Fix: ust-consumer: flush empty packets on snapshot channel
[lttng-tools.git] / src / common / ust-consumer / ust-consumer.c
index 6a508143e0d7ab22796e3e9ad6fcf233258ae2bc..89109b919a85231615fdb7f86a3c98518a9d422a 100644 (file)
@@ -16,7 +16,7 @@
  * 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>
 #include <urcu/list.h>
 #include <signal.h>
 
+#include <bin/lttng-consumerd/health-consumerd.h>
 #include <common/common.h>
 #include <common/sessiond-comm/sessiond-comm.h>
 #include <common/relayd/relayd.h>
 #include <common/compat/fcntl.h>
-#include <common/consumer-metadata-cache.h>
-#include <common/consumer-stream.h>
-#include <common/consumer-timer.h>
+#include <common/compat/endian.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;
@@ -63,6 +67,9 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
 
        cds_list_for_each_entry_safe(stream, stmp, &channel->streams.head,
                        send_node) {
+
+               health_code_update();
+
                cds_list_del(&stream->send_node);
                ustctl_destroy_stream(stream->ustream);
                free(stream);
@@ -74,6 +81,7 @@ static void destroy_channel(struct lttng_consumer_channel *channel)
         */
        if (channel->uchan) {
                lttng_ustconsumer_del_channel(channel);
+               lttng_ustconsumer_free_channel(channel);
        }
        free(channel);
 }
@@ -118,14 +126,16 @@ 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);
 }
 
 /*
@@ -234,6 +244,26 @@ 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.
  *
@@ -257,6 +287,8 @@ static int create_ust_streams(struct lttng_consumer_channel *channel,
                int wait_fd;
                int ust_metadata_pipe[2];
 
+               health_code_update();
+
                if (channel->type == CONSUMER_CHANNEL_TYPE_METADATA && channel->monitor) {
                        ret = utils_create_pipe_cloexec_nonblock(ust_metadata_pipe);
                        if (ret < 0) {
@@ -320,8 +352,12 @@ 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));
+                       }
                }
        }
 
@@ -332,20 +368,87 @@ 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,
+               struct ustctl_consumer_channel_attr *attr,
+               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 ", "
@@ -354,17 +457,64 @@ 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, attr, 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_recursive_rmdir(channel->root_shm_path,
+                               channel->uid, channel->gid);
+       }
+       free(stream_fds);
+error_alloc:
        return ret;
 }
 
@@ -401,8 +551,9 @@ static int send_sessiond_channel(int sock,
                struct lttng_consumer_channel *channel,
                struct lttng_consumer_local_data *ctx, int *relayd_error)
 {
-       int ret, ret_code = LTTNG_OK;
+       int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        struct lttng_consumer_stream *stream;
+       uint64_t net_seq_idx = -1ULL;
 
        assert(channel);
        assert(ctx);
@@ -412,6 +563,9 @@ static int send_sessiond_channel(int sock,
 
        if (channel->relayd_id != (uint64_t) -1ULL) {
                cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+
+                       health_code_update();
+
                        /* Try to send the stream to the relayd if one is available. */
                        ret = consumer_send_relayd_stream(stream, stream->chan->pathname);
                        if (ret < 0) {
@@ -422,14 +576,17 @@ 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;
                        }
                }
        }
 
        /* Inform sessiond that we are about to send channel and streams. */
        ret = consumer_send_status_msg(sock, ret_code);
-       if (ret < 0 || ret_code != LTTNG_OK) {
+       if (ret < 0 || ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                /*
                 * Either the session daemon is not responding or the relayd died so we
                 * stop now.
@@ -450,6 +607,9 @@ static int send_sessiond_channel(int sock,
 
        /* The channel was sent successfully to the sessiond at this point. */
        cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+
+               health_code_update();
+
                /* Send stream to session daemon. */
                ret = send_sessiond_stream(sock, stream);
                if (ret < 0) {
@@ -468,7 +628,7 @@ static int send_sessiond_channel(int sock,
        return 0;
 
