Introduce more parallelism into cross cluster test bootstrapping (#117820)

original-brownbear · web-flow · commit eb0020f0558f · 2024-12-04T21:04:11.000+01:00
We can parallelize starting the clusters and a few other things
to effectively speed up these tests by 2x which comes out to about a minute
of execution time saved for all of those in :server:internalClusterTests
on my workstation.
diff --git a/modules/data-streams/src/internalClusterTest/java/org/elasticsearch/datastreams/ResolveClusterDataStreamIT.java b/modules/data-streams/src/internalClusterTest/java/org/elasticsearch/datastreams/ResolveClusterDataStreamIT.java
@@ -78,7 +78,7 @@ public class ResolveClusterDataStreamIT extends AbstractMultiClustersTestCase {
     private static long LATEST_TIMESTAMP = 1691348820000L;
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER_1, REMOTE_CLUSTER_2);
     }
 
diff --git a/modules/lang-painless/src/internalClusterTest/java/org/elasticsearch/painless/action/CrossClusterPainlessExecuteIT.java b/modules/lang-painless/src/internalClusterTest/java/org/elasticsearch/painless/action/CrossClusterPainlessExecuteIT.java
@@ -54,7 +54,7 @@ public class CrossClusterPainlessExecuteIT extends AbstractMultiClustersTestCase
     private static final String KEYWORD_FIELD = "my_field";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/modules/reindex/src/internalClusterTest/java/org/elasticsearch/index/reindex/CrossClusterReindexIT.java b/modules/reindex/src/internalClusterTest/java/org/elasticsearch/index/reindex/CrossClusterReindexIT.java
@@ -36,7 +36,7 @@ protected boolean reuseClusters() {
     }
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/remote/RemoteInfoIT.java b/server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/remote/RemoteInfoIT.java
@@ -15,7 +15,6 @@
 import org.elasticsearch.test.InternalTestCluster;
 import org.elasticsearch.test.NodeRoles;
 
-import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Set;
@@ -24,7 +23,7 @@
 
 public class RemoteInfoIT extends AbstractMultiClustersTestCase {
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         if (randomBoolean()) {
             return List.of();
         } else {
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsRemoteIT.java b/server/src/internalClusterTest/java/org/elasticsearch/action/admin/cluster/stats/ClusterStatsRemoteIT.java
@@ -23,7 +23,6 @@
 import org.elasticsearch.test.InternalTestCluster;
 import org.junit.Assert;
 
-import java.util.Collection;
 import java.util.List;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
@@ -51,7 +50,7 @@ protected boolean reuseClusters() {
     }
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE1, REMOTE2);
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/action/search/CCSPointInTimeIT.java b/server/src/internalClusterTest/java/org/elasticsearch/action/search/CCSPointInTimeIT.java
@@ -44,7 +44,7 @@ public class CCSPointInTimeIT extends AbstractMultiClustersTestCase {
     public static final String REMOTE_CLUSTER = "remote_cluster";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/indices/cluster/ResolveClusterIT.java b/server/src/internalClusterTest/java/org/elasticsearch/indices/cluster/ResolveClusterIT.java
@@ -28,7 +28,6 @@
 import org.elasticsearch.transport.RemoteClusterAware;
 
 import java.io.IOException;
-import java.util.Collection;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
@@ -54,7 +53,7 @@ public class ResolveClusterIT extends AbstractMultiClustersTestCase {
     private static long LATEST_TIMESTAMP = 1691348820000L;
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER_1, REMOTE_CLUSTER_2);
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CCSCanMatchIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CCSCanMatchIT.java
@@ -55,7 +55,7 @@ public class CCSCanMatchIT extends AbstractMultiClustersTestCase {
     static final String REMOTE_CLUSTER = "cluster_a";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of("cluster_a");
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CCSUsageTelemetryIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CCSUsageTelemetryIT.java
@@ -11,16 +11,19 @@
 
