File watching is registering thousands of redundant watchers

[bpasero]

🔎 Search Terms

file watcher performance efficiency watching events

🕗 Version & Regression Information

I am not sure when this changed, but ever since typescript.tsserver.experimental.useVsCodeWatcher was added it becomes more visible now, at least to me as owner of the file watcher component in VS Code.

⏯ Playground Link

https://github.com/Microsoft/vscode/

💻 Code

No response

🙁 Actual behavior

When you open vscode repository (https://github.com/Microsoft/vscode/) and open a TS file (e.g. vs/base/strings.ts) and wait a bit until the TS/JS language service has settled, notice how there are the following recursive file watchers:

• node_modules
• src/vs
• src/@bpasero, src/node:vm, src/fs,... (actually 83 more for each and every module we depend on, these folders do not exist on disk)

And then there are >4000 (!) requests for non-recursive files for pretty much every single TS file in the project (for example src/vs/base/browser/ui/menu/menu.ts).

🙂 Expected behavior

A lot less requests for watching:

• all of the thousands of non-recursive watch requests are obsolete given you watch src/vs already recursively
• paths like src/fs are made up and do not exist, I am not even sure how it would make sense to watch src/<node module>?

Additional information about the issue

Here is how you can see the data:

• after you have opened vscode and a TS file, select "Set Log Level" and pick "Trace" from the command picker
• in the output panel, select the "File Watcher" channel
• you should see output like this:

[File Watcher] request stats:

[Summary]
- Recursive Requests:     total: 89, suspended: 85, polling: 2
- Non-Recursive Requests: total: 4344, suspended: 50, polling: 0
- Recursive Watchers:     total: 4, active: 4, failed: 0, stopped: 0
- Non-Recursive Watchers: total: 4294, active: 10, failed: 1, reusing: 4283
- I/O Handles Impact:     total: 16

//cc @sheetalkamat @DanielRosenwasser