Ust-consumer: Add channel key to error msg on channel clear
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index b8c1a3cd9a74559e3cf7a79ba8e4610ae8038097..0b0b8af56de69c029f8ba419a1d0e190d09004e6 100644 (file)
@@ -1,6 +1,7 @@
 /*
  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
  *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+ * Copyright (C) 2017 - Jérémie Galarneau <jeremie.galarneau@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,
@@ -16,7 +17,7 @@
  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  */
 
-#define _GNU_SOURCE
+#define _LGPL_SOURCE
 #include <assert.h>
 #include <lttng/ust-ctl.h>
 #include <poll.h>
@@ -31,6 +32,7 @@
 #include <unistd.h>
 #include <urcu/list.h>
 #include <signal.h>
+#include <stdbool.h>
 
 #include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
 #include <common/relayd/relayd.h>
 #include <common/compat/fcntl.h>
 #include <common/compat/endian.h>
-#include <common/consumer-metadata-cache.h>
-#include <common/consumer-stream.h>
-#include <common/consumer-timer.h>
+#include <common/consumer/consumer-metadata-cache.h>
+#include <common/consumer/consumer-stream.h>
+#include <common/consumer/consumer-timer.h>
 #include <common/utils.h>
 #include <common/index/index.h>
 
 #include "ust-consumer.h"
 
+#define INT_MAX_STR_LEN 12     /* includes \0 */
+
 extern struct lttng_consumer_global_data consumer_data;
 extern int consumer_poll_timeout;
-extern volatile int consumer_quit;
 
 /*
  * Free channel object and all streams associated with it. This MUST be used
@@ -79,6 +82,7 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
         */
        if (channel->uchan) {
                lttng_ustconsumer_del_channel(channel);
+               lttng_ustconsumer_free_channel(channel);
        }
        free(channel);
 }
@@ -123,14 +127,16 @@ static struct lttng_consumer_channel *allocate_channel(uint64_t session_id,
                uint64_t relayd_id, uint64_t key, enum lttng_event_output output,
                uint64_t tracefile_size, uint64_t tracefile_count,
                uint64_t session_id_per_pid, unsigned int monitor,
-               unsigned int live_timer_interval)
+               unsigned int live_timer_interval,
+               const char *root_shm_path, const char *shm_path)
 {
        assert(pathname);
        assert(name);
 
        return consumer_allocate_channel(key, session_id, pathname, name, uid,
                        gid, relayd_id, output, tracefile_size,
-                       tracefile_count, session_id_per_pid, monitor, live_timer_interval);
+                       tracefile_count, session_id_per_pid, monitor,
+                       live_timer_interval, root_shm_path, shm_path);
 }
 
 /*
@@ -141,7 +147,8 @@ static struct lttng_consumer_channel *allocate_channel(uint64_t session_id,
  */
 static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
                struct lttng_consumer_channel *channel,
-               struct lttng_consumer_local_data *ctx, int *_alloc_ret)
+               struct lttng_consumer_local_data *ctx, int *_alloc_ret,
+               uint64_t trace_archive_id)
 {
        int alloc_ret;
        struct lttng_consumer_stream *stream = NULL;
@@ -160,7 +167,8 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
                        cpu,
                        &alloc_ret,
                        channel->type,
-                       channel->monitor);
+                       channel->monitor,
+                       trace_archive_id);
        if (stream == NULL) {
                switch (alloc_ret) {
                case -ENOENT:
@@ -179,6 +187,7 @@ static struct lttng_consumer_stream *allocate_stream(int cpu, int key,
                goto error;
        }
 
+       consumer_stream_update_channel_attributes(stream, channel);
        stream->chan = channel;
 
 error:
@@ -201,28 +210,21 @@ static int send_stream_to_thread(struct lttng_consumer_stream *stream,
 
        /* Get the right pipe where the stream will be sent. */
        if (stream->metadata_flag) {
-               ret = consumer_add_metadata_stream(stream);
-               if (ret) {
-                       ERR("Consumer add metadata stream %" PRIu64 " failed.",
-                                       stream->key);
-                       goto error;
-               }
+               consumer_add_metadata_stream(stream);
                stream_pipe = ctx->consumer_metadata_pipe;
        } else {
-               ret = consumer_add_data_stream(stream);
-               if (ret) {
-                       ERR("Consumer add stream %" PRIu64 " failed.",
-                                       stream->key);
-                       goto error;
-               }
+               consumer_add_data_stream(stream);
                stream_pipe = ctx->consumer_data_pipe;
        }
 
        /*
         * From this point on, the stream's ownership has been moved away from
-        * the channel and becomes globally visible.
+        * the channel and it becomes globally visible. Hence, remove it from
+        * the local stream list to prevent the stream from being both local and
+        * global.
         */
        stream->globally_visible = 1;
+       cds_list_del(&stream->send_node);
 
        ret = lttng_pipe_write(stream_pipe, &stream, sizeof(stream));
        if (ret < 0) {
@@ -234,18 +236,41 @@ static int send_stream_to_thread(struct lttng_consumer_stream *stream,
                } else {
                        consumer_del_stream_for_data(stream);
                }
+               goto error;
        }
+
 error:
        return ret;
 }
 
+static
+int get_stream_shm_path(char *stream_shm_path, const char *shm_path, int cpu)
+{
+       char cpu_nr[INT_MAX_STR_LEN];  /* int max len */
+       int ret;
+
+       strncpy(stream_shm_path, shm_path, PATH_MAX);
+       stream_shm_path[PATH_MAX - 1] = '\0';
+       ret = snprintf(cpu_nr, INT_MAX_STR_LEN, "%i", cpu);
+       if (ret < 0) {
+               PERROR("snprintf");
+               goto end;
+       }
+       strncat(stream_shm_path, cpu_nr,
+               PATH_MAX - strlen(stream_shm_path) - 1);
+       ret = 0;
+end:
+       return ret;
+}
+
 /*
  * Create streams for the given channel using liblttng-ust-ctl.
  *
  * Return 0 on success else a negative value.
  */
 static int create_ust_streams(struct lttng_consumer_channel *channel,
-               struct lttng_consumer_local_data *ctx)
+               struct lttng_consumer_local_data *ctx,
+               uint64_t trace_archive_id)
 {
        int ret, cpu = 0;
        struct ustctl_consumer_stream *ustream;
@@ -276,7 +301,8 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                }
 
                /* Allocate consumer stream object. */
-               stream = allocate_stream(cpu, wait_fd, channel, ctx, &ret);
+               stream = allocate_stream(cpu, wait_fd, channel, ctx, &ret,
+                               trace_archive_id);
                if (!stream) {
                        goto error_alloc;
                }
@@ -327,8 +353,12 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                /* Keep stream reference when creating metadata. */
                if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA) {
                        channel->metadata_stream = stream;
-                       stream->ust_metadata_poll_pipe[0] = ust_metadata_pipe[0];
-                       stream->ust_metadata_poll_pipe[1] = ust_metadata_pipe[1];
+                       if (channel->monitor) {
+                               /* Set metadata poll pipe if we created one */
+                               memcpy(stream->ust_metadata_poll_pipe,
+                                               ust_metadata_pipe,
+                                               sizeof(ust_metadata_pipe));
+                       }
                }
        }
 