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
+import org.elasticsearch.action.ActionListener;
 import org.elasticsearch.action.admin.cluster.stats.CCSTelemetrySnapshot;
 import org.elasticsearch.action.admin.cluster.stats.CCSUsageTelemetry.Result;
+import org.elasticsearch.action.bulk.BulkRequestBuilder;
 import org.elasticsearch.action.search.ClosePointInTimeRequest;
 import org.elasticsearch.action.search.OpenPointInTimeRequest;
 import org.elasticsearch.action.search.SearchRequest;
-import org.elasticsearch.action.search.SearchResponse;
 import org.elasticsearch.action.search.TransportClosePointInTimeAction;
 import org.elasticsearch.action.search.TransportOpenPointInTimeAction;
 import org.elasticsearch.action.search.TransportSearchAction;
 import org.elasticsearch.action.support.PlainActionFuture;
+import org.elasticsearch.action.support.RefCountingListener;
+import org.elasticsearch.action.support.WriteRequest;
 import org.elasticsearch.client.internal.Client;
 import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.settings.Settings;
@@ -78,7 +81,7 @@ protected boolean reuseClusters() {
     }
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE1, REMOTE2);
     }
 
@@ -126,12 +129,9 @@ private CCSTelemetrySnapshot getTelemetryFromFailedSearch(SearchRequest searchRe
         // We want to send search to a specific node (we don't care which one) so that we could
         // collect the CCS telemetry from it later
         String nodeName = cluster(LOCAL_CLUSTER).getRandomNodeName();
-        PlainActionFuture<SearchResponse> queryFuture = new PlainActionFuture<>();
-        cluster(LOCAL_CLUSTER).client(nodeName).search(searchRequest, queryFuture);
-        assertBusy(() -> assertTrue(queryFuture.isDone()));
 
         // We expect failure, but we don't care too much which failure it is in this test
-        ExecutionException ee = expectThrows(ExecutionException.class, queryFuture::get);
+        ExecutionException ee = expectThrows(ExecutionException.class, cluster(LOCAL_CLUSTER).client(nodeName).search(searchRequest)::get);
         assertNotNull(ee.getCause());
 
         return getTelemetrySnapshot(nodeName);
@@ -637,56 +637,62 @@ private CCSTelemetrySnapshot getTelemetrySnapshot(String nodeName) {
         return usage.getCcsUsageHolder().getCCSTelemetrySnapshot();
     }
 
-    private Map<String, Object> setupClusters() {
+    private Map<String, Object> setupClusters() throws ExecutionException, InterruptedException {
         String localIndex = "demo";
+        String remoteIndex = "prod";
         int numShardsLocal = randomIntBetween(2, 10);
         Settings localSettings = indexSettings(numShardsLocal, randomIntBetween(0, 1)).build();
-        assertAcked(
+        final PlainActionFuture<Void> future = new PlainActionFuture<>();
+        try (RefCountingListener refCountingListener = new RefCountingListener(future)) {
             client(LOCAL_CLUSTER).admin()
                 .indices()
                 .prepareCreate(localIndex)
                 .setSettings(localSettings)
                 .setMapping("@timestamp", "type=date", "f", "type=text")
-        );
-        indexDocs(client(LOCAL_CLUSTER), localIndex);
-
-        String remoteIndex = "prod";
-        int numShardsRemote = randomIntBetween(2, 10);
-        for (String clusterAlias : remoteClusterAlias()) {
-            final InternalTestCluster remoteCluster = cluster(clusterAlias);
-            remoteCluster.ensureAtLeastNumDataNodes(randomIntBetween(2, 3));
-            assertAcked(
+                .execute(refCountingListener.acquire(r -> {
+                    assertAcked(r);
+                    indexDocs(client(LOCAL_CLUSTER), localIndex, refCountingListener.acquire());
+                }));
+
+            int numShardsRemote = randomIntBetween(2, 10);
+            var remotes = remoteClusterAlias();
+            runInParallel(remotes.size(), i -> {
+                final String clusterAlias = remotes.get(i);
+                final InternalTestCluster remoteCluster = cluster(clusterAlias);
+                remoteCluster.ensureAtLeastNumDataNodes(randomIntBetween(2, 3));
                 client(clusterAlias).admin()
                     .indices()
                     .prepareCreate(remoteIndex)
                     .setSettings(indexSettings(numShardsRemote, randomIntBetween(0, 1)))
                     .setMapping("@timestamp", "type=date", "f", "type=text")
-            );
-            assertFalse(
-                client(clusterAlias).admin()
-                    .cluster()
-                    .prepareHealth(TEST_REQUEST_TIMEOUT, remoteIndex)
-                    .setWaitForYellowStatus()
-                    .setTimeout(TimeValue.timeValueSeconds(10))
-                    .get()
-                    .isTimedOut()
-            );
-            indexDocs(client(clusterAlias), remoteIndex);
+                    .execute(refCountingListener.acquire(r -> {
+                        assertAcked(r);
+                        client(clusterAlias).admin()
+                            .cluster()
+                            .prepareHealth(TEST_REQUEST_TIMEOUT, remoteIndex)
+                            .setWaitForYellowStatus()
+                            .setTimeout(TimeValue.timeValueSeconds(10))
+                            .execute(refCountingListener.acquire(healthResponse -> {
+                                assertFalse(healthResponse.isTimedOut());
+                                indexDocs(client(clusterAlias), remoteIndex, refCountingListener.acquire());
+                            }));
+                    }));
+            });
         }
-
+        future.get();
         Map<String, Object> clusterInfo = new HashMap<>();
         clusterInfo.put("local.index", localIndex);
         clusterInfo.put("remote.index", remoteIndex);
         return clusterInfo;
     }
 
