lower priority for tablet metrics (#28554)

Author: vporyadke

ydb/core/mind/hive/hive_impl.cpp

@@ -3145,14 +3145,19 @@ void THive::RequestPoolsInformation() {
 }
 
 ui32 THive::GetEventPriority(IEventHandle* ev) {
+    // lower number = higher priority
     switch (ev->GetTypeRewrite()) {
+        // requests from viewer/healthcheck - need to be answered fast so that hive is not reported as unresponsive
         case TEvHive::EvRequestHiveInfo:
         case TEvHive::EvRequestHiveDomainStats:
         case TEvHive::EvRequestHiveNodeStats:
         case TEvHive::EvRequestHiveStorageStats:
             return 10;
         default:
             return 50;
+        // update metrics - there can be a lot of these, but they have no urgency
+        case TEvHive::EvTabletMetrics:
+            return 100;
     }
 }
 

ydb/core/mind/hive/hive_ut.cpp

@@ -5859,6 +5859,8 @@ Y_UNIT_TEST_SUITE(THiveTest) {
             runtime.SendToPipe(hiveTablet, senderA, metrics.Release());
         }
 
+        runtime.DispatchEvents({}, TDuration::MilliSeconds(300));
+
         auto createTablet = MakeHolder<TEvHive::TEvCreateTablet>(testerTablet, 100500 + tablets.size(), tabletType, BINDED_CHANNELS);
         ui64 newTablet = SendCreateTestTablet(runtime, hiveTablet, testerTablet, std::move(createTablet), 0, false);