Test that ClusterInfo is refreshed when a new node is added (elastic#134101)

Author: nicktindall

server/src/test/java/org/elasticsearch/cluster/InternalClusterInfoServiceSchedulingTests.java

@@ -49,13 +49,16 @@
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.spy;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
 
 public class InternalClusterInfoServiceSchedulingTests extends ESTestCase {
 
     public void testScheduling() {
         final DiscoveryNode discoveryNode = DiscoveryNodeUtils.create("test");
         final DiscoveryNodes noMaster = DiscoveryNodes.builder().add(discoveryNode).localNodeId(discoveryNode.getId()).build();
         final DiscoveryNodes localMaster = noMaster.withMasterNodeId(discoveryNode.getId());
+        final DiscoveryNode joiner = DiscoveryNodeUtils.create("joiner");
+        final DiscoveryNodes withJoiner = DiscoveryNodes.builder(localMaster).add(joiner).build();
 
         final Settings.Builder settingsBuilder = Settings.builder()
             .put(Node.NODE_NAME_SETTING.getKey(), discoveryNode.getName())
@@ -129,6 +132,45 @@ public void reroute(String reason, Priority priority, ActionListener<Void> liste
         );
         runUntilFlag(deterministicTaskQueue, becameMaster1);
 
+        // A node joins the cluster
+        {
+            Mockito.clearInvocations(mockEstimatedHeapUsageCollector, nodeUsageStatsForThreadPoolsCollector);
+            final int initialRequestCount = client.requestCount;
+            final AtomicBoolean nodeJoined = new AtomicBoolean();
+            clusterApplierService.onNewClusterState(
+                "node joins",
+                () -> ClusterState.builder(new ClusterName("cluster")).nodes(withJoiner).build(),
+                setFlagOnSuccess(nodeJoined)
+            );
+            // Don't use runUntilFlag because we don't want the scheduled task to run
+            deterministicTaskQueue.runAllRunnableTasks();
+            assertTrue(nodeJoined.get());
+            // Addition of node should have triggered refresh
+            // should have run two client requests: nodes stats request and indices stats request
+            assertThat(client.requestCount, equalTo(initialRequestCount + 2));
+            verify(mockEstimatedHeapUsageCollector).collectClusterHeapUsage(any()); // Should have polled for heap usage
+            verify(nodeUsageStatsForThreadPoolsCollector).collectUsageStats(any(), any(), any());
+        }
+
+        // ... then leaves
+        {
+            Mockito.clearInvocations(mockEstimatedHeapUsageCollector, nodeUsageStatsForThreadPoolsCollector);
+            final int initialRequestCount = client.requestCount;
+            final AtomicBoolean nodeLeft = new AtomicBoolean();
+            clusterApplierService.onNewClusterState(
+                "node leaves",
+                () -> ClusterState.builder(new ClusterName("cluster")).nodes(localMaster).build(),
+                setFlagOnSuccess(nodeLeft)
+            );
+            // Don't use runUntilFlag because we don't want the scheduled task to run
+            deterministicTaskQueue.runAllRunnableTasks();
+            assertTrue(nodeLeft.get());
+            // departing nodes don't trigger refreshes
+            assertThat(client.requestCount, equalTo(initialRequestCount));
+            verifyNoInteractions(mockEstimatedHeapUsageCollector);
+            verifyNoInteractions(nodeUsageStatsForThreadPoolsCollector);
+        }
+
         final AtomicBoolean failMaster1 = new AtomicBoolean();
         clusterApplierService.onNewClusterState(
             "fail master 1",