@@ -339,20 +369,85 @@ error_alloc:
        return ret;
 }
 
+/*
+ * create_posix_shm is never called concurrently within a process.
+ */
+static
+int create_posix_shm(void)
+{
+       char tmp_name[NAME_MAX];
+       int shmfd, ret;
+
+       ret = snprintf(tmp_name, NAME_MAX, "/ust-shm-consumer-%d", getpid());
+       if (ret < 0) {
+               PERROR("snprintf");
+               return -1;
+       }
+       /*
+        * Allocate shm, and immediately unlink its shm oject, keeping
+        * only the file descriptor as a reference to the object.
+        * We specifically do _not_ use the / at the beginning of the
+        * pathname so that some OS implementations can keep it local to
+        * the process (POSIX leaves this implementation-defined).
+        */
+       shmfd = shm_open(tmp_name, O_CREAT | O_EXCL | O_RDWR, 0700);
+       if (shmfd < 0) {
+               PERROR("shm_open");
+               goto error_shm_open;
+       }
+       ret = shm_unlink(tmp_name);
+       if (ret < 0 && errno != ENOENT) {
+               PERROR("shm_unlink");
+               goto error_shm_release;
+       }
+       return shmfd;
+
+error_shm_release:
+       ret = close(shmfd);
+       if (ret) {
+               PERROR("close");
+       }
+error_shm_open:
+       return -1;
+}
+
+static int open_ust_stream_fd(struct lttng_consumer_channel *channel, int cpu)
+{
+       char shm_path[PATH_MAX];
+       int ret;
+
+       if (!channel->shm_path[0]) {
+               return create_posix_shm();
+       }
+       ret = get_stream_shm_path(shm_path, channel->shm_path, cpu);
+       if (ret) {
+               goto error_shm_path;
+       }
+       return run_as_open(shm_path,
+               O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR,
+               channel->uid, channel->gid);
+
+error_shm_path:
+       return -1;
+}
+
 /*
  * Create an UST channel with the given attributes and send it to the session
  * daemon using the ust ctl API.
  *
  * Return 0 on success or else a negative value.
  */
-static int create_ust_channel(struct ustctl_consumer_channel_attr *attr,
-               struct ustctl_consumer_channel **chanp)
+static int create_ust_channel(struct lttng_consumer_channel *channel,
+               struct ustctl_consumer_channel_attr *attr,
+               struct ustctl_consumer_channel **ust_chanp)
 {
-       int ret;
-       struct ustctl_consumer_channel *channel;
+       int ret, nr_stream_fds, i, j;
+       int *stream_fds;
+       struct ustctl_consumer_channel *ust_channel;
 
+       assert(channel);
        assert(attr);
-       assert(chanp);
+       assert(ust_chanp);
 
        DBG3("Creating channel to ustctl with attr: [overwrite: %d, "
                        "subbuf_size: %" PRIu64 ", num_subbuf: %" PRIu64 ", "
@@ -361,17 +456,64 @@ static int create_ust_channel(struct ustctl_consumer_channel_attr *attr,
                        attr->num_subbuf, attr->switch_timer_interval,
                        attr->read_timer_interval, attr->output, attr->type);
 
-       channel = ustctl_create_channel(attr);
-       if (!channel) {
+       if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA)
+               nr_stream_fds = 1;
+       else
+               nr_stream_fds = ustctl_get_nr_stream_per_channel();
+       stream_fds = zmalloc(nr_stream_fds * sizeof(*stream_fds));
+       if (!stream_fds) {
+               ret = -1;
+               goto error_alloc;
+       }
+       for (i = 0; i < nr_stream_fds; i++) {
+               stream_fds[i] = open_ust_stream_fd(channel, i);
+               if (stream_fds[i] < 0) {
+                       ret = -1;
+                       goto error_open;
+               }
+       }
+       ust_channel = ustctl_create_channel(attr, stream_fds, nr_stream_fds);
+       if (!ust_channel) {
                ret = -1;
                goto error_create;
        }
-
-       *chanp = channel;
+       channel->nr_stream_fds = nr_stream_fds;
+       channel->stream_fds = stream_fds;
+       *ust_chanp = ust_channel;
 
        return 0;
 
 error_create:
+error_open:
+       for (j = i - 1; j >= 0; j--) {
+               int closeret;
+
+               closeret = close(stream_fds[j]);
+               if (closeret) {
+                       PERROR("close");
+               }
+               if (channel->shm_path[0]) {
+                       char shm_path[PATH_MAX];
+
+                       closeret = get_stream_shm_path(shm_path,
+                                       channel->shm_path, j);
+                       if (closeret) {
+                               ERR("Cannot get stream shm path");
+                       }
+                       closeret = run_as_unlink(shm_path,
+                                       channel->uid, channel->gid);
+                       if (closeret) {
+                               PERROR("unlink %s", shm_path);
+                       }
+               }
+       }
+       /* Try to rmdir all directories under shm_path root. */
+       if (channel->root_shm_path[0]) {
+               (void) run_as_rmdir_recursive(channel->root_shm_path,
+                               channel->uid, channel->gid);
+       }
+       free(stream_fds);
+error_alloc:
        return ret;
 }
 
@@ -400,11 +542,11 @@ error:
 }
 
 /*
- * Send channel to sessiond.
+ * Send channel to sessiond and relayd if applicable.
  *
  * Return 0 on success or else a negative value.
  */
-static int send_sessiond_channel(int sock,
+static int send_channel_to_sessiond_and_relayd(int sock,
                struct lttng_consumer_channel *channel,
                struct lttng_consumer_local_data *ctx, int *relayd_error)
 {
@@ -424,6 +566,8 @@ static int send_sessiond_channel(int sock,
                        health_code_update();
 
                        /* Try to send the stream to the relayd if one is available. */
+                       DBG("Sending stream %" PRIu64 " of channel \"%s\" to relayd",
+                                       stream->key, channel->name);
                        ret = consumer_send_relayd_stream(stream, stream->chan->pathname);
                        if (ret < 0) {
                                /*
@@ -433,7 +577,7 @@ static int send_sessiond_channel(int sock,
                                if (relayd_error) {
                                        *relayd_error = 1;
                                }
-                               ret_code = LTTNG_ERR_RELAYD_CONNECT_FAIL;
+                               ret_code = LTTCOMM_CONSUMERD_RELAYD_FAIL;
                        }
                        if (net_seq_idx == -1ULL) {
                                net_seq_idx = stream->net_seq_idx;
@@ -499,9 +643,10 @@ error:
  * Return 0 on success or else, a negative value is returned and the channel
  * MUST be destroyed by consumer_del_channel().
  */
-static int ask_channel(struct lttng_consumer_local_data *ctx, int sock,
+static int ask_channel(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_channel *channel,
-               struct ustctl_consumer_channel_attr *attr)
+               struct ustctl_consumer_channel_attr *attr,
+               uint64_t trace_archive_id)
 {
        int ret;
 
@@ -525,7 +670,7 @@ static int ask_channel(struct lttng_consumer_local_data *ctx, int sock,
        channel->nb_init_stream_left = 0;
 
        /* The reply msg status is handled in the following call. */
-       ret = create_ust_channel(attr, &channel->uchan);
+       ret = create_ust_channel(channel, attr, &channel->uchan);
        if (ret < 0) {
                goto end;
        }
@@ -542,7 +687,7 @@ static int ask_channel(struct lttng_consumer_local_data *ctx, int sock,
        }
 
        /* Open all streams for this channel. */
-       ret = create_ust_streams(channel, ctx);
+       ret = create_ust_streams(channel, ctx, trace_archive_id);
        if (ret < 0) {
                goto end;
        }
@@ -578,14 +723,8 @@ static int send_streams_to_thread(struct lttng_consumer_channel *channel,
                         * If we are unable to send the stream to the thread, there is
                         * a big problem so just stop everything.
                         */
-                       /* Remove node from the channel stream list. */
-                       cds_list_del(&stream->send_node);
                        goto error;
                }
-
-               /* Remove node from the channel stream list. */
-               cds_list_del(&stream->send_node);
-
        }
 
 error:
@@ -624,7 +763,54 @@ static int flush_channel(uint64_t chan_key)
 
                health_code_update();
 
