====== PM2 ======

Production process manager for Node.js apps with a built-in load balancer. http://pm2.io/

===== Usage =====

Start 2 instances of application in cluster mode:

  pm2 start -i 2 --name [name] bin/www

Set pm2 start on boot:

  pm2 startup
  
Save pm2 current process list:

  pm2 save
  
Remove init script:

  pm2 unstartup [systemv|systemd]

Manually Restore Processes:

  pm2 resurrect

===== gracefulReload =====

==== stop ====

拦截 **SIGINT** 信号，并关闭所有资源，然后退出。

<code javascript>
process.on('SIGINT', function () {
  process.exit(0)
})
</code>

==== start ====

配置 PM2 启动参数，添加 ''--wait-ready'' ，然后在应用成功监听端口，添加

<code javascript>
process.send('ready')
</code>

==== 信号处理流程 ====

当一个进程被停止或者重启时，发送信号的顺序如下：

  - **SIGINT** 信号发送至进程，可在此拦截并退出进程；
  - 如果 [[http://pm2.keymetrics.io/docs/usage/signals-clean-restart/#customize-exit-delay|1.6s]] 后进程还未退出，则发送 **SIGKILL** 信号强制其退出。

===== Configuration =====

A PM2 configuration sample:

<code json pm2.json>
{
  "name": "<%= appname %>",
  "script": "./server/index.js",
  "instances": 2,
  "exec_mode" : "cluster",
  "wait-ready": true,
  "cwd": "."
}
</code>

Run ''pm2 start pm2.json''