Change Remote state read thread pool to Fixed type (#16850)

* Change Remote state read thread pool to Fixed type

Signed-off-by: Sooraj Sinha <soosinha@amazon.com>

Author: soosinha

server/src/main/java/org/opensearch/action/support/clustermanager/TransportClusterManagerNodeAction.java

@@ -430,6 +430,13 @@ private ClusterState getStateFromLocalNode(GetTermVersionResponse termVersionRes
 
             if (remoteClusterStateService != null && termVersionResponse.isStatePresentInRemote()) {
                 try {
+                    logger.info(
+                        () -> new ParameterizedMessage(
+                            "Term version checker downloading full cluster state for term {}, version {}",
+                            termVersion.getTerm(),
+                            termVersion.getVersion()
+                        )
+                    );
                     ClusterStateTermVersion clusterStateTermVersion = termVersionResponse.getClusterStateTermVersion();
                     Optional<ClusterMetadataManifest> clusterMetadataManifest = remoteClusterStateService
                         .getClusterMetadataManifestByTermVersion(
@@ -454,7 +461,7 @@ private ClusterState getStateFromLocalNode(GetTermVersionResponse termVersionRes
                         return clusterStateFromRemote;
                     }
                 } catch (Exception e) {
-                    logger.trace("Error while fetching from remote cluster state", e);
+                    logger.error("Error while fetching from remote cluster state", e);
                 }
             }
             return null;

server/src/main/java/org/opensearch/cluster/coordination/PublicationTransportHandler.java

@@ -258,7 +258,7 @@ PublishWithJoinResponse handleIncomingRemotePublishRequest(RemotePublishRequest
             }
 
             if (applyFullState == true) {
-                logger.debug(
+                logger.info(
                     () -> new ParameterizedMessage(
                         "Downloading full cluster state for term {}, version {}, stateUUID {}",
                         manifest.getClusterTerm(),

server/src/main/java/org/opensearch/gateway/remote/RemoteClusterStateService.java

@@ -1494,8 +1494,22 @@ public ClusterState getClusterStateForManifest(
         try {
             ClusterState stateFromCache = remoteClusterStateCache.getState(clusterName, manifest);
             if (stateFromCache != null) {
+                logger.trace(
+                    () -> new ParameterizedMessage(
+                        "Found cluster state in cache for term {} and version {}",
+                        manifest.getClusterTerm(),
+                        manifest.getStateVersion()
+                    )
+                );
                 return stateFromCache;
             }
+            logger.info(
+                () -> new ParameterizedMessage(
+                    "Cluster state not found in cache for term {} and version {}",
+                    manifest.getClusterTerm(),
+                    manifest.getStateVersion()
+                )
+            );
 
             final ClusterState clusterState;
             final long startTimeNanos = relativeTimeNanosSupplier.getAsLong();

server/src/main/java/org/opensearch/threadpool/ThreadPool.java

@@ -198,7 +198,7 @@ public static ThreadPoolType fromType(String type) {
         map.put(Names.REMOTE_PURGE, ThreadPoolType.SCALING);
         map.put(Names.REMOTE_REFRESH_RETRY, ThreadPoolType.SCALING);
         map.put(Names.REMOTE_RECOVERY, ThreadPoolType.SCALING);
-        map.put(Names.REMOTE_STATE_READ, ThreadPoolType.SCALING);
+        map.put(Names.REMOTE_STATE_READ, ThreadPoolType.FIXED);
         map.put(Names.INDEX_SEARCHER, ThreadPoolType.RESIZABLE);
         map.put(Names.REMOTE_STATE_CHECKSUM, ThreadPoolType.FIXED);
         THREAD_POOL_TYPES = Collections.unmodifiableMap(map);
@@ -306,7 +306,7 @@ public ThreadPool(
         );
         builders.put(
             Names.REMOTE_STATE_READ,
-            new ScalingExecutorBuilder(Names.REMOTE_STATE_READ, 1, boundedBy(4 * allocatedProcessors, 4, 32), TimeValue.timeValueMinutes(5))
+            new FixedExecutorBuilder(settings, Names.REMOTE_STATE_READ, boundedBy(4 * allocatedProcessors, 4, 32), 120000)
         );
         builders.put(
             Names.INDEX_SEARCHER,

server/src/test/java/org/opensearch/gateway/remote/RemoteClusterStateServiceTests.java

@@ -2354,6 +2354,14 @@ public void testReadLatestClusterStateFromCache() throws IOException {
             .getState(clusterState.getClusterName().value(), expectedManifest);
         assertEquals(stateFromCache.getMetadata(), state.getMetadata());
 
+        ClusterState stateFromCache2 = remoteClusterStateService.getClusterStateForManifest(
+            clusterState.getClusterName().value(),
+            expectedManifest,
+            "nodeA",
+            true
+        );
+        assertEquals(stateFromCache2.getMetadata(), state.getMetadata());
+
         final ClusterMetadataManifest notExistMetadata = ClusterMetadataManifest.builder()
             .indices(List.of())
             .clusterTerm(1L)

server/src/test/java/org/opensearch/threadpool/ScalingThreadPoolTests.java

@@ -156,7 +156,6 @@ private int expectedSize(final String threadPoolName, final int numberOfProcesso
         sizes.put(ThreadPool.Names.REMOTE_PURGE, ThreadPool::halfAllocatedProcessors);
         sizes.put(ThreadPool.Names.REMOTE_REFRESH_RETRY, ThreadPool::halfAllocatedProcessors);
         sizes.put(ThreadPool.Names.REMOTE_RECOVERY, ThreadPool::twiceAllocatedProcessors);
-        sizes.put(ThreadPool.Names.REMOTE_STATE_READ, n -> ThreadPool.boundedBy(4 * n, 4, 32));
         return sizes.get(threadPoolName).apply(numberOfProcessors);
     }