code: public WorkerHeartbeat readWorkerHeartbeat(Map conf, String workerId) throws Exception {
          try {
              LocalState ls = StormConfig.worker_state(conf, workerId);
              return (WorkerHeartbeat) ls.get(Common.LS_WORKER_HEARTBEAT);
          } catch (Exception e) {
              LOG.error("Failed to get heartbeat for worker:{}", workerId, e);
              return null;
          }
      }
docs: get worker heartbeat by workerId
  
  @param conf     conf
  @param workerId worker id
  @return WorkerHeartbeat