 error:
-       if (ret_code != LTTNG_OK) {
+       if (ret_code != LTTCOMM_CONSUMERD_SUCCESS) {
                ret = -1;
        }
        return ret;
@@ -508,7 +668,7 @@ 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;
        }
@@ -551,6 +711,9 @@ static int send_streams_to_thread(struct lttng_consumer_channel *channel,
        /* Send streams to the corresponding thread. */
        cds_list_for_each_entry_safe(stream, stmp, &channel->streams.head,
                        send_node) {
+
+               health_code_update();
+
                /* Sending the stream to the thread. */
                ret = send_stream_to_thread(stream, ctx);
                if (ret < 0) {
@@ -601,49 +764,60 @@ static int flush_channel(uint64_t chan_key)
        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) {
-               ustctl_flush_buffer(stream->ustream, 1);
+
+               health_code_update();
+
+               pthread_mutex_lock(&stream->lock);
+               if (!stream->quiescent) {
+                       ustctl_flush_buffer(stream->ustream, 0);
+                       stream->quiescent = true;
+               }
+               pthread_mutex_unlock(&stream->lock);
        }
 error:
        rcu_read_unlock();
        return ret;
 }
+
 /*
- * Close metadata stream wakeup_fd using the given key to retrieve the channel.
- * RCU read side lock MUST be acquired before calling this function.
- *
- * NOTE: This function does NOT take any channel nor stream lock.
+ * Clear quiescent state from channel's streams using the given key to
+ * retrieve the channel.
  *
- * Return 0 on success else LTTng error code.
+ * Return 0 on success else an LTTng error code.
  */
-static int _close_metadata(struct lttng_consumer_channel *channel)
+static int clear_quiescent_channel(uint64_t chan_key)
 {
-       int ret = LTTNG_OK;
+       int ret = 0;
+       struct lttng_consumer_channel *channel;
+       struct lttng_consumer_stream *stream;
+       struct lttng_ht *ht;
+       struct lttng_ht_iter iter;
 
-       assert(channel);
-       assert(channel->type == CONSUMER_CHANNEL_TYPE_METADATA);
+       DBG("UST consumer clear quiescent channel key %" PRIu64, chan_key);
 
-       if (channel->switch_timer_enabled == 1) {
-               DBG("Deleting timer on metadata channel");
-               consumer_timer_switch_stop(channel);
+       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;
        }
 
-       if (channel->metadata_stream) {
-               ret = ustctl_stream_close_wakeup_fd(channel->metadata_stream->ustream);
-               if (ret < 0) {
-                       ERR("UST consumer unable to close fd of metadata (ret: %d)", ret);
-                       ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
-               }
+       ht = consumer_data.stream_per_chan_id_ht;
 
-               if (channel->monitor) {
-                       /* Close the read-side in consumer_del_metadata_stream */
-                       ret = close(channel->metadata_stream->ust_metadata_poll_pipe[1]);
-                       if (ret < 0) {
-                               PERROR("Close UST metadata write-side poll pipe");
-                               ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
-                       }
-               }
-       }
+       /* 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();
        return ret;
 }
 
@@ -680,7 +854,7 @@ static int close_metadata(uint64_t chan_key)
                goto error_unlock;
        }
 
-       ret = _close_metadata(channel);
+       lttng_ustconsumer_close_metadata(channel);
 
 error_unlock:
        pthread_mutex_unlock(&channel->lock);
@@ -736,6 +910,12 @@ static int setup_metadata(struct lttng_consumer_local_data *ctx, uint64_t key)
                        ret = LTTCOMM_CONSUMERD_ERROR_METADATA;
                        goto error;
                }
+               ret = consumer_send_relayd_streams_sent(
+                               metadata->metadata_stream->net_seq_idx);
+               if (ret < 0) {
+                       ret = LTTCOMM_CONSUMERD_RELAYD_FAIL;
+                       goto error;
+               }
        }
 
        ret = send_streams_to_thread(metadata, ctx);
@@ -760,8 +940,9 @@ error:
         * the stream is still in the local stream list of the channel. This call
         * will make sure to clean that list.
         */
-       cds_list_del(&metadata->metadata_stream->send_node);
        consumer_stream_destroy(metadata->metadata_stream, NULL);
+       cds_list_del(&metadata->metadata_stream->send_node);
+       metadata->metadata_stream = NULL;
 error_no_stream:
 end:
        return ret;
@@ -796,6 +977,8 @@ static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
        }
        assert(!metadata_channel->monitor);
 
+       health_code_update();
+
        /*
         * Ask the sessiond if we have new metadata waiting and update the
         * consumer metadata cache.
@@ -805,6 +988,8 @@ static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
                goto error;
        }
 
