@Override
      public void onCompletion(final GetBlobResult result, final Exception exception) {
        getBlobCallbackCalled.countDown();
        AsyncWritableChannel asyncWritableChannel = new AsyncWritableChannel() {
          boolean open = true;

          @Override
          public Future<Long> write(ByteBuffer src, Callback<Long> callback) {
            throw new RuntimeException("This will be thrown when the channel is written to.");
          }

          @Override
          public boolean isOpen() {
            return open;
          }

          @Override
          public void close() throws IOException {
            open = false;
          }
        };
        result.getBlobDataChannel().readInto(asyncWritableChannel, null);
      }
Test the case where async write results in an exception. Read should be notified,
operation should get completed.
ambry-router/src/test/java/com/github/ambry/router/GetManagerTest.java