private boolean isRetriable(Throwable throwable) {
      return throwable instanceof RouterException && retriableRouterError.contains(
          ((RouterException) throwable).getErrorCode());
    }
@param throwable the error to check.
@return true if the router error is retriable.
ambry-frontend/src/main/java/com/github/ambry/frontend/NamedBlobPutHandler.java