docs: public void requestDone() {
          currentRequest = null;
  
          if (anyAreSet(state, CLOSE_REQ)) {
              safeClose(connection);
          } else if (anyAreSet(state, UPGRADE_REQUESTED)) {
              safeClose(connection); //we don't support upgrade, just close the connection to be safe
              return;
          }
  
          AjpClientExchange next = pendingQueue.poll();
  
          if (next != null) {
              initiateRequest(next);
          }
      }