Is there a way to remotely record and capture a profile?

[tim-we]

Sorry for being slightly off-topic, feel free to point to a better place to ask this question.

I would like to record and capture a performance profile using Playwright. For Chrome/Chromium there is an API for this. Unfortunately it is not supported for Firefox, I think this is because Firefox implements only a subset of CDP. Is there any other way to trigger recording and capturing? Last resort would be sending fake keyevents (Ctrl+Shift+1 and Ctrl+Shift+2) but perhaps there is a "nicer" way to do this?

[julienw]

Thanks for looking at this!
Unfortunately we haven't invested a lot of time for this use case. It would be good to figure out which part of CDP we should implement to support this use case, in case this is just some glueing some parts together.
For the time being, one way that could work is using environment variables. You can find more information about that in this documentation page. By using both the startup and shutdown variables, you could be able to capture a profile for your full scenario.

If you manage to make it work, could please come back and share with us how you did it? Then we could add it in our documentation.

[tim-we]

Thanks for answering and thanks for the environment variables tip! I'll look into it and update this thread if I get this to work somehow.

Regarding the question of which part of the CDP need to be implemented for this to work its the following:

• Tracing.start Playwright usage in crBrowser.ts
• Tracing.tracingComplete and Tracing.end Playwright usage in crBrowser.ts
• IO.read and IO.close Playwright usage in crProtocolHelper.ts (used for saving the stream returned by Tracing.tracingComplete)

Unfortunately I'm not really familiar with the Firefox codebase but having a quick glance at https://searchfox.org/mozilla-central/source/remote/cdp it appears to me that none of those are implemented yet.