Fix ILMDownsampleDisruptionIT.testILMDownsampleRollingRestart (elastic#119196)

This removes a redundant thread creation when triggering a rolling
restart as the method is already async and drops the check for cluster
health as that might hit a node that's being shut down (the master node
in particular).

Author: nielsbauman

x-pack/plugin/downsample/src/internalClusterTest/java/org/elasticsearch/xpack/downsample/ILMDownsampleDisruptionIT.java

@@ -10,8 +10,6 @@
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.elasticsearch.action.DocWriteRequest;
-import org.elasticsearch.action.admin.cluster.shards.ClusterSearchShardsRequest;
-import org.elasticsearch.action.admin.cluster.shards.TransportClusterSearchShardsAction;
 import org.elasticsearch.action.admin.indices.get.GetIndexRequest;
 import org.elasticsearch.action.admin.indices.get.GetIndexResponse;
 import org.elasticsearch.action.admin.indices.settings.get.GetSettingsRequest;
@@ -57,9 +55,7 @@
 import java.util.List;
 import java.util.Locale;
 import java.util.Map;
-import java.util.concurrent.CountDownLatch;
 import java.util.concurrent.TimeUnit;
-import java.util.function.Consumer;
 
 import static org.elasticsearch.core.Strings.format;
 import static org.elasticsearch.test.hamcrest.ElasticsearchAssertions.assertAcked;
@@ -144,7 +140,7 @@ public void setup(final String sourceIndex, int numOfShards, int numOfReplicas,
 
     public void testILMDownsampleRollingRestart() throws Exception {
         final InternalTestCluster cluster = internalCluster();
-        final List<String> masterNodes = cluster.startMasterOnlyNodes(1);
+        cluster.startMasterOnlyNodes(1);
         cluster.startDataOnlyNodes(3);
         ensureStableCluster(cluster.size());
         ensureGreen();
@@ -169,46 +165,16 @@ public void testILMDownsampleRollingRestart() throws Exception {
                 .endObject();
         };
         int indexedDocs = bulkIndex(sourceIndex, sourceSupplier, DOC_COUNT);
-        final CountDownLatch disruptionStart = new CountDownLatch(1);
-        final CountDownLatch disruptionEnd = new CountDownLatch(1);
 
-        new Thread(new Disruptor(cluster, sourceIndex, new DisruptionListener() {
-            @Override
-            public void disruptionStart() {
-                disruptionStart.countDown();
-            }
-
-            @Override
-            public void disruptionEnd() {
-                disruptionEnd.countDown();
-            }
-        }, masterNodes.get(0), (ignored) -> {
-            try {
-                cluster.rollingRestart(new InternalTestCluster.RestartCallback() {
-                    @Override
-                    public boolean validateClusterForming() {
-                        return true;
-                    }
-                });
-            } catch (Exception e) {
-                throw new RuntimeException(e);
-            }
-        })).start();
+        cluster.rollingRestart(new InternalTestCluster.RestartCallback());
 
         final String targetIndex = "downsample-1h-" + sourceIndex;
-        startDownsampleTaskViaIlm(sourceIndex, targetIndex, disruptionStart, disruptionEnd);
-        waitUntil(() -> getClusterPendingTasks(cluster.client()).pendingTasks().isEmpty(), 60, TimeUnit.SECONDS);
-        ensureStableCluster(cluster.numDataAndMasterNodes());
-        assertTargetIndex(cluster, targetIndex, indexedDocs);
+        startDownsampleTaskViaIlm(sourceIndex, targetIndex);
+        assertBusy(() -> assertTargetIndex(cluster, targetIndex, indexedDocs));
+        ensureGreen(targetIndex);
     }
 
-    private void startDownsampleTaskViaIlm(
-        String sourceIndex,
-        String targetIndex,
-        CountDownLatch disruptionStart,
-        CountDownLatch disruptionEnd
-    ) throws Exception {
-        disruptionStart.await();
+    private void startDownsampleTaskViaIlm(String sourceIndex, String targetIndex) throws Exception {
         var request = new UpdateSettingsRequest(sourceIndex).settings(
             Settings.builder().put(LifecycleSettings.LIFECYCLE_NAME, POLICY_NAME)
         );
@@ -231,7 +197,6 @@ private void startDownsampleTaskViaIlm(
             var getSettingsResponse = client().admin().indices().getSettings(new GetSettingsRequest().indices(targetIndex)).actionGet();
             assertThat(getSettingsResponse.getSetting(targetIndex, IndexMetadata.INDEX_DOWNSAMPLE_STATUS.getKey()), equalTo("success"));
         }, 60, TimeUnit.SECONDS);
-        disruptionEnd.await();
     }
 
     private void assertTargetIndex(final InternalTestCluster cluster, final String targetIndex, int indexedDocs) {
@@ -294,53 +259,4 @@ private String randomDateForRange(long start, long end) {
     public interface SourceSupplier {
         XContentBuilder get() throws IOException;
     }
-
-    interface DisruptionListener {
-        void disruptionStart();
-
-        void disruptionEnd();
-    }
-
-    private class Disruptor implements Runnable {
-        final InternalTestCluster cluster;
-        private final String sourceIndex;
-        private final DisruptionListener listener;
-        private final String clientNode;
-        private final Consumer<String> disruption;
-
-        private Disruptor(
-            final InternalTestCluster cluster,
-            final String sourceIndex,
-            final DisruptionListener listener,
-            final String clientNode,
-            final Consumer<String> disruption
-        ) {
-            this.cluster = cluster;
-            this.sourceIndex = sourceIndex;
-            this.listener = listener;
-            this.clientNode = clientNode;
-            this.disruption = disruption;
-        }
-
-        @Override
-        public void run() {
-            listener.disruptionStart();
-            try {
-                final String candidateNode = safeExecute(
-                    cluster.client(clientNode),
-                    TransportClusterSearchShardsAction.TYPE,
-                    new ClusterSearchShardsRequest(TEST_REQUEST_TIMEOUT, sourceIndex)
-                ).getNodes()[0].getName();
-                logger.info("Candidate node [" + candidateNode + "]");
-                disruption.accept(candidateNode);
-                ensureGreen(sourceIndex);
-                ensureStableCluster(cluster.numDataAndMasterNodes(), clientNode);
-
-            } catch (Exception e) {
-                logger.error("Ignoring Error while injecting disruption [" + e.getMessage() + "]");
-            } finally {
-                listener.disruptionEnd();
-            }
-        }
-    }
 }