src.ctf.lttng-live: Extract `handle_late_message()` function for future fix
[babeltrace.git] / src / plugins / ctf / lttng-live / lttng-live.c
index e184b6328815703ef4d3693fac22380cfe896a4a..b0833061dfad1ffc0cb68b2ef3674a67a92e5059 100644 (file)
@@ -1,31 +1,11 @@
 /*
- * lttng-live.c
- *
- * Babeltrace CTF LTTng-live Client Component
+ * SPDX-License-Identifier: MIT
  *
  * Copyright 2019 Francis Deslauriers <francis.deslauriers@efficios.com>
  * Copyright 2016 Jérémie Galarneau <jeremie.galarneau@efficios.com>
  * Copyright 2016 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
  *
- * Author: Jérémie Galarneau <jeremie.galarneau@efficios.com>
- *
- * Permission is hereby granted, free of charge, to any person obtaining a copy
- * of this software and associated documentation files (the "Software"), to deal
- * in the Software without restriction, including without limitation the rights
- * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
- * copies of the Software, and to permit persons to whom the Software is
- * furnished to do so, subject to the following conditions:
- *
- * The above copyright notice and this permission notice shall be included in
- * all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
- * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
- * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
- * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
- * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
- * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
- * SOFTWARE.
+ * Babeltrace CTF LTTng-live Client Component
  */
 
 #define BT_COMP_LOG_SELF_COMP self_comp
@@ -62,7 +42,8 @@
 #define print_dbg(fmt, ...)    BT_COMP_LOGD(fmt, ## __VA_ARGS__)
 
 static
-const char *print_live_iterator_status(enum lttng_live_iterator_status status)
+const char *lttng_live_iterator_status_string(
+               enum lttng_live_iterator_status status)
 {
        switch (status) {
        case LTTNG_LIVE_ITERATOR_STATUS_CONTINUE:
@@ -87,9 +68,9 @@ const char *print_live_iterator_status(enum lttng_live_iterator_status status)
 }
 
 static
-const char *print_state(struct lttng_live_stream_iterator *s)
+const char *lttng_live_stream_state_string(enum lttng_live_stream_state state)
 {
-       switch (s->state) {
+       switch (state) {
        case LTTNG_LIVE_STREAM_ACTIVE_NO_DATA:
                return "ACTIVE_NO_DATA";
        case LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA:
@@ -105,11 +86,26 @@ const char *print_state(struct lttng_live_stream_iterator *s)
        }
 }
 
-#define print_stream_state(live_stream_iter) \
+void lttng_live_stream_iterator_set_state(struct lttng_live_stream_iterator *stream_iter,
+               enum lttng_live_stream_state new_state)
+{
+       bt_self_component *self_comp = stream_iter->self_comp;
+       bt_logging_level log_level = stream_iter->log_level;
+
+       BT_COMP_LOGD("Setting live stream iterator state: viewer-stream-id=%" PRIu64
+               ", old-state=%s, new-state=%s",
+               stream_iter->viewer_stream_id,
+               lttng_live_stream_state_string(stream_iter->state),
+               lttng_live_stream_state_string(new_state));
+
+       stream_iter->state = new_state;
+}
+
+#define LTTNG_LIVE_LOGD_STREAM_ITER(live_stream_iter) \
        do { \
-               BT_COMP_LOGD("stream state %s last_inact_ts %" PRId64  \
-                       ", curr_inact_ts %" PRId64, \
-                       print_state(live_stream_iter), \
+               BT_COMP_LOGD("Live stream iterator state=%s, last-inact-ts=%" PRId64  \
+                       ", curr-inact-ts %" PRId64, \
+                       lttng_live_stream_state_string(live_stream_iter->state), \
                        live_stream_iter->last_inactivity_ts, \
                        live_stream_iter->current_inactivity_ts); \
        } while (0);
@@ -132,7 +128,7 @@ end:
 }
 
 static
-struct lttng_live_trace *lttng_live_find_trace(struct lttng_live_session *session,
+struct lttng_live_trace *lttng_live_session_borrow_trace_by_id(struct lttng_live_session *session,
                uint64_t trace_id)
 {
        uint64_t trace_idx;
@@ -157,7 +153,7 @@ void lttng_live_destroy_trace(struct lttng_live_trace *trace)
        bt_logging_level log_level = trace->log_level;
        bt_self_component *self_comp = trace->self_comp;
 
-       BT_COMP_LOGD("Destroy lttng_live_trace");
+       BT_COMP_LOGD("Destroying live trace: trace-id=%"PRIu64, trace->id);
 
        BT_ASSERT(trace->stream_iterators);
        g_ptr_array_free(trace->stream_iterators, TRUE);
@@ -177,6 +173,9 @@ struct lttng_live_trace *lttng_live_create_trace(struct lttng_live_session *sess
        bt_logging_level log_level = session->log_level;
        bt_self_component *self_comp = session->self_comp;
 
+       BT_COMP_LOGD("Creating live trace: "
+               "session-id=%"PRIu64", trace-id=%"PRIu64,
+               session->id, trace_id);
        trace = g_new0(struct lttng_live_trace, 1);
        if (!trace) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
@@ -192,10 +191,9 @@ struct lttng_live_trace *lttng_live_create_trace(struct lttng_live_session *sess
        trace->stream_iterators = g_ptr_array_new_with_free_func(
                (GDestroyNotify) lttng_live_stream_iterator_destroy);
        BT_ASSERT(trace->stream_iterators);
-       trace->new_metadata_needed = true;
+       trace->metadata_stream_state = LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED;
        g_ptr_array_add(session->traces, trace);
 
-       BT_COMP_LOGI("Create trace");
        goto end;
 error:
        g_free(trace);
@@ -205,12 +203,12 @@ end:
 }
 
 BT_HIDDEN
-struct lttng_live_trace *lttng_live_borrow_trace(
+struct lttng_live_trace *lttng_live_session_borrow_or_create_trace_by_id(
                struct lttng_live_session *session, uint64_t trace_id)
 {
        struct lttng_live_trace *trace;
 
-       trace = lttng_live_find_trace(session, trace_id);
+       trace = lttng_live_session_borrow_trace_by_id(session, trace_id);
        if (trace) {
                goto end;
        }
@@ -232,6 +230,10 @@ int lttng_live_add_session(struct lttng_live_msg_iter *lttng_live_msg_iter,
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
 
