        call_rcu(&channel->node.head, free_channel_rcu);
 end:
        pthread_mutex_unlock(&channel->lock);
@@ -464,14 +487,13 @@ static void update_endpoint_status_by_netidx(uint64_t net_seq_idx,
  * 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)
+void lttng_consumer_cleanup_relayd(struct consumer_relayd_sock_pair *relayd)
 {
        uint64_t netidx;
 
        assert(relayd);
 
-       DBG("Cleaning up relayd sockets");
+       DBG("Cleaning up relayd object ID %"PRIu64, relayd->net_seq_idx);
 
        /* Save the net sequence index before destroying the object */
        netidx = relayd->net_seq_idx;
@@ -491,10 +513,8 @@ static void cleanup_relayd(struct consumer_relayd_sock_pair *relayd,
         * 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_lttng_pipe(ctx->consumer_data_pipe);
-               notify_thread_lttng_pipe(ctx->consumer_metadata_pipe);
-       }
+       notify_thread_lttng_pipe(relayd->ctx->consumer_data_pipe);
+       notify_thread_lttng_pipe(relayd->ctx->consumer_metadata_pipe);
 }
 
 /*
@@ -547,96 +567,6 @@ void consumer_stream_update_channel_attributes(
 {
        stream->channel_read_only_attributes.tracefile_size =
                        channel->tracefile_size;
-       memcpy(stream->channel_read_only_attributes.path, channel->pathname,
-                       sizeof(stream->channel_read_only_attributes.path));
-}
-
-struct lttng_consumer_stream *consumer_allocate_stream(uint64_t channel_key,
-               uint64_t stream_key,
-               enum lttng_consumer_stream_state state,
-               const char *channel_name,
-               uid_t uid,
-               gid_t gid,
-               uint64_t relayd_id,
-               uint64_t session_id,
-               int cpu,
-               int *alloc_ret,
-               enum consumer_channel_type type,
-               unsigned int monitor,
-               uint64_t trace_archive_id)
-{
-       int ret;
-       struct lttng_consumer_stream *stream;
-
-       stream = zmalloc(sizeof(*stream));
-       if (stream == NULL) {
-               PERROR("malloc struct lttng_consumer_stream");
-               ret = -ENOMEM;
-               goto end;
-       }
-
-       rcu_read_lock();
-
-       stream->key = stream_key;
-       stream->out_fd = -1;
-       stream->out_fd_offset = 0;
-       stream->output_written = 0;
-       stream->state = state;
-       stream->uid = uid;
-       stream->gid = gid;
-       stream->net_seq_idx = relayd_id;
-       stream->session_id = session_id;
-       stream->monitor = monitor;
-       stream->endpoint_status = CONSUMER_ENDPOINT_ACTIVE;
-       stream->index_file = NULL;
-       stream->last_sequence_number = -1ULL;
-       stream->trace_archive_id = trace_archive_id;
-       pthread_mutex_init(&stream->lock, NULL);
-       pthread_mutex_init(&stream->metadata_timer_lock, NULL);
-
-       /* If channel is the metadata, flag this stream as metadata. */
-       if (type == CONSUMER_CHANNEL_TYPE_METADATA) {
-               stream->metadata_flag = 1;
-               /* Metadata is flat out. */
-               strncpy(stream->name, DEFAULT_METADATA_NAME, sizeof(stream->name));
-               /* Live rendez-vous point. */
-               pthread_cond_init(&stream->metadata_rdv, NULL);
-               pthread_mutex_init(&stream->metadata_rdv_lock, NULL);
-       } else {
-               /* Format stream name to <channel_name>_<cpu_number> */
-               ret = snprintf(stream->name, sizeof(stream->name), "%s_%d",
-                               channel_name, cpu);
-               if (ret < 0) {
-                       PERROR("snprintf stream name");
-                       goto error;
-               }
-       }
-
-       /* Key is always the wait_fd for streams. */
-       lttng_ht_node_init_u64(&stream->node, stream->key);
-
-       /* Init node per channel id key */
-       lttng_ht_node_init_u64(&stream->node_channel_id, channel_key);
-
-       /* Init session id node with the stream session id */
-       lttng_ht_node_init_u64(&stream->node_session_id, stream->session_id);
-
-       DBG3("Allocated stream %s (key %" PRIu64 ", chan_key %" PRIu64
-                       " relayd_id %" PRIu64 ", session_id %" PRIu64,
-                       stream->name, stream->key, channel_key,
-                       stream->net_seq_idx, stream->session_id);
-
-       rcu_read_unlock();
-       return stream;
-
-error:
-       rcu_read_unlock();
-       free(stream);
-end:
-       if (alloc_ret) {
-               *alloc_ret = ret;
-       }
-       return NULL;
 }
 
 /*
@@ -696,11 +626,6 @@ void consumer_add_data_stream(struct lttng_consumer_stream *stream)
        pthread_mutex_unlock(&consumer_data.lock);
 }
 
-void consumer_del_data_stream(struct lttng_consumer_stream *stream)
-{
-       consumer_del_stream(stream, data_ht);
-}
-
 /*
  * Add relayd socket to global consumer data hashtable. RCU read side lock MUST
  * be acquired before calling this.
@@ -807,10 +732,14 @@ int consumer_send_relayd_stream(struct lttng_consumer_stream *stream,
                /* Add stream on the relayd */
                pthread_mutex_lock(&relayd->ctrl_sock_mutex);
                ret = relayd_add_stream(&relayd->control_sock, stream->name,
-                               path, &stream->relayd_stream_id,
-                               stream->chan->tracefile_size, stream->chan->tracefile_count);
+                               get_consumer_domain(), path, &stream->relayd_stream_id,
+                               stream->chan->tracefile_size,
+                               stream->chan->tracefile_count,
+                               stream->trace_chunk);
                pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
                if (ret < 0) {
+                       ERR("Relayd add stream failed. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+                       lttng_consumer_cleanup_relayd(relayd);
                        goto end;
                }
 
@@ -852,6 +781,8 @@ int consumer_send_relayd_streams_sent(uint64_t net_seq_idx)
                ret = relayd_streams_sent(&relayd->control_sock);
                pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
                if (ret < 0) {
+                       ERR("Relayd streams sent failed. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+                       lttng_consumer_cleanup_relayd(relayd);
                        goto end;
                }
        } else {
@@ -919,6 +850,7 @@ static int write_relayd_stream_header(struct lttng_consumer_stream *stream,
                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
@@ -945,6 +877,123 @@ error:
        return outfd;
 }
 
+/*
+ * Write a character on the metadata poll pipe to wake the metadata thread.
+ * Returns 0 on success, -1 on error.
+ */
+int consumer_metadata_wakeup_pipe(const struct lttng_consumer_channel *channel)
+{
+       int ret = 0;
+
+       DBG("Waking up metadata poll thread (writing to pipe): channel name = '%s'",
+                       channel->name);
+       if (channel->monitor && channel->metadata_stream) {
+               const char dummy = 'c';
+               const ssize_t write_ret = lttng_write(
+                               channel->metadata_stream->ust_metadata_poll_pipe[1],
+                               &dummy, 1);
+
+               if (write_ret < 1) {
+                       if (errno == EWOULDBLOCK) {
+                               /*
+                                * This is fine, the metadata poll thread
+                                * is having a hard time keeping-up, but
+                                * it will eventually wake-up and consume
+                                * the available data.
+                                */
+                               ret = 0;
+                       } else {
+                               PERROR("Failed to write to UST metadata pipe while attempting to wake-up the metadata poll thread");
+                               ret = -1;
+                               goto end;
+                       }
+               }
+       }
+
+end:
+       return ret;
+}
+
+/*
+ * Trigger a dump of the metadata content. Following/during the succesful
+ * completion of this call, the metadata poll thread will start receiving
+ * metadata packets to consume.
+ *
+ * The caller must hold the channel and stream locks.
+ */
+static
+int consumer_metadata_stream_dump(struct lttng_consumer_stream *stream)
+{
+       int ret;
+
+       ASSERT_LOCKED(stream->chan->lock);
+       ASSERT_LOCKED(stream->lock);
+       assert(stream->metadata_flag);
+       assert(stream->chan->trace_chunk);
+
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               /*
+                * Reset the position of what has been read from the
+                * metadata cache to 0 so we can dump it again.
+                */
+               ret = kernctl_metadata_cache_dump(stream->wait_fd);
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               /*
+                * Reset the position pushed from the metadata cache so it
+                * will write from the beginning on the next push.
+                */
+               stream->ust_metadata_pushed = 0;
+               ret = consumer_metadata_wakeup_pipe(stream->chan);
+               break;
+       default:
+               ERR("Unknown consumer_data type");
+               abort();
+       }
+       if (ret < 0) {
+               ERR("Failed to dump the metadata cache");
+       }
+       return ret;
+}
+
+static
+int lttng_consumer_channel_set_trace_chunk(
+               struct lttng_consumer_channel *channel,
+               struct lttng_trace_chunk *new_trace_chunk)
+{
+       pthread_mutex_lock(&channel->lock);
+       if (channel->is_deleted) {
+               /*
+                * The channel has been logically deleted and should no longer
+                * be used. It has released its reference to its current trace
+                * chunk and should not acquire a new one.
+                *
+                * Return success as there is nothing for the caller to do.
+                */
+               goto end;
+       }
+
+       /*
+        * The acquisition of the reference cannot fail (barring
+        * a severe internal error) since a reference to the published
+        * chunk is already held by the caller.
+        */
+       if (new_trace_chunk) {
+               const bool acquired_reference = lttng_trace_chunk_get(
+                               new_trace_chunk);
+
+               assert(acquired_reference);
+       }
+
+       lttng_trace_chunk_put(channel->trace_chunk);
+       channel->trace_chunk = new_trace_chunk;
+end:
+       pthread_mutex_unlock(&channel->lock);
+       return 0;
+}
+
 /*
  * Allocate and return a new lttng_consumer_channel object using the given key
  * to initialize the hash table node.
@@ -953,10 +1002,9 @@ error:
  */
 struct lttng_consumer_channel *consumer_allocate_channel(uint64_t key,
                uint64_t session_id,
+               const uint64_t *chunk_id,
                const char *pathname,
                const char *name,
-               uid_t uid,
-               gid_t gid,
                uint64_t relayd_id,
                enum lttng_event_output output,
                uint64_t tracefile_size,
@@ -964,10 +1012,22 @@ struct lttng_consumer_channel *consumer_allocate_channel(uint64_t key,
                uint64_t session_id_per_pid,
                unsigned int monitor,
                unsigned int live_timer_interval,
+               bool is_in_live_session,
                const char *root_shm_path,
                const char *shm_path)
 {
-       struct lttng_consumer_channel *channel;
+       struct lttng_consumer_channel *channel = NULL;
+       struct lttng_trace_chunk *trace_chunk = NULL;
+
+       if (chunk_id) {
+               trace_chunk = lttng_trace_chunk_registry_find_chunk(
+                               consumer_data.chunk_registry, session_id,
+                               *chunk_id);
+               if (!trace_chunk) {
+                       ERR("Failed to find trace chunk reference during creation of channel");
+                       goto end;
+               }
+       }
 
        channel = zmalloc(sizeof(*channel));
        if (channel == NULL) {
@@ -979,13 +1039,12 @@ struct lttng_consumer_channel *consumer_allocate_channel(uint64_t key,
        channel->refcount = 0;
        channel->session_id = session_id;
        channel->session_id_per_pid = session_id_per_pid;
-       channel->uid = uid;
-       channel->gid = gid;
        channel->relayd_id = relayd_id;
        channel->tracefile_size = tracefile_size;
        channel->tracefile_count = tracefile_count;
        channel->monitor = monitor;
        channel->live_timer_interval = live_timer_interval;
+       channel->is_live = is_in_live_session;
        pthread_mutex_init(&channel->lock, NULL);
        pthread_mutex_init(&channel->timer_lock, NULL);
 
@@ -1032,15 +1091,29 @@ struct lttng_consumer_channel *consumer_allocate_channel(uint64_t key,
        }
 
        lttng_ht_node_init_u64(&channel->node, channel->key);
+       lttng_ht_node_init_u64(&channel->channels_by_session_id_ht_node,
+                       channel->session_id);
 
        channel->wait_fd = -1;
-
        CDS_INIT_LIST_HEAD(&channel->streams.head);
 
+       if (trace_chunk) {
+               int ret = lttng_consumer_channel_set_trace_chunk(channel,
+                               trace_chunk);
+               if (ret) {
+                       goto error;
+               }
+       }
+
        DBG("Allocated channel (key %" PRIu64 ")", channel->key);
 
 end:
+       lttng_trace_chunk_put(trace_chunk);
        return channel;
+error:
+       consumer_del_channel(channel);
+       channel = NULL;
+       goto end;
 }
 
