src.ctf.lttng-live: use `common_muxing_compare_messages()` to break TS ties

[babeltrace.git] / src / plugins / ctf / lttng-live / lttng-live.c

diff --git a/src/plugins/ctf/lttng-live/lttng-live.c b/src/plugins/ctf/lttng-live/lttng-live.c
index 7760daf650099e25f89d9929396e859bf09531dc..72d3e74ea05b8d98f6bc62e6ac01ac0d9d5bade3 100644 (file)
--- a/src/plugins/ctf/lttng-live/lttng-live.c
+++ b/src/plugins/ctf/lttng-live/lttng-live.c
@@ -42,6 +42,8 @@
 #include "compat/compiler.h"
 #include <babeltrace2/types.h>
 
+#include "plugins/common/muxing/muxing.h"
+
 #include "data-stream.h"
 #include "metadata.h"
 #include "lttng-live.h"
@@ -1162,6 +1164,8 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
                bt_self_message_iterator_get_data(self_msg_it);
        struct lttng_live_component *lttng_live =
                lttng_live_msg_iter->lttng_live_comp;
+       bt_self_component *self_comp = lttng_live_msg_iter->self_comp;
+       bt_logging_level log_level = lttng_live_msg_iter->log_level;
        enum lttng_live_iterator_status stream_iter_status;
        uint64_t session_idx;
 
@@ -1273,9 +1277,38 @@ bt_component_class_message_iterator_next_method_status lttng_live_msg_iter_next(
                                goto end;
                        }
 
-                       if (candidate_stream_iter->current_msg_ts_ns <= next_msg_ts_ns) {
+                       if (G_UNLIKELY(next_stream_iter == NULL) ||
+                                       candidate_stream_iter->current_msg_ts_ns <= next_msg_ts_ns) {
                                next_msg_ts_ns = candidate_stream_iter->current_msg_ts_ns;
                                next_stream_iter = candidate_stream_iter;
+                       } else if (candidate_stream_iter->current_msg_ts_ns == next_msg_ts_ns) {
+                               /*
+                                * The currently selected message to be sent
+                                * downstream next has the exact same timestamp
+                                * that of the current candidate message. We
+                                * must break the tie in a predictable manner.
+                                */
+                               BT_COMP_LOGD_STR("Two of the next message candidates have the same timestamps, pick one deterministically.");
+                               /*
+                                * Order the messages in an arbitrary but
+                                * determinitic way.
+                                */
+                               int ret = common_muxing_compare_messages(candidate_stream_iter->current_msg,
+                                       next_stream_iter->current_msg);
+                               if (ret < 0) {
+                                       /*
+                                        * The `candidate_stream_iter->current_msg`
+                                        * should go first. Update the next
+                                        * iterator and the current timestamp.
+                                        */
+                                       next_msg_ts_ns = candidate_stream_iter->current_msg_ts_ns;
+                                       next_stream_iter = candidate_stream_iter;
+                               } else if (ret == 0) {
+                                       /* Unable to pick which one should go first. */
+                                       BT_COMP_LOGW("Cannot deterministically pick next live stream message iterator because they have identical next messages: "
+                                               "next-stream-iter-addr=%p" "candidate-stream-iter-addr=%p",
+                                               next_stream_iter, candidate_stream_iter);
+                               }
                        }
 
                        session_idx++;