message: Wait before retrying sending updates to dispatcher.
  Otherwise we retry in a tight loop.
diff: @@ -238,6 +238,7 @@ void DataServiceWorkerImpl::HeartbeatThread() {
  Status s = SendTaskUpdate();
  if (!s.ok()) {
  LOG(WARNING) << "Failed to send task updates to dispatcher: " << s;
  + Env::Default()->SleepForMicroseconds(kHeartbeatIntervalMicros);
  }
  }
  }
  