limit dev watcher to avoid overhead from third party processes writing to root #8341
Description
Clear and concise description of the problem
By default, vite devuses a chokidar watcher on root, ignoring only .git and node_modules.
https://github.com/vitejs/vite/blob/main/packages/vite/src/node/server/index.ts#L291-L302
This causes overhead when processes write files to root that are not needed to be watched. eg. @playwright/test writes to test-results - a lot - if tracing is enabled. (see details below)
Suggested solution
Limit watching to directories matching the fs.allow pattern inside root. This gives frameworks and users more control over what is watched and improves performance.
example code, not perfect but to illustrate whats suggested.
const { ignored = [], ...watchOptions } = serverConfig.watch || {}
- const watcher = chokidar.watch(path.resolve(root), {
+ const scope = path.resolve(root) + path.sep;
+ const watch = serverConfig.fs?.allow?.length ? serverConfig.fs.allow.filter(dir => dir.startsWith(scope)) : [];
+ if(watch.length === 0) {
+ watch.push(path.resolve(root))
+ }
+ const watcher = chokidar.watch(watch, {
ignored: [
'**/node_modules/**',
'**/.git/**',
...(Array.isArray(ignored) ? ignored : [ignored])
],
ignoreInitial: true,
ignorePermissionErrors: true,
disableGlobbing: true,
...watchOptions
}) as FSWatcherConsiderations:
- fs.allow can contain items outside root. simply watching all fs.allow entries could cause even more problems (what if someone put
/in fs.allow?) so keep the root boundary in place. - keep the current behavior if fs.allow contains root or only contains directories outside root (it has to watch something).
- could use some logging too what gets watched and maybe a warning on excessive flooding
Alternative
manually add ignore entries to known patterns.
watch: {
// perf, do not watch playwright output dir
ignored: ['**/test-results/**']
}
This would still incur some cost inside chokidar but at least it would not reach the downstream handlers
Additional context
example of a sveltekit testsuite run with enabled logging inside a watcher demonstrating the current behavior.
https://github.com/sveltejs/kit/runs/6599185996?check_suite_focus=true
...
@sveltejs/kit:test: [WebServer] config.kit.files.routes: D:\a\kit\kit\packages\kit\test\apps\basics\src\routes
@sveltejs/kit:test: [WebServer] add D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-0\41adcbc97f1df5cc5fc3997a22928727.zip
@sveltejs/kit:test: [WebServer] add D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-0\f845da79f5fc1bf257a216cc3e2eb100.png
@sveltejs/kit:test: [WebServer] unlink D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-0\41adcbc97f1df5cc5fc3997a22928727.zip
@sveltejs/kit:test: [WebServer] unlink D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-0\f845da79f5fc1bf257a216cc3e2eb100.png
@sveltejs/kit:test: [WebServer] add D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-1\ec2416cbd7c50f61810b6fac2a86d166.zip
@sveltejs/kit:test: [WebServer] add D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-1\639ae30030d1658af3b1a90aae33d8fc.png
@sveltejs/kit:test: [WebServer] unlink D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-1\ec2416cbd7c50f61810b6fac2a86d166.zip
@sveltejs/kit:test: unlink D:\a\kit\kit\packages\kit\test\apps\basics\test-results\.playwright-artifacts-1\639ae30030d1658af3b1a90aae33d8fc.png
...
Validations
- Follow our Code of Conduct
- Read the Contributing Guidelines.
- Read the docs.
- Check that there isn't already an issue that request the same feature to avoid creating a duplicate.