more comments

Author: ywangd

modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3BlobStore.java

@@ -116,6 +116,7 @@ class S3BlobStore implements BlobStore {
         S3RepositoriesMetrics s3RepositoriesMetrics,
         BackoffPolicy retryThrottledDeleteBackoffPolicy
     ) {
+        // TODO: add a projectId field, maybe null for cluster level blobstore
         this.service = service;
         this.bigArrays = bigArrays;
         this.bucket = bucket;
@@ -311,6 +312,7 @@ public String toString() {
     }
 
     public AmazonS3Reference clientReference() {
+        // TODO: change to service.client(projectId, repositoryMetadata)
         return service.client(repositoryMetadata);
     }
 

modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3Repository.java

@@ -292,6 +292,7 @@ class S3Repository extends MeteredBlobStoreRepository {
             buildBasePath(metadata),
             buildLocation(metadata)
         );
+        // TODO: add a projectId field
         this.service = service;
         this.s3RepositoriesMetrics = s3RepositoriesMetrics;
         this.snapshotExecutor = threadPool().executor(ThreadPool.Names.SNAPSHOT);

modules/repository-s3/src/main/java/org/elasticsearch/repositories/s3/S3Service.java

@@ -168,15 +168,20 @@ public AmazonS3Reference client(RepositoryMetadata repositoryMetadata) {
     }
 
     /**
-     * Delegates to {@link #client(RepositoryMetadata)} if per-project client is disabled.
+     * Delegates to {@link #client(RepositoryMetadata)} when
+     * 1. per-project client is disabled
+     * 2. or when the blobstore is cluster level (projectId = null)
      * Otherwise, attempts to retrieve a per-project client by the project-id and repository metadata from the
-     * per-project client manager.
-     * Throws if project-id or the client does not exist. The client maybe initialized lazily.
+     * per-project client manager. Throws if project-id or the client does not exist. The client maybe initialized lazily.
      */
     public AmazonS3Reference client(ProjectId projectId, RepositoryMetadata repositoryMetadata) {
         if (perProjectClientManager == null) {
+            // Multi-Project is disabled and we have a single default project
             assert ProjectId.DEFAULT.equals(projectId) : projectId;
             return client(repositoryMetadata);
+        } else if (projectId == null) {
+            // Multi-Project is enabled and we are retrieving a client for the cluster level blobstore
+            return client(repositoryMetadata);
         } else {
             return perProjectClientManager.client(projectId, repositoryMetadata);
         }