事件：'online'

【Event: 'online'】

• worker <cluster.Worker>

在派生一个新工作进程后，该工作进程应发送在线消息。
当主进程收到在线消息时，它将触发此事件。
'fork' 和 'online' 的区别在于，'fork' 在主进程派生工作进程时触发，而 'online' 在工作进程运行时触发。

【After forking a new worker, the worker should respond with an online message. When the primary receives an online message it will emit this event. The difference between 'fork' and 'online' is that fork is emitted when the primary forks a worker, and 'online' is emitted when the worker is running.】

cluster.on('online', (worker) => {
  console.log('Yay, the worker responded after it was forked');
}); 拷贝