+       health_code_update();
+
        /*
         * The metadata stream is NOT created in no monitor mode when the channel
         * is created on a sessiond ask channel command.
@@ -836,6 +1021,8 @@ static int snapshot_metadata(uint64_t key, char *path, uint64_t relayd_id,
        }
 
        do {
+               health_code_update();
+
                ret = lttng_consumer_read_subbuffer(metadata_stream, ctx);
                if (ret < 0) {
                        goto error_stream;
@@ -847,8 +1034,8 @@ error_stream:
         * Clean up the stream completly because the next snapshot will use a new
         * metadata stream.
         */
-       cds_list_del(&metadata_stream->send_node);
        consumer_stream_destroy(metadata_stream, NULL);
+       cds_list_del(&metadata_stream->send_node);
        metadata_channel->metadata_stream = NULL;
 
 error:
@@ -862,7 +1049,7 @@ error:
  * 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)
+               uint64_t nb_packets_per_stream, struct lttng_consumer_local_data *ctx)
 {
        int ret;
        unsigned use_relayd = 0;
@@ -889,6 +1076,11 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
        DBG("UST consumer snapshot channel %" PRIu64, key);
 
        cds_list_for_each_entry(stream, &channel->streams.head, send_node) {
+               /* Are we at a position _before_ the first available packet ? */
+               bool before_first_packet = true;
+
+               health_code_update();
+
                /* Lock stream because we are about to change its state. */
                pthread_mutex_lock(&stream->lock);
                stream->net_seq_idx = relayd_id;
@@ -912,8 +1104,20 @@ 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) {
+                       ustctl_flush_buffer(stream->ustream, 0);
+               }
 
                ret = lttng_ustconsumer_take_snapshot(stream);
                if (ret < 0) {
@@ -935,16 +1139,20 @@ 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;
                        unsigned long len, padded_len;
+                       int lost_packet = 0;
+
+                       health_code_update();
 
                        DBG("UST consumer taking snapshot at pos %lu", consumed_pos);
 
@@ -956,6 +1164,15 @@ 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;
+
+                               /*
+                                * Start accounting lost packets only when we
+                                * already have extracted packets (to match the
+                                * content of the final snapshot).
+                                */
+                               if (!before_first_packet) {
+                                       lost_packet = 1;
+                               }
                                continue;
                        }
 
@@ -991,6 +1208,16 @@ static int snapshot_channel(uint64_t key, char *path, uint64_t relayd_id,
                                goto error_close_stream;
                        }
                        consumed_pos += stream->max_sb_size;
+
+                       /*
+                        * Only account lost packets located between
+                        * succesfully extracted packets (do not account before
+                        * and after since they are not visible in the
+                        * resulting snapshot).
+                        */
+                       stream->chan->lost_packets += lost_packet;
+                       lost_packet = 0;
+                       before_first_packet = false;
                }
 
                /* Simply close the stream so we can use it on the next snapshot. */
@@ -1015,13 +1242,18 @@ error:
 }
 
 /*
- * 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 = LTTNG_OK;
+       int ret, ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        char *metadata_str;
 
        DBG("UST consumer push metadata key %" PRIu64 " of len %" PRIu64, key, len);
@@ -1033,6 +1265,8 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
                goto end;
        }
 
+       health_code_update();
+
        /* Receive metadata string. */
        ret = lttcomm_recv_unix_sock(sock, metadata_str, len);
        if (ret < 0) {
@@ -1041,8 +1275,11 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
                goto end_free;
        }
 
+       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;
@@ -1061,6 +1298,9 @@ int lttng_ustconsumer_recv_metadata(int sock, uint64_t key, uint64_t offset,
        }
        while (consumer_metadata_cache_flushed(channel, offset + len, timer)) {
                DBG("Waiting for metadata to be flushed");
+
+               health_code_update();
+
                usleep(DEFAULT_METADATA_AVAILABILITY_WAIT_TIME);
        }
 
@@ -1079,10 +1319,12 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                int sock, struct pollfd *consumer_sockpoll)
 {
        ssize_t ret;
-       enum lttng_error_code ret_code = LTTNG_OK;
+       enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
        struct lttcomm_consumer_msg msg;
        struct lttng_consumer_channel *channel = NULL;
 