-               ustctl_flush_buffer(stream->ustream, 1);
+               pthread_mutex_lock(&stream->lock);
+               if (!stream->quiescent) {
+                       lttng_ustconsumer_flush_buffer(stream, 0);
+                       stream->quiescent = true;
+               }
+               pthread_mutex_unlock(&stream->lock);
+       }
+error:
+       rcu_read_unlock();
+       return ret;
+}
+
+/*
+ * Clear quiescent state from channel's streams using the given key to
+ * retrieve the channel.
+ *
+ * Return 0 on success else an LTTng error code.
+ */
+static int clear_quiescent_channel(uint64_t chan_key)
+{
+       int ret = 0;
+       struct lttng_consumer_channel *channel;
+       struct lttng_consumer_stream *stream;
+       struct lttng_ht *ht;
+       struct lttng_ht_iter iter;
+
+       DBG("UST consumer clear quiescent channel key %" PRIu64, chan_key);
+
+       rcu_read_lock();
+       channel = consumer_find_channel(chan_key);
+       if (!channel) {
+               ERR("UST consumer clear quiescent channel %" PRIu64 " not found", chan_key);
+               ret = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+               goto error;
+       }
+
+       ht = consumer_data.stream_per_chan_id_ht;
+
+       /* For each stream of the channel id, clear quiescent state. */
+       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->lock);
+               stream->quiescent = false;
+               pthread_mutex_unlock(&stream->lock);
        }
 error:
        rcu_read_unlock();
@@ -641,6 +827,7 @@ static int close_metadata(uint64_t chan_key)
 {
        int ret = 0;
        struct lttng_consumer_channel *channel;
+       unsigned int channel_monitor;
 
        DBG("UST consumer close metadata key %" PRIu64, chan_key);
 
@@ -659,13 +846,48 @@ static int close_metadata(uint64_t chan_key)
 
        pthread_mutex_lock(&consumer_data.lock);
        pthread_mutex_lock(&channel->lock);
-
+       channel_monitor = channel->monitor;
        if (cds_lfht_is_node_deleted(&channel->node.node)) {
                goto error_unlock;
        }
 
        lttng_ustconsumer_close_metadata(channel);
+       pthread_mutex_unlock(&channel->lock);
+       pthread_mutex_unlock(&consumer_data.lock);
 
+       /*
+        * The ownership of a metadata channel depends on the type of
+        * session to which it belongs. In effect, the monitor flag is checked
+        * to determine if this metadata channel is in "snapshot" mode or not.
+        *
+        * In the non-snapshot case, the metadata channel is created along with
+        * a single stream which will remain present until the metadata channel
+        * is destroyed (on the destruction of its session). In this case, the
+        * metadata stream in "monitored" by the metadata poll thread and holds
+        * the ownership of its channel.
+        *
+        * Closing the metadata will cause the metadata stream's "metadata poll
+        * pipe" to be closed. Closing this pipe will wake-up the metadata poll
+        * thread which will teardown the metadata stream which, in return,
+        * deletes the metadata channel.
+        *
+        * In the snapshot case, the metadata stream is created and destroyed
+        * on every snapshot record. Since the channel doesn't have an owner
+        * other than the session daemon, it is safe to destroy it immediately
+        * on reception of the CLOSE_METADATA command.
+        */
+       if (!channel_monitor) {
+               /*
+                * The channel and consumer_data locks must be
+                * released before this call since consumer_del_channel
+                * re-acquires the channel and consumer_data locks to teardown
+                * the channel and queue its reclamation by the "call_rcu"
+                * worker thread.
+                */
+               consumer_del_channel(channel);
+       }
+
+       return ret;
 error_unlock:
        pthread_mutex_unlock(&channel->lock);
        pthread_mutex_unlock(&consumer_data.lock);
@@ -728,6 +950,10 @@ static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)
                }
        }
 
+       /*
+        * Ownership of metadata stream is passed along. Freeing is handled by
+        * the callee.
+        */
        ret = send_streams_to_thread(metadata, ctx);
        if (ret < 0) {
                /*
@@ -735,7 +961,7 @@ static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)
                 * a big problem so just stop everything.
                 */
                ret = LTTCOMM_CONSUMERD_FATAL;
-               goto error;
+               goto send_streams_error;
        }
        /* List MUST be empty after or else it could be reused. */
        assert(cds_list_empty(&metadata->streams.head));
@@ -753,6 +979,7 @@ error:
        consumer_stream_destroy(metadata->metadata_stream, NULL);
        cds_list_del(&metadata->metadata_stream->send_node);
        metadata->metadata_stream = NULL;
+send_streams_error:
 error_no_stream:
 end:
        return ret;
@@ -760,14 +987,17 @@ end:
 
 /*
  * Snapshot the whole metadata.
+ * RCU read-side lock must be held across this function to ensure existence of
+ * metadata_channel.
  *
  * Returns 0 on success, < 0 on error
  */
-static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
-               struct lttng_consumer_local_data *ctx)
+static int snapshot_metadata(struct lttng_consumer_channel *metadata_channel,
+               uint64_t key, char *path, uint64_t relayd_id,
+               struct lttng_consumer_local_data *ctx,
+               uint64_t trace_archive_id)
 {
        int ret = 0;
-       struct lttng_consumer_channel *metadata_channel;
        struct lttng_consumer_stream *metadata_stream;
 
        assert(path);
@@ -778,13 +1008,6 @@ static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
 
        rcu_read_lock();
 
-       metadata_channel = consumer_find_channel(key);
-       if (!metadata_channel) {
-               ERR("UST snapshot metadata channel not found for key %" PRIu64,
-                       key);
-               ret = -1;
-               goto error;
-       }
        assert(!metadata_channel->monitor);
 
        health_code_update();
@@ -804,7 +1027,7 @@ static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
         * The metadata stream is NOT created in no monitor mode when the channel
         * is created on a sessiond ask channel command.
         */
-       ret = create_ust_streams(metadata_channel, ctx);
+       ret = create_ust_streams(metadata_channel, ctx, trace_archive_id);
        if (ret < 0) {
                goto error;
        }
@@ -855,16 +1078,19 @@ error:
 
 /*
  * Take a snapshot of all the stream of a channel.
+ * RCU read-side lock must be held across this function to ensure existence of
+ * channel.
  *
  * Returns 0 on success, < 0 on error
  */
-static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
-               uint64_t max_stream_size, struct lttng_consumer_local_data *ctx)
+static int snapshot_channel(struct lttng_consumer_channel *channel,
+               uint64_t key, char *path, uint64_t relayd_id,
+               uint64_t nb_packets_per_stream,
+               struct lttng_consumer_local_data *ctx)
 {
        int ret;
        unsigned use_relayd = 0;
        unsigned long consumed_pos, produced_pos;
-       struct lttng_consumer_channel *channel;
        struct lttng_consumer_stream *stream;
 
        assert(path);
@@ -876,17 +1102,10 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                use_relayd = 1;
        }
 
-       channel = consumer_find_channel(key);
-       if (!channel) {
-               ERR("UST snapshot channel not found for key %" PRIu64, key);
-               ret = -1;
-               goto error;
-       }
        assert(!channel->monitor);
        DBG("UST consumer snapshot channel %" PRIu64, key);
 
        cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
-
                health_code_update();
 
                /* Lock stream because we are about to change its state. */
@@ -912,14 +1131,14 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                        DBG("UST consumer snapshot stream %s/%s (%" PRIu64 ")", path,
                                        stream->name, stream->key);
                }
-               if (relayd_id != -1ULL) {
-                       ret = consumer_send_relayd_streams_sent(relayd_id);
-                       if (ret < 0) {
-                               goto error_unlock;
-                       }
-               }
 
-               ustctl_flush_buffer(stream->ustream, 1);
+               /*
+                * If tracing is active, we want to perform a "full" buffer flush.
+                * Else, if quiescent, it has already been done by the prior stop.
+                */
+               if (!stream->quiescent) {
+                       lttng_ustconsumer_flush_buffer(stream, 0);
+               }
 
                ret = lttng_ustconsumer_take_snapshot(stream);
                if (ret < 0) {
@@ -941,12 +1160,13 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
 
