Ignore shared cache responses from earlier boot attempts

ydb/core/tablet_flat/flat_boot_bundle.h

@@ -58,7 +58,6 @@ namespace NBoot {
             LeftReads -= 1;
 
             if (msg.Status == NKikimrProto::OK) {
-                Y_ENSURE(msg.Cookie == 0);
                 Loader->Save(std::move(msg.Pages));
 
                 TryFinalize();

ydb/core/tablet_flat/flat_executor.cpp

@@ -857,7 +857,7 @@ void TExecutor::Boot(TEvTablet::TEvBoot::TPtr &ev, const TActorContext &ctx) {
 
     auto executorCaches = CleanupState();
 
-    BootLogic.Reset(new TExecutorBootLogic(this, SelfId(), Owner->Info(), maxBootBytesInFly));
+    BootLogic.Reset(new TExecutorBootLogic(this, SelfId(), ++BootAttempt, Owner->Info(), maxBootBytesInFly));
 
     ProcessIoStats(
         NBlockIO::EDir::Read, NBlockIO::EPriority::Fast,
@@ -898,7 +898,7 @@ void TExecutor::FollowerBoot(TEvTablet::TEvFBoot::TPtr &ev, const TActorContext
 
     auto executorCaches = CleanupState();
 
-    BootLogic.Reset(new TExecutorBootLogic(this, SelfId(), Owner->Info(), maxBootBytesInFly));
+    BootLogic.Reset(new TExecutorBootLogic(this, SelfId(), ++BootAttempt, Owner->Info(), maxBootBytesInFly));
 
     ProcessIoStats(
         NBlockIO::EDir::Read, NBlockIO::EPriority::Fast,
@@ -3102,6 +3102,10 @@ void TExecutor::Handle(NSharedCache::TEvResult::TPtr &ev) {
         }
         return;
 
+    case ESharedCacheRequestType::BootLogic:
+        // ignore outdated replies
+        return;
+
     default:
         Y_DEBUG_ABORT_S("Unexpected request " << ev->Cookie);
         break;

ydb/core/tablet_flat/flat_executor.h

@@ -447,6 +447,7 @@ class TExecutor
 
     TWaitingSnaps WaitingSnapshots;
 
+    ui64 BootAttempt = 0;
     THolder<TExecutorBootLogic> BootLogic;
     THolder<TPrivatePageCache> PrivatePageCache;
     THolder<TExecutorCounters> Counters;

ydb/core/tablet_flat/flat_executor_bootlogic.cpp

@@ -30,9 +30,10 @@ NBoot::TLoadBlobs::TLoadBlobs(IStep *owner, NPageCollection::TLargeGlobId largeG
     Logic->LoadEntry(this);
 }
 
-TExecutorBootLogic::TExecutorBootLogic(IOps *ops, const TActorId &self, TTabletStorageInfo *info, ui64 maxBytesInFly)
+TExecutorBootLogic::TExecutorBootLogic(IOps *ops, const TActorId &self, ui64 bootAttempt, TTabletStorageInfo *info, ui64 maxBytesInFly)
     : Ops(ops)
     , SelfId(self)
+    , BootAttempt(bootAttempt)
     , Info(info)
     , GroupResolveCachedChannel(Max<ui32>())
     , GroupResolveCachedGeneration(Max<ui32>())
@@ -186,7 +187,8 @@ NBoot::TSpawned TExecutorBootLogic::LoadPages(NBoot::IStep *step, NTable::TLoade
         new NSharedCache::TEvRequest(
             NBlockIO::EPriority::Fast,
             std::move(fetch.PageCollection),
-            std::move(fetch.Pages)),
+            std::move(fetch.Pages),
+            BootAttempt),
         0, (ui64)ESharedCacheRequestType::BootLogic);
 
     return NBoot::TSpawned(true);
@@ -272,6 +274,9 @@ TExecutorBootLogic::EOpResult TExecutorBootLogic::Receive(::NActors::IEventHandl
         if (ESharedCacheRequestType(ev.Cookie) != ESharedCacheRequestType::BootLogic)
             return OpResultUnhandled;
 
+        if (msg->Cookie != BootAttempt)
+            return OpResultUnhandled;
+
         auto it = Loads.find(msg->PageCollection.Get());
         if (it == Loads.end()) // could receive outdated results
             return OpResultUnhandled;

ydb/core/tablet_flat/flat_executor_bootlogic.h

@@ -78,6 +78,7 @@ class TExecutorBootLogic
     TAutoPtr<NBoot::TRoot> Steps;
     TActorId LeaseWaiter;
 
