code: private boolean addRequestToCheckForTimeouts(final Request<Object> request) {
  
          String key = Str.add("" + request.id(), "|", request.returnAddress());
          this.outstandingRequestMap.put(key, request);
  
          return outstandingRequestMap.size() < numberOfOutstandingRequests;
      }
docs: Add a request to the timeout queue. Server checks for timeouts when it is idle or when
  the max outstanding outstandingRequests is met.
  
  @param request request.