code: function onUnexpected(worker, code, signal) {
      var exitCode = worker.process.exitCode;
      var err = new Error(util.format('worker:%s died unexpected (code: %s, signal: %s, exitedAfterDisconnect: %s, state: %s)',
        worker.process.pid, exitCode, signal, worker.exitedAfterDisconnect, worker.state));
      err.name = 'WorkerDiedUnexpectedError';
  
      debug('[%s] [cfork:master:%s] (total %d disconnect, %d unexpected exit) %s',
        Date(), process.pid, disconnectCount, unexpectedCount, err.stack);
    }
docs: unexpectedExit default handler