 /*
@@ -1064,7 +1137,10 @@ int consumer_add_channel(struct lttng_consumer_channel *channel,
 
        rcu_read_lock();
        lttng_ht_add_unique_u64(consumer_data.channel_ht, &channel->node);
+       lttng_ht_add_u64(consumer_data.channels_by_session_id_ht,
+                       &channel->channels_by_session_id_ht_node);
        rcu_read_unlock();
+       channel->is_published = true;
 
        pthread_mutex_unlock(&channel->timer_lock);
        pthread_mutex_unlock(&channel->lock);
@@ -1114,16 +1190,13 @@ static int update_poll_array(struct lttng_consumer_local_data *ctx,
                 * closed by the polling thread after a wakeup on the data_pipe or
                 * metadata_pipe.
                 */
-               if (stream->state != LTTNG_CONSUMER_ACTIVE_STREAM ||
-                               stream->endpoint_status == CONSUMER_ENDPOINT_INACTIVE) {
+               if (stream->endpoint_status == CONSUMER_ENDPOINT_INACTIVE) {
                        (*nb_inactive_fd)++;
                        continue;
                }
                /*
                 * This clobbers way too much the debug output. Uncomment that if you
                 * need it for debugging purposes.
-                *
-                * DBG("Active FD %d", stream->wait_fd);
                 */
                (*pollfd)[i].fd = stream->wait_fd;
                (*pollfd)[i].events = POLLIN | POLLPRI;
@@ -1211,6 +1284,7 @@ void lttng_consumer_cleanup(void)
 {
        struct lttng_ht_iter iter;
        struct lttng_consumer_channel *channel;
+       unsigned int trace_chunks_left;
 
        rcu_read_lock();
 
@@ -1222,6 +1296,7 @@ void lttng_consumer_cleanup(void)
        rcu_read_unlock();
 
        lttng_ht_destroy(consumer_data.channel_ht);
+       lttng_ht_destroy(consumer_data.channels_by_session_id_ht);
 
        cleanup_relayd_ht();
 
@@ -1233,6 +1308,29 @@ void lttng_consumer_cleanup(void)
         * it.
         */
        lttng_ht_destroy(consumer_data.stream_list_ht);
+
+       /*
+        * Trace chunks in the registry may still exist if the session
+        * daemon has encountered an internal error and could not
+        * tear down its sessions and/or trace chunks properly.
+        *
+        * Release the session daemon's implicit reference to any remaining
+        * trace chunk and print an error if any trace chunk was found. Note
+        * that there are _no_ legitimate cases for trace chunks to be left,
+        * it is a leak. However, it can happen following a crash of the
+        * session daemon and not emptying the registry would cause an assertion
+        * to hit.
+        */
+       trace_chunks_left = lttng_trace_chunk_registry_put_each_chunk(
+                       consumer_data.chunk_registry);
+       if (trace_chunks_left) {
+               ERR("%u trace chunks are leaked by lttng-consumerd. "
+                               "This can be caused by an internal error of the session daemon.",
+                               trace_chunks_left);
+       }
+       /* Run all callbacks freeing each chunk. */
+       rcu_barrier();
+       lttng_trace_chunk_registry_destroy(consumer_data.chunk_registry);
 }
 
 /*
@@ -1315,7 +1413,7 @@ void lttng_consumer_sync_trace_file(struct lttng_consumer_stream *stream,
 struct lttng_consumer_local_data *lttng_consumer_create(
                enum lttng_consumer_type type,
                ssize_t (*buffer_ready)(struct lttng_consumer_stream *stream,
-                       struct lttng_consumer_local_data *ctx),
+                       struct lttng_consumer_local_data *ctx, bool locked_by_caller),
                int (*recv_channel)(struct lttng_consumer_channel *channel),
                int (*recv_stream)(struct lttng_consumer_stream *stream),
                int (*update_stream)(uint64_t stream_key, uint32_t state))
@@ -1515,29 +1613,30 @@ end:
  * core function for writing trace buffers to either the local filesystem or
  * the network.
  *
- * It must be called with the stream lock held.
+ * It must be called with the stream and the channel 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,
-               unsigned long padding,
-               struct ctf_packet_index *index)
+               struct lttng_consumer_stream *stream,
+               const struct lttng_buffer_view *buffer,
+               unsigned long padding)
 {
-       unsigned long mmap_offset;
-       void *mmap_base;
        ssize_t ret = 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;
+       const size_t subbuf_content_size = buffer->size - padding;
+       size_t write_len;
 
        /* RCU lock for the relayd pointer */
        rcu_read_lock();
+       assert(stream->net_seq_idx != (uint64_t) -1ULL ||
+                       stream->trace_chunk);
 
        /* Flag that the current stream if set for network streaming. */
        if (stream->net_seq_idx != (uint64_t) -1ULL) {
@@ -1548,39 +1647,9 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                }
        }
 
-       /* get the offset inside the fd to mmap */
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               mmap_base = stream->mmap_base;
-               ret = kernctl_get_mmap_read_offset(stream->wait_fd, &mmap_offset);
-               if (ret < 0) {
-                       PERROR("tracer ctl get_mmap_read_offset");
-                       goto end;
-               }
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               mmap_base = lttng_ustctl_get_mmap_base(stream);
-               if (!mmap_base) {
-                       ERR("read mmap get mmap base for stream %s", stream->name);
-                       ret = -EPERM;
-                       goto end;
-               }
-               ret = lttng_ustctl_get_mmap_read_offset(stream, &mmap_offset);
-               if (ret != 0) {
-                       PERROR("tracer ctl get_mmap_read_offset");
-                       ret = -EINVAL;
-                       goto end;
-               }
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-       }
-
        /* Handle stream on the relayd if the output is on the network */
        if (relayd) {
-               unsigned long netlen = len;
+               unsigned long netlen = subbuf_content_size;
 
                /*
                 * Lock the control socket for the complete duration of the function
@@ -1618,10 +1687,10 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                                goto write_error;
                        }
                }
-       } else {
-               /* No streaming, we have to set the len with the full padding */
-               len += padding;
 
+               write_len = subbuf_content_size;
+       } else {
+               /* No streaming; we have to write the full padding. */
                if (stream->metadata_flag && stream->reset_metadata_flag) {
                        ret = utils_truncate_stream_file(stream->out_fd, 0);
                        if (ret < 0) {
@@ -1635,49 +1704,26 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                 * Check if we need to change the tracefile before writing the packet.
                 */
                if (stream->chan->tracefile_size > 0 &&
-                               (stream->tracefile_size_current + len) >
+                               (stream->tracefile_size_current + buffer->size) >
                                stream->chan->tracefile_size) {
-                       ret = utils_rotate_stream_file(stream->chan->pathname,
-                                       stream->name, stream->chan->tracefile_size,
-                                       stream->chan->tracefile_count, stream->uid, stream->gid,
-                                       stream->out_fd, &(stream->tracefile_count_current),
-                                       &stream->out_fd);
-                       if (ret < 0) {
-                               ERR("Rotating output file");
+                       ret = consumer_stream_rotate_output_files(stream);
+                       if (ret) {
                                goto end;
                        }
                        outfd = stream->out_fd;
-
-                       if (stream->index_file) {
-                               lttng_index_file_put(stream->index_file);
-                               stream->index_file = lttng_index_file_create(stream->chan->pathname,
-                                               stream->name, stream->uid, stream->gid,
-                                               stream->chan->tracefile_size,
-                                               stream->tracefile_count_current,
-                                               CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
-                               if (!stream->index_file) {
-                                       goto end;
-                               }
-                       }
-
-                       /* Reset current size because we just perform a rotation. */
-                       stream->tracefile_size_current = 0;
-                       stream->out_fd_offset = 0;
                        orig_offset = 0;
                }
-               stream->tracefile_size_current += len;
-               if (index) {
-                       index->offset = htobe64(stream->out_fd_offset);
-               }
+               stream->tracefile_size_current += buffer->size;
+               write_len = buffer->size;
        }
 
        /*
         * This call guarantee that len or less is returned. It's impossible to
         * receive a ret value that is bigger than len.
         */
-       ret = lttng_write(outfd, mmap_base + mmap_offset, len);
-       DBG("Consumer mmap write() ret %zd (len %lu)", ret, len);
-       if (ret < 0 || ((size_t) ret != len)) {
+       ret = lttng_write(outfd, buffer->data, write_len);
+       DBG("Consumer mmap write() ret %zd (len %zu)", ret, write_len);
+       if (ret < 0 || ((size_t) ret != write_len)) {
                /*
                 * Report error to caller if nothing was written else at least send the
                 * amount written.
@@ -1688,7 +1734,7 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                relayd_hang_up = 1;
 
                /* Socket operation failed. We consider the relayd dead */
-               if (errno == EPIPE || errno == EINVAL || errno == EBADF) {
+               if (errno == EPIPE) {
                        /*
                         * 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
@@ -1698,7 +1744,8 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
                        DBG("Consumer mmap write detected relayd hang up");
                } else {
                        /* Unhandled error, print it and stop function right now. */
-                       PERROR("Error in write mmap (ret %zd != len %lu)", ret, len);
+                       PERROR("Error in write mmap (ret %zd != write_len %zu)", ret,
+                                       write_len);
                }
                goto write_error;
        }
@@ -1707,9 +1754,9 @@ ssize_t lttng_consumer_on_read_subbuffer_mmap(
        /* 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, len,
+               lttng_sync_file_range(outfd, stream->out_fd_offset, write_len,
                                SYNC_FILE_RANGE_WRITE);
-               stream->out_fd_offset += len;
+               stream->out_fd_offset += write_len;
                lttng_consumer_sync_trace_file(stream, orig_offset);
        }
 
@@ -1719,7 +1766,8 @@ write_error:
         * cleanup the relayd object and all associated streams.
         */
        if (relayd && relayd_hang_up) {
-               cleanup_relayd(relayd, ctx);
+               ERR("Relayd hangup. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+               lttng_consumer_cleanup_relayd(relayd);
        }
 
 end:
@@ -1742,8 +1790,7 @@ end:
 ssize_t lttng_consumer_on_read_subbuffer_splice(
                struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_stream *stream, unsigned long len,
-               unsigned long padding,
-               struct ctf_packet_index *index)
+               unsigned long padding)
 {
        ssize_t ret = 0, written = 0, ret_splice = 0;
        loff_t offset = 0;
@@ -1838,37 +1885,15 @@ ssize_t lttng_consumer_on_read_subbuffer_splice(
                if (stream->chan->tracefile_size > 0 &&
                                (stream->tracefile_size_current + len) >
                                stream->chan->tracefile_size) {
-                       ret = utils_rotate_stream_file(stream->chan->pathname,
-                                       stream->name, stream->chan->tracefile_size,
-                                       stream->chan->tracefile_count, stream->uid, stream->gid,
-                                       stream->out_fd, &(stream->tracefile_count_current),
-                                       &stream->out_fd);
+                       ret = consumer_stream_rotate_output_files(stream);
                        if (ret < 0) {
                                written = ret;
-                               ERR("Rotating output file");
                                goto end;
                        }
                        outfd = stream->out_fd;
-
-                       if (stream->index_file) {
-                               lttng_index_file_put(stream->index_file);
-                               stream->index_file = lttng_index_file_create(stream->chan->pathname,
-                                               stream->name, stream->uid, stream->gid,
-                                               stream->chan->tracefile_size,
-                                               stream->tracefile_count_current,
-                                               CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
-                               if (!stream->index_file) {
-                                       goto end;
-                               }
-                       }
-
-                       /* Reset current size because we just perform a rotation. */
-                       stream->tracefile_size_current = 0;
-                       stream->out_fd_offset = 0;
                        orig_offset = 0;
                }
                stream->tracefile_size_current += len;
-               index->offset = htobe64(stream->out_fd_offset);
        }
 
        while (len > 0) {
@@ -1945,7 +1970,8 @@ write_error:
         * cleanup the relayd object and all associated streams.
         */
        if (relayd && relayd_hang_up) {
-               cleanup_relayd(relayd, ctx);
+               ERR("Relayd hangup. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+               lttng_consumer_cleanup_relayd(relayd);
                /* Skip splice error so the consumer does not fail */
                goto end;
        }
@@ -2070,6 +2096,7 @@ int lttng_consumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
 }
 