+       health_code_update();
+
        ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
        if (ret != sizeof(msg)) {
                DBG("Consumer received unexpected message size %zd (expects %zu)",
@@ -1097,17 +1339,13 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                }
                return ret;
        }
-       if (msg.cmd_type == LTTNG_CONSUMER_STOP) {
-               /*
-                * Notify the session daemon that the command is completed.
-                *
-                * On transport layer error, the function call will print an error
-                * message so handling the returned code is a bit useless since we
-                * return an error code anyway.
-                */
-               (void) consumer_send_status_msg(sock, ret_code);
-               return -ENOENT;
-       }
+
+       health_code_update();
+
+       /* deprecated */
+       assert(msg.cmd_type != LTTNG_CONSUMER_STOP);
+
+       health_code_update();
 
        /* relayd needs RCU read-side lock */
        rcu_read_lock();
@@ -1133,7 +1371,7 @@ 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;
                }
 
                /*
@@ -1195,7 +1433,9 @@ 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;
                }
@@ -1214,9 +1454,16 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                attr.switch_timer_interval = msg.u.ask_channel.switch_timer_interval;
                attr.read_timer_interval = msg.u.ask_channel.read_timer_interval;
                attr.chan_id = msg.u.ask_channel.chan_id;
-               attr.output = msg.u.ask_channel.output;
                memcpy(attr.uuid, msg.u.ask_channel.uuid, sizeof(attr.uuid));
 
+               /* Match channel buffer type to the UST abi. */
+               switch (msg.u.ask_channel.output) {
+               case LTTNG_EVENT_MMAP:
+               default:
+                       attr.output = LTTNG_UST_MMAP;
+                       break;
+               }
+
                /* Translate and save channel type. */
                switch (msg.u.ask_channel.type) {
                case LTTNG_UST_CHAN_PER_CPU:
@@ -1238,6 +1485,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        goto error_fatal;
                };
 
+               health_code_update();
+
                ret = ask_channel(ctx, sock, channel, &attr);
                if (ret < 0) {
                        goto end_channel_error;
@@ -1256,6 +1505,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                        msg.u.ask_channel.live_timer_interval);
                }
 
+               health_code_update();
+
                /*
                 * Add the channel to the internal state AFTER all streams were created
                 * and successfully sent to session daemon. This way, all streams must
@@ -1277,6 +1528,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        goto end_channel_error;
                }
 
+               health_code_update();
+
                /*
                 * Channel and streams are now created. Inform the session daemon that
                 * everything went well and should wait to receive the channel and
@@ -1301,10 +1554,12 @@ 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);
                if (ret < 0) {
@@ -1324,6 +1579,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                        goto error_fatal;
                }
 
+               health_code_update();
+
                /*
                 * In no monitor mode, the streams ownership is kept inside the channel
                 * so don't send them to the data thread.
@@ -1378,12 +1635,25 @@ 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,
@@ -1391,25 +1661,50 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 
                channel = consumer_find_channel(key);
                if (!channel) {
-                       ERR("UST consumer push metadata %" PRIu64 " not found", key);
-                       ret_code = LTTNG_ERR_UST_CHAN_NOT_FOUND;
+                       /*
+                        * This is possible if the metadata creation on the consumer side
+                        * is in flight vis-a-vis a concurrent push metadata from the
+                        * session daemon.  Simply return that the channel failed and the
+                        * session daemon will handle that message correctly considering
+                        * that this race is acceptable thus the DBG() statement here.
+                        */
+                       DBG("UST consumer push metadata %" PRIu64 " not found", key);
+                       ret_code = LTTCOMM_CONSUMERD_CHANNEL_FAIL;
+                       goto end_msg_sessiond;
+               }
+
+               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, LTTNG_OK);
+               ret = consumer_send_status_msg(sock, LTTCOMM_CONSUMERD_SUCCESS);
                if (ret < 0) {
                        /* Somehow, the session daemon is not responding anymore. */
                        goto error_fatal;
                }
 
+               health_code_update();
+
                /* Wait for more data. */
-               if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
+               health_poll_entry();
+               ret = lttng_consumer_poll_socket(consumer_sockpoll);
+               health_poll_exit();
+               if (ret) {
                        goto error_fatal;
                }
 