+    const ui64 BootAttempt;
     TMonotonic BootTimestamp;
 
     const TIntrusiveConstPtr<TTabletStorageInfo> Info;
@@ -106,7 +107,7 @@ class TExecutorBootLogic
     inline NBoot::TBack& State() const noexcept { return *State_; }
 
 public:
-    TExecutorBootLogic(IOps*, const TActorId&, TTabletStorageInfo *info, ui64 maxBytesInFly);
+    TExecutorBootLogic(IOps*, const TActorId&, ui64 bootAttempt, TTabletStorageInfo *info, ui64 maxBytesInFly);
     ~TExecutorBootLogic();
 
     void Describe(IOutputStream&) const;

ydb/core/tablet_flat/flat_executor_ut.cpp

@@ -3811,6 +3811,71 @@ Y_UNIT_TEST_SUITE(TFlatTableExecutor_Follower) {
         UNIT_ASSERT_C(!blockedSnapshot.empty(), "expected tablet to make a log snapshot after part switch");
     }
 
+    Y_UNIT_TEST(FollowerPromoteToLeaderWhileLoadingPages) {
+        TMyEnvBase env;
+        TRowsModel rows;
+
+        env->SetLogPriority(NKikimrServices::TABLET_EXECUTOR, NActors::NLog::PRI_DEBUG);
+
+        // Start the source tablet
+        env.FireTablet(env.Edge, env.Tablet, [&env](const TActorId &tablet, TTabletStorageInfo *info) {
+            return new TTestFlatTablet(env.Edge, tablet, info);
+        });
+        env.WaitForWakeUp();
+
+        Cerr << "... initializing schema" << Endl;
+        env.SendSync(rows.MakeScheme(new TCompactionPolicy()));
+
+        Cerr << "... inserting rows" << Endl;
+        env.SendSync(rows.MakeRows(10, 0, 10));
+
+        Cerr << "...compacting table" << Endl;
+        env.SendSync(new NFake::TEvCompact(TRowsModel::TableId));
+        env.WaitFor<NFake::TEvCompacted>();
+
+        Cerr << "... starting follower" << Endl;
+        TActorId followerSysActor;
+        auto followerBootObserver = env->AddObserver<TEvTablet::TEvFBoot>([&](auto& ev) {
+            followerSysActor = ev->Sender;
+            Cerr << "... observed TEvTablet::TEvFBoot" << Endl;
+        });
+        TBlockEvents<NSharedCache::TEvRequest> blockedFollowerRequests(env.Env);
+        env.FireFollower(env.Edge, env.Tablet, [&env](const TActorId &tablet, TTabletStorageInfo *info) {
+            return new TTestFlatTablet(env.Edge, tablet, info);
+        }, /* followerId */ 1);
+        env->WaitFor("follower shared cache requests", [&]{ return blockedFollowerRequests.size() > 0; });
+
+        Cerr << "... stopping leader" << Endl;
+        env.SendSync(new TEvents::TEvPoison, false, true);
+        env.WaitForGone();
+
+        blockedFollowerRequests.Stop();
+        TBlockEvents<NSharedCache::TEvRequest> blockedLeaderRequests(env.Env);
+
+        TActorId leaderSysActor;
+        auto leaderBootObserver = env->AddObserver<TEvTablet::TEvBoot>([&](auto& ev) {
+            leaderSysActor = ev->Sender;
+            Cerr << "... observed TEvTablet::TEvBoot" << Endl;
+        });
+        Cerr << "... promoting follower" << Endl;
+        {
+            NFake::TStarter starter;
+            auto* info = starter.MakeTabletInfo(env.Tablet, env.StorageGroupCount);
+            auto* promote = new TEvTablet::TEvPromoteToLeader(0, info);
+            env->Send(new IEventHandle(followerSysActor, followerSysActor, promote), 0, /* viaActorSystem */ true);
+        }
+        env->WaitFor("promoted shared cache requests", [&]{ return blockedLeaderRequests.size() > 0; });
+
+        Cerr << "... unblocking promoted requests" << Endl;
+        blockedLeaderRequests.Stop().Unblock();
+        env->SimulateSleep(TDuration::MilliSeconds(10));
+
+        // Simulate reordering replies by reordering requests
+        Cerr << "... unblocking earlier requests" << Endl;
+        blockedFollowerRequests.Unblock();
+        env->SimulateSleep(TDuration::MilliSeconds(10));
+    }
+
 }
 
 Y_UNIT_TEST_SUITE(TFlatTableExecutor_RejectProbability) {