+static
 void lttng_consumer_close_all_metadata(void)
 {
        switch (consumer_data.type) {
@@ -2102,7 +2129,8 @@ void lttng_consumer_close_all_metadata(void)
 void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
                struct lttng_ht *ht)
 {
-       struct lttng_consumer_channel *free_chan = NULL;
+       struct lttng_consumer_channel *channel = NULL;
+       bool free_channel = false;
 
        assert(stream);
        /*
@@ -2114,11 +2142,17 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
        DBG3("Consumer delete metadata stream %d", stream->wait_fd);
 
        pthread_mutex_lock(&consumer_data.lock);
-       pthread_mutex_lock(&stream->chan->lock);
+       /*
+        * Note that this assumes that a stream's channel is never changed and
+        * that the stream's lock doesn't need to be taken to sample its
+        * channel.
+        */
+       channel = stream->chan;
+       pthread_mutex_lock(&channel->lock);
        pthread_mutex_lock(&stream->lock);
-       if (stream->chan->metadata_cache) {
+       if (channel->metadata_cache) {
                /* Only applicable to userspace consumers. */
-               pthread_mutex_lock(&stream->chan->metadata_cache->lock);
+               pthread_mutex_lock(&channel->metadata_cache->lock);
        }
 
        /* Remove any reference to that stream. */
@@ -2130,30 +2164,33 @@ void consumer_del_metadata_stream(struct lttng_consumer_stream *stream,
        consumer_stream_destroy_buffers(stream);
 
        /* Atomically decrement channel refcount since other threads can use it. */
-       if (!uatomic_sub_return(&stream->chan->refcount, 1)
-                       && !uatomic_read(&stream->chan->nb_init_stream_left)) {
+       if (!uatomic_sub_return(&channel->refcount, 1)
+                       && !uatomic_read(&channel->nb_init_stream_left)) {
                /* Go for channel deletion! */
-               free_chan = stream->chan;
+               free_channel = true;
        }
+       stream->chan = NULL;
 
        /*
         * Nullify the stream reference so it is not used after deletion. The
         * channel lock MUST be acquired before being able to check for a NULL
         * pointer value.
         */
-       stream->chan->metadata_stream = NULL;
+       channel->metadata_stream = NULL;
 
-       if (stream->chan->metadata_cache) {
-               pthread_mutex_unlock(&stream->chan->metadata_cache->lock);
+       if (channel->metadata_cache) {
+               pthread_mutex_unlock(&channel->metadata_cache->lock);
        }
        pthread_mutex_unlock(&stream->lock);
-       pthread_mutex_unlock(&stream->chan->lock);
+       pthread_mutex_unlock(&channel->lock);
        pthread_mutex_unlock(&consumer_data.lock);
 
-       if (free_chan) {
-               consumer_del_channel(free_chan);
+       if (free_channel) {
+               consumer_del_channel(channel);
        }
 
+       lttng_trace_chunk_put(stream->trace_chunk);
+       stream->trace_chunk = NULL;
        consumer_stream_free(stream);
 }
 
@@ -2278,73 +2315,6 @@ static void validate_endpoint_status_metadata_stream(
        rcu_read_unlock();
 }
 
-static
-int rotate_notify_sessiond(struct lttng_consumer_local_data *ctx,
-               uint64_t key)
-{
-       ssize_t ret;
-
-       do {
-               ret = write(ctx->channel_rotate_pipe, &key, sizeof(key));
-       } while (ret == -1 && errno == EINTR);
-       if (ret == -1) {
-               PERROR("Failed to write to the channel rotation pipe");
-       } else {
-               DBG("Sent channel rotation notification for channel key %"
-                               PRIu64, key);
-               ret = 0;
-       }
-
-       return (int) ret;
-}
-
-/*
- * Perform operations that need to be done after a stream has
- * rotated and released the stream lock.
- *
- * Multiple rotations cannot occur simultaneously, so we know the state of the
- * "rotated" stream flag cannot change.
- *
- * This MUST be called WITHOUT the stream lock held.
- */
-static
-int consumer_post_rotation(struct lttng_consumer_stream *stream,
-               struct lttng_consumer_local_data *ctx)
-{
-       int ret = 0;
-
-       pthread_mutex_lock(&stream->chan->lock);
-
-       switch (consumer_data.type) {
-               case LTTNG_CONSUMER_KERNEL:
-                       break;
-               case LTTNG_CONSUMER32_UST:
-               case LTTNG_CONSUMER64_UST:
-                       /*
-                        * The ust_metadata_pushed counter has been reset to 0, so now
-                        * we can wakeup the metadata thread so it dumps the metadata
-                        * cache to the new file.
-                        */
-                       if (stream->metadata_flag) {
-                               consumer_metadata_wakeup_pipe(stream->chan);
-                       }
-                       break;
-               default:
-                       ERR("Unknown consumer_data type");
-                       abort();
-       }
-
-       if (--stream->chan->nr_stream_rotate_pending == 0) {
-               DBG("Rotation of channel \"%s\" completed, notifying the session daemon",
-                               stream->chan->name);
-               ret = rotate_notify_sessiond(ctx, stream->chan->key);
-       }
-       assert(stream->chan->nr_stream_rotate_pending >= 0);
-       pthread_mutex_unlock(&stream->chan->lock);
-
-       return ret;
-}
-
 /*
  * Thread polls on metadata file descriptor and write them on disk or on the
  * network.
@@ -2418,11 +2388,6 @@ restart:
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);
 
-                       if (!revents) {
-                               /* No activity for this FD (poll implementation). */
-                               continue;
-                       }
-
                        if (pollfd == lttng_pipe_get_readfd(ctx->consumer_metadata_pipe)) {
                                if (revents & LPOLLIN) {
                                        ssize_t pipe_len;
@@ -2495,7 +2460,7 @@ restart:
                                do {
                                        health_code_update();
 
-                                       len = ctx->on_buffer_ready(stream, ctx);
+                                       len = ctx->on_buffer_ready(stream, ctx, false);
                                        /*
                                         * We don't check the return value here since if we get
                                         * a negative len, it means an error occurred thus we
@@ -2522,7 +2487,7 @@ restart:
                                        do {
                                                health_code_update();
 
-                                               len = ctx->on_buffer_ready(stream, ctx);
+                                               len = ctx->on_buffer_ready(stream, ctx, false);
                                                /*
                                                 * We don't check the return value here since if we get
                                                 * a negative len, it means an error occurred thus we
@@ -2576,7 +2541,9 @@ void *consumer_thread_data_poll(void *data)
        /* local view of the streams */
        struct lttng_consumer_stream **local_stream = NULL, *new_stream = NULL;
        /* local view of consumer_data.fds_count */
-       int nb_fd = 0, nb_pipes_fd;
+       int nb_fd = 0;
+       /* 2 for the consumer_data_pipe and wake up pipe */
+       const int nb_pipes_fd = 2;
        /* Number of FDs with CONSUMER_ENDPOINT_INACTIVE but still open. */
        int nb_inactive_fd = 0;
        struct lttng_consumer_local_data *ctx = data;
@@ -2616,12 +2583,7 @@ void *consumer_thread_data_poll(void *data)
                        free(local_stream);
                        local_stream = NULL;
 
-                       /*
-                        * Allocate for all fds + 2:
-                        *   +1 for the consumer_data_pipe
-                        *   +1 for wake up pipe
-                        */
-                       nb_pipes_fd = 2;
+                       /* Allocate for all fds */
                        pollfd = zmalloc((consumer_data.stream_count + nb_pipes_fd) * sizeof(struct pollfd));
                        if (pollfd == NULL) {
                                PERROR("pollfd malloc");
@@ -2741,7 +2703,7 @@ void *consumer_thread_data_poll(void *data)
                        if (pollfd[i].revents & POLLPRI) {
                                DBG("Urgent read on fd %d", pollfd[i].fd);
                                high_prio = 1;
-                               len = ctx->on_buffer_ready(local_stream[i], ctx);
+                               len = ctx->on_buffer_ready(local_stream[i], ctx, false);
                                /* it's ok to have an unavailable sub-buffer */
                                if (len < 0 && len != -EAGAIN && len != -ENODATA) {
                                        /* Clean the stream and free it. */
@@ -2772,7 +2734,7 @@ void *consumer_thread_data_poll(void *data)
                                        local_stream[i]->hangup_flush_done ||
                                        local_stream[i]->has_data) {
                                DBG("Normal read on fd %d", pollfd[i].fd);
-                               len = ctx->on_buffer_ready(local_stream[i], ctx);
+                               len = ctx->on_buffer_ready(local_stream[i], ctx, false);
                                /* it's ok to have an unavailable sub-buffer */
                                if (len < 0 && len != -EAGAIN && len != -ENODATA) {
                                        /* Clean the stream and free it. */
@@ -3015,11 +2977,6 @@ restart:
                        revents = LTTNG_POLL_GETEV(&events, i);
                        pollfd = LTTNG_POLL_GETFD(&events, i);
 
-                       if (!revents) {
-                               /* No activity for this FD (poll implementation). */
-                               continue;
-                       }
-
                        if (pollfd == ctx->consumer_channel_pipe[0]) {
                                if (revents & LPOLLIN) {
                                        enum consumer_channel_action action;
@@ -3333,7 +3290,7 @@ void *consumer_thread_sessiond_poll(void *data)
                        err = 0;        /* All is OK */
                        goto end;
                }
-               DBG("received command on sock");
+               DBG("Received command on sock");
        }
        /* All is OK */
        err = 0;
@@ -3390,47 +3347,132 @@ error_testpoint:
        return NULL;
 }
 
-ssize_t lttng_consumer_read_subbuffer(struct lttng_consumer_stream *stream,
+static int post_consume(struct lttng_consumer_stream *stream,
+               const struct stream_subbuffer *subbuffer,
                struct lttng_consumer_local_data *ctx)
 {
-       ssize_t ret;
-       int rotate_ret;
-       bool rotated = false;
+       size_t i;
+       int ret = 0;
+       const size_t count = lttng_dynamic_array_get_count(
+                       &stream->read_subbuffer_ops.post_consume_cbs);
 
-       pthread_mutex_lock(&stream->lock);
-       if (stream->metadata_flag) {
-               pthread_mutex_lock(&stream->metadata_rdv_lock);
+       for (i = 0; i < count; i++) {
+               const post_consume_cb op = *(post_consume_cb *) lttng_dynamic_array_get_element(
+                               &stream->read_subbuffer_ops.post_consume_cbs,
+                               i);
+
+               ret = op(stream, subbuffer, ctx);
+               if (ret) {
+                       goto end;
+               }
        }
+end:
+       return ret;
+}
 
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               ret = lttng_kconsumer_read_subbuffer(stream, ctx, &rotated);
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               ret = lttng_ustconsumer_read_subbuffer(stream, ctx, &rotated);
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               assert(0);
-               ret = -ENOSYS;
-               break;
+ssize_t lttng_consumer_read_subbuffer(struct lttng_consumer_stream *stream,
+               struct lttng_consumer_local_data *ctx,
+               bool locked_by_caller)
+{
+       ssize_t ret, written_bytes = 0;
+       int rotation_ret;
+       struct stream_subbuffer subbuffer = {};
+
+       if (!locked_by_caller) {
+               stream->read_subbuffer_ops.lock(stream);
        }
 
