What happens to performance.mark entries when the resource buffer gets full

Question

I am building a large private (ie used behind a firewall) PWA and wondering how to improve the diagnostics if/when my users hit issues. I already have an error manager which uses navigator.sendBeacon to log the error on the server, but that lacks detailed info of what led up to that point.

A thought I had was to liberally mark the code with performance.mark() statements and on an error dump the performance buffer to the server. It would give me an ordered list of recent activity.

However it only makes sense to do this if the browser throws away the oldest entry to make way for the new when the internal buffer is full. However all the documentation I found with a google search doesn't mention it. I am aware I can get an event when it is full and could use that to copy and clear it but I can find no words on what happens if I ignore the event. Neither can I find a typical size. I don't want to keep getting entries filling up the entire computer memory either

Can anyone give me a definite answer

Edit: The more I look into this, the more confused I become. It appears that you can control the size of the resourceTimingBuffer but "resource" performance entries are related to fetch and not Performance.mark() . I can't find any statement on limitations.

Answer 1

There are no meaningful limitations I could find. I did a test and generated more than 4000 marks and they were all there and the memory usage did not increase in any measurable way.