Set replica_unassigned_buffer_time default value (elastic#112612)

The default value of replica_unassigned_buffer_time was set
incorrectly to 0s and was never updated to the correct default
value. Instead it should be set in the constructor from the settings.

docs/changelog/112612.yaml

@@ -0,0 +1,5 @@
+pr: 112612
+summary: Set `replica_unassigned_buffer_time` in constructor
+area: Health
+type: bug
+issues: []

server/src/main/java/org/elasticsearch/cluster/routing/allocation/shards/ShardsAvailabilityHealthIndicatorService.java

@@ -132,7 +132,7 @@ public class ShardsAvailabilityHealthIndicatorService implements HealthIndicator
 
     private final SystemIndices systemIndices;
 
-    private volatile TimeValue replicaUnassignedBufferTime = TimeValue.timeValueSeconds(0);
+    private volatile TimeValue replicaUnassignedBufferTime;
 
     public ShardsAvailabilityHealthIndicatorService(
         ClusterService clusterService,
@@ -142,6 +142,7 @@ public ShardsAvailabilityHealthIndicatorService(
         this.clusterService = clusterService;
         this.allocationService = allocationService;
         this.systemIndices = systemIndices;
+        this.replicaUnassignedBufferTime = REPLICA_UNASSIGNED_BUFFER_TIME.get(clusterService.getSettings());
         clusterService.getClusterSettings().addSettingsUpdateConsumer(REPLICA_UNASSIGNED_BUFFER_TIME, this::setReplicaUnassignedBufferTime);
     }
 

server/src/test/java/org/elasticsearch/cluster/routing/allocation/ShardsAvailabilityActionGuideTests.java

@@ -11,6 +11,7 @@
 import org.elasticsearch.cluster.routing.allocation.shards.ShardsAvailabilityHealthIndicatorService;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.ClusterSettings;
+import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.indices.SystemIndices;
 import org.elasticsearch.test.ESTestCase;
 
@@ -43,6 +44,7 @@ public class ShardsAvailabilityActionGuideTests extends ESTestCase {
     public ShardsAvailabilityActionGuideTests() {
         ClusterService clusterService = mock(ClusterService.class);
         when(clusterService.getClusterSettings()).thenReturn(ClusterSettings.createBuiltInClusterSettings());
+        when(clusterService.getSettings()).thenReturn(Settings.EMPTY);
         service = new ShardsAvailabilityHealthIndicatorService(clusterService, mock(AllocationService.class), mock(SystemIndices.class));
     }
 

server/src/test/java/org/elasticsearch/cluster/routing/allocation/shards/ShardsAvailabilityHealthIndicatorServiceTests.java

@@ -1983,6 +1983,7 @@ public void testMappedFieldsForTelemetry() {
         );
         ClusterService clusterService = mock(ClusterService.class);
         when(clusterService.getClusterSettings()).thenReturn(ClusterSettings.createBuiltInClusterSettings());
+        when(clusterService.getSettings()).thenReturn(Settings.EMPTY);
         var service = new ShardsAvailabilityHealthIndicatorService(
             clusterService,
             mock(AllocationService.class),
@@ -2557,6 +2558,7 @@ private static ShardsAvailabilityHealthIndicatorService createAllocationHealthIn
         when(clusterService.state()).thenReturn(clusterState);
         var clusterSettings = new ClusterSettings(nodeSettings, ClusterSettings.BUILT_IN_CLUSTER_SETTINGS);
         when(clusterService.getClusterSettings()).thenReturn(clusterSettings);
+        when(clusterService.getSettings()).thenReturn(Settings.EMPTY);
         var allocationService = mock(AllocationService.class);
         when(allocationService.explainShardAllocation(any(), any())).thenAnswer((Answer<ShardAllocationDecision>) invocation -> {
             ShardRouting shardRouting = invocation.getArgument(0);