                /*
                 * The original value is sent back if max stream size is larger than
-                * the possible size of the snapshot. Also, we asume that the session
+                * the possible size of the snapshot. Also, we assume that the session
                 * daemon should never send a maximum stream size that is lower than
                 * subbuffer size.
                 */
-               consumed_pos = consumer_get_consumed_maxsize(consumed_pos,
-                               produced_pos, max_stream_size);
+               consumed_pos = consumer_get_consume_start_pos(consumed_pos,
+                               produced_pos, nb_packets_per_stream,
+                               stream->max_sb_size);
 
                while (consumed_pos < produced_pos) {
                        ssize_t read_len;
@@ -964,6 +1184,7 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                                }
                                DBG("UST consumer get subbuf failed. Skipping it.");
                                consumed_pos += stream->max_sb_size;
+                               stream->chan->lost_packets++;
                                continue;
                        }
 
@@ -1017,17 +1238,21 @@ error_close_stream:
        consumer_stream_close(stream);
 error_unlock:
        pthread_mutex_unlock(&stream->lock);
-error:
        rcu_read_unlock();
        return ret;
 }
 
 /*
- * Receive the metadata updates from the sessiond.
+ * Receive the metadata updates from the sessiond. Supports receiving
+ * overlapping metadata, but is needs to always belong to a contiguous
+ * range starting from 0.
+ * Be careful about the locks held when calling this function: it needs
+ * the metadata cache flush to concurrently progress in order to
+ * complete.
  */
 int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
-               uint64_t len, struct lttng_consumer_channel *channel,
-               int timer, int wait)
+               uint64_t len, uint64_t version,
+               struct lttng_consumer_channel *channel, int timer, int wait)
 {
        int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        char *metadata_str;
@@ -1054,7 +1279,8 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
        health_code_update();
 
        pthread_mutex_lock(&channel->metadata_cache->lock);
-       ret = consumer_metadata_cache_write(channel, offset, len, metadata_str);
+       ret = consumer_metadata_cache_write(channel, offset, len, version,
+                       metadata_str);
        if (ret < 0) {
                /* Unable to handle metadata. Notify session daemon. */
                ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
@@ -1129,7 +1355,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        case LTTNG_CONSUMER_ADD_RELAYD_SOCKET:
        {
                /* Session daemon status message are handled in the following call. */
-               ret = consumer_add_relayd_socket(msg.u.relayd_sock.net_index,
+               consumer_add_relayd_socket(msg.u.relayd_sock.net_index,
                                msg.u.relayd_sock.type, ctx, sock, consumer_sockpoll,
                                &msg.u.relayd_sock.sock, msg.u.relayd_sock.session_id,
                                msg.u.relayd_sock.relayd_session_id);
@@ -1146,7 +1372,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                relayd = consumer_find_relayd(index);
                if (relayd == NULL) {
                        DBG("Unable to find relayd %" PRIu64, index);
-                       ret_code = LTTNG_ERR_NO_CONSUMER;
+                       ret_code = LTTCOMM_CONSUMERD_RELAYD_FAIL;
                }
 
                /*
@@ -1208,7 +1434,9 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                msg.u.ask_channel.tracefile_count,
                                msg.u.ask_channel.session_id_per_pid,
                                msg.u.ask_channel.monitor,
-                               msg.u.ask_channel.live_timer_interval);
+                               msg.u.ask_channel.live_timer_interval,
+                               msg.u.ask_channel.root_shm_path,
+                               msg.u.ask_channel.shm_path);
                if (!channel) {
                        goto end_channel_error;
                }
@@ -1228,6 +1456,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                attr.read_timer_interval = msg.u.ask_channel.read_timer_interval;
                attr.chan_id = msg.u.ask_channel.chan_id;
                memcpy(attr.uuid, msg.u.ask_channel.uuid, sizeof(attr.uuid));
+               attr.blocking_timeout= msg.u.ask_channel.blocking_timeout;
 
                /* Match channel buffer type to the UST abi. */
                switch (msg.u.ask_channel.output) {
@@ -1260,7 +1489,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                health_code_update();
 
-               ret = ask_channel(ctx, sock, channel, &attr);
+               ret = ask_channel(ctx, channel, &attr,
+                               msg.u.ask_channel.trace_archive_id);
                if (ret < 0) {
                        goto end_channel_error;
                }
@@ -1274,8 +1504,17 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        consumer_timer_switch_start(channel, attr.switch_timer_interval);
                        attr.switch_timer_interval = 0;
                } else {
+                       int monitor_start_ret;
+
                        consumer_timer_live_start(channel,
                                        msg.u.ask_channel.live_timer_interval);
+                       monitor_start_ret = consumer_timer_monitor_start(
+                                       channel,
+                                       msg.u.ask_channel.monitor_timer_interval);
+                       if (monitor_start_ret < 0) {
+                               ERR("Starting channel monitoring timer failed");
+                               goto end_channel_error;
+                       }
                }
 
                health_code_update();
@@ -1298,6 +1537,9 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        if (channel->live_timer_enabled == 1) {
                                consumer_timer_live_stop(channel);
                        }
+                       if (channel->monitor_timer_enabled == 1) {
+                               consumer_timer_monitor_stop(channel);
+                       }
                        goto end_channel_error;
                }
 
@@ -1327,14 +1569,15 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                channel = consumer_find_channel(key);
                if (!channel) {
                        ERR("UST consumer get channel key %" PRIu64 " not found", key);
-                       ret_code = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                        goto end_msg_sessiond;
                }
 
                health_code_update();
 
-               /* Send everything to sessiond. */
-               ret = send_sessiond_channel(sock, channel, ctx, &relayd_err);
+               /* Send the channel to sessiond (and relayd, if applicable). */
+               ret = send_channel_to_sessiond_and_relayd(sock, channel, ctx,
+                               &relayd_err);
                if (ret < 0) {
                        if (relayd_err) {
                                /*
@@ -1408,12 +1651,25 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                goto end_msg_sessiond;
        }
+       case LTTNG_CONSUMER_CLEAR_QUIESCENT_CHANNEL:
+       {
+               int ret;
+
+               ret = clear_quiescent_channel(
+                               msg.u.clear_quiescent_channel.key);
+               if (ret != 0) {
+                       ret_code = ret;
+               }
+
+               goto end_msg_sessiond;
+       }
        case LTTNG_CONSUMER_PUSH_METADATA:
        {
                int ret;
                uint64_t len = msg.u.push_metadata.len;
                uint64_t key = msg.u.push_metadata.key;
                uint64_t offset = msg.u.push_metadata.target_offset;
+               uint64_t version = msg.u.push_metadata.version;
                struct lttng_consumer_channel *channel;
 
                DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key,
@@ -1435,6 +1691,15 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                health_code_update();
 
+               if (!len) {
+                       /*
+                        * There is nothing to receive. We have simply
+                        * checked whether the channel can be found.
+                        */
+                       ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+                       goto end_msg_sessiond;
+               }
+
                /* Tell session daemon we are ready to receive the metadata. */
                ret = consumer_send_status_msg(sock, LTTCOMM_CONSUMERD_SUCCESS);
                if (ret < 0) {
@@ -1455,7 +1720,7 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                health_code_update();
 