-       if (stream->metadata_flag) {
-               pthread_cond_broadcast(&stream->metadata_rdv);
-               pthread_mutex_unlock(&stream->metadata_rdv_lock);
+       if (stream->read_subbuffer_ops.on_wake_up) {
+               ret = stream->read_subbuffer_ops.on_wake_up(stream);
+               if (ret) {
+                       goto end;
+               }
        }
-       pthread_mutex_unlock(&stream->lock);
-       if (rotated) {
-               rotate_ret = consumer_post_rotation(stream, ctx);
-               if (rotate_ret < 0) {
-                       ERR("Failed after a rotation");
-                       ret = -1;
+
+       /*
+        * If the stream was flagged to be ready for rotation before we extract
+        * the next packet, rotate it now.
+        */
+       if (stream->rotate_ready) {
+               DBG("Rotate stream before consuming data");
+               ret = lttng_consumer_rotate_stream(ctx, stream);
+               if (ret < 0) {
+                       ERR("Stream rotation error before consuming data");
+                       goto end;
+               }
+       }
+
+       ret = stream->read_subbuffer_ops.get_next_subbuffer(stream, &subbuffer);
+       if (ret) {
+               if (ret == -ENODATA) {
+                       /* Not an error. */
+                       ret = 0;
+                       goto sleep_stream;
+               }
+               goto end;
+       }
+
+       ret = stream->read_subbuffer_ops.pre_consume_subbuffer(
+                       stream, &subbuffer);
+       if (ret) {
+               goto error_put_subbuf;
+       }
+
+       written_bytes = stream->read_subbuffer_ops.consume_subbuffer(
+                       ctx, stream, &subbuffer);
+       if (written_bytes <= 0) {
+               ERR("Error consuming subbuffer: (%zd)", written_bytes);
+               ret = (int) written_bytes;
+               goto error_put_subbuf;
+       }
+
+       ret = stream->read_subbuffer_ops.put_next_subbuffer(stream, &subbuffer);
+       if (ret) {
+               goto end;
+       }
+
+       ret = post_consume(stream, &subbuffer, ctx);
+       if (ret) {
+               goto end;
+       }
+
+       /*
+        * After extracting the packet, we check if the stream is now ready to
+        * be rotated and perform the action immediately.
+        *
+        * Don't overwrite `ret` as callers expect the number of bytes
+        * consumed to be returned on success.
+        */
+       rotation_ret = lttng_consumer_stream_is_rotate_ready(stream);
+       if (rotation_ret == 1) {
+               rotation_ret = lttng_consumer_rotate_stream(ctx, stream);
+               if (rotation_ret < 0) {
+                       ret = rotation_ret;
+                       ERR("Stream rotation error after consuming data");
+                       goto end;
                }
+
+       } else if (rotation_ret < 0) {
+               ret = rotation_ret;
+               ERR("Failed to check if stream was ready to rotate after consuming data");
+               goto end;
+       }
+
+sleep_stream:
+       if (stream->read_subbuffer_ops.on_sleep) {
+               stream->read_subbuffer_ops.on_sleep(stream, ctx);
+       }
+
+       ret = written_bytes;
+end:
+       if (!locked_by_caller) {
+               stream->read_subbuffer_ops.unlock(stream);
        }
 
        return ret;
+error_put_subbuf:
+       (void) stream->read_subbuffer_ops.put_next_subbuffer(stream, &subbuffer);
+       goto end;
 }
 
 int lttng_consumer_on_recv_stream(struct lttng_consumer_stream *stream)
@@ -3458,6 +3500,12 @@ int lttng_consumer_init(void)
                goto error;
        }
 
+       consumer_data.channels_by_session_id_ht =
+                       lttng_ht_new(0, LTTNG_HT_TYPE_U64);
+       if (!consumer_data.channels_by_session_id_ht) {
+               goto error;
+       }
+
        consumer_data.relayd_ht = lttng_ht_new(0, LTTNG_HT_TYPE_U64);
        if (!consumer_data.relayd_ht) {
                goto error;
@@ -3483,6 +3531,11 @@ int lttng_consumer_init(void)
                goto error;
        }
 
+       consumer_data.chunk_registry = lttng_trace_chunk_registry_create();
+       if (!consumer_data.chunk_registry) {
+               goto error;
+       }
+
        return 0;
 
 error:
@@ -3593,7 +3646,6 @@ error:
 
                /* Assign new file descriptor */
                relayd->control_sock.sock.fd = fd;
-               fd = -1;        /* For error path */
                /* Assign version values. */
                relayd->control_sock.major = relayd_sock->major;
                relayd->control_sock.minor = relayd_sock->minor;
@@ -3621,7 +3673,6 @@ error:
 
                /* Assign new file descriptor */
                relayd->data_sock.sock.fd = fd;
-               fd = -1;        /* for eventual error paths */
                /* Assign version values. */
                relayd->data_sock.major = relayd_sock->major;
                relayd->data_sock.minor = relayd_sock->minor;
@@ -3635,6 +3686,11 @@ error:
        DBG("Consumer %s socket created successfully with net idx %" PRIu64 " (fd: %d)",
                        sock_type == LTTNG_STREAM_CONTROL ? "control" : "data",
                        relayd->net_seq_idx, fd);
+       /*
+        * We gave the ownership of the fd to the relayd structure. Set the
+        * fd to -1 so we don't call close() on it in the error path below.
+        */
+       fd = -1;
 
        /* We successfully added the socket. Send status back. */
        ret = consumer_send_status_msg(sock, ret_code);
@@ -3648,6 +3704,7 @@ error:
         * Add relayd socket pair to consumer data hashtable. If object already
         * exists or on error, the function gracefully returns.
         */
+       relayd->ctx = ctx;
        add_relayd(relayd);
 
        /* All good! */
@@ -3671,34 +3728,6 @@ error_nosignal:
        }
 }
 
-/*
- * 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.
  *
@@ -3765,28 +3794,11 @@ int consumer_data_pending(uint64_t id)
        /* 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(&id, lttng_ht_seed),
                        ht->match_fct, &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;
-               }
+               pthread_mutex_lock(&stream->lock);
 
                /*
                 * A removed node from the hash table indicates that the stream has
@@ -3804,9 +3816,27 @@ int consumer_data_pending(uint64_t id)
                        }
                }
 
-               /* Relayd check */
-               if (relayd) {
-                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               pthread_mutex_unlock(&stream->lock);
+       }
+
+       relayd = find_relayd_by_session_id(id);
+       if (relayd) {
+               unsigned int is_data_inflight = 0;
+
+               /* 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);
+               if (ret < 0) {
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+                       /* Communication error thus the relayd so no data pending. */
+                       goto data_not_pending;
+               }
+
+               cds_lfht_for_each_entry_duplicate(ht->ht,
+                               ht->hash_fct(&id, lttng_ht_seed),
+                               ht->match_fct, &id,
+                               &iter.iter, stream, node_session_id.node) {
                        if (stream->metadata_flag) {
                                ret = relayd_quiescent_control(&relayd->control_sock,
                                                stream->relayd_stream_id);
@@ -3815,24 +3845,25 @@ int consumer_data_pending(uint64_t id)
                                                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);
+                               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
                                goto data_pending;
+                       } else if (ret < 0) {
+                               ERR("Relayd data pending failed. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+                               lttng_consumer_cleanup_relayd(relayd);
+                               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+                               goto data_not_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);
+               /* Send end command for data pending. */
                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) {
+                       ERR("Relayd end data pending failed. Cleaning up relayd %" PRIu64".", relayd->net_seq_idx);
+                       lttng_consumer_cleanup_relayd(relayd);
                        goto data_not_pending;
                }
                if (is_data_inflight) {
@@ -3915,26 +3946,30 @@ unsigned long consumer_get_consume_start_pos(unsigned long consumed_pos,
        return start_pos;
 }
 
-static
-int consumer_flush_buffer(struct lttng_consumer_stream *stream, int producer_active)
+/* Stream lock must be held by the caller. */
+static int sample_stream_positions(struct lttng_consumer_stream *stream,
+                           unsigned long *produced, unsigned long *consumed)
 {
-       int ret = 0;
+       int ret;
 
-       switch (consumer_data.type) {
-       case LTTNG_CONSUMER_KERNEL:
-               ret = kernctl_buffer_flush(stream->wait_fd);
-               if (ret < 0) {
-                       ERR("Failed to flush kernel stream");
-                       goto end;
-               }
-               break;
-       case LTTNG_CONSUMER32_UST:
-       case LTTNG_CONSUMER64_UST:
-               lttng_ustctl_flush_buffer(stream, producer_active);
-               break;
-       default:
-               ERR("Unknown consumer_data type");
-               abort();
+       ASSERT_LOCKED(stream->lock);
+
+       ret = lttng_consumer_sample_snapshot_positions(stream);
+       if (ret < 0) {
+               ERR("Failed to sample snapshot positions");
+               goto end;
+       }
+
+       ret = lttng_consumer_get_produced_snapshot(stream, produced);
+       if (ret < 0) {
+               ERR("Failed to sample produced position");
+               goto end;
+       }
+
+       ret = lttng_consumer_get_consumed_snapshot(stream, consumed);
+       if (ret < 0) {
+               ERR("Failed to sample consumed position");
+               goto end;
        }
 
 end:
@@ -3946,61 +3981,50 @@ end:
  * is already at the rotate position (produced == consumed), we flag it as
  * ready for rotation. The rotation of ready streams occurs after we have
  * replied to the session daemon that we have finished sampling the positions.
+ * Must be called with RCU read-side lock held to ensure existence of channel.
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_consumer_rotate_channel(uint64_t key, const char *path,
-               uint64_t relayd_id, uint32_t metadata, uint64_t new_chunk_id,
+int lttng_consumer_rotate_channel(struct lttng_consumer_channel *channel,
+               uint64_t key, uint64_t relayd_id, uint32_t metadata,
                struct lttng_consumer_local_data *ctx)
 {
        int ret;
-       struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
        struct lttng_ht_iter iter;
        struct lttng_ht *ht = consumer_data.stream_per_chan_id_ht;
+       struct lttng_dynamic_array stream_rotation_positions;
+       uint64_t next_chunk_id, stream_count = 0;
+       enum lttng_trace_chunk_status chunk_status;
+       const bool is_local_trace = relayd_id == -1ULL;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       bool rotating_to_new_chunk = true;
+       /* Array of `struct lttng_consumer_stream *` */
+       struct lttng_dynamic_pointer_array streams_packet_to_open;
+       size_t stream_idx;
 
        DBG("Consumer sample rotate position for channel %" PRIu64, key);
 
-       rcu_read_lock();
+       lttng_dynamic_array_init(&stream_rotation_positions,
+                       sizeof(struct relayd_stream_rotation_position), NULL);
+       lttng_dynamic_pointer_array_init(&streams_packet_to_open, NULL);
 
-       channel = consumer_find_channel(key);
-       if (!channel) {
-               ERR("No channel found for key %" PRIu64, key);
-               ret = -1;
-               goto end;
-       }
+       rcu_read_lock();
 
        pthread_mutex_lock(&channel->lock);
-       channel->current_chunk_id = new_chunk_id;
-
-       ret = lttng_strncpy(channel->pathname, path, sizeof(channel->pathname));
-       if (ret) {
-               ERR("Failed to copy new path to channel during channel rotation");
+       assert(channel->trace_chunk);
+       chunk_status = lttng_trace_chunk_get_id(channel->trace_chunk,
+                       &next_chunk_id);
+       if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
                ret = -1;
                goto end_unlock_channel;
        }
 
-       if (relayd_id == -1ULL) {
-               /*
-                * The domain path (/ust or /kernel) has been created before, we
-                * now need to create the last part of the path: the application/user
-                * specific section (uid/1000/64-bit).
-                */
-               ret = utils_mkdir_recursive(channel->pathname, S_IRWXU | S_IRWXG,
-                               channel->uid, channel->gid);
-               if (ret < 0) {
-                       ERR("Failed to create trace directory at %s during rotation",
-                                       channel->pathname);
-                       ret = -1;
-                       goto end_unlock_channel;
-               }
-       }
-
        cds_lfht_for_each_entry_duplicate(ht->ht,
                        ht->hash_fct(&channel->key, lttng_ht_seed),
                        ht->match_fct, &channel->key, &iter.iter,
                        stream, node_channel_id.node) {
-               unsigned long consumed_pos;
+               unsigned long produced_pos = 0, consumed_pos = 0;
 
                health_code_update();
 
@@ -4009,262 +4033,605 @@ int lttng_consumer_rotate_channel(uint64_t key, const char *path,
                 */
                pthread_mutex_lock(&stream->lock);
 
