how to use debug with PM2?

[bi-kai]

how to use debug with PM2?
DEBUG=* pm2 start app.js
There is no debug logs.

[DanielHeckrath]

Isn't it possible to use the ecosystem.config.js to configure different environment variables when starting a process with PM2?
See https://github.com/Unitech/pm2/wiki/Applications-Declaration

Should be possible to include DEBUG=* in the env section of your desired process

[bi-kai]

That works, and there is another question, the debug logs are all in PM2's error log, not in out.log, do you know why?

[DanielHeckrath]

When you use debug on nodejs it writes to stderr by default (see node.js)

It is possible though to redirect the output of a logger to another stream https://github.com/visionmedia/debug/blob/master/examples/node/stdout.js

The pattern I'm usually using when working with debug is this:

const logFactory = require('debug');

module.exports = function log(namespace) {
    const debug = logFactory(namespace);

    const error = logFactory(namespace);
    error.log = function(...args) {
        console.error(...args);
    };

    return {
        debug,
        error,
    };
};

then I just require my new log factory in my modules like this

const log = require('log')('tag');

log.debug('this logs to stdout');
log.error('this logs to stderr');

Note that you have to rewrite the error.log part to something like this if ES6 spread syntax is not available in your environment

error.log = console.error.bind(console);

[bi-kai]

That's greet!