ydb_topic: schedule SendImpl from OnCompressedImpl instead of calling it directly (#8372)

Author: qyryq

ydb/public/sdk/cpp/client/ydb_topic/impl/write_session_impl.cpp

@@ -1168,7 +1168,17 @@ TMemoryUsageChange TWriteSessionImpl::OnCompressedImpl(TBlock&& block) {
     (*Counters->BytesInflightCompressed) += block.Data.size();
 
     PackedMessagesToSend.emplace(std::move(block));
-    SendImpl();
+
+    if (!SendImplScheduled.exchange(true)) {
+        CompressionExecutor->Post([cbContext = SelfContext]() {
+            if (auto self = cbContext->LockShared()) {
+                self->SendImplScheduled = false;
+                with_lock (self->Lock) {
+                    self->SendImpl();
+                }
+            }
+        });
+    }
     return memoryUsage;
 }
 

ydb/public/sdk/cpp/client/ydb_topic/impl/write_session_impl.h

@@ -450,6 +450,7 @@ class TWriteSessionImpl : public TContinuationTokenIssuer,
     const size_t MaxBlockMessageCount = 1; //!< Max message count that can be packed into a single block. In block version 0 is equal to 1 for compatibility
     bool Connected = false;
     bool Started = false;
+    std::atomic<bool> SendImplScheduled = false;
     TAtomic Aborting = 0;
     bool SessionEstablished = false;
     ui32 PartitionId = 0;

ydb/public/sdk/cpp/client/ydb_topic/ut/basic_usage_ut.cpp

@@ -455,14 +455,15 @@ Y_UNIT_TEST_SUITE(BasicUsage) {
 
         UNIT_ASSERT(!futureWrite.HasValue());
         Cerr << ">>>TEST: future write has no value " << Endl;
-        RunTasks(stepByStepExecutor, {0});
+        RunTasks(stepByStepExecutor, {0});  // Run compression task.
+        RunTasks(stepByStepExecutor, {1});  // Run send task.
         futureWrite.GetValueSync();
         UNIT_ASSERT(futureWrite.HasValue());
         Cerr << ">>>TEST: future write has value " << Endl;
 
         UNIT_ASSERT(!futureRead.HasValue());
         Cerr << ">>>TEST: future read has no value " << Endl;
-        RunTasks(stepByStepExecutor, {1});
+        RunTasks(stepByStepExecutor, {2});  // Run decompression task.
         futureRead.GetValueSync();
         UNIT_ASSERT(futureRead.HasValue());
         Cerr << ">>>TEST: future read has value " << Endl;