Address comments

Author: Sophie Guo

ambry-commons/src/main/java/com/github/ambry/commons/RetainingAsyncWritableChannel.java

@@ -170,6 +170,26 @@ public ByteBuf consumeContentAsByteBuf() {
     }
   }
 
+  /**
+   * Consume the collected content buffer and return its contents as a byte array.
+   *
+   * @return a byte array containing all data received up to this point.
+   * @throws IllegalStateException if the content has already been consumed or the channel was closed.
+   */
+  public byte[] consumeContentAsBytes() {
+    ByteBuf buf = null;
+    try {
+      buf = consumeContentAsByteBuf();
+      byte[] data = new byte[buf.readableBytes()];
+      buf.readBytes(data);
+      return data;
+    } finally {
+      if (buf != null) {
+        buf.release();
+      }
+    }
+  }
+
   /**
    * @return an {@link InputStream} that contains the data from the chunks received up to this point in time.
    */

ambry-frontend/src/main/java/com/github/ambry/frontend/s3/S3BatchDeleteHandler.java

@@ -187,19 +187,12 @@ private Callback<Long> parseRequestBodyAndDeleteCallback(RetainingAsyncWritableC
    */
   public S3MessagePayload.S3BatchDeleteObjects deserializeRequest(RetainingAsyncWritableChannel channel)
       throws RestServiceException {
-    ByteBuf byteBuffer = null;
     try {
-      byteBuffer = channel.consumeContentAsByteBuf();
-      byte[] byteArray = new byte[byteBuffer.readableBytes()];
-      byteBuffer.readBytes(byteArray);
+      byte[] byteArray = channel.consumeContentAsBytes();
       return new XmlMapper().readValue(byteArray, S3MessagePayload.S3BatchDeleteObjects.class);
     } catch (Exception e) {
       logger.trace("s3batchdelete failed to deserialize request");
       throw new RestServiceException("failed to deserialize", e, RestServiceErrorCode.BadRequest);
-    } finally {
-      if (byteBuffer != null) {
-        byteBuffer.release();
-      }
     }
   }
 }

ambry-frontend/src/test/java/com/github/ambry/frontend/S3BatchDeleteHandlerTest.java

@@ -144,12 +144,9 @@ public void deleteObjectTest() throws Exception {
   }
 
   @Test
-  public void testBufferReleaseInDeserializeRequest() throws Exception {
-    // Arrange
-    S3BatchDeleteHandler handler = new S3BatchDeleteHandler(null, null);
-    RetainingAsyncWritableChannel channel = mock(RetainingAsyncWritableChannel.class);
-    ByteBuf mockByteBuf = mock(ByteBuf.class);
-
+  public void testConsumeContentAsBytesReleasesBuffer() {
+    // Arrange: Create a ByteBuf with some data
+    ByteBuf testBuf = Unpooled.buffer();
     String validXml = "<?xml version=\"1.0\" encoding=\"UTF-8\"?>" +
         "<Delete xmlns=\"http://s3.amazonaws.com/doc/2006-03-01\">" +
         "<Object>" +
@@ -165,21 +162,22 @@ public void testBufferReleaseInDeserializeRequest() throws Exception {
         "<Key>key-success-2</Key>" +
         "</Object>" +
         "</Delete>";
-
     byte[] xmlBytes = validXml.getBytes();
+    testBuf.writeBytes(xmlBytes);
+    // Wrap the consumeContentAsByteBuf method to return the test buffer
+    RetainingAsyncWritableChannel channel = new RetainingAsyncWritableChannel() {
+      @Override
+      public ByteBuf consumeContentAsByteBuf() {
+        return testBuf;
+      }
+    };
 
-    when(channel.consumeContentAsByteBuf()).thenReturn(mockByteBuf);
-    when(mockByteBuf.readableBytes()).thenReturn(xmlBytes.length);
-    doAnswer(invocation -> {
-      byte[] buffer = invocation.getArgument(0);
-      System.arraycopy(xmlBytes, 0, buffer, 0, xmlBytes.length);
-      return null;
-    }).when(mockByteBuf).readBytes(Mockito.any(byte[].class));
-
-    S3MessagePayload.S3BatchDeleteObjects result = handler.deserializeRequest(channel);
+    // Act: Call the method
+    byte[] result = channel.consumeContentAsBytes();
 
-    assertNotNull(result);
-    verify(mockByteBuf, times(1)).release(); // Verify that release() was called
+    // Assert: Verify the buffer was released and the data matches
+    assertArrayEquals(xmlBytes, result);
+    assertEquals("Buffer should be released", 0, testBuf.refCnt());
   }
 
   @Test