schedule to run a cron only on one instance?

My question is how to use node-schedule to run a cron only on one instance out of two instances of node server. Currently it is running on both instances but I want it to be executed only on one instance. So How can you make a cluster run a task only once? Thanks in advance.

{
  "apps": [
    {
      "name": "Example",
      "script": "boot/app/app.js",
      "watch": false,
      "exec_mode": "cluster_mode",
      "instances": 2,
      "merge_logs": true,
      "cwd": "/srv/www.example.com/server",
      "env": {
        "NODE_ENV": "development",
        .......
    .......
      }
    }
  ]
}

---

You should use enviroment variables.

In your code you will check this env var:

if(process.env.WITH_SCHEDULE) {
    ...
}

When you start your instances, you will set WITH_SCHEDULE only for one instance.

Example pm2.json:

{
  "apps": [
    {
      "name": "Example",
      "script": "boot/app/app.js",
      "args": [],
      "error_file": "/srv/www.example.com/logs/error.log",
      "out_file": "/srv/www.example.com/logs/info.log",
      "ignore_watch": [
        "node_modules"
      ],
      "watch": false,
      "cwd": "/srv/www.example.com/server",
      "env": {
        "NODE_ENV": "production",
        "WITH_SCHEDULE": "1",
        "HOST": "127.0.0.1",
        "PORT": "9030"
      }
    },
    {
      "name": "Example",
      "script": "boot/app/app.js",
      "args": [],
      "error_file": "/srv/www.example.com/logs/error.log",
      "out_file": "/srv/www.example.com/logs/info.log",
      "ignore_watch": [
        "node_modules"
      ],
      "watch": false,
      "cwd": "/srv/www.example.com/server",
      "env": {
        "NODE_ENV": "production",
        "HOST": "127.0.0.1",
        "PORT": "9030"
      }
    }
  ]
}

---

You can use an environment variable provided by PM2 itself called NODE_APP_INSTANCE which requires PM2 2.5.

NODE_APP_INSTANCE environment variable is used to determine difference between process, for example you may want to run a cronjob only on one process, you can just check if process.env.NODE_APP_INSTANCE === 0, Since two processes can never have the same number.

More Info on PM2 official doc here.

链接地址: http://www.djcxy.com/p/37034.html

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