public static boolean isSourceExternal(int regionId) {
    // regionId that is less than 0 is a special value marking an external pipe source
    return regionId < 0;
  }
We use negative regionId to identify the external pipe source, which is not a consensus group
id. Then we can reuse the regionId to schedule the external pipe source and store the progress
information.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/pipe/agent/task/meta/PipeRuntimeMeta.java