void shutdown() throws InterruptedException {
    running = false;
    lock.lock();
    try {
      pauseCondition.signal();
    } finally {
      lock.unlock();
    }
    if (networkClient != null) {
      networkClient.close();
    }
    shutdownLatch.await();
  }
Get the keys corresponding to the missing messages in the local store
@return store keys missing in the local store
ambry-replication/src/main/java/com/github/ambry/replication/ReplicaThread.java