YQ-3844 Shared reading: add restart session sensor / to stable (#11529)

Author: kardymonds

ydb/core/fq/libs/row_dispatcher/events/topic_session_stats.h

@@ -15,6 +15,7 @@ struct TopicSessionClientStatistic {
 
 struct TopicSessionCommonStatistic {
     ui64 UnreadBytes = 0;
+    ui64 RestartSessionByOffsets = 0;
 };
 
 struct TopicSessionParams {

ydb/core/fq/libs/row_dispatcher/row_dispatcher.cpp

@@ -484,7 +484,7 @@ TString TRowDispatcher::GetInternalState() {
         str << "  " << key.Endpoint << " / " << key.Database << " / " << key.TopicPath << " / " << key.PartitionId;
         for (auto& [actorId, sessionInfo] : sessionsInfo.Sessions) {
             str << " / " << actorId << "\n";
-            str << "    unread bytes " << sessionInfo.Stat.UnreadBytes << "\n";
+            str << "    unread bytes " << sessionInfo.Stat.UnreadBytes << " restarts by offsets " << sessionInfo.Stat.RestartSessionByOffsets << "\n";
             for (auto& [readActorId, consumer] : sessionInfo.Consumers) {
                 str << "    " << consumer->QueryId << " " << readActorId << " unread rows "
                     << consumer->Stat.UnreadRows << " unread bytes " << consumer->Stat.UnreadBytes << " offset " << consumer->Stat.Offset

ydb/core/fq/libs/row_dispatcher/topic_session.cpp

@@ -34,6 +34,7 @@ struct TTopicSessionMetrics {
         RowsRead = SubGroup->GetCounter("RowsRead", true);
         InFlySubscribe = SubGroup->GetCounter("InFlySubscribe");
         ReconnectRate = SubGroup->GetCounter("ReconnectRate", true);
+        RestartSessionByOffsets = counters->GetCounter("RestartSessionByOffsets", true);
     }
 
     ~TTopicSessionMetrics() {
@@ -45,6 +46,7 @@ struct TTopicSessionMetrics {
     ::NMonitoring::TDynamicCounters::TCounterPtr RowsRead;
     ::NMonitoring::TDynamicCounters::TCounterPtr InFlySubscribe;
     ::NMonitoring::TDynamicCounters::TCounterPtr ReconnectRate;
+    ::NMonitoring::TDynamicCounters::TCounterPtr RestartSessionByOffsets;
 };
 
 struct TEvPrivate {
@@ -171,6 +173,7 @@ class TTopicSession : public TActorBootstrapped<TTopicSession> {
     THashMap<TString, ui64> FieldsIndexes;
     NYql::IPqGateway::TPtr PqGateway;
     TMaybe<TString> ConsumerName;
+    ui64 RestartSessionByOffsets = 0;
 
 public:
     explicit TTopicSession(
@@ -750,6 +753,8 @@ void TTopicSession::Handle(NFq::TEvRowDispatcher::TEvStartSession::TPtr& ev) {
         if (ReadSession) {
             if (clientInfo.Settings.HasOffset() && (clientInfo.Settings.GetOffset() <= LastMessageOffset)) {
                 LOG_ROW_DISPATCHER_INFO("New client has less offset (" << clientInfo.Settings.GetOffset() << ") than the last message (" << LastMessageOffset << "), stop (restart) topic session");
+                Metrics.RestartSessionByOffsets->Inc();
+                ++RestartSessionByOffsets;
                 StopReadSession();
             }
         }
@@ -917,6 +922,7 @@ void TTopicSession::HandleException(const std::exception& e) {
 void TTopicSession::SendStatistic() {
     TopicSessionStatistic stat;
     stat.Common.UnreadBytes = UnreadBytes;
+    stat.Common.RestartSessionByOffsets = RestartSessionByOffsets;
     stat.SessionKey = TopicSessionParams{Endpoint, Database, TopicPath, PartitionId};
     stat.Clients.reserve(Clients.size());
     for (auto& [readActorId, info] : Clients) {