public void cleanUp() {
    regionToDispatchedKeysMap.clear();
    removalThread.shutdown();
    cleanupConflationThreadPool(sender);
  }
This method does the cleanup of any threads, sockets, connection that are held up by the queue.
Note that this cleanup doesn't clean the data held by the queue.
geode-core/src/main/java/org/apache/geode/internal/cache/wan/parallel/ParallelGatewaySenderQueue.java