+       BT_COMP_LOGD("Adding live session: "
+               "session-id=%" PRIu64 ", hostname=\"%s\" session-name=\"%s\"",
+               session_id, hostname, session_name);
+
        session = g_new0(struct lttng_live_session, 1);
        if (!session) {
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
@@ -253,8 +255,6 @@ int lttng_live_add_session(struct lttng_live_msg_iter *lttng_live_msg_iter,
        session->session_name = g_string_new(session_name);
        BT_ASSERT(session->session_name);
 
-       BT_COMP_LOGI("Reading from session: %" PRIu64 " hostname: %s session_name: %s",
-               session->id, hostname, session_name);
        g_ptr_array_add(lttng_live_msg_iter->sessions, session);
        goto end;
 error:
@@ -276,9 +276,11 @@ void lttng_live_destroy_session(struct lttng_live_session *session)
 
        log_level = session->log_level;
        self_comp = session->self_comp;
-       BT_COMP_LOGD("Destroy lttng live session");
+       BT_COMP_LOGD("Destroying live session: "
+               "session-id=%"PRIu64", session-name=\"%s\"",
+               session->id, session->session_name->str);
        if (session->id != -1ULL) {
-               if (lttng_live_detach_session(session)) {
+               if (lttng_live_session_detach(session)) {
                        if (!lttng_live_graph_is_canceled(
                                        session->lttng_live_msg_iter)) {
                                /* Old relayd cannot detach sessions. */
@@ -370,12 +372,12 @@ enum lttng_live_iterator_status lttng_live_iterator_next_check_stream_state(
 }
 
 /*
- * For active no data stream, fetch next data. It can be either:
- * - quiescent: need to put it in the prio heap at quiescent end
- *   timestamp,
- * - have data: need to wire up first event into the prio heap,
- * - have no data on this stream at this point: need to retry (AGAIN) or
- *   return EOF.
+ * For active no data stream, fetch next index. As a result of that it can
+ * become either:
+ * - quiescent: won't have events for a bit,
+ * - have data: need to get that data and produce the event,
+ * - have no data on this stream at this point: need to retry (AGAIN) or return
+ *   EOF.
  */
 static
 enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_no_data_stream(
@@ -388,24 +390,33 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_no_data_stre
        enum lttng_live_stream_state orig_state = lttng_live_stream->state;
        struct packet_index index;
 
-       if (lttng_live_stream->trace->new_metadata_needed) {
+       if (lttng_live_stream->trace->metadata_stream_state ==
+                       LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED) {
+               BT_COMP_LOGD("Need to get an update for the metadata stream before proceeding further with this stream: "
+                       "stream-name=\"%s\"", lttng_live_stream->name->str);
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }
+
        if (lttng_live_stream->trace->session->new_streams_needed) {
+               BT_COMP_LOGD("Need to get an update of all streams before proceeding further with this stream: "
+                       "stream-name=\"%s\"", lttng_live_stream->name->str);
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }
+
        if (lttng_live_stream->state != LTTNG_LIVE_STREAM_ACTIVE_NO_DATA &&
                        lttng_live_stream->state != LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA) {
                goto end;
        }
        ret = lttng_live_get_next_index(lttng_live_msg_iter, lttng_live_stream,
-               &index);
+                       &index);
        if (ret != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                goto end;
        }
+
        BT_ASSERT_DBG(lttng_live_stream->state != LTTNG_LIVE_STREAM_EOF);
+
        if (lttng_live_stream->state == LTTNG_LIVE_STREAM_QUIESCENT) {
                uint64_t last_inact_ts = lttng_live_stream->last_inactivity_ts,
                         curr_inact_ts = lttng_live_stream->current_inactivity_ts;
@@ -413,15 +424,25 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_no_data_stre
                if (orig_state == LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA &&
                                last_inact_ts == curr_inact_ts) {
                        ret = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
-                       print_stream_state(lttng_live_stream);
+                       LTTNG_LIVE_LOGD_STREAM_ITER(lttng_live_stream);
                } else {
                        ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                }
                goto end;
        }
+
        lttng_live_stream->base_offset = index.offset;
        lttng_live_stream->offset = index.offset;
        lttng_live_stream->len = index.packet_size / CHAR_BIT;
+
+       BT_COMP_LOGD("Setting live stream reading info: stream-name=\"%s\", "
+                       "viewer-stream-id=%" PRIu64 ", stream-base-offset=%" PRIu64
+                       ", stream-offset=%" PRIu64 ", stream-len=%" PRIu64,
+                       lttng_live_stream->name->str,
+                       lttng_live_stream->viewer_stream_id,
+                       lttng_live_stream->base_offset,
+                       lttng_live_stream->offset, lttng_live_stream->len);
+
 end:
        if (ret == LTTNG_LIVE_ITERATOR_STATUS_OK) {
                ret = lttng_live_iterator_next_check_stream_state(lttng_live_stream);
@@ -447,10 +468,12 @@ enum lttng_live_iterator_status lttng_live_get_session(
        uint64_t trace_idx;
 
        if (!session->attached) {
-               enum lttng_live_attach_session_status attach_status =
-                       lttng_live_attach_session(session,
+               BT_COMP_LOGD("Attach to session: session-id=%" PRIu64,
+                       session->id);
+               enum lttng_live_viewer_status attach_status =
+                       lttng_live_session_attach(session,
                                lttng_live_msg_iter->self_msg_iter);
-               if (attach_status != LTTNG_LIVE_ATTACH_SESSION_STATUS_OK) {
+               if (attach_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                        if (lttng_live_graph_is_canceled(lttng_live_msg_iter)) {
                                /*
                                 * Clear any causes appended in
@@ -469,12 +492,17 @@ enum lttng_live_iterator_status lttng_live_get_session(
                }
        }
 