+               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;
@@ -1437,25 +1732,129 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
                                        ctx);
                        if (ret < 0) {
                                ERR("Snapshot metadata failed");
-                               ret_code = LTTNG_ERR_UST_META_FAIL;
+                               ret_code = LTTCOMM_CONSUMERD_ERROR_METADATA;
                        }
                } 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,
+                                       msg.u.snapshot_channel.nb_packets_per_stream,
                                        ctx);
                        if (ret < 0) {
                                ERR("Snapshot channel failed");
-                               ret_code = LTTNG_ERR_UST_CHAN_FAIL;
+                               ret_code = LTTCOMM_CONSUMERD_CHANNEL_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;
                }
+               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;
        }
        default:
@@ -1465,6 +1864,8 @@ int lttng_ustconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
 end_nosignal:
        rcu_read_unlock();
 
+       health_code_update();
+
        /*
         * Return 1 to indicate success since the 0 value can be a socket
         * shutdown during the recv() or send() call.
@@ -1482,6 +1883,9 @@ end_msg_sessiond:
                goto error_fatal;
        }
        rcu_read_unlock();
+
+       health_code_update();
+
        return 1;
 end_channel_error:
        if (channel) {
@@ -1498,6 +1902,9 @@ end_channel_error:
                goto error_fatal;
        }
        rcu_read_unlock();
+
+       health_code_update();
+
        return 1;
 error_fatal:
        rcu_read_unlock();
@@ -1592,28 +1999,78 @@ 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) {
+               ustctl_flush_buffer(stream->ustream, 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_recursive_rmdir(chan->root_shm_path,
+                               chan->uid, chan->gid);
+       }
+       free(chan->stream_fds);
 }
 
 void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
@@ -1627,12 +2084,28 @@ void lttng_ustconsumer_del_stream(struct lttng_consumer_stream *stream)
        ustctl_destroy_stream(stream->ustream);
 }
 
+int lttng_ustconsumer_get_wakeup_fd(struct lttng_consumer_stream *stream)
+{
+       assert(stream);
+       assert(stream->ustream);
+
+       return ustctl_stream_get_wakeup_fd(stream->ustream);
+}
+
+int lttng_ustconsumer_close_wakeup_fd(struct lttng_consumer_stream *stream)
+{
+       assert(stream);
+       assert(stream->ustream);
+
+       return ustctl_stream_close_wakeup_fd(stream->ustream);
+}
+
 /*
  * Populate index values of a UST stream. Values are set in big endian order.
  *
  * Return 0 on success or else a negative value.
  */
-static int get_index_values(struct lttng_packet_index *index,
+static int get_index_values(struct ctf_packet_index *index,
                struct ustctl_consumer_stream *ustream)
 {
        int ret;
@@ -1679,10 +2152,56 @@ static int get_index_values(struct lttng_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.
  *
@@ -1696,7 +2215,11 @@ 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;
@@ -1704,7 +2227,7 @@ 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) {
@@ -1714,7 +2237,7 @@ 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;
 
@@ -1728,7 +2251,9 @@ 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.
@@ -1742,6 +2267,7 @@ 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.
@@ -1750,6 +2276,7 @@ int lttng_ustconsumer_sync_metadata(struct lttng_consumer_local_data *ctx,
        if (ret < 0) {
                goto end;
        }
+       pthread_mutex_lock(&metadata->lock);
 
        ret = commit_one_metadata_packet(metadata);
        if (ret <= 0) {
@@ -1782,6 +2309,112 @@ end:
        return ret;
 }
 
+/*
+ * Return 0 on success else a negative value.
+ */
+static int notify_if_more_data(struct lttng_consumer_stream *stream,
+               struct lttng_consumer_local_data *ctx)
+{
+       int ret;
+       struct ustctl_consumer_stream *ustream;
+
+       assert(stream);
+       assert(ctx);
+
+       ustream = stream->ustream;
+
+       /*
+        * First, we are going to check if there is a new subbuffer available
+        * before reading the stream wait_fd.
+        */
+       /* Get the next subbuffer */
+       ret = ustctl_get_next_subbuf(ustream);
+       if (ret) {
+               /* No more data found, flag the stream. */
+               stream->has_data = 0;
+               ret = 0;
+               goto end;
+       }
+
+       ret = ustctl_put_subbuf(ustream);
+       assert(!ret);
+
+       /* This stream still has data. Flag it and wake up the data thread. */
+       stream->has_data = 1;
+
+       if (stream->monitor && !stream->hangup_flush_done && !ctx->has_wakeup) {
+               ssize_t writelen;
+
+               writelen = lttng_pipe_write(ctx->consumer_wakeup_pipe, "!", 1);
+               if (writelen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
+                       ret = writelen;
+                       goto end;
+               }
+
+               /* The wake up pipe has been notified. */
+               ctx->has_wakeup = 1;
+       }
+       ret = 0;
+
+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 occured. We assume only one wrap-around
+                * has occured.
+                */
+               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.
  *
@@ -1795,9 +2428,8 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
        unsigned long len, subbuf_size, padding;
        int err, write_index = 1;
        long ret = 0;
-       char dummy;
        struct ustctl_consumer_stream *ustream;
-       struct lttng_packet_index index;
+       struct ctf_packet_index index;
 