                ret = lttng_ustconsumer_recv_metadata(sock, key, offset,
-                               len, channel, 0, 1);
+                               len, version, channel, 0, 1);
                if (ret < 0) {
                        /* error receiving from sessiond */
                        goto error_fatal;
@@ -1476,34 +1741,397 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
        }
        case LTTNG_CONSUMER_SNAPSHOT_CHANNEL:
        {
-               if (msg.u.snapshot_channel.metadata) {
-                       ret = snapshot_metadata(msg.u.snapshot_channel.key,
-                                       msg.u.snapshot_channel.pathname,
-                                       msg.u.snapshot_channel.relayd_id,
-                                       ctx);
-                       if (ret < 0) {
-                               ERR("Snapshot metadata failed");
-                               ret_code = LTTNG_ERR_UST_META_FAIL;
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.snapshot_channel.key;
+
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       DBG("UST snapshot channel not found for key %" PRIu64, key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               } else {
+                       if (msg.u.snapshot_channel.metadata) {
+                               ret = snapshot_metadata(channel, key,
+                                               msg.u.snapshot_channel.pathname,
+                                               msg.u.snapshot_channel.relayd_id,
+                                               ctx,
+                                               msg.u.snapshot_channel.trace_archive_id);
+                               if (ret < 0) {
+                                       ERR("Snapshot metadata failed");
+                                       ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
+                               }
+                       } else {
+                               ret = snapshot_channel(channel, key,
+                                               msg.u.snapshot_channel.pathname,
+                                               msg.u.snapshot_channel.relayd_id,
+                                               msg.u.snapshot_channel.nb_packets_per_stream,
+                                               ctx);
+                               if (ret < 0) {
+                                       ERR("Snapshot channel failed");
+                                       ret_code = LTTCOMM_CONSUMERD_SNAPSHOT_FAILED;
+                               }
+                       }
+               }
+               health_code_update();
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+               health_code_update();
+               break;
+       }
+       case LTTNG_CONSUMER_DISCARDED_EVENTS:
+       {
+               int ret = 0;
+               uint64_t discarded_events;
+               struct lttng_ht_iter iter;
+               struct lttng_ht *ht;
+               struct lttng_consumer_stream *stream;
+               uint64_t id = msg.u.discarded_events.session_id;
+               uint64_t key = msg.u.discarded_events.channel_key;
+
+               DBG("UST consumer discarded events command for session id %"
+                               PRIu64, id);
+               rcu_read_lock();
+               pthread_mutex_lock(&consumer_data.lock);
+
+               ht = consumer_data.stream_list_ht;
+
+               /*
+                * We only need a reference to the channel, but they are not
+                * directly indexed, so we just use the first matching stream
+                * to extract the information we need, we default to 0 if not
+                * found (no events are dropped if the channel is not yet in
+                * use).
+                */
+               discarded_events = 0;
+               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->chan->key == key) {
+                               discarded_events = stream->chan->discarded_events;
+                               break;
                        }
+               }
+               pthread_mutex_unlock(&consumer_data.lock);
+               rcu_read_unlock();
+
+               DBG("UST consumer discarded events command for session id %"
+                               PRIu64 ", channel key %" PRIu64, id, key);
+
+               health_code_update();
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &discarded_events, sizeof(discarded_events));
+               if (ret < 0) {
+                       PERROR("send discarded events");
+                       goto error_fatal;
+               }
+
+               break;
+       }
+       case LTTNG_CONSUMER_LOST_PACKETS:
+       {
+               int ret;
+               uint64_t lost_packets;
+               struct lttng_ht_iter iter;
+               struct lttng_ht *ht;
+               struct lttng_consumer_stream *stream;
+               uint64_t id = msg.u.lost_packets.session_id;
+               uint64_t key = msg.u.lost_packets.channel_key;
+
+               DBG("UST consumer lost packets command for session id %"
+                               PRIu64, id);
+               rcu_read_lock();
+               pthread_mutex_lock(&consumer_data.lock);
+
+               ht = consumer_data.stream_list_ht;
+
+               /*
+                * We only need a reference to the channel, but they are not
+                * directly indexed, so we just use the first matching stream
+                * to extract the information we need, we default to 0 if not
+                * found (no packets lost if the channel is not yet in use).
+                */
+               lost_packets = 0;
+               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->chan->key == key) {
+                               lost_packets = stream->chan->lost_packets;
+                               break;
+                       }
+               }
+               pthread_mutex_unlock(&consumer_data.lock);
+               rcu_read_unlock();
+
+               DBG("UST consumer lost packets command for session id %"
+                               PRIu64 ", channel key %" PRIu64, id, key);
+
+               health_code_update();
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &lost_packets,
+                               sizeof(lost_packets));
+               if (ret < 0) {
+                       PERROR("send lost packets");
+                       goto error_fatal;
+               }
+
+               break;
+       }
+       case LTTNG_CONSUMER_SET_CHANNEL_MONITOR_PIPE:
+       {
+               int channel_monitor_pipe;
+
+               ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+               /* Successfully received the command's type. */
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       goto error_fatal;
+               }
+
+               ret = lttcomm_recv_fds_unix_sock(sock, &channel_monitor_pipe,
+                               1);
+               if (ret != sizeof(channel_monitor_pipe)) {
+                       ERR("Failed to receive channel monitor pipe");
+                       goto error_fatal;
+               }
+
+               DBG("Received channel monitor pipe (%d)", channel_monitor_pipe);
+               ret = consumer_timer_thread_set_channel_monitor_pipe(
+                               channel_monitor_pipe);
+               if (!ret) {
+                       int flags;
+
+                       ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+                       /* Set the pipe as non-blocking. */
+                       ret = fcntl(channel_monitor_pipe, F_GETFL, 0);
+                       if (ret == -1) {
+                               PERROR("fcntl get flags of the channel monitoring pipe");
+                               goto error_fatal;
+                       }
+                       flags = ret;
+
+                       ret = fcntl(channel_monitor_pipe, F_SETFL,
+                                       flags | O_NONBLOCK);
+                       if (ret == -1) {
+                               PERROR("fcntl set O_NONBLOCK flag of the channel monitoring pipe");
+                               goto error_fatal;
+                       }
+                       DBG("Channel monitor pipe set as non-blocking");
+               } else {
+                       ret_code = LTTCOMM_CONSUMERD_ALREADY_SET;
+               }
+               goto end_msg_sessiond;
+       }
+       case LTTNG_CONSUMER_ROTATE_CHANNEL:
+       {
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.rotate_channel.key;
+
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       DBG("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
                } else {
-                       ret = snapshot_channel(msg.u.snapshot_channel.key,
-                                       msg.u.snapshot_channel.pathname,
-                                       msg.u.snapshot_channel.relayd_id,
-                                       msg.u.snapshot_channel.max_stream_size,
+                       /*
+                        * Sample the rotate position of all the streams in
+                        * this channel.
+                        */
+                       ret = lttng_consumer_rotate_sample_channel(channel, key,
+                                       msg.u.rotate_channel.pathname,
+                                       msg.u.rotate_channel.relayd_id,
+                                       msg.u.rotate_channel.metadata,
+                                       msg.u.rotate_channel.new_chunk_id,
                                        ctx);
                        if (ret < 0) {
-                               ERR("Snapshot channel failed");
-                               ret_code = LTTNG_ERR_UST_CHAN_FAIL;
+                               ERR("Rotate channel failed");
+                               ret_code = LTTCOMM_CONSUMERD_ROTATION_FAIL;
                        }
+
+                       health_code_update();
+               }
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+
+               /*
+                * Rotate the streams that are ready right now.
+                * FIXME: this is a second consecutive iteration over the
+                * streams in a channel, there is probably a better way to
+                * handle this, but it needs to be after the
+                * consumer_send_status_msg() call.
+                */
+               if (channel) {
+                       ret = lttng_consumer_rotate_ready_streams(
+                                       channel, key, ctx);
+                       if (ret < 0) {
+                               ERR("Rotate channel failed");
+                       }
+               }
+               break;
+       }
+       case LTTNG_CONSUMER_ROTATE_RENAME:
+       {
+               DBG("Consumer rename session %" PRIu64 " after rotation",
+                               msg.u.rotate_rename.session_id);
+               ret = lttng_consumer_rotate_rename(msg.u.rotate_rename.old_path,
+                               msg.u.rotate_rename.new_path,
+                               msg.u.rotate_rename.uid,
+                               msg.u.rotate_rename.gid,
+                               msg.u.rotate_rename.relayd_id);
+               if (ret < 0) {
+                       ERR("Rotate rename failed");
+                       ret_code = LTTCOMM_CONSUMERD_ROTATE_RENAME_FAILED;
                }
 