-               ret = lttng_strncpy(stream->channel_read_only_attributes.path,
-                               channel->pathname,
-                               sizeof(stream->channel_read_only_attributes.path));
-               if (ret) {
-                       ERR("Failed to sample channel path name during channel rotation");
-                       goto end_unlock_stream;
+               if (stream->trace_chunk == stream->chan->trace_chunk) {
+                       rotating_to_new_chunk = false;
                }
-               ret = lttng_consumer_sample_snapshot_positions(stream);
-               if (ret < 0) {
-                       ERR("Failed to sample snapshot position during channel rotation");
-                       goto end_unlock_stream;
+
+               /*
+                * Do not flush a packet when rotating from a NULL trace
+                * chunk. The stream has no means to output data, and the prior
+                * rotation which rotated to NULL performed that side-effect
+                * already. No new data can be produced when a stream has no
+                * associated trace chunk (e.g. a stop followed by a rotate).
+                */
+               if (stream->trace_chunk) {
+                       bool flush_active;
+
+                       if (stream->metadata_flag) {
+                               /*
+                                * Don't produce an empty metadata packet,
+                                * simply close the current one.
+                                *
+                                * Metadata is regenerated on every trace chunk
+                                * switch; there is no concern that no data was
+                                * produced.
+                                */
+                               flush_active = true;
+                       } else {
+                               /*
+                                * Only flush an empty packet if the "packet
+                                * open" could not be performed on transition
+                                * to a new trace chunk and no packets were
+                                * consumed within the chunk's lifetime.
+                                */
+                               if (stream->opened_packet_in_current_trace_chunk) {
+                                       flush_active = true;
+                               } else {
+                                       /*
+                                        * Stream could have been full at the
+                                        * time of rotation, but then have had
+                                        * no activity at all.
+                                        *
+                                        * It is important to flush a packet
+                                        * to prevent 0-length files from being
+                                        * produced as most viewers choke on
+                                        * them.
+                                        *
+                                        * Unfortunately viewers will not be
+                                        * able to know that tracing was active
+                                        * for this stream during this trace
+                                        * chunk's lifetime.
+                                        */
+                                       ret = sample_stream_positions(stream, &produced_pos, &consumed_pos);
+                                       if (ret) {
+                                               goto end_unlock_stream;
+                                       }
+
+                                       /*
+                                        * Don't flush an empty packet if data
+                                        * was produced; it will be consumed
+                                        * before the rotation completes.
+                                        */
+                                       flush_active = produced_pos != consumed_pos;
+                                       if (!flush_active) {
+                                               const char *trace_chunk_name;
+                                               uint64_t trace_chunk_id;
+
+                                               chunk_status = lttng_trace_chunk_get_name(
+                                                               stream->trace_chunk,
+                                                               &trace_chunk_name,
+                                                               NULL);
+                                               if (chunk_status == LTTNG_TRACE_CHUNK_STATUS_NONE) {
+                                                       trace_chunk_name = "none";
+                                               }
+
+                                               /*
+                                                * Consumer trace chunks are
+                                                * never anonymous.
+                                                */
+                                               chunk_status = lttng_trace_chunk_get_id(
+                                                               stream->trace_chunk,
+                                                               &trace_chunk_id);
+                                               assert(chunk_status ==
+                                                               LTTNG_TRACE_CHUNK_STATUS_OK);
+
+                                               DBG("Unable to open packet for stream during trace chunk's lifetime. "
+                                                               "Flushing an empty packet to prevent an empty file from being created: "
+                                                               "stream id = %" PRIu64 ", trace chunk name = `%s`, trace chunk id = %" PRIu64,
+                                                               stream->key, trace_chunk_name, trace_chunk_id);
+                                       }
+                               }
+                       }
+
+                       /*
+                        * Close the current packet before sampling the
+                        * ring buffer positions.
+                        */
+                       ret = consumer_stream_flush_buffer(stream, flush_active);
+                       if (ret < 0) {
+                               ERR("Failed to flush stream %" PRIu64 " during channel rotation",
+                                               stream->key);
+                               goto end_unlock_stream;
+                       }
                }
 
-               ret = lttng_consumer_get_produced_snapshot(stream,
-                               &stream->rotate_position);
-               if (ret < 0) {
-                       ERR("Failed to sample produced position during channel rotation");
+               ret = lttng_consumer_take_snapshot(stream);
+               if (ret < 0 && ret != -ENODATA && ret != -EAGAIN) {
+                       ERR("Failed to sample snapshot position during channel rotation");
                        goto end_unlock_stream;
                }
+               if (!ret) {
+                       ret = lttng_consumer_get_produced_snapshot(stream,
+                                       &produced_pos);
+                       if (ret < 0) {
+                               ERR("Failed to sample produced position during channel rotation");
+                               goto end_unlock_stream;
+                       }
 
-               lttng_consumer_get_consumed_snapshot(stream,
-                               &consumed_pos);
-               if (consumed_pos == stream->rotate_position) {
+                       ret = lttng_consumer_get_consumed_snapshot(stream,
+                                       &consumed_pos);
+                       if (ret < 0) {
+                               ERR("Failed to sample consumed position during channel rotation");
+                               goto end_unlock_stream;
+                       }
+               }
+               /*
+                * Align produced position on the start-of-packet boundary of the first
+                * packet going into the next trace chunk.
+                */
+               produced_pos = ALIGN_FLOOR(produced_pos, stream->max_sb_size);
+               if (consumed_pos == produced_pos) {
+                       DBG("Set rotate ready for stream %" PRIu64 " produced = %lu consumed = %lu",
+                                       stream->key, produced_pos, consumed_pos);
                        stream->rotate_ready = true;
+               } else {
+                       DBG("Different consumed and produced positions "
+                                       "for stream %" PRIu64 " produced = %lu consumed = %lu",
+                                       stream->key, produced_pos, consumed_pos);
                }
-               channel->nr_stream_rotate_pending++;
-
-               ret = consumer_flush_buffer(stream, 1);
-               if (ret < 0) {
-                       ERR("Failed to flush stream %" PRIu64 " during channel rotation",
+               /*
+                * The rotation position is based on the packet_seq_num of the
+                * packet following the last packet that was consumed for this
+                * stream, incremented by the offset between produced and
+                * consumed positions. This rotation position is a lower bound
+                * (inclusive) at which the next trace chunk starts. Since it
+                * is a lower bound, it is OK if the packet_seq_num does not
+                * correspond exactly to the same packet identified by the
+                * consumed_pos, which can happen in overwrite mode.
+                */
+               if (stream->sequence_number_unavailable) {
+                       /*
+                        * Rotation should never be performed on a session which
+                        * interacts with a pre-2.8 lttng-modules, which does
+                        * not implement packet sequence number.
+                        */
+                       ERR("Failure to rotate stream %" PRIu64 ": sequence number unavailable",
                                        stream->key);
+                       ret = -1;
                        goto end_unlock_stream;
                }
+               stream->rotate_position = stream->last_sequence_number + 1 +
+                               ((produced_pos - consumed_pos) / stream->max_sb_size);
+               DBG("Set rotation position for stream %" PRIu64 " at position %" PRIu64,
+                               stream->key, stream->rotate_position);
+
+               if (!is_local_trace) {
+                       /*
+                        * The relay daemon control protocol expects a rotation
+                        * position as "the sequence number of the first packet
+                        * _after_ the current trace chunk".
+                        */
+                       const struct relayd_stream_rotation_position position = {
+                               .stream_id = stream->relayd_stream_id,
+                               .rotate_at_seq_num = stream->rotate_position,
+                       };
+
+                       ret = lttng_dynamic_array_add_element(
+                                       &stream_rotation_positions,
+                                       &position);
+                       if (ret) {
+                               ERR("Failed to allocate stream rotation position");
+                               goto end_unlock_stream;
+                       }
+                       stream_count++;
+               }
+
+               stream->opened_packet_in_current_trace_chunk = false;
+
+               if (rotating_to_new_chunk && !stream->metadata_flag) {
+                       /*
+                        * Attempt to flush an empty packet as close to the
+                        * rotation point as possible. In the event where a
+                        * stream remains inactive after the rotation point,
+                        * this ensures that the new trace chunk has a
+                        * beginning timestamp set at the begining of the
+                        * trace chunk instead of only creating an empty
+                        * packet when the trace chunk is stopped.
+                        *
+                        * This indicates to the viewers that the stream
+                        * was being recorded, but more importantly it
+                        * allows viewers to determine a useable trace
+                        * intersection.
+                        *
+                        * This presents a problem in the case where the
+                        * ring-buffer is completely full.
+                        *
+                        * Consider the following scenario:
+                        *   - The consumption of data is slow (slow network,
+                        *     for instance),
+                        *   - The ring buffer is full,
+                        *   - A rotation is initiated,
+                        *     - The flush below does nothing (no space left to
+                        *       open a new packet),
+                        *   - The other streams rotate very soon, and new
+                        *     data is produced in the new chunk,
+                        *   - This stream completes its rotation long after the
+                        *     rotation was initiated
+                        *   - The session is stopped before any event can be
+                        *     produced in this stream's buffers.
+                        *
+                        * The resulting trace chunk will have a single packet
+                        * temporaly at the end of the trace chunk for this
+                        * stream making the stream intersection more narrow
+                        * than it should be.
+                        *
+                        * To work-around this, an empty flush is performed
+                        * after the first consumption of a packet during a
+                        * rotation if open_packet fails. The idea is that
+                        * consuming a packet frees enough space to switch
+                        * packets in this scenario and allows the tracer to
+                        * "stamp" the beginning of the new trace chunk at the
+                        * earliest possible point.
+                        *
+                        * The packet open is performed after the channel
+                        * rotation to ensure that no attempt to open a packet
+                        * is performed in a stream that has no active trace
+                        * chunk.
+                        */
+                       ret = lttng_dynamic_pointer_array_add_pointer(
+                                       &streams_packet_to_open, stream);
+                       if (ret) {
+                               PERROR("Failed to add a stream pointer to array of streams in which to open a packet");
+                               ret = -1;
+                               goto end_unlock_stream;
+                       }
+               }
 
                pthread_mutex_unlock(&stream->lock);
        }
-       pthread_mutex_unlock(&channel->lock);
+       stream = NULL;
 
-       ret = 0;
-       goto end;
-
-end_unlock_stream:
-       pthread_mutex_unlock(&stream->lock);
-end_unlock_channel:
-       pthread_mutex_unlock(&channel->lock);
-end:
-       rcu_read_unlock();
-       return ret;
-}
+       if (!is_local_trace) {
+               relayd = consumer_find_relayd(relayd_id);
+               if (!relayd) {
+                       ERR("Failed to find relayd %" PRIu64, relayd_id);
+                       ret = -1;
+                       goto end_unlock_channel;
+               }
 
-/*
- * Check if a stream is ready to be rotated after extracting it.
- *
- * Return 1 if it is ready for rotation, 0 if it is not, a negative value on
- * error. Stream lock must be held.
- */
-int lttng_consumer_stream_is_rotate_ready(struct lttng_consumer_stream *stream)
-{
-       int ret;
-       unsigned long consumed_pos;
-
-       if (!stream->rotate_position && !stream->rotate_ready) {
-               ret = 0;
-               goto end;
+               pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+               ret = relayd_rotate_streams(&relayd->control_sock, stream_count,
+                               rotating_to_new_chunk ? &next_chunk_id : NULL,
+                               (const struct relayd_stream_rotation_position *)
+                                               stream_rotation_positions.buffer
+                                                               .data);
+               pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               if (ret < 0) {
+                       ERR("Relayd rotate stream failed. Cleaning up relayd %" PRIu64,
+                                       relayd->net_seq_idx);
+                       lttng_consumer_cleanup_relayd(relayd);
+                       goto end_unlock_channel;
+               }
        }
 
-       if (stream->rotate_ready) {
-               ret = 1;
-               goto end;
+       for (stream_idx = 0;
+                       stream_idx < lttng_dynamic_pointer_array_get_count(
+                               &streams_packet_to_open);
+                       stream_idx++) {
+               enum consumer_stream_open_packet_status status;
+
+               stream = lttng_dynamic_pointer_array_get_pointer(
+                               &streams_packet_to_open, stream_idx);
+
+               pthread_mutex_lock(&stream->lock);
+               status = consumer_stream_open_packet(stream);
+               pthread_mutex_unlock(&stream->lock);
+               switch (status) {
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_OPENED:
+                       DBG("Opened a packet after a rotation: stream id = %" PRIu64
+                           ", channel name = %s, session id = %" PRIu64,
+                                       stream->key, stream->chan->name,
+                                       stream->chan->session_id);
+                       break;
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_NO_SPACE:
+                       /*
+                        * Can't open a packet as there is no space left
+                        * in the buffer. A new packet will be opened
+                        * once one has been consumed.
+                        */
+                       DBG("No space left to open a packet after a rotation: stream id = %" PRIu64
+                           ", channel name = %s, session id = %" PRIu64,
+                                       stream->key, stream->chan->name,
+                                       stream->chan->session_id);
+                       break;
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR:
+                       /* Logged by callee. */
+                       ret = -1;
+                       goto end_unlock_channel;
+               default:
+                       abort();
+               }
        }
 
-       /*
-        * If we don't have the rotate_ready flag, check the consumed position
-        * to determine if we need to rotate.
-        */
+       pthread_mutex_unlock(&channel->lock);
+       ret = 0;
+       goto end;
+
+end_unlock_stream:
+       pthread_mutex_unlock(&stream->lock);
+end_unlock_channel:
+       pthread_mutex_unlock(&channel->lock);
+end:
+       rcu_read_unlock();
+       lttng_dynamic_array_reset(&stream_rotation_positions);
+       lttng_dynamic_pointer_array_reset(&streams_packet_to_open);
+       return ret;
+}
+
+static
+int consumer_clear_buffer(struct lttng_consumer_stream *stream)
+{
+       int ret = 0;
+       unsigned long consumed_pos_before, consumed_pos_after;
+
        ret = lttng_consumer_sample_snapshot_positions(stream);
        if (ret < 0) {
                ERR("Taking snapshot positions");
                goto end;
        }
 