        assert(stream);
        assert(stream->ustream);
@@ -1809,14 +2441,22 @@ int lttng_ustconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
        /* Ease our life for what's next. */
        ustream = stream->ustream;
 
-       /* We can consume the 1 byte written into the wait_fd by UST */
-       if (stream->monitor && !stream->hangup_flush_done) {
+       /*
+        * We can consume the 1 byte written into the wait_fd by UST. Don't trigger
+        * error if we cannot read this one byte (read returns 0), or if the error
+        * is EAGAIN or EWOULDBLOCK.
+        *
+        * This is only done when the stream is monitored by a thread, before the
+        * flush is done after a hangup and if the stream is not flagged with data
+        * since there might be nothing to consume in the wait fd but still have
+        * data available flagged by the consumer wake up pipe.
+        */
+       if (stream->monitor && !stream->hangup_flush_done && !stream->has_data) {
+               char dummy;
                ssize_t readlen;
 
-               do {
-                       readlen = read(stream->wait_fd, &dummy, 1);
-               } while (readlen == -1 && errno == EINTR);
-               if (readlen == -1 && errno != EAGAIN && errno != EWOULDBLOCK) {
+               readlen = lttng_read(stream->wait_fd, &dummy, 1);
+               if (readlen < 0 && errno != EAGAIN && errno != EWOULDBLOCK) {
                        ret = readlen;
                        goto end;
                }
@@ -1858,6 +2498,13 @@ retry:
                if (ret < 0) {
                        goto end;
                }
+
+               /* Update the stream's sequence and discarded events count. */
+               ret = update_stream_stats(stream);
+               if (ret < 0) {
+                       PERROR("kernctl_get_events_discarded");
+                       goto end;
+               }
        } else {
                write_index = 0;
        }
@@ -1898,6 +2545,17 @@ retry:
        err = ustctl_put_next_subbuf(ustream);
        assert(err == 0);
 
+       /*
+        * This will consumer the byte on the wait_fd if and only if there is not
+        * next subbuffer to be acquired.
+        */
+       if (!stream->metadata_flag) {
+               ret = notify_if_more_data(stream, ctx);
+               if (ret < 0) {
+                       goto end;
+               }
+       }
+
        /* Write index if needed. */
        if (!write_index) {
                goto end;
@@ -1907,7 +2565,23 @@ retry:
                /*
                 * 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;
                }
@@ -1988,7 +2662,7 @@ 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;
 
                /*
@@ -2003,7 +2677,7 @@ 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 */
@@ -2030,6 +2704,45 @@ end:
        return ret;
 }
 