-       status = lttng_live_get_new_streams(session,
+       BT_COMP_LOGD("Updating all streams and metadata for session: "
+               "session-id=%" PRIu64 ", session-name=\"%s\"",
+               session->id, session->session_name->str);
+
+       status = lttng_live_session_get_new_streams(session,
                lttng_live_msg_iter->self_msg_iter);
        if (status != LTTNG_LIVE_ITERATOR_STATUS_OK &&
                        status != LTTNG_LIVE_ITERATOR_STATUS_END) {
                goto end;
        }
+
        trace_idx = 0;
        while (trace_idx < session->traces->len) {
                struct lttng_live_trace *trace =
@@ -482,26 +510,27 @@ enum lttng_live_iterator_status lttng_live_get_session(
 
                status = lttng_live_metadata_update(trace);
                switch (status) {
+               case LTTNG_LIVE_ITERATOR_STATUS_END:
                case LTTNG_LIVE_ITERATOR_STATUS_OK:
                        trace_idx++;
                        break;
-               case LTTNG_LIVE_ITERATOR_STATUS_END:
-                       /*
-                        * The trace has ended. Remove it of the array an
-                        * continue the iteration.
-                        * We can remove the trace safely when using the
-                        * g_ptr_array_remove_index_fast because it replaces
-                        * the element at trace_idx with the array's last
-                        * element. trace_idx is not incremented because of
-                        * that.
-                        */
-                       (void) g_ptr_array_remove_index_fast(session->traces,
-                               trace_idx);
-                       break;
+               case LTTNG_LIVE_ITERATOR_STATUS_CONTINUE:
+               case LTTNG_LIVE_ITERATOR_STATUS_AGAIN:
+                       goto end;
                default:
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Error updating trace metadata: "
+                               "stream-iter-status=%s, trace-id=%"PRIu64,
+                               lttng_live_iterator_status_string(status),
+                               trace->id);
                        goto end;
                }
        }
+
+       /*
+        * Now that we have the metadata we can initialize the downstream
+        * iterator.
+        */
        status = lttng_live_lazy_msg_init(session,
                lttng_live_msg_iter->self_msg_iter);
 
@@ -509,34 +538,32 @@ end:
        return status;
 }
 
-BT_HIDDEN
-void lttng_live_need_new_streams(struct lttng_live_msg_iter *lttng_live_msg_iter)
-{
-       uint64_t session_idx;
-
-       for (session_idx = 0; session_idx < lttng_live_msg_iter->sessions->len;
-                       session_idx++) {
-               struct lttng_live_session *session =
-                       g_ptr_array_index(lttng_live_msg_iter->sessions, session_idx);
-               session->new_streams_needed = true;
-       }
-}
-
 static
 void lttng_live_force_new_streams_and_metadata(struct lttng_live_msg_iter *lttng_live_msg_iter)
 {
        uint64_t session_idx, trace_idx;
+       bt_logging_level log_level = lttng_live_msg_iter->log_level;
+       bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
 
        for (session_idx = 0; session_idx < lttng_live_msg_iter->sessions->len;
                        session_idx++) {
                struct lttng_live_session *session =
                        g_ptr_array_index(lttng_live_msg_iter->sessions, session_idx);
+               BT_COMP_LOGD("Force marking session as needing new streams: "
+                               "session-id=%" PRIu64, session->id);
                session->new_streams_needed = true;
                for (trace_idx = 0; trace_idx < session->traces->len;
                                trace_idx++) {
                        struct lttng_live_trace *trace =
                                g_ptr_array_index(session->traces, trace_idx);
-                       trace->new_metadata_needed = true;
+                       BT_COMP_LOGD("Force marking trace metadata state as needing an update: "
+                                       "session-id=%" PRIu64 ", trace-id=%" PRIu64,
+                                       session->id, trace->id);
+
+                       BT_ASSERT(trace->metadata_stream_state !=
+                               LTTNG_LIVE_METADATA_STREAM_STATE_CLOSED);
+
+                       trace->metadata_stream_state = LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED;
                }
        }
 }
@@ -546,7 +573,8 @@ enum lttng_live_iterator_status
 lttng_live_iterator_handle_new_streams_and_metadata(
                struct lttng_live_msg_iter *lttng_live_msg_iter)
 {
-       enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
+       enum lttng_live_iterator_status status;
+       enum lttng_live_viewer_status viewer_status;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        uint64_t session_idx = 0, nr_sessions_opened = 0;
@@ -554,6 +582,8 @@ lttng_live_iterator_handle_new_streams_and_metadata(
        enum session_not_found_action sess_not_found_act =
                lttng_live_msg_iter->lttng_live_comp->params.sess_not_found_act;
 
+       BT_COMP_LOGD("Update data and metadata of all sessions: "
+               "live-msg-iter-addr=%p", lttng_live_msg_iter);
        /*
         * In a remotely distant future, we could add a "new
         * session" flag to the protocol, which would tell us that we
@@ -562,17 +592,26 @@ lttng_live_iterator_handle_new_streams_and_metadata(
         */
        if (lttng_live_msg_iter->sessions->len == 0) {
                if (sess_not_found_act != SESSION_NOT_FOUND_ACTION_CONTINUE) {
-                       ret = LTTNG_LIVE_ITERATOR_STATUS_END;
+                       BT_COMP_LOGD("No session found. Exiting in accordance with the `session-not-found-action` parameter");
+                       status = LTTNG_LIVE_ITERATOR_STATUS_END;
                        goto end;
                } else {
+                       BT_COMP_LOGD("No session found. Try creating a new one in accordance with the `session-not-found-action` parameter");
                        /*
                         * Retry to create a viewer session for the requested
                         * session name.
                         */
-                       if (lttng_live_create_viewer_session(lttng_live_msg_iter)) {
-                               ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
-                               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
-                                       "Error creating LTTng live viewer session");
+                       viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
+                       if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
+                               if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
+                                       status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+                                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                                               "Error creating LTTng live viewer session");
+                               } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
+                                       status = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
+                               } else {
+                                       bt_common_abort();
+                               }
                                goto end;
                        }
                }
@@ -582,12 +621,12 @@ lttng_live_iterator_handle_new_streams_and_metadata(
                        session_idx++) {
                session = g_ptr_array_index(lttng_live_msg_iter->sessions,
                                session_idx);
-               ret = lttng_live_get_session(lttng_live_msg_iter, session);
-               switch (ret) {
+               status = lttng_live_get_session(lttng_live_msg_iter, session);
+               switch (status) {
                case LTTNG_LIVE_ITERATOR_STATUS_OK:
                        break;
                case LTTNG_LIVE_ITERATOR_STATUS_END:
-                       ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
+                       status = LTTNG_LIVE_ITERATOR_STATUS_OK;
                        break;
                default:
                        goto end;
@@ -596,20 +635,23 @@ lttng_live_iterator_handle_new_streams_and_metadata(
                        nr_sessions_opened++;
                }
        }
-end:
-       if (ret == LTTNG_LIVE_ITERATOR_STATUS_OK &&
-                       sess_not_found_act != SESSION_NOT_FOUND_ACTION_CONTINUE &&
+
+       if (sess_not_found_act != SESSION_NOT_FOUND_ACTION_CONTINUE &&
                        nr_sessions_opened == 0) {
-               ret = LTTNG_LIVE_ITERATOR_STATUS_END;
+               status = LTTNG_LIVE_ITERATOR_STATUS_END;
+       } else {
+               status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        }
-       return ret;
+
+end:
+       return status;
 }
 
 static
 enum lttng_live_iterator_status emit_inactivity_message(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
-               bt_message **message, uint64_t timestamp)
+               const bt_message **message, uint64_t timestamp)
 {
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
@@ -618,6 +660,11 @@ enum lttng_live_iterator_status emit_inactivity_message(
 