-       ret = lttng_consumer_get_consumed_snapshot(stream, &consumed_pos);
+       ret = lttng_consumer_get_consumed_snapshot(stream, &consumed_pos_before);
        if (ret < 0) {
                ERR("Consumed snapshot position");
                goto end;
        }
 
-       /* Rotate position not reached yet (with check for overflow). */
-       if ((long) (consumed_pos - stream->rotate_position) < 0) {
-               ret = 0;
-               goto end;
+       switch (consumer_data.type) {
+       case LTTNG_CONSUMER_KERNEL:
+               ret = kernctl_buffer_clear(stream->wait_fd);
+               if (ret < 0) {
+                       ERR("Failed to clear kernel stream (ret = %d)", ret);
+                       goto end;
+               }
+               break;
+       case LTTNG_CONSUMER32_UST:
+       case LTTNG_CONSUMER64_UST:
+               lttng_ustconsumer_clear_buffer(stream);
+               break;
+       default:
+               ERR("Unknown consumer_data type");
+               abort();
        }
-       ret = 1;
 
+       ret = lttng_consumer_sample_snapshot_positions(stream);
+       if (ret < 0) {
+               ERR("Taking snapshot positions");
+               goto end;
+       }
+       ret = lttng_consumer_get_consumed_snapshot(stream, &consumed_pos_after);
+       if (ret < 0) {
+               ERR("Consumed snapshot position");
+               goto end;
+       }
+       DBG("clear: before: %lu after: %lu", consumed_pos_before, consumed_pos_after);
 end:
        return ret;
 }
 
-/*
- * Reset the state for a stream after a rotation occurred.
- */
-void lttng_consumer_reset_stream_rotate_state(struct lttng_consumer_stream *stream)
-{
-       stream->rotate_position = 0;
-       stream->rotate_ready = false;
-}
-
-/*
- * Perform the rotation a local stream file.
- */
-int rotate_local_stream(struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream)
+static
+int consumer_clear_stream(struct lttng_consumer_stream *stream)
 {
        int ret;
 
-       DBG("Rotate local stream: stream key %" PRIu64 ", channel key %" PRIu64 " at path %s",
-                       stream->key,
-                       stream->chan->key,
-                       stream->channel_read_only_attributes.path);
-
-       ret = close(stream->out_fd);
+       ret = consumer_stream_flush_buffer(stream, 1);
        if (ret < 0) {
-               PERROR("Closing trace file (fd %d), stream %" PRIu64,
-                               stream->out_fd, stream->key);
-               assert(0);
+               ERR("Failed to flush stream %" PRIu64 " during channel clear",
+                               stream->key);
+               ret = LTTCOMM_CONSUMERD_FATAL;
                goto error;
        }
 
-       ret = utils_create_stream_file(
-                       stream->channel_read_only_attributes.path,
-                       stream->name,
-                       stream->channel_read_only_attributes.tracefile_size,
-                       stream->tracefile_count_current,
-                       stream->uid, stream->gid, NULL);
+       ret = consumer_clear_buffer(stream);
        if (ret < 0) {
-               ERR("Rotate create stream file");
+               ERR("Failed to clear stream %" PRIu64 " during channel clear",
+                               stream->key);
+               ret = LTTCOMM_CONSUMERD_FATAL;
                goto error;
        }
-       stream->out_fd = ret;
-       stream->tracefile_size_current = 0;
 
-       if (!stream->metadata_flag) {
-               struct lttng_index_file *index_file;
+       ret = LTTCOMM_CONSUMERD_SUCCESS;
+error:
+       return ret;
+}
 
-               lttng_index_file_put(stream->index_file);
+static
+int consumer_clear_unmonitored_channel(struct lttng_consumer_channel *channel)
+{
+       int ret;
+       struct lttng_consumer_stream *stream;
 
-               index_file = lttng_index_file_create(
-                               stream->channel_read_only_attributes.path,
-                               stream->name, stream->uid, stream->gid,
-                               stream->channel_read_only_attributes.tracefile_size,
-                               stream->tracefile_count_current,
-                               CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
-               if (!index_file) {
-                       ERR("Create index file during rotation");
-                       goto error;
+       rcu_read_lock();
+       pthread_mutex_lock(&channel->lock);
+       cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+               health_code_update();
+               pthread_mutex_lock(&stream->lock);
+               ret = consumer_clear_stream(stream);
+               if (ret) {
+                       goto error_unlock;
                }
-               stream->index_file = index_file;
-               stream->out_fd_offset = 0;
+               pthread_mutex_unlock(&stream->lock);
        }
+       pthread_mutex_unlock(&channel->lock);
+       rcu_read_unlock();
+       return 0;
 
-       ret = 0;
-       goto end;
-
-error:
-       ret = -1;
-end:
+error_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       pthread_mutex_unlock(&channel->lock);
+       rcu_read_unlock();
        return ret;
+}
+
+/*
+ * Check if a stream is ready to be rotated after extracting it.
+ *
+ * Return 1 if it is ready for rotation, 0 if it is not, a negative value on
+ * error. Stream lock must be held.
+ */
+int lttng_consumer_stream_is_rotate_ready(struct lttng_consumer_stream *stream)
+{
+       DBG("Check is rotate ready for stream %" PRIu64
+                       " ready %u rotate_position %" PRIu64
+                       " last_sequence_number %" PRIu64,
+                       stream->key, stream->rotate_ready,
+                       stream->rotate_position, stream->last_sequence_number);
+       if (stream->rotate_ready) {
+               return 1;
+       }
+
+       /*
+        * If packet seq num is unavailable, it means we are interacting
+        * with a pre-2.8 lttng-modules which does not implement the
+        * sequence number. Rotation should never be used by sessiond in this
+        * scenario.
+        */
+       if (stream->sequence_number_unavailable) {
+               ERR("Internal error: rotation used on stream %" PRIu64
+                               " with unavailable sequence number",
+                               stream->key);
+               return -1;
+       }
+
+       if (stream->rotate_position == -1ULL ||
+                       stream->last_sequence_number == -1ULL) {
+               return 0;
+       }
+
+       /*
+        * Rotate position not reached yet. The stream rotate position is
+        * the position of the next packet belonging to the next trace chunk,
+        * but consumerd considers rotation ready when reaching the last
+        * packet of the current chunk, hence the "rotate_position - 1".
+        */
 
+       DBG("Check is rotate ready for stream %" PRIu64
+                       " last_sequence_number %" PRIu64
+                       " rotate_position %" PRIu64,
+                       stream->key, stream->last_sequence_number,
+                       stream->rotate_position);
+       if (stream->last_sequence_number >= stream->rotate_position - 1) {
+               return 1;
+       }
+
+       return 0;
+}
+
+/*
+ * Reset the state for a stream after a rotation occurred.
+ */
+void lttng_consumer_reset_stream_rotate_state(struct lttng_consumer_stream *stream)
+{
+       DBG("lttng_consumer_reset_stream_rotate_state for stream %" PRIu64,
+                       stream->key);
+       stream->rotate_position = -1ULL;
+       stream->rotate_ready = false;
 }
 
 /*
- * Perform the rotation a stream file on the relay.
+ * Perform the rotation a local stream file.
  */
-int rotate_relay_stream(struct lttng_consumer_local_data *ctx,
+static
+int rotate_local_stream(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_stream *stream)
 {
-       int ret;
-       struct consumer_relayd_sock_pair *relayd;
+       int ret = 0;
 
-       DBG("Rotate relay stream");
-       relayd = consumer_find_relayd(stream->net_seq_idx);
-       if (!relayd) {
-               ERR("Failed to find relayd");
-               ret = -1;
-               goto end;
+       DBG("Rotate local stream: stream key %" PRIu64 ", channel key %" PRIu64,
+                       stream->key,
+                       stream->chan->key);
+       stream->tracefile_size_current = 0;
+       stream->tracefile_count_current = 0;
+
+       if (stream->out_fd >= 0) {
+               ret = close(stream->out_fd);
+               if (ret) {
+                       PERROR("Failed to close stream out_fd of channel \"%s\"",
+                               stream->chan->name);
+               }
+               stream->out_fd = -1;
        }
 
-       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
-       ret = relayd_rotate_stream(&relayd->control_sock,
-                       stream->relayd_stream_id,
-                       stream->channel_read_only_attributes.path,
-                       stream->chan->current_chunk_id,
-                       stream->last_sequence_number);
-       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
-       if (ret) {
-               ERR("Rotate relay stream");
+       if (stream->index_file) {
+               lttng_index_file_put(stream->index_file);
+               stream->index_file = NULL;
+       }
+
+       if (!stream->trace_chunk) {
+               goto end;
        }
 
+       ret = consumer_stream_create_output_files(stream, true);
 end:
        return ret;
 }
 
 /*
  * Performs the stream rotation for the rotate session feature if needed.
- * It must be called with the stream lock held.
+ * It must be called with the channel and stream locks held.
  *
  * Return 0 on success, a negative number of error.
  */
 int lttng_consumer_rotate_stream(struct lttng_consumer_local_data *ctx,
-               struct lttng_consumer_stream *stream, bool *rotated)
+               struct lttng_consumer_stream *stream)
 {
        int ret;
 
        DBG("Consumer rotate stream %" PRIu64, stream->key);
 
-       if (stream->net_seq_idx != (uint64_t) -1ULL) {
-               ret = rotate_relay_stream(ctx, stream);
-       } else {
-               ret = rotate_local_stream(ctx, stream);
-       }
-       if (ret < 0) {
-               ERR("Rotate stream");
+       /*
+        * Update the stream's 'current' chunk to the session's (channel)
+        * now-current chunk.
+        */
+       lttng_trace_chunk_put(stream->trace_chunk);
+       if (stream->chan->trace_chunk == stream->trace_chunk) {
+               /*
+                * A channel can be rotated and not have a "next" chunk
+                * to transition to. In that case, the channel's "current chunk"
+                * has not been closed yet, but it has not been updated to
+                * a "next" trace chunk either. Hence, the stream, like its
+                * parent channel, becomes part of no chunk and can't output
+                * anything until a new trace chunk is created.
+                */
+               stream->trace_chunk = NULL;
+       } else if (stream->chan->trace_chunk &&
+                       !lttng_trace_chunk_get(stream->chan->trace_chunk)) {
+               ERR("Failed to acquire a reference to channel's trace chunk during stream rotation");
+               ret = -1;
                goto error;
+       } else {
+               /*
+                * Update the stream's trace chunk to its parent channel's
+                * current trace chunk.
+                */
+               stream->trace_chunk = stream->chan->trace_chunk;
        }
 
-       if (stream->metadata_flag) {
-               switch (consumer_data.type) {
-               case LTTNG_CONSUMER_KERNEL:
-                       /*
-                        * Reset the position of what has been read from the metadata
-                        * cache to 0 so we can dump it again.
-                        */
-                       ret = kernctl_metadata_cache_dump(stream->wait_fd);
-                       if (ret < 0) {
-                               ERR("Failed to dump the kernel metadata cache after rotation");
-                               goto error;
-                       }
-                       break;
-               case LTTNG_CONSUMER32_UST:
-               case LTTNG_CONSUMER64_UST:
-                       /*
-                        * Reset the position pushed from the metadata cache so it
-                        * will write from the beginning on the next push.
-                        */
-                       stream->ust_metadata_pushed = 0;
-                       break;
-               default:
-                       ERR("Unknown consumer_data type");
-                       abort();
+       if (stream->net_seq_idx == (uint64_t) -1ULL) {
+               ret = rotate_local_stream(ctx, stream);
+               if (ret < 0) {
+                       ERR("Failed to rotate stream, ret = %i", ret);
+                       goto error;
                }
        }
-       lttng_consumer_reset_stream_rotate_state(stream);
 
-       if (rotated) {
-               *rotated = true;
+       if (stream->metadata_flag && stream->trace_chunk) {
+               /*
+                * If the stream has transitioned to a new trace
+                * chunk, the metadata should be re-dumped to the
+                * newest chunk.
+                *
+                * However, it is possible for a stream to transition to
+                * a "no-chunk" state. This can happen if a rotation
+                * occurs on an inactive session. In such cases, the metadata
+                * regeneration will happen when the next trace chunk is
+                * created.
+                */
+               ret = consumer_metadata_stream_dump(stream);
+               if (ret) {
+                       goto error;
+               }
        }
+       lttng_consumer_reset_stream_rotate_state(stream);
 
        ret = 0;
 
