private void dropAllPipeTasksInternal() {
    for (final PipeMeta pipeMeta : pipeMetaKeeper.getPipeMetaList()) {
      try {
        dropPipe(
            pipeMeta.getStaticMeta().getPipeName(), pipeMeta.getStaticMeta().getCreationTime());
      } catch (final Exception e) {
        LOGGER.warn(
            "Failed to drop pipe {} with creation time {}",
            pipeMeta.getStaticMeta().getPipeName(),
            pipeMeta.getStaticMeta().getCreationTime(),
            e);
      }
    }
  }
State transition diagram of a pipe task:

<p><code>
|----------------|                     |---------| --> stop  pipe --> |---------|                   |---------|
| initial status | --> create pipe --> | RUNNING |                    | STOPPED | --> drop pipe --> | DROPPED |
|----------------|                     |---------| <-- start pipe <-- |---------|                   |---------|
                                            |                                                            |
                                            | ----------------------> drop pipe -----------------------> |
</code>

<p>Other transitions are not allowed, will be ignored when received in the {@link PipeTaskAgent}.
iotdb-core/node-commons/src/main/java/org/apache/iotdb/commons/pipe/agent/task/PipeTaskAgent.java