        BT_ASSERT(stream_iter->trace->clock_class);
 
+       BT_COMP_LOGD("Emitting inactivity message for stream: ctf-stream-id=%" PRIu64
+               ", viewer-stream-id=%" PRIu64 ", timestamp=%" PRIu64,
+               stream_iter->ctf_stream_class_id,
+               stream_iter->viewer_stream_id, timestamp);
+
        msg = bt_message_message_iterator_inactivity_create(
                lttng_live_msg_iter->self_msg_iter,
                stream_iter->trace->clock_class, timestamp);
@@ -641,7 +688,7 @@ static
 enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_quiescent_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *lttng_live_stream,
-               bt_message **message)
+               const bt_message **message)
 {
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
 
@@ -649,9 +696,15 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_quiescent_st
                return LTTNG_LIVE_ITERATOR_STATUS_OK;
        }
 
+       /*
+        * Check if we already sent an inactivty message downstream for this
+        * `current_inactivity_ts` value.
+        */
        if (lttng_live_stream->current_inactivity_ts ==
                        lttng_live_stream->last_inactivity_ts) {
-               lttng_live_stream->state = LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA;
+               lttng_live_stream_iterator_set_state(lttng_live_stream,
+                       LTTNG_LIVE_STREAM_QUIESCENT_NO_DATA);
+
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                goto end;
        }
@@ -726,7 +779,7 @@ int live_get_msg_ts_ns(struct lttng_live_stream_iterator *stream_iter,
                        msg);
                break;
        case BT_MESSAGE_TYPE_MESSAGE_ITERATOR_INACTIVITY:
-               clock_snapshot = bt_message_message_iterator_inactivity_borrow_default_clock_snapshot_const(
+               clock_snapshot = bt_message_message_iterator_inactivity_borrow_clock_snapshot_const(
                        msg);
                break;
        default:
@@ -767,7 +820,7 @@ static
 enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *lttng_live_stream,
-               bt_message **message)
+               const bt_message **message)
 {
        enum lttng_live_iterator_status ret = LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
@@ -781,6 +834,8 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_
                        g_ptr_array_index(lttng_live_msg_iter->sessions, session_idx);
 
                if (session->new_streams_needed) {
+                       BT_COMP_LOGD("Need an update for streams: "
+                                       "session-id=%" PRIu64, session->id);
                        ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                        goto end;
                }
@@ -788,7 +843,10 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_
                                trace_idx++) {
                        struct lttng_live_trace *trace =
                                g_ptr_array_index(session->traces, trace_idx);
-                       if (trace->new_metadata_needed) {
+                       if (trace->metadata_stream_state == LTTNG_LIVE_METADATA_STREAM_STATE_NEEDED) {
+                               BT_COMP_LOGD("Need an update for metadata stream: "
+                                               "session-id=%" PRIu64 ", trace-id=%" PRIu64,
+                                               session->id, trace->id);
                                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                                goto end;
                        }
@@ -797,6 +855,10 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_
 
        if (lttng_live_stream->state != LTTNG_LIVE_STREAM_ACTIVE_DATA) {
                ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Invalid state of live stream iterator"
+                       "stream-iter-status=%s",
+                       lttng_live_stream_state_string(lttng_live_stream->state));
                goto end;
        }
 
@@ -817,14 +879,14 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_active_data_
                 */
                ret = LTTNG_LIVE_ITERATOR_STATUS_CONTINUE;
                break;
-       case CTF_MSG_ITER_STATUS_INVAL:
-               /* No argument provided by the user, so don't return INVAL. */
        case CTF_MSG_ITER_STATUS_ERROR:
        default:
                ret = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                BT_COMP_LOGE_APPEND_CAUSE(self_comp,
-                       "CTF message iterator return an error or failed: "
-                       "msg_iter=%p", lttng_live_stream->msg_iter);
+                       "CTF message iterator failed to get next message: "
+                       "msg-iter=%p, msg-iter-status=%s",
+                       lttng_live_stream->msg_iter,
+                       ctf_msg_iter_status_string(status));
                break;
        }
 
@@ -836,12 +898,17 @@ static
 enum lttng_live_iterator_status lttng_live_iterator_close_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
-               bt_message **curr_msg)
+               const bt_message **curr_msg)
 {
        enum lttng_live_iterator_status live_status =
                LTTNG_LIVE_ITERATOR_STATUS_OK;
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
+
+       BT_COMP_LOGD("Closing live stream iterator: stream-name=\"%s\", "
+                       "viewer-stream-id=%" PRIu64, stream_iter->name->str,
+                       stream_iter->viewer_stream_id);
+
        /*
         * The viewer has hung up on us so we are closing the stream. The
         * `ctf_msg_iter` should simply realize that it needs to close the
@@ -855,6 +922,10 @@ enum lttng_live_iterator_status lttng_live_iterator_close_stream(
                        "Error getting the next message from CTF message iterator");
                live_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
                goto end;
+       } else if (status == CTF_MSG_ITER_STATUS_EOF) {
+               BT_COMP_LOGI("Reached the end of the live stream iterator.");
+               live_status = LTTNG_LIVE_ITERATOR_STATUS_END;
+               goto end;
        }
 
        BT_ASSERT(status == CTF_MSG_ITER_STATUS_OK);
@@ -915,12 +986,16 @@ static
 enum lttng_live_iterator_status lttng_live_iterator_next_msg_on_stream(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
                struct lttng_live_stream_iterator *stream_iter,
-               bt_message **curr_msg)
+               const bt_message **curr_msg)
 {
        bt_logging_level log_level = lttng_live_msg_iter->log_level;
        bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
        enum lttng_live_iterator_status live_status;
 