@@ -4278,14 +4645,15 @@ error:
  * This is especially important for low throughput streams that have already
  * been consumed, we cannot wait for their next packet to perform the
  * rotation.
+ * Need to be called with RCU read-side lock held to ensure existence of
+ * channel.
  *
  * Returns 0 on success, < 0 on error
  */
-int lttng_consumer_rotate_ready_streams(uint64_t key,
-               struct lttng_consumer_local_data *ctx)
+int lttng_consumer_rotate_ready_streams(struct lttng_consumer_channel *channel,
+               uint64_t key, struct lttng_consumer_local_data *ctx)
 {
        int ret;
-       struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
        struct lttng_ht_iter iter;
        struct lttng_ht *ht = consumer_data.stream_per_chan_id_ht;
@@ -4294,34 +4662,25 @@ int lttng_consumer_rotate_ready_streams(uint64_t key,
 
        DBG("Consumer rotate ready streams in channel %" PRIu64, key);
 
-       channel = consumer_find_channel(key);
-       if (!channel) {
-               ERR("No channel found for key %" PRIu64, key);
-               ret = -1;
-               goto end;
-       }
-
        cds_lfht_for_each_entry_duplicate(ht->ht,
                        ht->hash_fct(&channel->key, lttng_ht_seed),
                        ht->match_fct, &channel->key, &iter.iter,
                        stream, node_channel_id.node) {
                health_code_update();
 
+               pthread_mutex_lock(&stream->chan->lock);
                pthread_mutex_lock(&stream->lock);
 
                if (!stream->rotate_ready) {
                        pthread_mutex_unlock(&stream->lock);
+                       pthread_mutex_unlock(&stream->chan->lock);
                        continue;
                }
                DBG("Consumer rotate ready stream %" PRIu64, stream->key);
 
-               ret = lttng_consumer_rotate_stream(ctx, stream, NULL);
+               ret = lttng_consumer_rotate_stream(ctx, stream);
                pthread_mutex_unlock(&stream->lock);
-               if (ret) {
-                       goto end;
-               }
-
-               ret = consumer_post_rotation(stream, ctx);
+               pthread_mutex_unlock(&stream->chan->lock);
                if (ret) {
                        goto end;
                }
@@ -4334,128 +4693,545 @@ end:
        return ret;
 }
 
-static
-int rotate_rename_local(const char *old_path, const char *new_path,
-               uid_t uid, gid_t gid)
+enum lttcomm_return_code lttng_consumer_init_command(
+               struct lttng_consumer_local_data *ctx,
+               const lttng_uuid sessiond_uuid)
 {
-       int ret;
-
-       assert(old_path);
-       assert(new_path);
-
-       ret = utils_mkdir_recursive(new_path, S_IRWXU | S_IRWXG, uid, gid);
-       if (ret < 0) {
-               ERR("Create directory on rotate");
-               goto end;
-       }
+       enum lttcomm_return_code ret;
+       char uuid_str[LTTNG_UUID_STR_LEN];
 
-       ret = rename(old_path, new_path);
-       if (ret < 0 && errno != ENOENT) {
-               PERROR("Rename completed rotation chunk");
+       if (ctx->sessiond_uuid.is_set) {
+               ret = LTTCOMM_CONSUMERD_ALREADY_SET;
                goto end;
        }
 
-       ret = 0;
+       ctx->sessiond_uuid.is_set = true;
+       memcpy(ctx->sessiond_uuid.value, sessiond_uuid, sizeof(lttng_uuid));
+       ret = LTTCOMM_CONSUMERD_SUCCESS;
+       lttng_uuid_to_str(sessiond_uuid, uuid_str);
+       DBG("Received session daemon UUID: %s", uuid_str);
 end:
        return ret;
 }
 
-static
-int rotate_rename_relay(const char *old_path, const char *new_path,
-               uint64_t relayd_id)
+enum lttcomm_return_code lttng_consumer_create_trace_chunk(
+               const uint64_t *relayd_id, uint64_t session_id,
+               uint64_t chunk_id,
+               time_t chunk_creation_timestamp,
+               const char *chunk_override_name,
+               const struct lttng_credentials *credentials,
+               struct lttng_directory_handle *chunk_directory_handle)
 {
        int ret;
-       struct consumer_relayd_sock_pair *relayd;
+       enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+       struct lttng_trace_chunk *created_chunk = NULL, *published_chunk = NULL;
+       enum lttng_trace_chunk_status chunk_status;
+       char relayd_id_buffer[MAX_INT_DEC_LEN(*relayd_id)];
+       char creation_timestamp_buffer[ISO8601_STR_LEN];
+       const char *relayd_id_str = "(none)";
+       const char *creation_timestamp_str;
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_channel *channel;
 
-       relayd = consumer_find_relayd(relayd_id);
-       if (!relayd) {
-               ERR("Failed to find relayd while running rotate_rename_relay command");
-               ret = -1;
-               goto end;
+       if (relayd_id) {
+               /* Only used for logging purposes. */
+               ret = snprintf(relayd_id_buffer, sizeof(relayd_id_buffer),
+                               "%" PRIu64, *relayd_id);
+               if (ret > 0 && ret < sizeof(relayd_id_buffer)) {
+                       relayd_id_str = relayd_id_buffer;
+               } else {
+                       relayd_id_str = "(formatting error)";
+               }
        }
 
-       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
-       ret = relayd_rotate_rename(&relayd->control_sock, old_path, new_path);
-       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
-end:
-       return ret;
+       /* Local protocol error. */
+       assert(chunk_creation_timestamp);
+       ret = time_to_iso8601_str(chunk_creation_timestamp,
+                       creation_timestamp_buffer,
+                       sizeof(creation_timestamp_buffer));
+       creation_timestamp_str = !ret ? creation_timestamp_buffer :
+                       "(formatting error)";
+
+       DBG("Consumer create trace chunk command: relay_id = %s"
+                       ", session_id = %" PRIu64 ", chunk_id = %" PRIu64
+                       ", chunk_override_name = %s"
+                       ", chunk_creation_timestamp = %s",
+                       relayd_id_str, session_id, chunk_id,
+                       chunk_override_name ? : "(none)",
+                       creation_timestamp_str);
+
+       /*
+        * The trace chunk registry, as used by the consumer daemon, implicitly
+        * owns the trace chunks. This is only needed in the consumer since
+        * the consumer has no notion of a session beyond session IDs being
+        * used to identify other objects.
+        *
+        * The lttng_trace_chunk_registry_publish() call below provides a
+        * reference which is not released; it implicitly becomes the session
+        * daemon's reference to the chunk in the consumer daemon.
+        *
+        * The lifetime of trace chunks in the consumer daemon is managed by
+        * the session daemon through the LTTNG_CONSUMER_CREATE_TRACE_CHUNK
+        * and LTTNG_CONSUMER_DESTROY_TRACE_CHUNK commands.
+        */
+       created_chunk = lttng_trace_chunk_create(chunk_id,
+                       chunk_creation_timestamp, NULL);
+       if (!created_chunk) {
+               ERR("Failed to create trace chunk");
+               ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+               goto error;
+       }
+
+       if (chunk_override_name) {
+               chunk_status = lttng_trace_chunk_override_name(created_chunk,
+                               chunk_override_name);
+               if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+                       ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+                       goto error;
+               }
+       }
+
+       if (chunk_directory_handle) {
+               chunk_status = lttng_trace_chunk_set_credentials(created_chunk,
+                               credentials);
+               if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+                       ERR("Failed to set trace chunk credentials");
+                       ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+                       goto error;
+               }
+               /*
+                * The consumer daemon has no ownership of the chunk output
+                * directory.
+                */
+               chunk_status = lttng_trace_chunk_set_as_user(created_chunk,
+                               chunk_directory_handle);
+               chunk_directory_handle = NULL;
+               if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+                       ERR("Failed to set trace chunk's directory handle");
+                       ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+                       goto error;
+               }
+       }
+
+       published_chunk = lttng_trace_chunk_registry_publish_chunk(
+                       consumer_data.chunk_registry, session_id,
+                       created_chunk);
+       lttng_trace_chunk_put(created_chunk);
+       created_chunk = NULL;
+       if (!published_chunk) {
+               ERR("Failed to publish trace chunk");
+               ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+               goto error;
+       }
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry_duplicate(consumer_data.channels_by_session_id_ht->ht,
+                       consumer_data.channels_by_session_id_ht->hash_fct(
+                                       &session_id, lttng_ht_seed),
+                       consumer_data.channels_by_session_id_ht->match_fct,
+                       &session_id, &iter.iter, channel,
+                       channels_by_session_id_ht_node.node) {
+               ret = lttng_consumer_channel_set_trace_chunk(channel,
+                               published_chunk);
+               if (ret) {
+                       /*
+                        * Roll-back the creation of this chunk.
+                        *
+                        * This is important since the session daemon will
+                        * assume that the creation of this chunk failed and
+                        * will never ask for it to be closed, resulting
+                        * in a leak and an inconsistent state for some
+                        * channels.
+                        */
+                       enum lttcomm_return_code close_ret;
+                       char path[LTTNG_PATH_MAX];
+
+                       DBG("Failed to set new trace chunk on existing channels, rolling back");
+                       close_ret = lttng_consumer_close_trace_chunk(relayd_id,
+                                       session_id, chunk_id,
+                                       chunk_creation_timestamp, NULL,
+                                       path);
+                       if (close_ret != LTTCOMM_CONSUMERD_SUCCESS) {
+                               ERR("Failed to roll-back the creation of new chunk: session_id = %" PRIu64 ", chunk_id = %" PRIu64,
+                                               session_id, chunk_id);
+                       }
+
+                       ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+                       break;
+               }
+       }
+
+       if (relayd_id) {
+               struct consumer_relayd_sock_pair *relayd;
+
+               relayd = consumer_find_relayd(*relayd_id);
+               if (relayd) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+                       ret = relayd_create_trace_chunk(
+                                       &relayd->control_sock, published_chunk);
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               } else {
+                       ERR("Failed to find relay daemon socket: relayd_id = %" PRIu64, *relayd_id);
+               }
+
+               if (!relayd || ret) {
+                       enum lttcomm_return_code close_ret;
+                       char path[LTTNG_PATH_MAX];
+
+                       close_ret = lttng_consumer_close_trace_chunk(relayd_id,
+                                       session_id,
+                                       chunk_id,
+                                       chunk_creation_timestamp,
+                                       NULL, path);
+                       if (close_ret != LTTCOMM_CONSUMERD_SUCCESS) {
+                               ERR("Failed to roll-back the creation of new chunk: session_id = %" PRIu64 ", chunk_id = %" PRIu64,
+                                               session_id,
+                                               chunk_id);
+                       }
+
+                       ret_code = LTTCOMM_CONSUMERD_CREATE_TRACE_CHUNK_FAILED;
+                       goto error_unlock;
+               }
+       }
+error_unlock:
+       rcu_read_unlock();
+error:
+       /* Release the reference returned by the "publish" operation. */
+       lttng_trace_chunk_put(published_chunk);
+       lttng_trace_chunk_put(created_chunk);
+       return ret_code;
 }
 
