Upstart resulting in two processes - why?

Question

I am using upstart to start a NodeJS process which is using NVM (node version manager).

The upstart command is like this:

description "Service to start node app"
author "Barry Steyn"

setuid devuser
setgid devuser

env DIR=/home/devuser/nodejs/authentication

script
    chdir $DIR
    exec bash -c 'source /home/devuser/nvm/nvm.sh && node app'
end script

respawn

This starts node fine, but when I do a ps wax | grep node, I get these two processes:

 4284 ?        Ss     0:00 bash -c source /home/devuser/nvm/nvm.sh && node app
 4316 ?        Sl     1:09 node app

Why do I get two processes? Is this in anyway less efficient?

Answer 1

The first process is the instance of bash that started node.js. The second process is the actual node.js process.

The bash process is using a few resources (mostly memory), but is just sitting around waiting on node.js to exit.

I believe you can get rid of the extra bash by doing this:

Replace:

exec bash -c 'source /home/devuser/nvm/nvm.sh && node app'

With:

exec bash -c 'source /home/devuser/nvm/nvm.sh && exec node app'

This gets the bash process to exec node.js without using a fork first. Mostly that means it won't wait around for node.js to exit.