From 66912fea6b77514b93678f611012f62adccaa715 Mon Sep 17 00:00:00 2001
From: vporyadke <zalyalov@ydb.tech>
Date: Wed, 5 Nov 2025 14:31:24 +0100
Subject: [PATCH 1/2] fix stuck reassign actor (#28195)

---
 ydb/core/mind/hive/monitoring.cpp | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/ydb/core/mind/hive/monitoring.cpp b/ydb/core/mind/hive/monitoring.cpp
index ca1830c75cd9..9248554b1027 100644
--- a/ydb/core/mind/hive/monitoring.cpp
+++ b/ydb/core/mind/hive/monitoring.cpp
@@ -2880,7 +2880,7 @@ class TTxMonEvent_RebalanceFromScratch : public TTransactionBase<THive> {
 class TReassignTabletWaitActor : public TActor<TReassignTabletWaitActor>, public ISubActor {
 public:
     TActorId Source;
-    ui32 TabletsTotal = std::numeric_limits<ui32>::max();
+    ui32 TabletsTotal = 0;
     ui32 TabletsDone = 0;
     THive* Hive;
 
@@ -2907,14 +2907,23 @@ class TReassignTabletWaitActor : public TActor<TReassignTabletWaitActor>, public
         return SelfId().LocalId();
     }
 
-    void Handle(TEvPrivate::TEvRestartComplete::TPtr&) {
-        ++TabletsDone;
+    void AddTablet(TLeaderTabletInfo* tablet) {
+        tablet->ActorsToNotifyOnRestart.push_back(SelfId());
+        ++TabletsTotal;
+    }
+
+    void CheckCompletion() {
         if (TabletsDone >= TabletsTotal) {
             Send(Source, new NMon::TEvRemoteJsonInfoRes(TStringBuilder() << "{\"total\":" << TabletsDone << "}"));
             PassAway();
         }
     }
 
+    void Handle(TEvPrivate::TEvRestartComplete::TPtr&) {
+        ++TabletsDone;
+        CheckCompletion();
+    }
+
     STATEFN(StateWork) {
         switch (ev->GetTypeRewrite()) {
             cFunc(TEvents::TSystem::PoisonPill, PassAway);
@@ -3042,12 +3051,12 @@ class TTxMonEvent_ReassignTablet : public TTransactionBase<THive> {
                 continue;
             }
             if (Wait) {
-                tablet->ActorsToNotifyOnRestart.emplace_back(waitActorId); // volatile settings, will not persist upon restart
+                waitActor->AddTablet(tablet);
             }
             operations.emplace_back(new TEvHive::TEvReassignTablet(tablet->Id, channels, forcedGroupIds, Async));
         }
         if (Wait) {
-            waitActor->TabletsTotal = operations.size();
+            waitActor->CheckCompletion();
         }
         for (auto& op : operations) {
             ctx.Send(Self->SelfId(), op.Release());

From 3c2e809f2b0d1ccf0edf5830ab38f7fb83f9c3e7 Mon Sep 17 00:00:00 2001
From: vporyadke <zalyalov@ydb.tech>
Date: Wed, 12 Nov 2025 16:30:28 +0300
Subject: [PATCH 2/2] test for invalid reassign (#28404)

---
 ydb/core/mind/hive/hive_ut.cpp | 63 ++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/ydb/core/mind/hive/hive_ut.cpp b/ydb/core/mind/hive/hive_ut.cpp
index 46ddba9dad96..56f5b1364ce6 100644
--- a/ydb/core/mind/hive/hive_ut.cpp
+++ b/ydb/core/mind/hive/hive_ut.cpp
@@ -8229,6 +8229,69 @@ Y_UNIT_TEST_SUITE(THiveTest) {
         }
     }
 
+    Y_UNIT_TEST(TestReassignNonexistentTablet) {
+        TTestBasicRuntime runtime(1, false);
+        Setup(runtime, true);
+
+        const ui64 hiveTablet = MakeDefaultHiveID();
+        const ui64 testerTablet = MakeTabletID(false, 1);
+        const TActorId hiveActor = CreateTestBootstrapper(runtime, CreateTestTabletInfo(hiveTablet, TTabletTypes::Hive), &CreateDefaultHive);
+        runtime.EnableScheduleForActor(hiveActor);
+        MakeSureTabletIsUp(runtime, hiveTablet, 0);
+        TActorId sender = runtime.AllocateEdgeActor(0);
+
+        {
+            TDispatchOptions options;
+            options.FinalEvents.emplace_back(TEvLocal::EvSyncTablets);
+            runtime.DispatchEvents(options);
+        }
+
+        THolder<TEvHive::TEvCreateTablet> createTablet = MakeHolder<TEvHive::TEvCreateTablet>(testerTablet, 1, TTabletTypes::Dummy, BINDED_CHANNELS);
+        ui64 tablet = SendCreateTestTablet(runtime, hiveTablet, testerTablet, std::move(createTablet), 0, true);
+
+        MakeSureTabletIsUp(runtime, tablet, 0);
+
+        {
+            NActorsProto::TRemoteHttpInfo pb;
+            pb.SetMethod(HTTP_METHOD_POST);
+            pb.SetPath("/app");
+            auto* p1 = pb.AddQueryParams();
+            p1->SetKey("TabletID");
+            p1->SetValue(TStringBuilder() << hiveTablet);
+            auto* p2 = pb.AddQueryParams();
+            p2->SetKey("page");
+            p2->SetValue("ReassignTablet");
+            auto* p3 = pb.AddQueryParams();
+            p3->SetKey("tablet");
+            p3->SetValue("52");
+            runtime.SendToPipe(hiveTablet, sender, new NMon::TEvRemoteHttpInfo(std::move(pb)), 0, GetPipeConfigWithRetries());
+
+            TAutoPtr<IEventHandle> handle;
+            auto resp = runtime.GrabEdgeEventRethrow<NMon::TEvRemoteJsonInfoRes>(handle);
+            Ctest << "Hive response: " << resp->Json << Endl;
+            NJson::TJsonValue value;
+            ReadJsonTree(resp->Json, &value, false);
+            UNIT_ASSERT_VALUES_EQUAL(value["total"].GetIntegerSafe(), 0);
+        }
+
+        // this must not block balancer
+
+       {
+            THolder<TEvHive::TEvTabletMetrics> metrics = MakeHolder<TEvHive::TEvTabletMetrics>();
+            NKikimrHive::TTabletMetrics* metric = metrics->Record.AddTabletMetrics();
+            metric->SetTabletID(tablet);
+            metric->MutableResourceUsage()->SetNetwork(9000);
+
+            runtime.SendToPipe(hiveTablet, sender, metrics.Release());
+       }
+
+       {
+           TDispatchOptions options;
+           options.FinalEvents.push_back(NHive::TEvPrivate::EvBalancerOut);
+           runtime.DispatchEvents(options);
+       }
+    }
+
     Y_UNIT_TEST(TestTabletsStartingCounter) {
       TTestBasicRuntime runtime(1, false);
       Setup(runtime, true);