-    private int indexDocs(Client client, String index) {
+    private void indexDocs(Client client, String index, ActionListener<Void> listener) {
         int numDocs = between(5, 20);
+        final BulkRequestBuilder bulkRequest = client.prepareBulk();
         for (int i = 0; i < numDocs; i++) {
-            client.prepareIndex(index).setSource("f", "v", "@timestamp", randomNonNegativeLong()).get();
+            bulkRequest.add(client.prepareIndex(index).setSource("f", "v", "@timestamp", randomNonNegativeLong()));
         }
-        client.admin().indices().prepareRefresh(index).get();
-        return numDocs;
+        bulkRequest.setRefreshPolicy(WriteRequest.RefreshPolicy.IMMEDIATE).execute(listener.safeMap(r -> null));
     }
 
     /**
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterIT.java
@@ -86,7 +86,7 @@
 public class CrossClusterIT extends AbstractMultiClustersTestCase {
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of("cluster_a");
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchIT.java
@@ -60,7 +60,7 @@ public class CrossClusterSearchIT extends AbstractMultiClustersTestCase {
     private static long LATEST_TIMESTAMP = 1691348820000L;
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchLeakIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/ccs/CrossClusterSearchLeakIT.java
@@ -38,7 +38,7 @@
 public class CrossClusterSearchLeakIT extends AbstractMultiClustersTestCase {
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of("cluster_a");
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/fieldcaps/CCSFieldCapabilitiesIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/fieldcaps/CCSFieldCapabilitiesIT.java
@@ -34,7 +34,7 @@
 public class CCSFieldCapabilitiesIT extends AbstractMultiClustersTestCase {
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of("remote_cluster");
     }
 
diff --git a/server/src/internalClusterTest/java/org/elasticsearch/search/retriever/MinimalCompoundRetrieverIT.java b/server/src/internalClusterTest/java/org/elasticsearch/search/retriever/MinimalCompoundRetrieverIT.java
@@ -26,7 +26,6 @@
 import org.elasticsearch.xcontent.XContentBuilder;
 
 import java.io.IOException;
-import java.util.Collection;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
@@ -43,7 +42,7 @@ public class MinimalCompoundRetrieverIT extends AbstractMultiClustersTestCase {
     private static final String REMOTE_CLUSTER = "cluster_a";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/test/framework/src/main/java/org/elasticsearch/test/AbstractMultiClustersTestCase.java b/test/framework/src/main/java/org/elasticsearch/test/AbstractMultiClustersTestCase.java
@@ -36,10 +36,10 @@
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.Collections;
-import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 import java.util.Set;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.function.Function;
 import java.util.stream.Collectors;
 
@@ -58,7 +58,7 @@ public abstract class AbstractMultiClustersTestCase extends ESTestCase {
 
     private static volatile ClusterGroup clusterGroup;
 
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return randomSubsetOf(List.of("cluster-a", "cluster-b"));
     }
 
