@Override
  protected void stitchBlob(BlobProperties blobProperties, byte[] userMetadata, List<ChunkInfo> chunksToStitch,
      FutureResult<String> futureResult, Callback<String> callback, QuotaChargeCallback quotaChargeCallback) {
    RouterException routerException = new RouterException("Illegal attempt to stitch blob through BackgroundDeleter",
        RouterErrorCode.UnexpectedInternalError);
    routerMetrics.operationDequeuingRate.mark();
    routerMetrics.onPutBlobError(routerException, blobProperties != null && blobProperties.isEncrypted(), true);
    nonBlockingRouter.completeOperation(futureResult, callback, null, routerException);
  }
Stitch operations are disallowed in the BackgroundDeleter.
ambry-router/src/main/java/com/github/ambry/router/OperationController.java