fix neighbours count (#6409)

ydb/core/mind/hive/hive_ut.cpp

@@ -4776,6 +4776,84 @@ Y_UNIT_TEST_SUITE(THiveTest) {
         }
     }
 
+    Y_UNIT_TEST(TestHiveBalancerUselessNeighbourMoves) {
+        // 7 tablets of same object, 3 nodes, one of nodes cannot run them
+        // distribution should be (4, 3, 0)
+        // this should trigger balancer, but not lead to any moves
+        static constexpr ui64 NUM_NODES = 3;
+        static constexpr ui64 NUM_TABLETS = 7;
+        TTestBasicRuntime runtime(NUM_NODES, false);
+        Setup(runtime, true, 1, [](TAppPrepare& app) {
+            app.HiveConfig.SetTabletKickCooldownPeriod(0);
+            app.HiveConfig.SetResourceChangeReactionPeriod(0);
+            app.HiveConfig.SetMetricsWindowSize(1);
+        });
+        const int nodeBase = runtime.GetNodeId(0);
+        TActorId senderA = runtime.AllocateEdgeActor();
+        const ui64 hiveTablet = MakeDefaultHiveID();
+        const ui64 testerTablet = MakeTabletID(false, 1);
+
+        auto getDistribution = [hiveTablet, nodeBase, senderA, &runtime]() -> std::array<std::vector<ui64>, NUM_NODES> {
+            std::array<std::vector<ui64>, NUM_NODES> nodeTablets = {};
+            {
+                runtime.SendToPipe(hiveTablet, senderA, new TEvHive::TEvRequestHiveInfo());
+                TAutoPtr<IEventHandle> handle;
+                TEvHive::TEvResponseHiveInfo* response = runtime.GrabEdgeEventRethrow<TEvHive::TEvResponseHiveInfo>(handle);
+                for (const NKikimrHive::TTabletInfo& tablet : response->Record.GetTablets()) {
+                    UNIT_ASSERT_C(((int)tablet.GetNodeID() - nodeBase >= 0) && (tablet.GetNodeID() - nodeBase < NUM_NODES),
+                            "nodeId# " << tablet.GetNodeID() << " nodeBase# " << nodeBase);
+                    nodeTablets[tablet.GetNodeID() - nodeBase].push_back(tablet.GetTabletID());
+                }
+            }
+            return nodeTablets;
+        };
+
+        CreateTestBootstrapper(runtime, CreateTestTabletInfo(hiveTablet, TTabletTypes::Hive), &CreateDefaultHive);
+
+        // wait for creation of nodes
+        {
+            TDispatchOptions options;
+            options.FinalEvents.emplace_back(TEvLocal::EvStatus, NUM_NODES);
+            runtime.DispatchEvents(options);
+        }
+
+        TTabletTypes::EType tabletType = TTabletTypes::Dummy;
+        std::vector<ui64> tablets;
+        tablets.reserve(NUM_TABLETS);
+        for (size_t i = 0; i < NUM_TABLETS; ++i) {
+            THolder<TEvHive::TEvCreateTablet> ev(new TEvHive::TEvCreateTablet(testerTablet, 100500 + i, tabletType, BINDED_CHANNELS));
+            ev->Record.SetObjectId(1);
+            ev->Record.AddAllowedNodeIDs(nodeBase);
+            ev->Record.AddAllowedNodeIDs(nodeBase + 1);
+            ui64 tabletId = SendCreateTestTablet(runtime, hiveTablet, testerTablet, std::move(ev), 0, true);
+            MakeSureTabletIsUp(runtime, tabletId, 0);
+            tablets.push_back(tabletId);
+        }
+
+        auto initialDistribution = getDistribution();
+
+        for (auto tablet : tablets) {
+            THolder<TEvHive::TEvTabletMetrics> metrics = MakeHolder<TEvHive::TEvTabletMetrics>();
+            NKikimrHive::TTabletMetrics* metric = metrics->Record.AddTabletMetrics();
+            metric->SetTabletID(tablet);
+            metric->MutableResourceUsage()->SetCPU(0);
+            metric->MutableResourceUsage()->SetMemory(0);
+
+            runtime.SendToPipe(hiveTablet, senderA, metrics.Release());
+        }
+
+        {
+            TDispatchOptions options;
+            options.FinalEvents.emplace_back(NHive::TEvPrivate::EvBalancerOut);
+            runtime.DispatchEvents(options, TDuration::Seconds(10));
+        }
+
+        // Check that balancer moved no tablets
+        auto newDistribution = getDistribution();
+
+        UNIT_ASSERT_EQUAL(initialDistribution, newDistribution);
+    }
+
     Y_UNIT_TEST(TestHiveBalancerWithImmovableTablets) {
         static constexpr ui64 TABLETS_PER_NODE = 10;
         TTestBasicRuntime runtime(3, false);

ydb/core/mind/hive/node_info.h

@@ -132,7 +132,11 @@ struct TNodeInfo {
     ui32 GetTabletNeighboursCount(const TTabletInfo& tablet) const {
         auto it = TabletsOfObject.find(tablet.GetObjectId());
         if (it != TabletsOfObject.end()) {
-            return it->second.size();
+            auto count = it->second.size();
+            if (tablet.IsAliveOnLocal(Local)) {
+                --count;
+            }
+            return count;
         } else {
             return 0;
         }