Disable rebalancing in DataStreamLifecycleDownsampleDisruptionIT

We were seeing test failures here due by the relocation of some shards
taking more than 30 seconds. This happened after downsampling had
already completed, causing the `ensureGreen` at the end of the test to
time out.

The Distributed Coordination team suggested disabling shard rebalancing
in this test (among other things, which have already been implemented).

Fixes #131394

Author: nielsbauman

muted-tests.yml

@@ -390,9 +390,6 @@ tests:
 - class: org.elasticsearch.packaging.test.DockerTests
   method: test130JavaHasCorrectOwnership
   issue: https://github.com/elastic/elasticsearch/issues/131369
-- class: org.elasticsearch.xpack.downsample.DataStreamLifecycleDownsampleDisruptionIT
-  method: testDataStreamLifecycleDownsampleRollingRestart
-  issue: https://github.com/elastic/elasticsearch/issues/131394
 - class: org.elasticsearch.packaging.test.DockerTests
   method: test072RunEsAsDifferentUserAndGroup
   issue: https://github.com/elastic/elasticsearch/issues/131412

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

@@ -14,6 +14,7 @@
 import org.elasticsearch.action.downsample.DownsampleConfig;
 import org.elasticsearch.cluster.metadata.DataStreamLifecycle;
 import org.elasticsearch.cluster.metadata.IndexMetadata;
+import org.elasticsearch.cluster.routing.allocation.decider.EnableAllocationDecider;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.core.TimeValue;
@@ -34,9 +35,12 @@ public class DataStreamLifecycleDownsampleDisruptionIT extends DownsamplingInteg
 
     @Override
     protected Settings nodeSettings(int nodeOrdinal, Settings otherSettings) {
-        Settings.Builder settings = Settings.builder().put(super.nodeSettings(nodeOrdinal, otherSettings));
-        settings.put(DataStreamLifecycleService.DATA_STREAM_LIFECYCLE_POLL_INTERVAL, "1s");
-        return settings.build();
+        return Settings.builder()
+            .put(super.nodeSettings(nodeOrdinal, otherSettings))
+            .put(DataStreamLifecycleService.DATA_STREAM_LIFECYCLE_POLL_INTERVAL, "1s")
+            // We disable shard rebalancing to avoid shard relocations timing out the `ensureGreen` call at the end of the test. See #131394
+            .put(EnableAllocationDecider.CLUSTER_ROUTING_REBALANCE_ENABLE_SETTING.getKey(), "none")
+            .build();
     }
 
     public void testDataStreamLifecycleDownsampleRollingRestart() throws Exception {
@@ -85,7 +89,7 @@ public void testDataStreamLifecycleDownsampleRollingRestart() throws Exception {
 
         ensureDownsamplingStatus(targetIndex, IndexMetadata.DownsampleTaskStatus.SUCCESS, TimeValue.timeValueSeconds(120));
         ensureGreen(targetIndex);
-        logger.info("-> Relocation has finished");
+        logger.info("-> Index is green and downsampling completed successfully.");
     }
 
     private void ensureDownsamplingStatus(String downsampledIndex, IndexMetadata.DownsampleTaskStatus expectedStatus, TimeValue timeout) {