@@ -100,17 +100,18 @@ public final void startClusters() throws Exception {
             return;
         }
         stopClusters();
-        final Map<String, InternalTestCluster> clusters = new HashMap<>();
+        final Map<String, InternalTestCluster> clusters = new ConcurrentHashMap<>();
         final List<String> clusterAliases = new ArrayList<>(remoteClusterAlias());
         clusterAliases.add(LOCAL_CLUSTER);
-        for (String clusterAlias : clusterAliases) {
+        final List<Class<? extends Plugin>> mockPlugins = List.of(
+            MockHttpTransport.TestPlugin.class,
+            MockTransportService.TestPlugin.class,
+            getTestTransportPlugin()
+        );
+        runInParallel(clusterAliases.size(), i -> {
+            String clusterAlias = clusterAliases.get(i);
             final String clusterName = clusterAlias.equals(LOCAL_CLUSTER) ? "main-cluster" : clusterAlias;
             final int numberOfNodes = randomIntBetween(1, 3);
-            final List<Class<? extends Plugin>> mockPlugins = List.of(
-                MockHttpTransport.TestPlugin.class,
-                MockTransportService.TestPlugin.class,
-                getTestTransportPlugin()
-            );
             final Collection<Class<? extends Plugin>> nodePlugins = nodePlugins(clusterAlias);
 
             final NodeConfigurationSource nodeConfigurationSource = nodeConfigurationSource(nodeSettings(), nodePlugins);
@@ -128,10 +129,14 @@ public final void startClusters() throws Exception {
                 mockPlugins,
                 Function.identity()
             );
-            cluster.beforeTest(random());
+            try {
+                cluster.beforeTest(random());
+            } catch (Exception e) {
+                throw new RuntimeException(e);
+            }
             clusters.put(clusterAlias, cluster);
-        }
-        clusterGroup = new ClusterGroup(clusters);
+        });
+        clusterGroup = new ClusterGroup(Map.copyOf(clusters));
         configureAndConnectsToRemoteClusters();
     }
 
diff --git a/x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CCSUsageTelemetryAsyncSearchIT.java b/x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CCSUsageTelemetryAsyncSearchIT.java
@@ -60,7 +60,7 @@ protected boolean reuseClusters() {
     }
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE1, REMOTE2);
     }
 
diff --git a/x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CrossClusterAsyncSearchIT.java b/x-pack/plugin/async-search/src/internalClusterTest/java/org/elasticsearch/xpack/search/CrossClusterAsyncSearchIT.java
@@ -88,7 +88,7 @@ public class CrossClusterAsyncSearchIT extends AbstractMultiClustersTestCase {
     private static final long LATEST_TIMESTAMP = 1691348820000L;
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER);
     }
 
diff --git a/x-pack/plugin/core/src/internalClusterTest/java/org/elasticsearch/xpack/core/termsenum/CCSTermsEnumIT.java b/x-pack/plugin/core/src/internalClusterTest/java/org/elasticsearch/xpack/core/termsenum/CCSTermsEnumIT.java
@@ -26,7 +26,7 @@
 public class CCSTermsEnumIT extends AbstractMultiClustersTestCase {
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of("remote_cluster");
     }
 
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterAsyncQueryIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterAsyncQueryIT.java
@@ -66,7 +66,7 @@ public class CrossClusterAsyncQueryIT extends AbstractMultiClustersTestCase {
     private static final String INDEX_WITH_RUNTIME_MAPPING = "blocking";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER_1, REMOTE_CLUSTER_2);
     }
 
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterEnrichUnavailableClustersIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterEnrichUnavailableClustersIT.java
@@ -53,7 +53,7 @@ public class CrossClusterEnrichUnavailableClustersIT extends AbstractMultiCluste
     public static String REMOTE_CLUSTER_2 = "c2";
 
     @Override
-    protected Collection<String> remoteClusterAlias() {
+    protected List<String> remoteClusterAlias() {
         return List.of(REMOTE_CLUSTER_1, REMOTE_CLUSTER_2);
     }
 
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterQueryUnavailableRemotesIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClusterQueryUnavailableRemotesIT.java
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersCancellationIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersCancellationIT.java
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersEnrichIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersEnrichIT.java
diff --git a/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersQueryIT.java b/x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/CrossClustersQueryIT.java
diff --git a/x-pack/plugin/ml/src/internalClusterTest/java/org/elasticsearch/xpack/ml/integration/DatafeedCcsIT.java b/x-pack/plugin/ml/src/internalClusterTest/java/org/elasticsearch/xpack/ml/integration/DatafeedCcsIT.java
diff --git a/x-pack/plugin/transform/src/internalClusterTest/java/org/elasticsearch/xpack/transform/checkpoint/TransformCCSCanMatchIT.java b/x-pack/plugin/transform/src/internalClusterTest/java/org/elasticsearch/xpack/transform/checkpoint/TransformCCSCanMatchIT.java