                health_code_update();
+
                ret = consumer_send_status_msg(sock, ret_code);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto end_nosignal;
                }
+               break;
+       }
+       case LTTNG_CONSUMER_CHECK_ROTATION_PENDING_LOCAL:
+       {
+               int pending;
+               uint32_t pending_reply;
+
+               DBG("Perform local check of pending rotation for session id %" PRIu64,
+                               msg.u.check_rotation_pending_local.session_id);
+               pending = lttng_consumer_check_rotation_pending_local(
+                               msg.u.check_rotation_pending_local.session_id,
+                               msg.u.check_rotation_pending_local.chunk_id);
+               if (pending < 0) {
+                       ERR("Local rotation pending check failed with code %i", pending);
+                       ret_code = LTTCOMM_CONSUMERD_ROTATION_PENDING_LOCAL_FAILED;
+               } else {
+                       pending_reply = !!pending;
+               }
+
+               health_code_update();
+
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+
+               if (pending < 0) {
+                       /*
+                        * An error occurred while running the command;
+                        * don't send the 'pending' flag as the sessiond
+                        * will not read it.
+                        */
+                       break;
+               }
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &pending_reply,
+                               sizeof(pending_reply));
+               if (ret < 0) {
+                       PERROR("Failed to send rotation pending return code");
+                       goto error_fatal;
+               }
+               break;
+       }
+       case LTTNG_CONSUMER_CHECK_ROTATION_PENDING_RELAY:
+       {
+               int pending;
+               uint32_t pending_reply;
+
+               DBG("Perform relayd check of pending rotation for session id %" PRIu64,
+                               msg.u.check_rotation_pending_relay.session_id);
+               pending = lttng_consumer_check_rotation_pending_relay(
+                               msg.u.check_rotation_pending_relay.session_id,
+                               msg.u.check_rotation_pending_relay.relayd_id,
+                               msg.u.check_rotation_pending_relay.chunk_id);
+               if (pending < 0) {
+                       ERR("Relayd rotation pending check failed with code %i", pending);
+                       ret_code = LTTCOMM_CONSUMERD_ROTATION_PENDING_RELAY_FAILED;
+               } else {
+                       pending_reply = !!pending;
+               }
+
+               health_code_update();
+
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+
+               if (pending < 0) {
+                       /*
+                        * An error occurred while running the command;
+                        * don't send the 'pending' flag as the sessiond
+                        * will not read it.
+                        */
+                       break;
+               }
+
+               /* Send back returned value to session daemon */
+               ret = lttcomm_send_unix_sock(sock, &pending_reply,
+                               sizeof(pending_reply));
+               if (ret < 0) {
+                       PERROR("Failed to send rotation pending return code");
+                       goto error_fatal;
+               }
+               break;
+       }
+       case LTTNG_CONSUMER_MKDIR:
+       {
+               DBG("Consumer mkdir %s in session %" PRIu64,
+                               msg.u.mkdir.path,
+                               msg.u.mkdir.session_id);
+               ret = lttng_consumer_mkdir(msg.u.mkdir.path,
+                               msg.u.mkdir.uid,
+                               msg.u.mkdir.gid,
+                               msg.u.mkdir.relayd_id);
+               if (ret < 0) {
+                       ERR("consumer mkdir failed");
+                       ret_code = LTTCOMM_CONSUMERD_MKDIR_FAILED;
+               }
+
                health_code_update();
+
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
+               break;
+       }
+       case LTTNG_CONSUMER_CLEAR_CHANNEL:
+       {
+               struct lttng_consumer_channel *channel;
+               uint64_t key = msg.u.clear_channel.key;
+
+               channel = consumer_find_channel(key);
+               if (!channel) {
+                       DBG("Channel %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHAN_NOT_FOUND;
+               } else {
+                       ret = lttng_consumer_clear_channel(channel);
+                       if (ret) {
+                               ERR("Clear channel failed key %" PRIu64, key);
+                               ret_code = ret;
+                       }
+
+                       health_code_update();
+               }
+               ret = consumer_send_status_msg(sock, ret_code);
+               if (ret < 0) {
+                       /* Somehow, the session daemon is not responding anymore. */
+                       goto end_nosignal;
+               }
                break;
        }
        default:
@@ -1587,7 +2215,7 @@ void *lttng_ustctl_get_mmap_base(struct lttng_consumer_stream *stream)
 }
 
 /*
- * Take a snapshot for a specific fd
+ * Take a snapshot for a specific stream.
  *
  * Returns 0 on success, < 0 on error
  */
@@ -1599,6 +2227,20 @@ int lttng_ustconsumer_take_snapshot(struct lttng_consumer_stream *stream)
        return ustctl_snapshot(stream->ustream);
 }
 
+/*
+ * Sample consumed and produced positions for a specific stream.
+ *
+ * Returns 0 on success, < 0 on error.
+ */
+int lttng_ustconsumer_sample_snapshot_positions(
+               struct lttng_consumer_stream *stream)
+{
+       assert(stream);
+       assert(stream->ustream);
+
+       return ustctl_snapshot_sample_positions(stream->ustream);
+}
+
 /*
  * Get the produced position
  *
@@ -1638,6 +2280,14 @@ void lttng_ustconsumer_flush_buffer(struct lttng_consumer_stream *stream,
        ustctl_flush_buffer(stream->ustream, producer);
 }
 
+void lttng_ustconsumer_clear_buffer(struct lttng_consumer_stream *stream)
+{
+       assert(stream);
+       assert(stream->ustream);
+
+       ustctl_clear_buffer(stream->ustream);
+}
+
 int lttng_ustconsumer_get_current_timestamp(
                struct lttng_consumer_stream *stream, uint64_t *ts)
 {
@@ -1648,28 +2298,78 @@ int lttng_ustconsumer_get_current_timestamp(
        return ustctl_get_current_timestamp(stream->ustream, ts);
 }
 
+int lttng_ustconsumer_get_sequence_number(
+               struct lttng_consumer_stream *stream, uint64_t *seq)
+{
+       assert(stream);
+       assert(stream->ustream);
+       assert(seq);
+
+       return ustctl_get_sequence_number(stream->ustream, seq);
+}
+
 /*
- * Called when the stream signal the consumer that it has hang up.
+ * Called when the stream signals the consumer that it has hung up.
  */
 void lttng_ustconsumer_on_stream_hangup(struct lttng_consumer_stream *stream)
 {
        assert(stream);
        assert(stream->ustream);
 
-       ustctl_flush_buffer(stream->ustream, 0);
+       pthread_mutex_lock(&stream->lock);
+       if (!stream->quiescent) {
+               lttng_ustconsumer_flush_buffer(stream, 0);
+               stream->quiescent = true;
+       }
+       pthread_mutex_unlock(&stream->lock);
        stream->hangup_flush_done = 1;
 }
 
 void lttng_ustconsumer_del_channel(struct lttng_consumer_channel *chan)
 {
+       int i;
+
        assert(chan);
        assert(chan->uchan);
 
        if (chan->switch_timer_enabled == 1) {
                consumer_timer_switch_stop(chan);
        }
+       for (i = 0; i < chan->nr_stream_fds; i++) {
+               int ret;
+
+               ret = close(chan->stream_fds[i]);
+               if (ret) {
+                       PERROR("close");
+               }
+               if (chan->shm_path[0]) {
+                       char shm_path[PATH_MAX];
+
+                       ret = get_stream_shm_path(shm_path, chan->shm_path, i);
+                       if (ret) {
+                               ERR("Cannot get stream shm path");
+                       }
+                       ret = run_as_unlink(shm_path, chan->uid, chan->gid);
+                       if (ret) {
+                               PERROR("unlink %s", shm_path);
+                       }
+               }
+       }
+}
+
+void lttng_ustconsumer_free_channel(struct lttng_consumer_channel *chan)
+{
+       assert(chan);
+       assert(chan->uchan);
+
        consumer_metadata_cache_destroy(chan);
        ustctl_destroy_channel(chan->uchan);
+       /* Try to rmdir all directories under shm_path root. */
+       if (chan->root_shm_path[0]) {
+               (void) run_as_rmdir_recursive(chan->root_shm_path,
+                               chan->uid, chan->gid);
+       }
+       free(chan->stream_fds);
 }
 
 void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
@@ -1751,10 +2451,56 @@ static int get_index_values(struct ctf_packet_index *index,
        }
        index->stream_id = htobe64(index->stream_id);
 
