Decrease merge task checker periodicity in tests (#130082) (#130119)

Decreases the periodicity (from 5s to 100ms), for some tests, with which merge tasks are checked if there's sufficient available disk space to execute or if they've been aborted since enqueued for execution.

Fixes #130044

x-pack/plugin/autoscaling/src/internalClusterTest/java/org/elasticsearch/xpack/autoscaling/storage/AutoscalingStorageIntegTestCase.java

@@ -15,6 +15,7 @@ import org.elasticsearch.cluster.routing.allocation.DiskThresholdSettings;
 import org.elasticsearch.cluster.routing.allocation.decider.DiskThresholdDecider;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.datastreams.DataStreamsPlugin;
+import org.elasticsearch.index.engine.ThreadPoolMergeExecutorService;
 import org.elasticsearch.plugins.Plugin;
 import org.elasticsearch.xpack.autoscaling.LocalStateAutoscaling;
 import org.elasticsearch.xpack.autoscaling.action.GetAutoscalingCapacityAction;
@@ -41,7 +42,10 @@ public abstract class AutoscalingStorageIntegTestCase extends DiskUsageIntegTest
             .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_HIGH_DISK_WATERMARK_SETTING.getKey(), HIGH_WATERMARK_BYTES + "b")
             .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_DISK_FLOOD_STAGE_WATERMARK_SETTING.getKey(), "0b")
             .put(DiskThresholdSettings.CLUSTER_ROUTING_ALLOCATION_REROUTE_INTERVAL_SETTING.getKey(), "0ms")
-            .put(DiskThresholdDecider.ENABLE_FOR_SINGLE_DATA_NODE.getKey(), "true");
+            .put(DiskThresholdDecider.ENABLE_FOR_SINGLE_DATA_NODE.getKey(), "true")
+            // the periodicity for the checker for the available disk space as well as the merge tasks' aborting status
+            // the default of 5 seconds might timeout some tests
+            .put(ThreadPoolMergeExecutorService.INDICES_MERGE_DISK_CHECK_INTERVAL_SETTING.getKey(), "100ms");
         return builder.build();
     }