+/*
+ * Stop a given metadata channel timer if enabled and close the wait fd which
+ * is the poll pipe of the metadata stream.
+ *
+ * This MUST be called with the metadata channel acquired.
+ */
+void lttng_ustconsumer_close_metadata(struct lttng_consumer_channel *metadata)
+{
+       int ret;
+
+       assert(metadata);
+       assert(metadata->type == CONSUMER_CHANNEL_TYPE_METADATA);
+
+       DBG("Closing metadata channel key %" PRIu64, metadata->key);
+
+       if (metadata->switch_timer_enabled == 1) {
+               consumer_timer_switch_stop(metadata);
+       }
+
+       if (!metadata->metadata_stream) {
+               goto end;
+       }
+
+       /*
+        * Closing write side so the thread monitoring the stream wakes up if any
+        * and clean the metadata stream.
+        */
+       if (metadata->metadata_stream->ust_metadata_poll_pipe[1] >= 0) {
+               ret = close(metadata->metadata_stream->ust_metadata_poll_pipe[1]);
+               if (ret < 0) {
+                       PERROR("closing metadata pipe write side");
+               }
+               metadata->metadata_stream->ust_metadata_poll_pipe[1] = -1;
+       }
+
+end:
+       return;
+}
+
 /*
  * Close every metadata stream wait fd of the metadata hash table. This
  * function MUST be used very carefully so not to run into a race between the
@@ -2039,7 +2752,7 @@ end:
  * producer so calling this is safe because we are assured that no state change
  * can occur in the metadata thread for the streams in the hash table.
  */
-void lttng_ustconsumer_close_metadata(struct lttng_ht *metadata_ht)
+void lttng_ustconsumer_close_all_metadata(struct lttng_ht *metadata_ht)
 {
        struct lttng_ht_iter iter;
        struct lttng_consumer_stream *stream;
@@ -2052,14 +2765,11 @@ void lttng_ustconsumer_close_metadata(struct lttng_ht *metadata_ht)
        rcu_read_lock();
        cds_lfht_for_each_entry(metadata_ht->ht, &iter.iter, stream,
                        node.node) {
+
+               health_code_update();
+
                pthread_mutex_lock(&stream->chan->lock);
-               /*
-                * Whatever returned value, we must continue to try to close everything
-                * so ignore it.
-                */
-               (void) _close_metadata(stream->chan);
-               DBG("Metadata wait fd %d and poll pipe fd %d closed", stream->wait_fd,
-                               stream->ust_metadata_poll_pipe[1]);
+               lttng_ustconsumer_close_metadata(stream->chan);
                pthread_mutex_unlock(&stream->chan->lock);
 
        }
@@ -2081,19 +2791,25 @@ 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)
 {
        struct lttcomm_metadata_request_msg request;
        struct lttcomm_consumer_msg msg;
-       enum lttng_error_code ret_code = LTTNG_OK;
-       uint64_t len, key, offset;
+       enum lttcomm_return_code ret_code = LTTCOMM_CONSUMERD_SUCCESS;
+       uint64_t len, key, offset, version;
        int ret;
 
        assert(channel);
        assert(channel->metadata_cache);
 
+       memset(&request, 0, sizeof(request));
+
        /* send the metadata request to sessiond */
        switch (consumer_data.type) {
        case LTTNG_CONSUMER64_UST:
@@ -2123,6 +2839,9 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                        request.key);
 
        pthread_mutex_lock(&ctx->metadata_socket_lock);
+
+       health_code_update();
+
        ret = lttcomm_send_unix_sock(ctx->consumer_metadata_socket, &request,
                        sizeof(request));
        if (ret < 0) {
@@ -2130,6 +2849,8 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                goto end;
        }
 
+       health_code_update();
+
        /* Receive the metadata from sessiond */
        ret = lttcomm_recv_unix_sock(ctx->consumer_metadata_socket, &msg,
                        sizeof(msg));
@@ -2144,6 +2865,8 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                goto end;
        }
 
+       health_code_update();
+
        if (msg.cmd_type == LTTNG_ERR_UND) {
                /* No registry found */
                (void) consumer_send_status_msg(ctx->consumer_metadata_socket,
@@ -2159,15 +2882,18 @@ 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) {
                DBG("No new metadata to receive for key %" PRIu64, key);
        }
 
+       health_code_update();
+
        /* Tell session daemon we are ready to receive the metadata. */
        ret = consumer_send_status_msg(ctx->consumer_metadata_socket,
-                       LTTNG_OK);
+                       LTTCOMM_CONSUMERD_SUCCESS);
        if (ret < 0 || len == 0) {
                /*
                 * Somehow, the session daemon is not responding anymore or there is
@@ -2176,18 +2902,34 @@ int lttng_ustconsumer_request_metadata(struct lttng_consumer_local_data *ctx,
                goto end;
        }
 
-       ret_code = lttng_ustconsumer_recv_metadata(ctx->consumer_metadata_socket,
-                       key, offset, len, channel, timer, wait);
-       if (ret_code >= 0) {
+       health_code_update();
+
+       ret = lttng_ustconsumer_recv_metadata(ctx->consumer_metadata_socket,
+                       key, offset, len, version, channel, timer, wait);
+       if (ret >= 0) {
                /*
                 * Only send the status msg if the sessiond is alive meaning a positive
                 * ret code.
                 */
-               (void) consumer_send_status_msg(ctx->consumer_metadata_socket, ret_code);
+               (void) consumer_send_status_msg(ctx->consumer_metadata_socket, ret);
        }
        ret = 0;
 
 end:
+       health_code_update();
+
        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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