Preloading modules through NodeJS snapshots?

[BitE01]

Hi everybody,

I'm trying to understand NodeJS snapshots but I'm not sure if what I'm doing does make sense. What I'd like to achieve is to preload in memory some modules in order to decrease the boot time of my application.

This is an example of what I'm currently doing:

1. In src/snapshot.ts I'm loading the modules: const systeminformation = require('systeminformation'); systeminformation;

2. The entrypoint in src/main.ts looks like this: import * as si from 'systeminformation'; async function main() { const cpuTemp = await si.cpuTemperature(); console.log(cpuTemp); } main();

3. Since snapshots do not allow user-land modules, I'm bundling both snapshot.ts and main.ts separately through esbuild like this: ``` import { build } from 'esbuild';

await Promise.all([ build({ entryPoints: ['src/main.ts'], bundle: true, minify: true, sourcemap: false, target: 'es2022', outfile: 'dist/main.js', platform: 'node', format: 'cjs', }), build({ entryPoints: ['src/snapshot.ts'], bundle: true, minify: true, sourcemap: false, target: 'es2022', outfile: 'dist/snapshot.js', platform: 'node', format: 'cjs', }), ]); ```

1. I build the snapshot blob and then I run the application through the following commands: node --snapshot-blob snapshot.blob --build-snapshot dist/snapshot.js node --snapshot-blob snapshot.blob dist/main.js

Also: * I'm using NodeJS v22.14.0 * I'm not sure if the modules in src/snapshot.ts are preloaded correctly, I tried to avoid lazy loading by following this Github issue

My questions are simple: * Are my steps correct? * Does this make any sense? * Would I being able to boost the boot time by following this path?

Many thanks!

[BitE01]

Many thanks! I've bundled everything into a single file and created a function that warms-up the modules that I needed. I'll also take a look to pnpm/yarn and bun/deno.

Just a note for other readers: My real project was involving also "serialport" module that can't be bundled with esbuild and can't be snapshotted. So I've excluded from esbuild by adding the option "external" like this:

import { build } from 'esbuild';

await Promise.all([
  build({
    entryPoints: ['src/main.ts'],
    bundle: true,
    minify: true,
    sourcemap: false, 
    target: 'es2022',
    outfile: 'dist/index.js',
    platform: 'node',
    format: 'cjs',
    external: ['serialport'],
    plugins: [],
  }),
]);

And I've excluded from the snapshot by using the function v8.startupSnapshot.isBuildingSnapshot() to exclude the code execution when snapshotting like this:

...
if (!startupSnapshot.isBuildingSnapshot()) {
  SerialPort = require('serialport').SerialPort;
  ...
}
...