Node: Enable hooks in fs.statWatchers

[Himself65]

Is your feature request related to a problem? Please describe.
People sometimes will encounter the error that System limit for number of file watchers reached.. If we enable users to add hooks in fs.statWatchers, they could track the codes that which module call fs.watchFile many times

Describe the solution you'd like

const { statWatchers, watchFile } = require(‘fs’)
statWatchers.on(‘statAdd’, () => {})
statWatchers.on(‘statRemove’, () => {})

watchFile(‘xxx‘, () => {})

Related code
https://github.com/nodejs/node/blob/9949a2e1e3100c4ff1f228bac57c1af95cdc3e9d/lib/fs.js#L1458

[Zheaoli]

I think this feature would be necessary

In Linux or other platforms, the file watcher is very expensive resources for user. For example, there are some limit about file watcher count for the unique user id in Linux

So I think it would be necessary to allow people get a way to trace/output log/do other things meaningful for their 'file watch' action

[addaleax]

If we enable users to add hooks in fs.statWatchers, they could track the codes that which module call fs.watchFile many times

Two questions:

• Doesn’t this happen with fs.watch() only? The stat watchers shouldn’t count towards a global limit?
• Doesn’t it suffice to override/wrap fs.watch() and fs.unwatch() if this is what you’re looking for?

[Himself65]

Doesn’t this happen with fs.watch() only? The stat watchers shouldn’t count towards a global limit?

Yes, it do is the global limit, but sometimes we need to monitor which module reach the limit.

Doesn’t it suffice to override/wrap fs.watch() and fs.unwatch() if this is what you’re looking for?

I noticed that we already have fs. statWatchers using Map, to memory the stats. What about we enhance it to the EventEmitter or anything else, not just a third part module to achieve this.

[addaleax]

Doesn’t this happen with fs.watch() only? The stat watchers shouldn’t count towards a global limit?

Yes, it do is the global limit, but sometimes we need to monitor which module reach the limit.

I don’t really understand how this relates to the difference between fs.watch() and fs.watchFile()? fs.watchFile() does not take up OS resources, as I understand it.

Doesn’t it suffice to override/wrap fs.watch() and fs.unwatch() if this is what you’re looking for?

I noticed that we already have fs. statWatchers using Map, to memory the stats. What about we enhance it to the EventEmitter or anything else, not just a third part module to achieve this.

I guess to be more explicit, what is the advantage of using an EventEmitter here, as opposed to keeping the API surface as it is?