+       ret = ustctl_get_instance_id(ustream, &index->stream_instance_id);
+       if (ret < 0) {
+               PERROR("ustctl_get_instance_id");
+               goto error;
+       }
+       index->stream_instance_id = htobe64(index->stream_instance_id);
+
+       ret = ustctl_get_sequence_number(ustream, &index->packet_seq_num);
+       if (ret < 0) {
+               PERROR("ustctl_get_sequence_number");
+               goto error;
+       }
+       index->packet_seq_num = htobe64(index->packet_seq_num);
+
 error:
        return ret;
 }
 
+static
+void metadata_stream_reset_cache(struct lttng_consumer_stream *stream,
+               struct consumer_metadata_cache *cache)
+{
+       DBG("Metadata stream update to version %" PRIu64,
+                       cache->version);
+       stream->ust_metadata_pushed = 0;
+       stream->metadata_version = cache->version;
+       stream->reset_metadata_flag = 1;
+}
+
+/*
+ * Check if the version of the metadata stream and metadata cache match.
+ * If the cache got updated, reset the metadata stream.
+ * The stream lock and metadata cache lock MUST be held.
+ * Return 0 on success, a negative value on error.
+ */
+static
+int metadata_stream_check_version(struct lttng_consumer_stream *stream)
+{
+       int ret = 0;
+       struct consumer_metadata_cache *cache = stream->chan->metadata_cache;
+
+       if (cache->version == stream->metadata_version) {
+               goto end;
+       }
+       metadata_stream_reset_cache(stream, cache);
+
+end:
+       return ret;
+}
+
 /*
  * Write up to one packet from the metadata cache to the channel.
  *
@@ -1768,7 +2514,11 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        int ret;
 
        pthread_mutex_lock(&stream->chan->metadata_cache->lock);
-       if (stream->chan->metadata_cache->contiguous
+       ret = metadata_stream_check_version(stream);
+       if (ret < 0) {
+               goto end;
+       }
+       if (stream->chan->metadata_cache->max_offset
                        == stream->ust_metadata_pushed) {
                ret = 0;
                goto end;
@@ -1776,7 +2526,7 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
 
        write_len = ustctl_write_one_packet_to_channel(stream->chan->uchan,
                        &stream->chan->metadata_cache->data[stream->ust_metadata_pushed],
-                       stream->chan->metadata_cache->contiguous
+                       stream->chan->metadata_cache->max_offset
                        - stream->ust_metadata_pushed);
        assert(write_len != 0);
        if (write_len < 0) {
@@ -1786,7 +2536,7 @@ int commit_one_metadata_packet(struct lttng_consumer_stream *stream)
        }
        stream->ust_metadata_pushed += write_len;
 
-       assert(stream->chan->metadata_cache->contiguous >=
+       assert(stream->chan->metadata_cache->max_offset >=
                        stream->ust_metadata_pushed);
        ret = write_len;
 
@@ -1800,7 +2550,9 @@ end:
  * Sync metadata meaning request them to the session daemon and snapshot to the
  * metadata thread can consumer them.
  *
- * Metadata stream lock MUST be acquired.
+ * Metadata stream lock is held here, but we need to release it when
+ * interacting with sessiond, else we cause a deadlock with live
+ * awaiting on metadata to be pushed out.
  *
  * Return 0 if new metadatda is available, EAGAIN if the metadata stream
  * is empty or a negative value on error.
@@ -1814,11 +2566,13 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
        assert(ctx);
        assert(metadata);
 
+       pthread_mutex_unlock(&metadata->lock);
        /*
         * Request metadata from the sessiond, but don't wait for the flush
         * because we locked the metadata thread.
         */
        ret = lttng_ustconsumer_request_metadata(ctx, metadata->chan, 0, 0);
+       pthread_mutex_lock(&metadata->lock);
        if (ret < 0) {
                goto end;
        }
@@ -1830,7 +2584,7 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
                retry = 1;
        }
 
-       ustctl_flush_buffer(metadata->ustream, 1);
+       lttng_ustconsumer_flush_buffer(metadata, 1);
        ret = ustctl_snapshot(metadata->ustream);
        if (ret < 0) {
                if (errno != EAGAIN) {
@@ -1881,7 +2635,7 @@ static int notify_if_more_data(struct lttng_consumer_stream *stream,
                goto end;
        }
 
-       ret = ustctl_put_next_subbuf(ustream);
+       ret = ustctl_put_subbuf(ustream);
        assert(!ret);
 
        /* This stream still has data. Flag it and wake up the data thread. */
@@ -1905,6 +2659,61 @@ end:
        return ret;
 }
 
+static
+int update_stream_stats(struct lttng_consumer_stream *stream)
+{
+       int ret;
+       uint64_t seq, discarded;
+
+       ret = ustctl_get_sequence_number(stream->ustream, &seq);
+       if (ret < 0) {
+               PERROR("ustctl_get_sequence_number");
+               goto end;
+       }
+       /*
+        * Start the sequence when we extract the first packet in case we don't
+        * start at 0 (for example if a consumer is not connected to the
+        * session immediately after the beginning).
+        */
+       if (stream->last_sequence_number == -1ULL) {
+               stream->last_sequence_number = seq;
+       } else if (seq > stream->last_sequence_number) {
+               stream->chan->lost_packets += seq -
+                               stream->last_sequence_number - 1;
+       } else {
+               /* seq <= last_sequence_number */
+               ERR("Sequence number inconsistent : prev = %" PRIu64
+                               ", current = %" PRIu64,
+                               stream->last_sequence_number, seq);
+               ret = -1;
+               goto end;
+       }
+       stream->last_sequence_number = seq;
+
+       ret = ustctl_get_events_discarded(stream->ustream, &discarded);
+       if (ret < 0) {
+               PERROR("kernctl_get_events_discarded");
+               goto end;
+       }
+       if (discarded < stream->last_discarded_events) {
+               /*
+                * Overflow has occurred. We assume only one wrap-around
+                * has occurred.
+                */
+               stream->chan->discarded_events +=
+                               (1ULL << (CAA_BITS_PER_LONG - 1)) -
+                               stream->last_discarded_events + discarded;
+       } else {
+               stream->chan->discarded_events += discarded -
+                               stream->last_discarded_events;
+       }
+       stream->last_discarded_events = discarded;
+       ret = 0;
+
+end:
+       return ret;
+}
+
 /*
  * Read subbuffer from the given stream.
  *
@@ -1913,10 +2722,10 @@ end:
  * Return 0 on success else a negative value.
  */
 int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
-               struct lttng_consumer_local_data *ctx)
+               struct lttng_consumer_local_data *ctx, bool *rotated)
 {
        unsigned long len, subbuf_size, padding;
-       int err, write_index = 1;
+       int err, write_index = 1, rotation_ret;
        long ret = 0;
        struct ustctl_consumer_stream *ustream;
        struct ctf_packet_index index;
@@ -1948,7 +2757,21 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
                readlen = lttng_read(stream->wait_fd, &dummy, 1);
                if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
                        ret = readlen;
-                       goto end;
+                       goto error;
+               }
+       }
+
+       /*
+        * 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 extracting data");
+               rotation_ret = lttng_consumer_rotate_stream(ctx, stream, rotated);
+               if (rotation_ret < 0) {
+                       ERR("Stream rotation error");
+                       ret = -1;
+                       goto error;
                }
        }
 
