Correct command for running node.js project with pm2 in ApplicationStart hook

Question

I want to set up ApplicationStart hook for node.js project where pm2 is used as a process manager in aws ec2 server.

I checked some tutorials and the shell script for ApplicationStart hook contains commands for running the project by using:

• node/npm
• pm2

for example in this tutorial, the shell script contains:

npm start
pm2 start npm --name "covidapp" -- start

in this tutorial, the shell script contains:

pm2 start npm --name "myApp"
node app.js > app.out.log 2> app.err.log < /dev/null &

Why we are running the project two times? Why we just don't use pm2?

Answer 1

I've deployed several apps on EC2 using PM2 and in my experience there should be no need (or benefit) to use node app.js, npm start or similar.

As you are probably already guessing, the whole point of PM2 is to run the process(es).

My recommendation would be to create a PM2 ecosystem configuration with all needed configurations, number of processes, ENV vars etc. I personally prefer this way even when running only one single node application on the server.

https://pm2.keymetrics.io/docs/usage/application-declaration/

And start the process(es) using the configuration, eg.:

pm2 start ecosystem.config.js

I also recommend using PM2 startup generator to make sure PM2 is started on server reboot: pm2 startup

https://pm2.keymetrics.io/docs/usage/startup/

Once you have the startup script generated. Start your processes using pm2 manually or by using a configuration file (see example above). Verify with pm2 status that all processes are running as expected and execute pm2 save to "snapshot" the current state. The saved state will now automatically respawn on reboot.