To the person who is assigned this ticket - Please note that I wrote step-by-step instructions for how I've been adding synthetic tests in my offboarding document at https://docs.google.com/document/d/13NypRIkc3-jOFNR6wTOnMfUXMjL11ny5OiyX4XulDK4/edit#heading=h.a26i7l3crf5f under the heading "Comparative synthetic tests" that I hope you will find helpful

@pmiazga's dared me to write a blog post about this experience during our super happy dev time meeting, so it's at https://www.nray.dev/blog/300ms-faster-reducing-wikipedias-total-blocking-time/ 🙂

I've reassigned this to Mo to reflect our above discussion ^^. Unfortunately, it doesn't appear that I have the ability to add myself as the "Other assignee":

• Write a proposed set of basic web team-centric performance SLOs

@Etonkovidova Thank you so much for leading this! 🎉

Discussed the remaining work on this with @Mabualruz, and we decided that he will create the necessary tickets (e.g. adding metrics to Grafana Dashboard, creating alerting, etc) for future work related to our proposed performance budget:

@Mabualruz and I met today to discuss remaining work on this and decided that @Mabualruz will lead the remaining work on this ticket with me transitioning to more of a support role :

Sorry for the noise everybody. This ticket is no longer needed.

Hey @Peter, that all sounds great to me and love the name Wikipedia Web Vitals. We don't have any performance SLOs right now.

I think this work resulted in a ~50% reduction in JavaScript execution time for the task on long pages like the "Barack_Obama" page which represents around ~260ms improvement in Total Blocking Time on the Moto G (5) phone that our synthetic tests use:

• Talk to designer about whether it should be replaced with indicators. Create a ticket if necessary.

Related to T329397

Looks like this is caused by a memory error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 1662976 bytes) but only on master. It doesn't occur on 1.41.0-wmf.5. It was hanging because we assumed mw was present in moduleReady.js. https://github.com/wikimedia/pixel/pull/187 should at least fix that problem

In Toggler.js, there was a small block of JavaScript that wasn't working correctly and was taking ~250ms to execute on my xiaomi redmi 9a phone. Therefore, I'm removing it in https://gerrit.wikimedia.org/r/908333. For long pages like the "United_States" page, this small step cuts the task's JS execution time by nearly half.

Should now be resolved by https://github.com/wikimedia/pixel/pull/185

Should now be resolve by https://github.com/wikimedia/pixel/pull/185

Before (with client preferences disabled and the inline script removed)
After (with 20 client preferences stored in a cookie)

Scheduled a meeting for this Wednesday with @Mabualruz and @Edtadros to go over the synthetic testing

Data has started to roll in from the synthetic tests:

Static pages have been deployed and tests have been merged. I'm not seeing anything on the graphs yet — I'm asking Peter about this now, but I'm leaving this ticket in code review so that someone else on the web team can become a bit more familiar with the synthetic testing process. I'm happy to meet and discuss these changes!

Thank you @Edtadros, great write up!