24-3: Adjust change queue reserved capacity at Enqueue() (ydb-platform#9509)

Author: CyberROFL

ydb/core/tx/datashard/cdc_stream_scan.cpp

@@ -240,7 +240,8 @@ class TDataShard::TTxCdcStreamScanProgress
         const auto& valueTags = ev.ValueTags;
 
         LOG_D("Progress"
-            << ": streamPathId# " << streamPathId);
+            << ": streamPathId# " << streamPathId
+            << ", rows# " << ev.Rows.size());
 
         if (!Self->GetUserTables().contains(tablePathId.LocalPathId)) {
             LOG_W("Cannot progress on unknown table"

ydb/core/tx/datashard/datashard.cpp

@@ -1092,19 +1092,33 @@ void TDataShard::RemoveChangeRecord(NIceDb::TNiceDb& db, ui64 order) {
         if (!--rIt->second) {
             ChangeQueueReservations.erase(rIt);
         }
+
+        SetCounter(COUNTER_CHANGE_QUEUE_RESERVED_CAPACITY, ChangeQueueReservedCapacity);
     }
 
     UpdateChangeExchangeLag(AppData()->TimeProvider->Now());
     ChangesQueue.erase(it);
 
     IncCounter(COUNTER_CHANGE_RECORDS_REMOVED);
     SetCounter(COUNTER_CHANGE_QUEUE_SIZE, ChangesQueue.size());
-    SetCounter(COUNTER_CHANGE_QUEUE_RESERVED_CAPACITY, ChangeQueueReservedCapacity);
 
     CheckChangesQueueNoOverflow();
 }
 
 void TDataShard::EnqueueChangeRecords(TVector<IDataShardChangeCollector::TChange>&& records, ui64 cookie, bool afterMove) {
+    if (auto it = ChangeQueueReservations.find(cookie); it != ChangeQueueReservations.end()) {
+        Y_ABORT_UNLESS(!afterMove);
+
+        ChangeQueueReservedCapacity -= it->second;
+        it->second = records.size();
+        ChangeQueueReservedCapacity += it->second;
+        if (!it->second) {
+            ChangeQueueReservations.erase(it);
+        }
+
+        SetCounter(COUNTER_CHANGE_QUEUE_RESERVED_CAPACITY, ChangeQueueReservedCapacity);
+    }
+
     if (!records) {
         return;
     }
@@ -1140,22 +1154,15 @@ void TDataShard::EnqueueChangeRecords(TVector<IDataShardChangeCollector::TChange
         ChangesQueueBytes += record.BodySize;
     }
 
-    if (auto it = ChangeQueueReservations.find(cookie); it != ChangeQueueReservations.end()) {
-        Y_ABORT_UNLESS(!afterMove);
-        ChangeQueueReservedCapacity -= it->second;
-        ChangeQueueReservedCapacity += records.size();
-    }
-
     UpdateChangeExchangeLag(now);
     IncCounter(COUNTER_CHANGE_RECORDS_ENQUEUED, forward.size());
     SetCounter(COUNTER_CHANGE_QUEUE_SIZE, ChangesQueue.size());
-    SetCounter(COUNTER_CHANGE_QUEUE_RESERVED_CAPACITY, ChangeQueueReservedCapacity);
 
     Y_ABORT_UNLESS(OutChangeSender);
     Send(OutChangeSender, new NChangeExchange::TEvChangeExchange::TEvEnqueueRecords(std::move(forward)));
 }
 
-ui32 TDataShard::GetFreeChangeQueueCapacity(ui64 cookie) {
+ui32 TDataShard::GetFreeChangeQueueCapacity(ui64 cookie) const {
     const ui64 sizeLimit = AppData()->DataShardConfig.GetChangesQueueItemsLimit();
     if (sizeLimit < ChangesQueue.size()) {
         return 0;

ydb/core/tx/datashard/datashard_impl.h

@@ -1914,7 +1914,7 @@ class TDataShard
     void RemoveChangeRecord(NIceDb::TNiceDb& db, ui64 order);
     // TODO(ilnaz): remove 'afterMove' after #6541
     void EnqueueChangeRecords(TVector<IDataShardChangeCollector::TChange>&& records, ui64 cookie = 0, bool afterMove = false);
-    ui32 GetFreeChangeQueueCapacity(ui64 cookie);
+    ui32 GetFreeChangeQueueCapacity(ui64 cookie) const;
     ui64 ReserveChangeQueueCapacity(ui32 capacity);
     void UpdateChangeExchangeLag(TInstant now);
     void CreateChangeSender(const TActorContext& ctx);

ydb/core/tx/datashard/datashard_ut_change_exchange.cpp

@@ -3041,6 +3041,63 @@ Y_UNIT_TEST_SUITE(Cdc) {
         });
     }
 
+    Y_UNIT_TEST(InitialScanEnqueuesZeroRecords) {
+        TPortManager portManager;
+        TServer::TPtr server = new TServer(TServerSettings(portManager.GetPort(2134), {}, DefaultPQConfig())
+            .SetUseRealThreads(false)
+            .SetDomainName("Root")
+            .SetEnableChangefeedInitialScan(true)
+            .SetChangesQueueItemsLimit(2)
+        );
+
+        auto& runtime = *server->GetRuntime();
+        const auto edgeActor = runtime.AllocateEdgeActor();
+
+        SetupLogging(runtime);
+        InitRoot(server, edgeActor);
+        CreateShardedTable(server, edgeActor, "/Root", "Table", SimpleTable());
+
+        ExecSQL(server, edgeActor, R"(
+            UPSERT INTO `/Root/Table` (key, value) VALUES
+            (1, 10),
+            (2, 20),
+            (3, 30),
+            (4, 40);
+        )");
+
+        TBlockEvents<TEvDataShard::TEvCdcStreamScanRequest> blockScanRequest(runtime, [&](auto& ev) {
+            ev->Get()->Record.MutableLimits()->SetBatchMaxRows(1);
+            return true;
+        });
+
+        WaitTxNotification(server, edgeActor, AsyncAlterAddStream(server, "/Root", "Table",
+            WithInitialScan(Updates(NKikimrSchemeOp::ECdcStreamFormatJson))));
+
+        runtime.WaitFor("Scan request", [&]{ return blockScanRequest.size(); });
+        runtime.AddObserver<TEvDataShard::TEvCdcStreamScanRequest>([&](auto& ev) {
+            ev->Get()->Record.MutableLimits()->SetBatchMaxRows(1);
+        });
+
+        ExecSQL(server, edgeActor, R"(
+            UPSERT INTO `/Root/Table` (key, value) VALUES
+            (1, 100),
+            (2, 200),
+            (3, 300);
+        )");
+
+        blockScanRequest.Unblock().Stop();
+
+        WaitForContent(server, edgeActor, "/Root/Table/Stream", {
+            R"({"update":{"value":10},"key":[1]})",
+            R"({"update":{"value":100},"key":[1]})",
+            R"({"update":{"value":20},"key":[2]})",
+            R"({"update":{"value":200},"key":[2]})",
+            R"({"update":{"value":30},"key":[3]})",
+            R"({"update":{"value":300},"key":[3]})",
+            R"({"update":{"value":40},"key":[4]})",
+        });
+    }
+
     Y_UNIT_TEST(InitialScanRacyProgressAndDrop) {
         TPortManager portManager;
         TServer::TPtr server = new TServer(TServerSettings(portManager.GetPort(2134), {}, DefaultPQConfig())