Refactoring for Singleton pattern

GoogleCloudDataproc · Jul 25, 2024 · 86014d6 · 86014d6
1 parent 7d2a507
commit 86014d6
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Showing 2 changed files with 23 additions and 12 deletions.
diff --git a/gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageEventSubscriber.java b/gcs/src/main/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageEventSubscriber.java
@@ -18,26 +18,40 @@
 
 import com.google.api.client.googleapis.json.GoogleJsonResponseException;
 import com.google.cloud.hadoop.util.GcsRequestExecutionEvent;
+import com.google.common.annotations.VisibleForTesting;
 import com.google.common.eventbus.Subscribe;
+import com.google.common.flogger.GoogleLogger;
 import io.grpc.Status;
 import java.io.IOException;
 import javax.annotation.Nonnull;
 
 /* Stores the subscriber methods corresponding to GoogleCloudStorageEventBus */
 public class GoogleCloudStorageEventSubscriber {
+  private static final GoogleLogger logger = GoogleLogger.forEnclosingClass();
   private static GhfsStorageStatistics storageStatistics;
   private static GoogleCloudStorageEventSubscriber INSTANCE = null;
 
-  public GoogleCloudStorageEventSubscriber(@Nonnull GhfsStorageStatistics storageStatistics) {
+  private GoogleCloudStorageEventSubscriber(@Nonnull GhfsStorageStatistics storageStatistics) {
     this.storageStatistics = storageStatistics;
   }
 
-  public static GoogleCloudStorageEventSubscriber getInstance(
+  /*
+   * Singleton class such that registration of subscriber methods is only once.
+   * */
+  public static synchronized GoogleCloudStorageEventSubscriber getInstance(
       @Nonnull GhfsStorageStatistics storageStatistics) {
-    if (INSTANCE == null) INSTANCE = new GoogleCloudStorageEventSubscriber(storageStatistics);
+    if (INSTANCE == null) {
+      logger.atFiner().log("Subscriber class invoked for first time");
+      INSTANCE = new GoogleCloudStorageEventSubscriber(storageStatistics);
+    }
     return INSTANCE;
   }
 
+  @VisibleForTesting
+  protected static void reset() {
+    INSTANCE = null;
+  }
+
   /**
    * Updating the required gcs specific statistics based on GoogleJsonResponseException.
    *

diff --git a/gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageStatisticsTest.java b/gcs/src/test/java/com/google/cloud/hadoop/fs/gcs/GoogleCloudStorageStatisticsTest.java
@@ -50,18 +50,17 @@ public class GoogleCloudStorageStatisticsTest {
   private static final GoogleLogger logger = GoogleLogger.forEnclosingClass();
   private GhfsStorageStatistics storageStatistics = new GhfsStorageStatistics();
   protected GoogleCloudStorageEventSubscriber subscriber =
-      new GoogleCloudStorageEventSubscriber(storageStatistics);
+      GoogleCloudStorageEventSubscriber.getInstance(storageStatistics);
 
   @Before
   public void setUp() throws Exception {
-    GoogleCloudStorageEventBus.register(
-        GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
+    GoogleCloudStorageEventBus.register(subscriber);
   }
 
   @After
   public void cleanup() throws Exception {
-    GoogleCloudStorageEventBus.unregister(
-        GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
+    GoogleCloudStorageEventBus.unregister(subscriber);
+    GoogleCloudStorageEventSubscriber.reset();
   }
 
   private void verifyStatistics(GhfsStorageStatistics expectedStats) {
@@ -83,10 +82,8 @@ private void verifyStatistics(GhfsStorageStatistics expectedStats) {
 
   @Test
   public void test_multiple_register_of_statistics() throws Exception {
-    GoogleCloudStorageEventBus.register(
-        GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
-    GoogleCloudStorageEventBus.register(
-        GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
+    GoogleCloudStorageEventBus.register(subscriber);
+    GoogleCloudStorageEventBus.register(subscriber);
     GoogleCloudStorageEventBus.register(
         GoogleCloudStorageEventSubscriber.getInstance(storageStatistics));
     GoogleCloudStorageEventBus.register(