public int secondaryEventQueueSize() {
    if (queue == null) {
      return 0;
    }

    // if parallel, get both primary and secondary queues' size, then substract primary queue's size
    if (queue instanceof ConcurrentParallelGatewaySenderQueue) {
      final ConcurrentParallelGatewaySenderQueue concurrentParallelGatewaySenderQueue =
          (ConcurrentParallelGatewaySenderQueue) queue;
      return concurrentParallelGatewaySenderQueue.localSize(true)
          - concurrentParallelGatewaySenderQueue.localSize(false);
    }
    return queue.size();
  }
Returns the current batch id to be used to identify the next batch.

@return the current batch id to be used to identify the next batch
geode-core/src/main/java/org/apache/geode/internal/cache/wan/AbstractGatewaySenderEventProcessor.java