-int lttng_consumer_rotate_rename(const char *old_path, const char *new_path,
-               uid_t uid, gid_t gid, uint64_t relayd_id)
+enum lttcomm_return_code lttng_consumer_close_trace_chunk(
+               const uint64_t *relayd_id, uint64_t session_id,
+               uint64_t chunk_id, time_t chunk_close_timestamp,
+               const enum lttng_trace_chunk_command_type *close_command,
+               char *path)
 {
-       if (relayd_id != -1ULL) {
-               return rotate_rename_relay(old_path, new_path, relayd_id);
-       } else {
-               return rotate_rename_local(old_path, new_path, uid, gid);
+       enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+       struct lttng_trace_chunk *chunk;
+       char relayd_id_buffer[MAX_INT_DEC_LEN(*relayd_id)];
+       const char *relayd_id_str = "(none)";
+       const char *close_command_name = "none";
+       struct lttng_ht_iter iter;
+       struct lttng_consumer_channel *channel;
+       enum lttng_trace_chunk_status chunk_status;
+
+       if (relayd_id) {
+               int ret;
+
+               /* Only used for logging purposes. */
+               ret = snprintf(relayd_id_buffer, sizeof(relayd_id_buffer),
+                               "%" PRIu64, *relayd_id);
+               if (ret > 0 && ret < sizeof(relayd_id_buffer)) {
+                       relayd_id_str = relayd_id_buffer;
+               } else {
+                       relayd_id_str = "(formatting error)";
+               }
+       }
+       if (close_command) {
+               close_command_name = lttng_trace_chunk_command_type_get_name(
+                               *close_command);
+       }
+
+       DBG("Consumer close trace chunk command: relayd_id = %s"
+                       ", session_id = %" PRIu64 ", chunk_id = %" PRIu64
+                       ", close command = %s",
+                       relayd_id_str, session_id, chunk_id,
+                       close_command_name);
+
+       chunk = lttng_trace_chunk_registry_find_chunk(
+                       consumer_data.chunk_registry, session_id, chunk_id);
+       if (!chunk) {
+               ERR("Failed to find chunk: session_id = %" PRIu64
+                               ", chunk_id = %" PRIu64,
+                               session_id, chunk_id);
+               ret_code = LTTCOMM_CONSUMERD_UNKNOWN_TRACE_CHUNK;
+               goto end;
+       }
+
+       chunk_status = lttng_trace_chunk_set_close_timestamp(chunk,
+                       chunk_close_timestamp);
+       if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+               ret_code = LTTCOMM_CONSUMERD_CLOSE_TRACE_CHUNK_FAILED;
+               goto end;
        }
+
+       if (close_command) {
+               chunk_status = lttng_trace_chunk_set_close_command(
+                               chunk, *close_command);
+               if (chunk_status != LTTNG_TRACE_CHUNK_STATUS_OK) {
+                       ret_code = LTTCOMM_CONSUMERD_CLOSE_TRACE_CHUNK_FAILED;
+                       goto end;
+               }
+       }
+
+       /*
+        * chunk is now invalid to access as we no longer hold a reference to
+        * it; it is only kept around to compare it (by address) to the
+        * current chunk found in the session's channels.
+        */
+       rcu_read_lock();
+       cds_lfht_for_each_entry(consumer_data.channel_ht->ht, &iter.iter,
+                       channel, node.node) {
+               int ret;
+
+               /*
+                * Only change the channel's chunk to NULL if it still
+                * references the chunk being closed. The channel may
+                * reference a newer channel in the case of a session
+                * rotation. When a session rotation occurs, the "next"
+                * chunk is created before the "current" chunk is closed.
+                */
+               if (channel->trace_chunk != chunk) {
+                       continue;
+               }
+               ret = lttng_consumer_channel_set_trace_chunk(channel, NULL);
+               if (ret) {
+                       /*
+                        * Attempt to close the chunk on as many channels as
+                        * possible.
+                        */
+                       ret_code = LTTCOMM_CONSUMERD_CLOSE_TRACE_CHUNK_FAILED;
+               }
+       }
+
+       if (relayd_id) {
+               int ret;
+               struct consumer_relayd_sock_pair *relayd;
+
+               relayd = consumer_find_relayd(*relayd_id);
+               if (relayd) {
+                       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
+                       ret = relayd_close_trace_chunk(
+                                       &relayd->control_sock, chunk,
+                                       path);
+                       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+               } else {
+                       ERR("Failed to find relay daemon socket: relayd_id = %" PRIu64,
+                                       *relayd_id);
+               }
+
+               if (!relayd || ret) {
+                       ret_code = LTTCOMM_CONSUMERD_CLOSE_TRACE_CHUNK_FAILED;
+                       goto error_unlock;
+               }
+       }
+error_unlock:
+       rcu_read_unlock();
+end:
+       /*
+        * Release the reference returned by the "find" operation and
+        * the session daemon's implicit reference to the chunk.
+        */
+       lttng_trace_chunk_put(chunk);
+       lttng_trace_chunk_put(chunk);
+
+       return ret_code;
 }
 
-int lttng_consumer_rotate_pending_relay(uint64_t session_id,
-               uint64_t relayd_id, uint64_t chunk_id)
+enum lttcomm_return_code lttng_consumer_trace_chunk_exists(
+               const uint64_t *relayd_id, uint64_t session_id,
+               uint64_t chunk_id)
 {
        int ret;
-       struct consumer_relayd_sock_pair *relayd;
+       enum lttcomm_return_code ret_code;
+       char relayd_id_buffer[MAX_INT_DEC_LEN(*relayd_id)];
+       const char *relayd_id_str = "(none)";
+       const bool is_local_trace = !relayd_id;
+       struct consumer_relayd_sock_pair *relayd = NULL;
+       bool chunk_exists_local, chunk_exists_remote;
+
+       if (relayd_id) {
+               /* Only used for logging purposes. */
+               ret = snprintf(relayd_id_buffer, sizeof(relayd_id_buffer),
+                               "%" PRIu64, *relayd_id);
+               if (ret > 0 && ret < sizeof(relayd_id_buffer)) {
+                       relayd_id_str = relayd_id_buffer;
+               } else {
+                       relayd_id_str = "(formatting error)";
+               }
+       }
 
-       relayd = consumer_find_relayd(relayd_id);
-       if (!relayd) {
-               ERR("Failed to find relayd");
-               ret = -1;
+       DBG("Consumer trace chunk exists command: relayd_id = %s"
+                       ", chunk_id = %" PRIu64, relayd_id_str,
+                       chunk_id);
+       ret = lttng_trace_chunk_registry_chunk_exists(
+                       consumer_data.chunk_registry, session_id,
+                       chunk_id, &chunk_exists_local);
+       if (ret) {
+               /* Internal error. */
+               ERR("Failed to query the existence of a trace chunk");
+               ret_code = LTTCOMM_CONSUMERD_FATAL;
+               goto end;
+       }
+       DBG("Trace chunk %s locally",
+                       chunk_exists_local ? "exists" : "does not exist");
+       if (chunk_exists_local) {
+               ret_code = LTTCOMM_CONSUMERD_TRACE_CHUNK_EXISTS_LOCAL;
+               goto end;
+       } else if (is_local_trace) {
+               ret_code = LTTCOMM_CONSUMERD_UNKNOWN_TRACE_CHUNK;
                goto end;
        }
 
+       rcu_read_lock();
+       relayd = consumer_find_relayd(*relayd_id);
+       if (!relayd) {
+               ERR("Failed to find relayd %" PRIu64, *relayd_id);
+               ret_code = LTTCOMM_CONSUMERD_INVALID_PARAMETERS;
+               goto end_rcu_unlock;
+       }
+       DBG("Looking up existence of trace chunk on relay daemon");
        pthread_mutex_lock(&relayd->ctrl_sock_mutex);
-       ret = relayd_rotate_pending(&relayd->control_sock, chunk_id);
+       ret = relayd_trace_chunk_exists(&relayd->control_sock, chunk_id,
+                       &chunk_exists_remote);
        pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
+       if (ret < 0) {
+               ERR("Failed to look-up the existence of trace chunk on relay daemon");
+               ret_code = LTTCOMM_CONSUMERD_RELAYD_FAIL;
+               goto end_rcu_unlock;
+       }
+
+       ret_code = chunk_exists_remote ?
+                       LTTCOMM_CONSUMERD_TRACE_CHUNK_EXISTS_REMOTE :
+                       LTTCOMM_CONSUMERD_UNKNOWN_TRACE_CHUNK;
+       DBG("Trace chunk %s on relay daemon",
+                       chunk_exists_remote ? "exists" : "does not exist");
 
+end_rcu_unlock:
+       rcu_read_unlock();
 end:
-       return ret;
+       return ret_code;
 }
 
 static
-int mkdir_local(const char *path, uid_t uid, gid_t gid)
+int consumer_clear_monitored_channel(struct lttng_consumer_channel *channel)
 {
+       struct lttng_ht *ht;
+       struct lttng_consumer_stream *stream;
+       struct lttng_ht_iter iter;
        int ret;
 
-       ret = utils_mkdir_recursive(path, S_IRWXU | S_IRWXG, uid, gid);
-       if (ret < 0) {
-               /* utils_mkdir_recursive logs an error. */
-               goto end;
+       ht = consumer_data.stream_per_chan_id_ht;
+
+       rcu_read_lock();
+       cds_lfht_for_each_entry_duplicate(ht->ht,
+                       ht->hash_fct(&channel->key, lttng_ht_seed),
+                       ht->match_fct, &channel->key,
+                       &iter.iter, stream, node_channel_id.node) {
+               /*
+                * Protect against teardown with mutex.
+                */
+               pthread_mutex_lock(&stream->lock);
+               if (cds_lfht_is_node_deleted(&stream->node.node)) {
+                       goto next;
+               }
+               ret = consumer_clear_stream(stream);
+               if (ret) {
+                       goto error_unlock;
+               }
+       next:
+               pthread_mutex_unlock(&stream->lock);
        }
+       rcu_read_unlock();
+       return LTTCOMM_CONSUMERD_SUCCESS;
 
-       ret = 0;
-end:
+error_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       rcu_read_unlock();
        return ret;
 }
 
-static
-int mkdir_relay(const char *path, uint64_t relayd_id)
+int lttng_consumer_clear_channel(struct lttng_consumer_channel *channel)
 {
        int ret;
-       struct consumer_relayd_sock_pair *relayd;
 
-       relayd = consumer_find_relayd(relayd_id);
-       if (!relayd) {
-               ERR("Failed to find relayd");
-               ret = -1;
+       DBG("Consumer clear channel %" PRIu64, channel->key);
+
+       if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA) {
+               /*
+                * Nothing to do for the metadata channel/stream.
+                * Snapshot mechanism already take care of the metadata
+                * handling/generation, and monitored channels only need to
+                * have their data stream cleared..
+                */
+               ret = LTTCOMM_CONSUMERD_SUCCESS;
                goto end;
        }
 
-       pthread_mutex_lock(&relayd->ctrl_sock_mutex);
-       ret = relayd_mkdir(&relayd->control_sock, path);
-       pthread_mutex_unlock(&relayd->ctrl_sock_mutex);
-
+       if (!channel->monitor) {
+               ret = consumer_clear_unmonitored_channel(channel);
+       } else {
+               ret = consumer_clear_monitored_channel(channel);
+       }
 end:
        return ret;
-
 }
 
-int lttng_consumer_mkdir(const char *path, uid_t uid, gid_t gid,
-               uint64_t relayd_id)
+enum lttcomm_return_code lttng_consumer_open_channel_packets(
+               struct lttng_consumer_channel *channel)
 {
-       if (relayd_id != -1ULL) {
-               return mkdir_relay(path, relayd_id);
-       } else {
-               return mkdir_local(path, uid, gid);
+       struct lttng_consumer_stream *stream;
+       enum lttcomm_return_code ret = LTTCOMM_CONSUMERD_SUCCESS;
+
+       if (channel->metadata_stream) {
+               ERR("Open channel packets command attempted on a metadata channel");
+               ret = LTTCOMM_CONSUMERD_INVALID_PARAMETERS;
+               goto end;
        }
+
+       rcu_read_lock();
+       cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+               enum consumer_stream_open_packet_status status;
+
+               pthread_mutex_lock(&stream->lock);
+               if (cds_lfht_is_node_deleted(&stream->node.node)) {
+                       goto next;
+               }
+
+               status = consumer_stream_open_packet(stream);
+               switch (status) {
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_OPENED:
+                       DBG("Opened a packet in \"open channel packets\" command: stream id = %" PRIu64
+                                       ", channel name = %s, session id = %" PRIu64,
+                                       stream->key, stream->chan->name,
+                                       stream->chan->session_id);
+                       stream->opened_packet_in_current_trace_chunk = true;
+                       break;
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_NO_SPACE:
+                       DBG("No space left to open a packet in \"open channel packets\" command: stream id = %" PRIu64
+                                       ", channel name = %s, session id = %" PRIu64,
+                                       stream->key, stream->chan->name,
+                                       stream->chan->session_id);
+                       break;
+               case CONSUMER_STREAM_OPEN_PACKET_STATUS_ERROR:
+                       /*
+                        * Only unexpected internal errors can lead to this
+                        * failing. Report an unknown error.
+                        */
+                       ERR("Failed to flush empty buffer in \"open channel packets\" command: stream id = %" PRIu64
+                                       ", channel id = %" PRIu64
+                                       ", channel name = %s"
+                                       ", session id = %" PRIu64,
+                                       stream->key, channel->key,
+                                       channel->name, channel->session_id);
+                       ret = LTTCOMM_CONSUMERD_UNKNOWN_ERROR;
+                       goto error_unlock;
+               default:
+                       abort();
+               }
+
+       next:
+               pthread_mutex_unlock(&stream->lock);
+       }
+
+end_rcu_unlock:
+       rcu_read_unlock();
+end:
+       return ret;
+
+error_unlock:
+       pthread_mutex_unlock(&stream->lock);
+       goto end_rcu_unlock;
 }
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