Original file line number	Diff line number	Diff line change
`@@ -78,7 +78,7 @@ public class ResolveClusterDataStreamIT extends AbstractMultiClustersTestCase {`
`78`	`78`	`private static long LATEST_TIMESTAMP = 1691348820000L;`
`79`	`79`
`80`	`80`	`@Override`
`81`		`- protected Collection<String> remoteClusterAlias() {`
	`81`	`+ protected List<String> remoteClusterAlias() {`
`82`	`82`	`return List.of(REMOTE_CLUSTER_1, REMOTE_CLUSTER_2);`
`83`	`83`	`}`
`84`	`84`
Original file line number	Diff line number	Diff line change
`@@ -54,7 +54,7 @@ public class CrossClusterPainlessExecuteIT extends AbstractMultiClustersTestCase`
`54`	`54`	`private static final String KEYWORD_FIELD = "my_field";`
`55`	`55`
`56`	`56`	`@Override`
`57`		`- protected Collection<String> remoteClusterAlias() {`
	`57`	`+ protected List<String> remoteClusterAlias() {`
`58`	`58`	`return List.of(REMOTE_CLUSTER);`
`59`	`59`	`}`
`60`	`60`
Original file line number	Diff line number	Diff line change
`@@ -36,7 +36,7 @@ protected boolean reuseClusters() {`
`36`	`36`	`}`
`37`	`37`
`38`	`38`	`@Override`
`39`		`- protected Collection<String> remoteClusterAlias() {`
	`39`	`+ protected List<String> remoteClusterAlias() {`
`40`	`40`	`return List.of(REMOTE_CLUSTER);`
`41`	`41`	`}`
`42`	`42`
Original file line number	Diff line number	Diff line change
`@@ -23,7 +23,6 @@`
`23`	`23`	`import org.elasticsearch.test.InternalTestCluster;`
`24`	`24`	`import org.junit.Assert;`
`25`	`25`
`26`		`-import java.util.Collection;`
`27`	`26`	`import java.util.List;`
`28`	`27`	`import java.util.Map;`
`29`	`28`	`import java.util.concurrent.ExecutionException;`
`@@ -51,7 +50,7 @@ protected boolean reuseClusters() {`
`51`	`50`	`}`
`52`	`51`
`53`	`52`	`@Override`
`54`		`- protected Collection<String> remoteClusterAlias() {`
	`53`	`+ protected List<String> remoteClusterAlias() {`
`55`	`54`	`return List.of(REMOTE1, REMOTE2);`
`56`	`55`	`}`
`57`	`56`
Original file line number	Diff line number	Diff line change
`@@ -44,7 +44,7 @@ public class CCSPointInTimeIT extends AbstractMultiClustersTestCase {`
`44`	`44`	`public static final String REMOTE_CLUSTER = "remote_cluster";`
`45`	`45`
`46`	`46`	`@Override`
`47`		`- protected Collection<String> remoteClusterAlias() {`
	`47`	`+ protected List<String> remoteClusterAlias() {`
`48`	`48`	`return List.of(REMOTE_CLUSTER);`
`49`	`49`	`}`
`50`	`50`
Original file line number	Diff line number	Diff line change
`@@ -55,7 +55,7 @@ public class CCSCanMatchIT extends AbstractMultiClustersTestCase {`
`55`	`55`	`static final String REMOTE_CLUSTER = "cluster_a";`
`56`	`56`
`57`	`57`	`@Override`
`58`		`- protected Collection<String> remoteClusterAlias() {`
	`58`	`+ protected List<String> remoteClusterAlias() {`
`59`	`59`	`return List.of("cluster_a");`
`60`	`60`	`}`
`61`	`61`
Original file line number	Diff line number	Diff line change
`@@ -86,7 +86,7 @@`
`86`	`86`	`public class CrossClusterIT extends AbstractMultiClustersTestCase {`
`87`	`87`
`88`	`88`	`@Override`
`89`		`- protected Collection<String> remoteClusterAlias() {`
	`89`	`+ protected List<String> remoteClusterAlias() {`
`90`	`90`	`return List.of("cluster_a");`
`91`	`91`	`}`
`92`	`92`