What are the differences between the processes run by npm command:

Question

Recently I made a simple API server using node.js+express. And the script below is a part of my package.json file I use to run with npm commands.

"scripts": {
  ...
  "release": "cross-env NODE_ENV=production MODE=release node server/app.js",
}

After I starts the server with npm run release, I can see multiple processes such as below are running on my Linux server.

/bin/sh /api/node_modules/.bin/cross-env NODE_ENV=development MODE=test node server/app.js
node /api/node_modules/.bin/../cross-env/bin/cross-env.js NODE_ENV=development MODE=test node server/app.js
node server/app.js

I read a related documentation here, but I don't understand what actually happens in background.

1. What is the order of creating processes? npm => /bin/sh => node /api/.. => node server/app.js ?
2. What does each process do? All three processes are necessary to run my server?
3. If I wants to kill the server with pid, which process id should I use?

Answer 1

What is the order of creating processes? npm => /bin/sh => node /api/.. => node server/app.js ?

What does each process do? All three processes are necessary to run my server?

Well, the flow is like this:

• NPM is spawned (you run it) inside your shell, npm itself runs with NPX in order to set the local path.
• Your npm script spawns a process from a package called cross-env for cross-OS environment variable setting.
• That process in turn spawns Node.js (after setting the environment variables)

That's why you see 3 processes. After your server itself run - only the actual server process is needed to run the server.

If I wants to kill the server with pid, which process id should I use?

This one: node server/app.js - since that's your actual server, the others are just "utility processes" (one for the npm script you ran and the other for the environment variables").

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It's worth mentioning that in general - servers are run inside containers or other orchestrators/managers that have built-in logic for restarting/killing the process. Typically the orchestrator sends SIGTERM to the process.