cherry pick GoogleCloudDataproc#1227

gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageEventSubscriber.java

@@ -28,17 +28,19 @@
 
 /* Stores the subscriber methods corresponding to GoogleCloudStorageEventBus */
 public class GoogleCloudStorageEventSubscriber {
+  private static final GoogleLogger logger = GoogleLogger.forEnclosingClass();
   private static GhfsGlobalStorageStatistics storageStatistics;
+  private static GoogleCloudStorageEventSubscriber INSTANCE = null;
 
-  public GoogleCloudStorageEventSubscriber(GhfsGlobalStorageStatistics storageStatistics) {
+  private GoogleCloudStorageEventSubscriber(GhfsGlobalStorageStatistics storageStatistics) {
     this.storageStatistics = storageStatistics;
   }
 
   /*
    * Singleton class such that registration of subscriber methods is only once.
    * */
   public static synchronized GoogleCloudStorageEventSubscriber getInstance(
-      @Nonnull GhfsStorageStatistics storageStatistics) {
+      @Nonnull GhfsGlobalStorageStatistics storageStatistics) {
     if (INSTANCE == null) {
       logger.atFiner().log("Subscriber class invoked for first time");
       INSTANCE = new GoogleCloudStorageEventSubscriber(storageStatistics);

gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GoogleHadoopFileSystem.java

@@ -250,7 +250,7 @@ public GoogleHadoopFileSystem() {
     }
 
     GoogleCloudStorageEventBus.register(
-        new GoogleCloudStorageEventSubscriber(globalStorageStatistics));
+        GoogleCloudStorageEventSubscriber.getInstance(globalStorageStatistics));
   }
 
   /**

gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageStatisticsTest.java

@@ -89,7 +89,7 @@ public void test_multiple_register_of_statistics() throws Exception {
         GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
 
     GoogleCloudStorageEventBus.onGcsRequest(new GcsRequestExecutionEvent());
-    GhfsStorageStatistics verifyCounterStats = new GhfsStorageStatistics();
+    GhfsGlobalStorageStatistics verifyCounterStats = new GhfsGlobalStorageStatistics();
     verifyCounterStats.incrementCounter(GCS_API_REQUEST_COUNT, 1);
     verifyStatistics(verifyCounterStats);
   }