Environment Variables

When starting a new process

PM2 will inject environment in this order when starting a new process :

• First the PM2 CLI will use its environment so the current environment of your shell will be injected.
• PM2 will then inject the environment that you can configure with the ecosystem file :

module.exports = { apps : [ { name: "myapp", script: "./app.js", watch: true, env: { "NODE_ENV": "development", } } ] } 

Here you can see that PM2 will override the current environment to add NODE_ENV=development. But you can also define different environments like this :

module.exports = { apps : [ { name: "myapp", script: "./app.js", watch: true, env: { "PORT": 3000, "NODE_ENV": "development" }, env_production: { "PORT": 80, "NODE_ENV": "production", } } ] } 

Here the default environment is in the env, but you can decide to use env_production by using pm2 start ecosystem.config.js --env production.

You can define as many environments as you like, just remember that you must pass the name of the environment (after env_) you want to use with --env.

Specific environment variables

NODE_APP_INSTANCE (PM2 2.5 minimum)

There is the NODE_APP_INSTANCE environment variable that is used to make a 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'. Two processes can never have the same number, its still true after pm2 restart and pm2 scale commands.

You may have problems with node-config with the NODE_APP_INSTANCE name, so you can rename it with instance_var options :

module.exports = { apps : [ { name: "myapp", script: "./app.js", watch: true, instance_var: 'INSTANCE_ID', env: { "PORT": 3000, "NODE_ENV": "development" } } ] } 

In this case the variable will have the same behavior but will be in process.env.INSTANCE_ID.

increment_var (PM2 2.5 minimum)

There is an option to ask PM2 to increment an environment variable for each instance launched, for example:

module.exports = { apps : [ { name: "myapp", script: "./app.js", instances: 2, exec_mode: "cluster", watch: true, increment_var : 'PORT', env: { "PORT": 3000, "NODE_ENV": "development" } } ] } 

In this example, if i run pm2 start ecosystem.config.js :

• PM2 will see that i want to increment the PORT variable for each instance
• It will see that i have defined the default to 3000
• The first instance will have process.env.PORT = 3000 and the second process.env.PORT = 3001

NOTE : It will increment also when scaling using pm2 scale myapp 4, both new instances will have 3002 and 3003 as PORT variable.