+       BT_COMP_LOGD("Advancing live stream iterator until next message if possible: "
+               "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
+               stream_iter->name->str, stream_iter->viewer_stream_id);
+
        if (stream_iter->has_stream_hung_up) {
                /*
                 * The stream has hung up and the stream was properly closed
@@ -933,15 +1008,20 @@ enum lttng_live_iterator_status lttng_live_iterator_next_msg_on_stream(
        }
 
 retry:
-       print_stream_state(stream_iter);
+       LTTNG_LIVE_LOGD_STREAM_ITER(stream_iter);
+
+       /*
+        * Make sure we have the most recent metadata and possibly some new
+        * streams.
+        */
        live_status = lttng_live_iterator_handle_new_streams_and_metadata(
                lttng_live_msg_iter);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                goto end;
        }
+
        live_status = lttng_live_iterator_next_handle_one_no_data_stream(
                lttng_live_msg_iter, stream_iter);
-
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
                if (live_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                        /*
@@ -953,6 +1033,7 @@ retry:
                }
                goto end;
        }
+
        live_status = lttng_live_iterator_next_handle_one_quiescent_stream(
                lttng_live_msg_iter, stream_iter, curr_msg);
        if (live_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
@@ -970,12 +1051,180 @@ retry:
 
 end:
        if (live_status == LTTNG_LIVE_ITERATOR_STATUS_CONTINUE) {
+               BT_COMP_LOGD("Ask the relay daemon for an updated view of the data and metadata streams");
                goto retry;
        }
 
+       BT_COMP_LOGD("Returning from advancing live stream iterator: status=%s"
+                       "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
+                       lttng_live_iterator_status_string(live_status),
+                       stream_iter->name->str, stream_iter->viewer_stream_id);
+
        return live_status;
 }
 
+static
+bool is_discarded_packet_or_event_message(const bt_message *msg)
+{
+       const enum bt_message_type msg_type = bt_message_get_type(msg);
+
+       return msg_type == BT_MESSAGE_TYPE_DISCARDED_EVENTS ||
+                       msg_type == BT_MESSAGE_TYPE_DISCARDED_PACKETS;
+}
+
+static
+enum lttng_live_iterator_status adjust_discarded_packets_message(
+               bt_self_message_iterator *iter,
+               const bt_stream *stream,
+               const bt_message *msg_in, bt_message **msg_out,
+               uint64_t new_begin_ts)
+{
+       enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+       enum bt_property_availability availability;
+       const bt_clock_snapshot *clock_snapshot;
+       uint64_t end_ts;
+       uint64_t count;
+
+       clock_snapshot = bt_message_discarded_packets_borrow_end_default_clock_snapshot_const(msg_in);
+       end_ts = bt_clock_snapshot_get_value(clock_snapshot);
+
+       availability = bt_message_discarded_packets_get_count(msg_in, &count);
+       BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);
+
+       *msg_out = bt_message_discarded_packets_create_with_default_clock_snapshots(
+               iter, stream, new_begin_ts, end_ts);
+       if (!*msg_out) {
+               status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
+               goto end;
+       }
+
+       bt_message_discarded_packets_set_count(*msg_out, count);
+end:
+       return status;
+}
+
+static
+enum lttng_live_iterator_status adjust_discarded_events_message(
+               bt_self_message_iterator *iter,
+               const bt_stream *stream,
+               const bt_message *msg_in, bt_message **msg_out,
+               uint64_t new_begin_ts)
+{
+       enum lttng_live_iterator_status status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+       enum bt_property_availability availability;
+       const bt_clock_snapshot *clock_snapshot;
+       uint64_t end_ts;
+       uint64_t count;
+
+       clock_snapshot = bt_message_discarded_events_borrow_end_default_clock_snapshot_const(msg_in);
+       end_ts = bt_clock_snapshot_get_value(clock_snapshot);
+
+       availability = bt_message_discarded_events_get_count(msg_in, &count);
+       BT_ASSERT_DBG(availability == BT_PROPERTY_AVAILABILITY_AVAILABLE);
+
+       *msg_out = bt_message_discarded_events_create_with_default_clock_snapshots(
+               iter, stream, new_begin_ts, end_ts);
+       if (!*msg_out) {
+               status = LTTNG_LIVE_ITERATOR_STATUS_NOMEM;
+               goto end;
+       }
+
+       bt_message_discarded_events_set_count(*msg_out, count);
+end:
+       return status;
+}
+
+static
+enum lttng_live_iterator_status handle_late_message(
+               struct lttng_live_msg_iter *lttng_live_msg_iter,
+               struct lttng_live_stream_iterator *stream_iter,
+               int64_t late_msg_ts_ns, const bt_message *late_msg)
+{
+       bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
+       bt_logging_level log_level = lttng_live_msg_iter->log_level;
+       const bt_clock_class *clock_class;
+       const bt_stream_class *stream_class;
+       enum bt_clock_class_cycles_to_ns_from_origin_status ts_ns_status;
+       int64_t last_inactivity_ts_ns;
+       enum lttng_live_iterator_status stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
+
+       stream_class = bt_stream_borrow_class_const(stream_iter->stream);
+       clock_class = bt_stream_class_borrow_default_clock_class_const(stream_class);
+
+       ts_ns_status = bt_clock_class_cycles_to_ns_from_origin(clock_class,
+                       stream_iter->last_inactivity_ts, &last_inactivity_ts_ns);
+       if (ts_ns_status != BT_CLOCK_CLASS_CYCLES_TO_NS_FROM_ORIGIN_STATUS_OK) {
+               stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+               goto end;
+       }
+
+       if (last_inactivity_ts_ns > late_msg_ts_ns &&
+               is_discarded_packet_or_event_message(late_msg)) {
+               /*
+                * The CTF message iterator emits Discarded Packets and Events
+                * with synthesized begin and end timestamps from the bounds of
+                * the last known packet and the newly decoded packet header.
+                *
+                * The CTF message iterator is not aware of stream inactivity
+                * beacons. Hence, we have to adjust the begin timestamp of
+                * those types of messages if a stream signaled its inactivity
+                * up until _after_ the last known packet's begin timestamp.
+                *
+                * Otherwise, the monotonicity guarantee would not be
+                * preserved.
+                */
+               const enum bt_message_type msg_type = bt_message_get_type(
+                               late_msg);
+               enum lttng_live_iterator_status adjust_status =
+                       LTTNG_LIVE_ITERATOR_STATUS_OK;
+               bt_message *adjusted_message;
+
+               switch (msg_type) {
+               case BT_MESSAGE_TYPE_DISCARDED_EVENTS:
+                       adjust_status = adjust_discarded_events_message(
+                                       lttng_live_msg_iter->self_msg_iter,
+                                       stream_iter->stream,
+                                       late_msg, &adjusted_message,
+                                       stream_iter->last_inactivity_ts);
+                       break;
+               case BT_MESSAGE_TYPE_DISCARDED_PACKETS:
+                       adjust_status = adjust_discarded_packets_message(
+                                       lttng_live_msg_iter->self_msg_iter,
+                                       stream_iter->stream,
+                                       late_msg, &adjusted_message,
+                                       stream_iter->last_inactivity_ts);
+                       break;
+               default:
+                       bt_common_abort();
+               }
+
+               if (adjust_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
+                       stream_iter_status = adjust_status;
+                       goto end;
+               }
+
+               BT_ASSERT_DBG(adjusted_message);
+               stream_iter->current_msg = adjusted_message;
+               stream_iter->current_msg_ts_ns = last_inactivity_ts_ns;
+       } else {
+               /*
+                * We received a message in the past. To ensure
+                * monotonicity, we can't send it forward.
+                */
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Message's timestamp is less than lttng-live's message "
+                       "iterator's last returned timestamp: "
+                       "lttng-live-msg-iter-addr=%p, ts=%" PRId64 ", "
+                       "last-msg-ts=%" PRId64,
+                       lttng_live_msg_iter, late_msg_ts_ns,
+                       lttng_live_msg_iter->last_msg_ts_ns);
+               stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+               goto end;
+       }
+end:
+       return stream_iter_status;
+}
+
 static
 enum lttng_live_iterator_status next_stream_iterator_for_trace(
                struct lttng_live_msg_iter *lttng_live_msg_iter,
@@ -991,6 +1240,9 @@ enum lttng_live_iterator_status next_stream_iterator_for_trace(
 