@@ -1963,9 +2786,9 @@ retry:
                if (stream->metadata_flag) {
                        ret = commit_one_metadata_packet(stream);
                        if (ret <= 0) {
-                               goto end;
+                               goto error;
                        }
-                       ustctl_flush_buffer(stream->ustream, 1);
+                       lttng_ustconsumer_flush_buffer(stream, 1);
                        goto retry;
                }
 
@@ -1978,7 +2801,7 @@ retry:
                 */
                DBG("Reserving sub buffer failed (everything is normal, "
                                "it is due to concurrency) [ret: %d]", err);
-               goto end;
+               goto error;
        }
        assert(stream->chan->output == CONSUMER_CHANNEL_MMAP);
 
@@ -1986,7 +2809,18 @@ retry:
                index.offset = htobe64(stream->out_fd_offset);
                ret = get_index_values(&index, ustream);
                if (ret < 0) {
-                       goto end;
+                       err = ustctl_put_subbuf(ustream);
+                       assert(err == 0);
+                       goto error;
+               }
+
+               /* Update the stream's sequence and discarded events count. */
+               ret = update_stream_stats(stream);
+               if (ret < 0) {
+                       PERROR("kernctl_get_events_discarded");
+                       err = ustctl_put_subbuf(ustream);
+                       assert(err == 0);
+                       goto error;
                }
        } else {
                write_index = 0;
@@ -2004,6 +2838,7 @@ retry:
        assert(len >= subbuf_size);
 
        padding = len - subbuf_size;
+
        /* write the subbuffer to the tracefile */
        ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, subbuf_size, padding, &index);
        /*
@@ -2035,32 +2870,66 @@ retry:
        if (!stream->metadata_flag) {
                ret = notify_if_more_data(stream, ctx);
                if (ret < 0) {
-                       goto end;
+                       goto error;
                }
        }
 
        /* Write index if needed. */
        if (!write_index) {
-               goto end;
+               goto rotate;
        }
 
        if (stream->chan->live_timer_interval && !stream->metadata_flag) {
                /*
                 * In live, block until all the metadata is sent.
                 */
+               pthread_mutex_lock(&stream->metadata_timer_lock);
+               assert(!stream->missed_metadata_flush);
+               stream->waiting_on_metadata = true;
+               pthread_mutex_unlock(&stream->metadata_timer_lock);
+
                err = consumer_stream_sync_metadata(ctx, stream->session_id);
+
+               pthread_mutex_lock(&stream->metadata_timer_lock);
+               stream->waiting_on_metadata = false;
+               if (stream->missed_metadata_flush) {
+                       stream->missed_metadata_flush = false;
+                       pthread_mutex_unlock(&stream->metadata_timer_lock);
+                       (void) consumer_flush_ust_index(stream);
+               } else {
+                       pthread_mutex_unlock(&stream->metadata_timer_lock);
+               }
+
                if (err < 0) {
-                       goto end;
+                       goto error;
                }
        }
 
        assert(!stream->metadata_flag);
        err = consumer_stream_write_index(stream, &index);
        if (err < 0) {
-               goto end;
+               goto error;
        }
 
-end:
+rotate:
+       /*
+        * After extracting the packet, we check if the stream is now ready to be
+        * rotated and perform the action immediately.
+        */
+       rotation_ret = lttng_consumer_stream_is_rotate_ready(stream);
+       if (rotation_ret == 1) {
+               rotation_ret = lttng_consumer_rotate_stream(ctx, stream, rotated);
+               if (rotation_ret < 0) {
+                       ERR("Stream rotation error");
+                       ret = -1;
+                       goto error;
+               }
+       } else if (rotation_ret < 0) {
+               ERR("Checking if stream is ready to rotate");
+               ret = -1;
+               goto error;
+       }
+error:
        return ret;
 }
 
@@ -2087,14 +2956,18 @@ int lttng_ustconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
                stream->tracefile_size_current = 0;
 
                if (!stream->metadata_flag) {
-                       ret = index_create_file(stream->chan->pathname,
+                       struct lttng_index_file *index_file;
+
+                       index_file = lttng_index_file_create(stream->chan->pathname,
                                        stream->name, stream->uid, stream->gid,
                                        stream->chan->tracefile_size,
-                                       stream->tracefile_count_current);
-                       if (ret < 0) {
+                                       stream->tracefile_count_current,
+                                       CTF_INDEX_MAJOR, CTF_INDEX_MINOR);
+                       if (!index_file) {
                                goto error;
                        }
-                       stream->index_fd = ret;
+                       assert(!stream->index_file);
+                       stream->index_file = index_file;
                }
        }
        ret = 0;
@@ -2129,7 +3002,7 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                uint64_t contiguous, pushed;
 
                /* Ease our life a bit. */
-               contiguous = stream->chan->metadata_cache->contiguous;
+               contiguous = stream->chan->metadata_cache->max_offset;
                pushed = stream->ust_metadata_pushed;
 
                /*
@@ -2144,7 +3017,7 @@ int lttng_ustconsumer_data_pending(struct lttng_consumer_stream *stream)
                 */
                DBG("UST consumer metadata pending check: contiguous %" PRIu64 " vs pushed %" PRIu64,
                                contiguous, pushed);
-               assert(((int64_t) contiguous - pushed) >= 0);
+               assert(((int64_t) (contiguous - pushed)) >= 0);
                if ((contiguous != pushed) ||
                                (((int64_t) contiguous - pushed) > 0 || contiguous == 0)) {
                        ret = 1;        /* Data is pending */
@@ -2258,6 +3131,10 @@ void lttng_ustconsumer_close_stream_wakeup(struct lttng_consumer_stream *stream)
  * function or any of its callees. Timers have a very strict locking
  * semantic with respect to teardown. Failure to respect this semantic
  * introduces deadlocks.
+ *
+ * DON'T hold the metadata lock when calling this function, else this
+ * can cause deadlock involving consumer awaiting for metadata to be
+ * pushed out due to concurrent interaction with the session daemon.
  */
 int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                struct lttng_consumer_channel *channel, int timer, int wait)
@@ -2265,7 +3142,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        struct lttcomm_metadata_request_msg request;
        struct lttcomm_consumer_msg msg;
        enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
-       uint64_t len, key, offset;
+       uint64_t len, key, offset, version;
        int ret;
 
        assert(channel);
@@ -2297,7 +3174,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        request.key = channel->key;
 
        DBG("Sending metadata request to sessiond, session id %" PRIu64
-                       ", per-pid %" PRIu64 ", app UID %u and channek key %" PRIu64,
+                       ", per-pid %" PRIu64 ", app UID %u and channel key %" PRIu64,
                        request.session_id, request.session_id_per_pid, request.uid,
                        request.key);
 
@@ -2345,6 +3222,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        len = msg.u.push_metadata.len;
        key = msg.u.push_metadata.key;
        offset = msg.u.push_metadata.target_offset;
+       version = msg.u.push_metadata.version;
 
        assert(key == channel->key);
        if (len == 0) {
@@ -2367,7 +3245,7 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
        health_code_update();
 
        ret = lttng_ustconsumer_recv_metadata(ctx->consumer_metadata_socket,
-                       key, offset, len, channel, timer, wait);
+                       key, offset, len, version, channel, timer, wait);
        if (ret >= 0) {
                /*
                 * Only send the status msg if the sessiond is alive meaning a positive
@@ -2383,3 +3261,15 @@ end:
        pthread_mutex_unlock(&ctx->metadata_socket_lock);
        return ret;
 }
+
+/*
+ * Return the ustctl call for the get stream id.
+ */
+int lttng_ustconsumer_get_stream_id(struct lttng_consumer_stream *stream,
+               uint64_t *stream_id)
+{
+       assert(stream);
+       assert(stream_id);
+
+       return ustctl_get_stream_id(stream->ustream, stream_id);
+}
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