Fix get future exception message

samza-core/src/main/java/org/apache/samza/storage/blobstore/util/BlobStoreUtil.java

@@ -185,7 +185,7 @@ public CompletableFuture<SnapshotIndex> getSnapshotIndex(String blobId, Metadata
           .thenApplyAsync(f -> snapshotIndexSerde.fromBytes(indexBlobStream.toByteArray()), executor)
           .handle((snapshotIndex, ex) -> {
             if (ex != null) {
-              throw new SamzaException(String.format("Unable to deserialize SnapshotIndex bytes for blob ID: %s", blobId), ex);
+              throw new SamzaException(String.format("Unable to get SnapshotIndex blob. The blob ID is : %s", blobId), ex);
             }
             return snapshotIndex;
           });

samza-core/src/test/java/org/apache/samza/storage/blobstore/util/TestBlobStoreUtil.java

@@ -28,6 +28,7 @@
 import java.io.IOException;
 import java.io.InputStream;
 import java.io.OutputStream;
+import java.nio.charset.StandardCharsets;
 import java.nio.file.Files;
 import java.nio.file.Path;
 import java.nio.file.Paths;
@@ -50,6 +51,7 @@
 import java.util.concurrent.CompletionStage;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.TimeoutException;
 import java.util.zip.CRC32;
@@ -78,6 +80,7 @@
 import org.apache.samza.storage.blobstore.index.SnapshotMetadata;
 import org.apache.samza.util.FileUtil;
 import org.apache.samza.util.FutureUtil;
+import org.junit.Assert;
 import org.junit.Ignore;
 import org.junit.Test;
 import org.mockito.ArgumentCaptor;
@@ -920,6 +923,24 @@ public void testGetSSIThrowsExceptionOnSyncBlobStoreErrors() {
         checkpoint, storesToBackupOrRestore, false);
   }
 
+  @Test
+  public void testSerdeException() throws ExecutionException, InterruptedException {
+    final String blobId = "foo";
+
+    final BlobStoreManager testBlobStoreManager = new DeserTestBlobStoreManager();
+    final BlobStoreUtil util = new BlobStoreUtil(testBlobStoreManager, Executors.newSingleThreadExecutor(), blobStoreConfig, null, null);
+
+    final CompletableFuture<SnapshotIndex> future = util.getSnapshotIndex(blobId, mock(Metadata.class), true)
+        .handle((snapshotIndex, throwable) -> {
+          if (throwable != null) {
+            Assert.assertEquals(throwable.getMessage(), String.format("Unable to get SnapshotIndex blob. The blob ID is : %s", blobId));
+            Assert.assertEquals(throwable.getCause().getMessage(), "org.apache.samza.SamzaException: Exception in deserializing SnapshotIndex bytes foobar");
+          }
+          return snapshotIndex;
+        });
+    future.get();
+  }
+
   @Test
   public void testGetSSIThrowsExceptionIfAnyNonIgnoredAsyncBlobStoreErrors() {
     String store = "storeName1";
@@ -1045,4 +1066,57 @@ private CheckpointV2 createCheckpointV2(String stateBackendFactory, Map<String,
     factoryStoreSCMs.put(stateBackendFactory, storeSCMs);
     return new CheckpointV2(checkpointId, ImmutableMap.of(), factoryStoreSCMs);
   }
+
+  /**
+   * Test {@link BlobStoreManager} to be used to assert SnapshotIndex deserialization failure
+   * exception message.
+   * We write a dummy string's bytes to the OutputStream parameter of get method instead of a SnapshotIndex
+   * blob. The OutputStream is used by SnapshotIndexSerde which will fail during deserialization.
+   * */
+  private static class DeserTestBlobStoreManager extends TestBlobStoreManager {
+    @Override
+    public CompletionStage<Void> get(String id, OutputStream outputStream, Metadata metadata, boolean getDeletedBlob) {
+      final String randBlob = "foobar";
+      final byte[] byteArray = randBlob.getBytes(StandardCharsets.UTF_8);
+      try {
+        outputStream.write(byteArray);
+      } catch (IOException e) {
+        throw new RuntimeException(e);
+      }
+      return CompletableFuture.completedFuture(null);
+    }
+  }
+
+  /**
+   * Test BlobStoreManager for unit tests.
+   * */
+  private static class TestBlobStoreManager implements BlobStoreManager {
+    @Override
+    public void init() {
+    }
+
+    @Override
+    public CompletionStage<String> put(InputStream inputStream, Metadata metadata) {
+      return null;
+    }
+
+    @Override
+    public CompletionStage<Void> get(String id, OutputStream outputStream, Metadata metadata, boolean getDeletedBlob) {
+      return null;
+    }
+
+    @Override
+    public CompletionStage<Void> delete(String id, Metadata metadata) {
+      return null;
+    }
+
+    @Override
+    public CompletionStage<Void> removeTTL(String blobId, Metadata metadata) {
+      return null;
+    }
+
+    @Override
+    public void close() {
+    }
+  }
 }