unintentional 2 second delay on random API requests

[tobywilliams]

We are experiencing some problems with our cypress setup. We are using vite + proxy and the cypress intercepts. We've noticed that some of our api/static asset requests (not intercepted) have started routinely taking 2 seconds to complete. It happens fairly consistently on the tail end of the files being loaded but can often add 10+ seconds to load a page.

We use the production build in our CI and we haven't seen the issue there - so I'm fairly sure that the large quantity of files produced by the vite dev build is causing issues however it's only recently that we've noticed the dramatic slowdown in some requests out of each page load.

I've included a screenshot below that shows some of the requests taking also exactly 2 seconds, then the rest come in really fast.

Any help in identifying the source of the 2 second delay would be greatly appreciated.

[damiankoper]

Same here but I can confirm that intercepted requests also have a 2s delay in our case. Reopening the browser window helps for a few runs.

[tobywilliams]

We've noticed that it only happens when Dev Tools is open, so for the moment we are closing and opening dev tools all the time to speed up our development cycle.

I'll post an issue on the issues section soon, now that we have a clearer idea of what is triggering the issue.

[damiankoper]

Thanks. I confirm this is somehow devtools related. Reopening helps. Maybe this has sth to do with #27592 in v13.0.

[ben-scanbot]

Can confirm this is still present in v13.16.1
I double checked that it is not present in v12.17.4

There seem to be some complex triggers for this problem because I was unable create a simple standalone testcase to trigger this 🤷

[ben-scanbot]

I have put together a small example project that exhibits the problem:
cypress-bug.zip

The problem does not only occur when the debug tools are open. It also occurs when running the tests headlessly.

Might be related to #28113