        BT_ASSERT_DBG(live_trace);
        BT_ASSERT_DBG(live_trace->stream_iterators);
+
+       BT_COMP_LOGD("Finding the next stream iterator for trace: "
+               "trace-id=%"PRIu64, live_trace->id);
        /*
         * Update the current message of every stream iterators of this trace.
         * The current msg of every stream must have a timestamp equal or
@@ -1005,17 +1257,16 @@ enum lttng_live_iterator_status next_stream_iterator_for_trace(
                                stream_iter_idx);
 
                /*
-                * Find if there is are now current message for this stream
-                * iterator get it.
+                * If there is no current message for this stream, go fetch
+                * one.
                 */
                while (!stream_iter->current_msg) {
-                       bt_message *msg = NULL;
+                       const bt_message *msg = NULL;
                        int64_t curr_msg_ts_ns = INT64_MAX;
+
                        stream_iter_status = lttng_live_iterator_next_msg_on_stream(
                                lttng_live_msg_iter, stream_iter, &msg);
 
-                       BT_COMP_LOGD("live stream iterator returned status :%s",
-                               print_live_iterator_status(stream_iter_status));
                        if (stream_iter_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                                stream_iter_is_ended = true;
                                break;
@@ -1027,6 +1278,11 @@ enum lttng_live_iterator_status next_stream_iterator_for_trace(
 
                        BT_ASSERT_DBG(msg);
 
+                       BT_COMP_LOGD("Live stream iterator returned message: msg-type=%s"
+                                       "stream-name=\"%s\", viewer-stream-id=%" PRIu64,
+                                       bt_common_message_type_string(bt_message_get_type(msg)),
+                                       stream_iter->name->str, stream_iter->viewer_stream_id);
+
                        /*
                         * Get the timestamp in nanoseconds from origin of this
                         * messsage.
@@ -1037,7 +1293,7 @@ enum lttng_live_iterator_status next_stream_iterator_for_trace(
 
                        /*
                         * Check if the message of the current live stream
-                        * iterator occured at the exact same time or after the
+                        * iterator occurred at the exact same time or after the
                         * last message returned by this component's message
                         * iterator. If not, we return an error.
                         */
@@ -1046,19 +1302,26 @@ enum lttng_live_iterator_status next_stream_iterator_for_trace(
                                stream_iter->current_msg_ts_ns = curr_msg_ts_ns;
                        } else {
                                /*
-                                * We received a message in the past. To ensure
-                                * monotonicity, we can't send it forward.
+                                * We received a message from the past. This
+                                * may be fixable but it can also be an error.
                                 */
-                               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
-                                       "Message's timestamp is less than "
-                                       "lttng-live's message iterator's last "
-                                       "returned timestamp: "
-                                       "lttng-live-msg-iter-addr=%p, ts=%" PRId64 ", "
-                                       "last-msg-ts=%" PRId64,
-                                       lttng_live_msg_iter, curr_msg_ts_ns,
-                                       lttng_live_msg_iter->last_msg_ts_ns);
-                               stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
-                               goto end;
+                               stream_iter_status = handle_late_message(
+                                               lttng_live_msg_iter, stream_iter,
+                                               curr_msg_ts_ns, msg);
+                               if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
+                                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                                               "Late message could not be handled correctly: "
+                                               "lttng-live-msg-iter-addr=%p, "
+                                               "stream-name=\"%s\", "
+                                               "curr-msg-ts=%" PRId64
+                                               ", last-msg-ts=%" PRId64,
+                                               lttng_live_msg_iter,
+                                               stream_iter->name->str,
+                                               curr_msg_ts_ns,
+                                               lttng_live_msg_iter->last_msg_ts_ns);
+                                       stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_ERROR;
+                                       goto end;
+                               }
                        }
                }
 
@@ -1150,6 +1413,8 @@ enum lttng_live_iterator_status next_stream_iterator_for_session(
        int64_t youngest_candidate_msg_ts = INT64_MAX;
        struct lttng_live_stream_iterator *youngest_candidate_stream_iter = NULL;
 
+       BT_COMP_LOGD("Finding the next stream iterator for session: "
+               "session-id=%"PRIu64, session->id);
        /*
         * Make sure we are attached to the session and look for new streams
         * and metadata.
@@ -1253,12 +1518,13 @@ void put_messages(bt_message_array_const msgs, uint64_t count)
 }
 
 BT_HIDDEN
-bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
+bt_message_iterator_class_next_method_status lttng_live_msg_iter_next(
                bt_self_message_iterator *self_msg_it,
                bt_message_array_const msgs, uint64_t capacity,
                uint64_t *count)
 {
-       bt_component_class_message_iterator_next_method_status status;
+       bt_message_iterator_class_next_method_status status;
+       enum lttng_live_viewer_status viewer_status;
        struct lttng_live_msg_iter *lttng_live_msg_iter =
                bt_self_message_iterator_get_data(self_msg_it);
        struct lttng_live_component *lttng_live =
@@ -1272,6 +1538,21 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
 
