@Override
  public String toString() {
    return "SubscriptionPollRequest{requestType="
        + SubscriptionPollRequestType.valueOf(requestType).toString()
        + ", payload="
        + payload
        + ", timeoutMs="
        + timeoutMs
        + ", maxBytes="
        + maxBytes
        + "}";
  }
The maximum size, in bytes, for the response payload.
iotdb-client/service-rpc/src/main/java/org/apache/iotdb/rpc/subscription/payload/poll/SubscriptionPollRequest.java