Improved logging around remote cluster state

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

@@ -243,7 +243,7 @@ public ClusterMetadataManifest writeFullMetadata(ClusterState clusterState, Stri
         } else {
             // todo change to debug
             logger.info(
-                "writing cluster state took [{}ms]; " + "wrote full state with [{}] indices",
+                "writing cluster state took [{}ms]; " + "wrote full state with [{}] indices and global metadata",
                 durationMillis,
                 allUploadedIndexMetadata.size()
             );
@@ -282,6 +282,7 @@ public ClusterMetadataManifest writeIncrementalMetadata(
         if (updateGlobalMetadata || previousManifest.getGlobalMetadataFileName() == null) {
             globalMetadataFile = writeGlobalMetadata(clusterState);
         } else {
+            logger.debug("Global metadata has not updated in cluster state, skipping upload of it");
             globalMetadataFile = previousManifest.getGlobalMetadataFileName();
         }
 
@@ -337,18 +338,22 @@ public ClusterMetadataManifest writeIncrementalMetadata(
         if (durationMillis >= slowWriteLoggingThreshold.getMillis()) {
             logger.warn(
                 "writing cluster state took [{}ms] which is above the warn threshold of [{}]; "
-                    + "wrote  metadata for [{}] indices and skipped [{}] unchanged indices",
+                    + "wrote  metadata for [{}] indices and skipped [{}] unchanged indices, global metadata updated : [{}]",
                 durationMillis,
                 slowWriteLoggingThreshold,
                 numIndicesUpdated,
-                numIndicesUnchanged
+                numIndicesUnchanged,
+                updateGlobalMetadata
             );
         } else {
-            logger.trace(
-                "writing cluster state took [{}ms]; " + "wrote metadata for [{}] indices and skipped [{}] unchanged indices",
+            logger.info(
+                "writing cluster state for version [{}] took [{}ms]; "
+                    + "wrote metadata for [{}] indices and skipped [{}] unchanged indices, global metadata updated : [{}]",
+                manifest.getStateVersion(),
                 durationMillis,
                 numIndicesUpdated,
-                numIndicesUnchanged
+                numIndicesUnchanged,
+                updateGlobalMetadata
             );
         }
         return manifest;
@@ -476,6 +481,7 @@ private List<UploadedIndexMetadata> writeIndexMetadataParallel(ClusterState clus
                 )
             );
             exceptionList.forEach(exception::addSuppressed);
+            logger.error("Exception in transferring index metadata to remote store", exception);
             throw exception;
         }
         return result;
@@ -596,6 +602,11 @@ private void writeMetadataManifest(String clusterName, String clusterUUID, Clust
             blobStoreRepository.getCompressor(),
             FORMAT_PARAMS
         );
+        logger.debug(
+            "Metadata manifest file [{}] written during [{}] phase. ",
+            fileName,
+            uploadManifest.isCommitted() ? "commit" : "publish"
+        );
     }
 
     private String fetchPreviousClusterUUID(String clusterName, String clusterUUID) {
@@ -903,6 +914,7 @@ private List<String> createClusterChain(final Map<String, ClusterMetadataManifes
             // Getting the previous cluster UUID of a cluster UUID from the clusterUUID Graph
             currentUUID = clusterUUIDGraph.get(currentUUID);
         }
+        logger.debug("Known UUIDs found in remote store : [{}]", validChain);
         return validChain;
     }
 
@@ -1217,7 +1229,7 @@ private void deleteClusterMetadata(
             });
 
             if (staleManifestPaths.isEmpty()) {
-                logger.info("No stale Remote Cluster Metadata files found");
+                logger.debug("No stale Remote Cluster Metadata files found");
                 return;
             }
 

server/src/main/java/org/opensearch/index/recovery/RemoteStoreRestoreService.java

@@ -149,6 +149,7 @@ public RemoteRestoreResult restore(
                 if (currentState.metadata().clusterUUID().equals(restoreClusterUUID)) {
                     throw new IllegalArgumentException("clusterUUID to restore from should be different from current cluster UUID");
                 }
+                logger.info("Restoring cluster state from remote store from cluster UUID : [{}]", restoreClusterUUID);
                 remoteMetadata = remoteClusterStateService.getLatestMetadata(currentState.getClusterName().value(), restoreClusterUUID);
                 remoteMetadata.getIndices().values().forEach(indexMetadata -> {
                     indexMetadataMap.put(indexMetadata.getIndex().getName(), new Tuple<>(true, indexMetadata));