public int getDurableClientHAQueueSize(String durableClientId) {
    CacheClientProxy ccp = getClientProxy(durableClientId);
    if (ccp == null) {
      return -1;
    }
    return ccp.getQueueSizeStat();
  }
Returns (possibly stale) map of queue sizes for all clients notified by this server.

@return map with CacheClientProxy as key, and Integer as a value
geode-core/src/main/java/org/apache/geode/internal/cache/tier/sockets/CacheClientNotifier.java