src.ctf.lttng-live: Extract `handle_late_message()` function for future fix
[babeltrace.git] / src / plugins / ctf / lttng-live / lttng-live.c
index 82ebbff9b01f91afe8a15b2fc88c4c307fcb0d96..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
@@ -106,6 +86,21 @@ const char *lttng_live_stream_state_string(enum lttng_live_stream_state state)
        }
 }
 
+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("Live stream iterator state=%s, last-inact-ts=%" PRId64  \
@@ -133,7 +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;
@@ -196,7 +191,7 @@ 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);
 
        goto end;
@@ -208,12 +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;
        }
@@ -285,7 +280,7 @@ void lttng_live_destroy_session(struct lttng_live_session *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. */
@@ -377,12 +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(
@@ -395,24 +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;
@@ -426,9 +430,19 @@ enum lttng_live_iterator_status lttng_live_iterator_next_handle_one_no_data_stre
                }
                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);
@@ -453,13 +467,11 @@ enum lttng_live_iterator_status lttng_live_get_session(
        enum lttng_live_iterator_status status;
        uint64_t trace_idx;
 
-       BT_COMP_LOGD("Updating all streams for session: "
-               "session-id=%"PRIu64", session-name=\"%s\"",
-               session->id, session->session_name->str);
-
        if (!session->attached) {
+               BT_COMP_LOGD("Attach to session: session-id=%" PRIu64,
+                       session->id);
                enum lttng_live_viewer_status attach_status =
-                       lttng_live_attach_session(session,
+                       lttng_live_session_attach(session,
                                lttng_live_msg_iter->self_msg_iter);
                if (attach_status != LTTNG_LIVE_VIEWER_STATUS_OK) {
                        if (lttng_live_graph_is_canceled(lttng_live_msg_iter)) {
@@ -480,12 +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 =
@@ -509,6 +526,11 @@ enum lttng_live_iterator_status lttng_live_get_session(
                        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);
 
@@ -516,34 +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;
                }
        }
 }
@@ -562,7 +582,7 @@ 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"
+       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
@@ -631,7 +651,7 @@ 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;
@@ -640,6 +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);
@@ -663,7 +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;
 
@@ -671,9 +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;
        }
@@ -748,7 +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:
@@ -789,7 +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;
@@ -803,6 +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;
                }
@@ -810,7 +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;
                        }
@@ -843,8 +879,6 @@ 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;
@@ -864,12 +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
@@ -883,6 +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);
@@ -943,14 +986,15 @@ 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("Finding the next message for stream iterator: "
-               "stream-name=\"%s\"", stream_iter->name->str);
+       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) {
                /*
@@ -965,14 +1009,19 @@ enum lttng_live_iterator_status lttng_live_iterator_next_msg_on_stream(
 
 retry:
        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) {
                        /*
@@ -984,6 +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) {
@@ -1001,12 +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,
@@ -1039,17 +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",
-                               lttng_live_iterator_status_string(stream_iter_status));
                        if (stream_iter_status == LTTNG_LIVE_ITERATOR_STATUS_END) {
                                stream_iter_is_ended = true;
                                break;
@@ -1061,6 +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.
@@ -1071,7 +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.
                         */
@@ -1080,19 +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;
+                               }
                        }
                }
 
@@ -1289,12 +1518,12 @@ 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);
@@ -1318,7 +1547,7 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
                 * is to prevent other graph users from using this live
                 * iterator in an messed up internal state.
                 */
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_ERROR;
+               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;
@@ -1338,7 +1567,7 @@ 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;
+                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_END;
                        goto end;
                } else {
                        /*
@@ -1349,11 +1578,11 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
                        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_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_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_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_AGAIN;
+                                       status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_AGAIN;
                                } else {
                                        bt_common_abort();
                                }
@@ -1504,20 +1733,20 @@ return_status:
                 * doesn't support restarting after an interruption.
                 */
                if (*count > 0) {
-                       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:
                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_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_MEMORY_ERROR;
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_MEMORY_ERROR;
                break;
        case LTTNG_LIVE_ITERATOR_STATUS_ERROR:
        case LTTNG_LIVE_ITERATOR_STATUS_INVAL:
@@ -1527,7 +1756,7 @@ return_status:
                        "live-iter-status=%s",
                        lttng_live_iterator_status_string(stream_iter_status));
 
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_NEXT_METHOD_STATUS_ERROR;
+               status = BT_MESSAGE_ITERATOR_CLASS_NEXT_METHOD_STATUS_ERROR;
                /* Put all existing messages on error. */
                put_messages(msgs, *count);
                break;
@@ -1574,21 +1803,18 @@ end:
 }
 
 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 status;
-       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;
@@ -1602,7 +1828,7 @@ bt_component_class_message_iterator_initialize_method_status lttng_live_msg_iter
        lttng_live_msg_iter = lttng_live_msg_iter_create(lttng_live,
                self_msg_it);
        if (!lttng_live_msg_iter) {
-               status = BT_COMPONENT_CLASS_MESSAGE_ITERATOR_INITIALIZE_METHOD_STATUS_MEMORY_ERROR;
+               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;
@@ -1672,11 +1898,11 @@ 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_COMPONENT_CLASS_MESSAGE_ITERATOR_INITIALIZE_METHOD_STATUS_OK;
+       status = BT_MESSAGE_ITERATOR_CLASS_INITIALIZE_METHOD_STATUS_OK;
        goto end;
 
 error:
-       status = 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 status;
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