Fix BS_QUEUE death (merge from main #14081) (#14109)

Author: alexvru

ydb/core/blobstorage/backpressure/queue_backpressure_client.cpp

@@ -462,9 +462,7 @@ class TVDiskBackpressureClientActor : public TActorBootstrapped<TVDiskBackpressu
                 QLOG_NOTICE_S("BSQ96", "connection lost status# " << NKikimrProto::EReplyStatus_Name(status)
                     << " errorReason# " << errorReason << " timeout# " << timeout);
                 ctx.Send(BlobStorageProxy, new TEvProxyQueueState(VDiskId, QueueId, false, false, nullptr));
-                Queue.DrainQueue(status, TStringBuilder() << "BS_QUEUE: " << errorReason, ctx);
-                DrainStatus(status, ctx);
-                DrainAssimilate(status, errorReason, ctx);
+                Drain(ctx, status, errorReason);
                 break;
         }
         State = EState::INITIAL;
@@ -476,6 +474,12 @@ class TVDiskBackpressureClientActor : public TActorBootstrapped<TVDiskBackpressu
         }
     }
 
+    void Drain(const TActorContext& ctx, NKikimrProto::EReplyStatus status, const TString& errorReason) {
+        Queue.DrainQueue(status, TStringBuilder() << "BS_QUEUE: " << errorReason, ctx);
+        DrainStatus(status, ctx);
+        DrainAssimilate(status, errorReason, ctx);
+    }
+
     void HandleConnected(TEvInterconnect::TEvNodeConnected::TPtr ev, const TActorContext& ctx) {
         if (ev->Get()->NodeId == RemoteVDisk.NodeId()) {
             Y_ABORT_UNLESS(!SessionId || SessionId == ev->Sender, "SessionId# %s Sender# %s", SessionId.ToString().data(),
@@ -789,6 +793,7 @@ class TVDiskBackpressureClientActor : public TActorBootstrapped<TVDiskBackpressu
             RegisterActorInUniversalScheduler(SelfId(), nullptr, ctx.ExecutorThread.ActorSystem);
         }
         Unsubscribe(RemoteVDisk.NodeId(), ctx);
+        Drain(ctx, NKikimrProto::ERROR, "BS_QUEUE terminated");
         return TActor::Die(ctx);
     }