        BT_ASSERT_DBG(lttng_live_msg_iter);
 
+       if (G_UNLIKELY(lttng_live_msg_iter->was_interrupted)) {
+               /*
+                * The iterator was interrupted in a previous call to the
+                * `_next()` method. We currently do not support generating
+                * messages after such event. The babeltrace2 CLI should never
+                * be running the graph after being interrupted. So this check
+                * is to prevent other graph users from using this live
+                * iterator in an messed up internal state.
+                */
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Message iterator was interrupted during a previous call to the `next()` and currently does not support continuing after such event.");
+               goto end;
+       }
+
        /*
         * Clear all the invalid message reference that might be left over in
         * the output array.
@@ -1286,17 +1567,26 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
        if (lttng_live_msg_iter->sessions->len == 0) {
                if (lttng_live->params.sess_not_found_act !=
                                SESSION_NOT_FOUND_ACTION_CONTINUE) {
-                       status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_END;
-                       goto no_session;
+                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_END;
+                       goto end;
                } else {
                        /*
                         * The are no more active session for this session
                         * name. Retry to create a viewer session for the
                         * requested session name.
                         */
-                       if (lttng_live_create_viewer_session(lttng_live_msg_iter)) {
-                               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_ERROR;
-                               goto no_session;
+                       viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
+                       if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
+                               if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
+                                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
+                                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                                               "Error creating LTTng live viewer session");
+                               } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
+                                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_AGAIN;
+                               } else {
+                                       bt_common_abort();
+                               }
+                               goto end;
                        }
                }
        }
@@ -1364,7 +1654,7 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
                        }
 
                        if (stream_iter_status != LTTNG_LIVE_ITERATOR_STATUS_OK) {
-                               goto end;
+                               goto return_status;
                        }
 
                        if (G_UNLIKELY(youngest_stream_iter == NULL) ||
@@ -1407,7 +1697,7 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
 
                if (!youngest_stream_iter) {
                        stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_AGAIN;
-                       goto end;
+                       goto return_status;
                }
 
                BT_ASSERT_DBG(youngest_stream_iter->current_msg);
@@ -1429,32 +1719,44 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
 
                stream_iter_status = LTTNG_LIVE_ITERATOR_STATUS_OK;
        }
-end:
+
+return_status:
        switch (stream_iter_status) {
        case LTTNG_LIVE_ITERATOR_STATUS_OK:
        case LTTNG_LIVE_ITERATOR_STATUS_AGAIN:
+               /*
+                * If we gathered messages, return _OK even if the graph was
+                * interrupted. This allows for the components downstream to at
+                * least get the thoses messages. If the graph was indeed
+                * interrupted there should not be another _next() call as the
+                * application will tear down the graph. This component class
+                * doesn't support restarting after an interruption.
+                */
                if (*count > 0) {
-                       /*
-                        * We received a again status but we have some messages
-                        * to send downstream. We send them and return OK for
-                        * now. On the next call we return again if there are
-                        * still no new message to send.
-                        */
-                       status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_OK;
+                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_OK;
                } else {
-                       status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_AGAIN;
+                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_AGAIN;
                }
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_END:
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_END;
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_END;
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_NOMEM:
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_MEMORY_ERROR;
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Memory error preparing the next batch of messages: "
+                       "live-iter-status=%s",
+                       lttng_live_iterator_status_string(stream_iter_status));
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_MEMORY_ERROR;
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_ERROR:
        case LTTNG_LIVE_ITERATOR_STATUS_INVAL:
        case LTTNG_LIVE_ITERATOR_STATUS_UNSUPPORTED:
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_ERROR;
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Error preparing the next batch of messages: "
+                       "live-iter-status=%s",
+                       lttng_live_iterator_status_string(stream_iter_status));
+
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
                /* Put all existing messages on error. */
                put_messages(msgs, *count);
                break;
@@ -1462,84 +1764,129 @@ end:
                bt_common_abort();
        }
 
-no_session:
+end:
        return status;
 }
 
+static
+struct lttng_live_msg_iter *lttng_live_msg_iter_create(
+               struct lttng_live_component *lttng_live_comp,
+               bt_self_message_iterator *self_msg_it)
+{
+       bt_self_component *self_comp = lttng_live_comp->self_comp;
+       bt_logging_level log_level = lttng_live_comp->log_level;
+
+       struct lttng_live_msg_iter *lttng_live_msg_iter =
+               g_new0(struct lttng_live_msg_iter, 1);
+       if (!lttng_live_msg_iter) {
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Failed to allocate lttng_live_msg_iter");
+               goto end;
+       }
+
+       lttng_live_msg_iter->log_level = lttng_live_comp->log_level;
+       lttng_live_msg_iter->self_comp = lttng_live_comp->self_comp;
+       lttng_live_msg_iter->lttng_live_comp = lttng_live_comp;
+       lttng_live_msg_iter->self_msg_iter = self_msg_it;
+
+       lttng_live_msg_iter->active_stream_iter = 0;
+       lttng_live_msg_iter->last_msg_ts_ns = INT64_MIN;
+       lttng_live_msg_iter->was_interrupted = false;
+
+       lttng_live_msg_iter->sessions = g_ptr_array_new_with_free_func(
+               (GDestroyNotify) lttng_live_destroy_session);
+       BT_ASSERT(lttng_live_msg_iter->sessions);
+
+end:
+       return lttng_live_msg_iter;
+
+}
+
 BT_HIDDEN
-bt_component_class_message_iterator_initialize_method_status lttng_live_msg_iter_init(
+bt_message_iterator_class_initialize_method_status lttng_live_msg_iter_init(
                bt_self_message_iterator *self_msg_it,
                bt_self_message_iterator_configuration *config,
-               bt_self_component_source *self_comp_src,
                bt_self_component_port_output *self_port)
 {
-       bt_component_class_message_iterator_initialize_method_status ret =
-               BT_COMPONENT_CLASS_MESSAGE_ITERATOR_INITIALIZE_METHOD_STATUS_OK;
-       bt_self_component *self_comp =
-               bt_self_component_source_as_self_component(self_comp_src);
+       bt_message_iterator_class_initialize_method_status status;
        struct lttng_live_component *lttng_live;
        struct lttng_live_msg_iter *lttng_live_msg_iter;
+       enum lttng_live_viewer_status viewer_status;
        bt_logging_level log_level;
-
-       BT_ASSERT(self_msg_it);
+       bt_self_component *self_comp =
+               bt_self_message_iterator_borrow_component(self_msg_it);
 
        lttng_live = bt_self_component_get_data(self_comp);
        log_level = lttng_live->log_level;
        self_comp = lttng_live->self_comp;
 
+
        /* There can be only one downstream iterator at the same time. */
        BT_ASSERT(!lttng_live->has_msg_iter);
        lttng_live->has_msg_iter = true;
 
-       lttng_live_msg_iter = g_new0(struct lttng_live_msg_iter, 1);
+       lttng_live_msg_iter = lttng_live_msg_iter_create(lttng_live,
+               self_msg_it);
        if (!lttng_live_msg_iter) {
-               ret = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_INITIALIZE_METHOD_STATUS_ERROR;
-               goto end;
+               status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
+               BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                       "Failed to create lttng_live_msg_iter");
+               goto error;
        }
 
-       lttng_live_msg_iter->log_level = lttng_live->log_level;
-       lttng_live_msg_iter->self_comp = lttng_live->self_comp;
-       lttng_live_msg_iter->lttng_live_comp = lttng_live;
-       lttng_live_msg_iter->self_msg_iter = self_msg_it;
-
-       lttng_live_msg_iter->active_stream_iter = 0;
-       lttng_live_msg_iter->last_msg_ts_ns = INT64_MIN;
-       lttng_live_msg_iter->sessions = g_ptr_array_new_with_free_func(
-               (GDestroyNotify) lttng_live_destroy_session);
-       BT_ASSERT(lttng_live_msg_iter->sessions);
-
-       lttng_live_msg_iter->viewer_connection =
-               live_viewer_connection_create(lttng_live->params.url->str, false,
-                       lttng_live_msg_iter, self_comp, NULL, log_level);
-       if (!lttng_live_msg_iter->viewer_connection) {
+        viewer_status = live_viewer_connection_create(self_comp, NULL,
+               log_level, lttng_live->params.url->str, false,
+               lttng_live_msg_iter, &lttng_live_msg_iter->viewer_connection);
+       if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
+               if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Failed to create viewer connection");
+               } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
+                       /*
+                        * Interruption in the _iter_init() method is not
+                        * supported. Return an error.
+                        */
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Interrupted while creating viewer connection");
+               }
                goto error;
        }
 
-       if (lttng_live_create_viewer_session(lttng_live_msg_iter)) {
+       viewer_status = lttng_live_create_viewer_session(lttng_live_msg_iter);
+       if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
+               if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Failed to create viewer session");
+               } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
+                       /*
+                        * Interruption in the _iter_init() method is not
+                        * supported. Return an error.
+                        */
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Interrupted when creating viewer session");
+               }
                goto error;
        }
+
        if (lttng_live_msg_iter->sessions->len == 0) {
                switch (lttng_live->params.sess_not_found_act) {
                case SESSION_NOT_FOUND_ACTION_CONTINUE:
-                       BT_COMP_LOGI("Unable to connect to the requested live viewer "
-                               "session. Keep trying to connect because of "
+                       BT_COMP_LOGI("Unable to connect to the requested live viewer session. Keep trying to connect because of "
                                "%s=\"%s\" component parameter: url=\"%s\"",
                                SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_CONTINUE_STR,
                                lttng_live->params.url->str);
                        break;
                case SESSION_NOT_FOUND_ACTION_FAIL:
-                       BT_COMP_LOGE_APPEND_CAUSE(self_comp, "Unable to connect to the requested live viewer "
-                               "session. Fail the message iterator"
-                               "initialization because of %s=\"%s\" "
+                       BT_COMP_LOGE_APPEND_CAUSE(self_comp,
+                               "Unable to connect to the requested live viewer session. Fail the message iterator initialization because of %s=\"%s\" "
                                "component parameter: url =\"%s\"",
                                SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_FAIL_STR,
                                lttng_live->params.url->str);
                        goto error;
                case SESSION_NOT_FOUND_ACTION_END:
-                       BT_COMP_LOGI("Unable to connect to the requested live viewer "
-                               "session. End gracefully at the first _next() "
+                       BT_COMP_LOGI("Unable to connect to the requested live viewer session. End gracefully at the first _next() "
                                "call because of %s=\"%s\" component parameter: "
                                "url=\"%s\"", SESS_NOT_FOUND_ACTION_PARAM,
                                SESS_NOT_FOUND_ACTION_END_STR,
@@ -1551,13 +1898,14 @@ bt_component_class_message_iterator_initialize_method_status lttng_live_msg_iter
        }
 
        bt_self_message_iterator_set_data(self_msg_it, lttng_live_msg_iter);
-
+       status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_OK;
        goto end;
+
 error:
-       ret = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_INITIALIZE_METHOD_STATUS_ERROR;
+       status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_ERROR;
        lttng_live_msg_iter_destroy(lttng_live_msg_iter);
 end:
-       return ret;
+       return status;
 }
 
 static struct bt_param_validation_map_value_entry_descr list_sessions_params[] = {
@@ -1575,6 +1923,7 @@ bt_component_class_query_method_status lttng_live_query_list_sessions(
        const bt_value *url_value = NULL;
        const char *url;
        struct live_viewer_connection *viewer_connection = NULL;
+       enum lttng_live_viewer_status viewer_status;
        enum bt_param_validation_status validation_status;
        gchar *validate_error = NULL;
 
@@ -1593,12 +1942,18 @@ bt_component_class_query_method_status lttng_live_query_list_sessions(
        url_value = bt_value_map_borrow_entry_value_const(params, URL_PARAM);
        url = bt_value_string_get(url_value);
 
-       viewer_connection = live_viewer_connection_create(url, true, NULL,
-               NULL, self_comp_class, log_level);
-       if (!viewer_connection) {
-               BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
-                       "Failed to create viewer connection");
-               status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
+       viewer_status = live_viewer_connection_create(NULL, self_comp_class,
+               log_level, url, true, NULL, &viewer_connection);
+       if (viewer_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
+               if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_ERROR) {
+                       BT_COMP_CLASS_LOGE_APPEND_CAUSE(self_comp_class,
+                               "Failed to create viewer connection");
+                       status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_ERROR;
+               } else if (viewer_status == LTTNG_LIVE_VIEWER_STATUS_INTERRUPTED) {
+                       status = BT_COMPONENT_CLASS_QUERY_METHOD_STATUS_AGAIN;
+               } else {
+                       bt_common_abort();
+               }
                goto error;
        }
 
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