Performance testing next steps

[swissspidy]

From the below, top of mind are currently:

• Lack of care around the dashboard (no alerts, people not checking it)
• Outdated test suite (still testing TT3, not testing TT5, baseline is 6.1)
• Stability
• Project ownership

---

Improve core performance tests

• Core
  • Unclear ownership / maintenance
  • Measure interactivity metrics in performance tests
  • Measure layout stability metrics in performance tests
  • Add tests for Twenty Twenty-Five
  • Test more combinations (e.g. Multisite, object cache enabled)
    • Expand performance tests setup wordpress-develop#6515
  • Outdated baseline (6.1)
• Gutenberg
  • Measure more frontend metrics
• Tests quality and stability
  • Alignment between core and Gutenberg
    • Core relies on GitHub Actions, while GB uses a sophisticated node script for running tests
    • GB regressions are often only found after merging into trunk (too late)
  • Improve demo content
    • Consider covering specific realistic use cases (e.g., homepage, page with large LCP image, etc)
    • Relevant for testing interactivity and layout stability
  • Performance Metrics Stabilization #849
    • Use WordPress Playground for more stability
      • Just for context, this was something that @dmsnell brought up, most recently in this Slack message
      • We could simulate different I/O latencies and intercept every DB and file operation
      • wp-now has some design problems that make it less favorable for testing (needs some refactoring first?)
• Dashboard
  • Current custom dashboard is limited
  • Maybe build a more powerful dashboard using Grafana or similar
  • Lack of alerts for significant changes or broken workflow

Adoption

• Run performance tests at scale using Tide?
• More outreach (1:1, developer blog, etc.)
• Directly reach out to a few bigger plugins to help them set up performance testing, setting a precedent for others
• Consider moving GitHub Action to the WordPress GitHub org to make it more official

Typical reasons why plugin developers do not adopt similar performance tests:

• They use a different testing setup (Codeception, Cypress, Puppeteer, k6) or CI (Bitbucket, GitLab)
• Lack of tests setup in general (e.g. not even unit tests in place)
• Focus is more on backend performance rather than frontend performance
• Lack of resources for implementing additional kinds of testing
• No testing strategy, e.g. even if they had the whole setup, they wouldn't know where to start
• Metrics stability concerns
  • Makes it especially difficult to tie metrics change to specific code change

[joemcgill]

Thanks for kicking this discussion off, @swissspidy.

I appreciate the distinction between two main objectives. For now, I'm going to limit my thoughts to the first objective, "Improve Core/GB performance testing".

One of the things that I observed during the 6.5 release is that finding the source of a server timing regression was challenging when that regression was committed to the Core repo as part of a larger Gutenberg sync. I think we can improve this somewhat by updating the performance tests in the Gutenberg repo to include the same server timing metrics that we record for each commit to the WP Core repo (i.e., wpTotal, wpBeforeTemplate, and wpTemplate). While TTFB is a close proximity, the additional noise from network requests and calculating the metric in a headless browser makes pinpointing potential regressions more difficult.

I also strongly agree with your suggestion to improve our demo content, and think this applies as much to the Core tests as the Gutenberg tests. Currently in Core, we are only testing the default homepage for the Twenty Twenty-One and Twenty Twenty-Three themes after importing a Theme Test Data from this commit. While this keeps test content consistent over time, there are a number of limitations to this approach including the fact that some specific use cases that we care about (e.g., measuring the effect of image optimizations on LCP) are not covered by our current test content.

From a visualization point of view, our current dashboards at codevitals.run have become harder to use over time as we've added additional metrics. I'd love to investigate improving or replacing these dashboards with a system where we could more granularly filter results by metric, theme, template, object cache, etc. In doing so, we should also evaluate how we are normalizing and storing the raw data which currently gets normalized before it's saved to the dashboard's database meaning we don't have the ability to build new reports using the original unfiltered data.

Last idea for now, is that when we introduced these tests we used Twenty Twenty-One and Twenty Twenty-Three as representative themes for classic and block themes, but that has proven to be overly simplistic as some performance regressions are only visible based on characteristics of a theme (e.g., how many template part variations they register). At minimum, we should add Twenty Twenty-Four to our test matrix in both repos.

TL;DR:

• Add server timing metrics to the GB performance workflow
• Improve demo content for the performance workflow in both repos
• Add specific use cases (e.g., homepage, page with large LCP image, etc) to our workflows for both repos
• Improve the dashboard for tracking performance over time so it's more user friendly
• Improve data collection process to make raw data queryable in the future
• Add tests for Twenty Twenty-Four

[swissspidy]

That all makes sense to me. I think most of those suggestions are already mentioned in some place or another. I also previously explored a Grafana-based dashboard that would be more user friendly and could be fed raw data.

Some more thoughts on adoption:

Let's start with directly reaching out to some top plugins that we think could benefit from performance testing but don't leverage that yet. Find out why, figure out what's missing, and help them get started.
This way, we can iterate on the tooling before publishing another blog post or improving the GitHub Action.

[joemcgill]

@swissspidy, I think it would be great to add a summary page to Performance Metrics in the GB repo, similar to what we have in WP-dev, so the potential performance impact of a PR can be spot-checked. As an example, here are PRs for basically the same change in both the GB repo and the WP-dev repo:

• GB PR Performance test
• WP PR Performance Test

Do you already have any plans to try to apply updates to the GB Performance tests, or should I open independent issues over there?

[swissspidy]

Sure that can be done together with the Server-Timing enhancements etc., bringing the learnings from core to GB. A dedicated issue there sounds good.

[joemcgill]

@swissspidy – WordPress/gutenberg#61411

[swissspidy]

WordPress/gutenberg#61450

[swissspidy]

Improve Core/GB performance testing

Mentioned above:

• Improve demo content
  • Needs an owner
  • Priority?
• Add specific use cases (e.g., homepage, page with large LCP image, etc)
  • Also relevant for things like interactivity and layout stability metrics
  • Needs some fleshing out
  • Priority?
• Better dashboard with raw data
  • Needs an owner
  • Priority?
• Add tests for Twenty Twenty-Four
  • This was added in one of the recent refactorings. 2021, 2023, and 2024 are now tested.
• Alignment between core and Gutenberg
  • Core relies on GitHub Actions, while GB uses a sophisticated node script for running tests.
  • Should we have 1 script for both that could also be used by the ecosystem via npm or similar? Or is a GitHub Action good enough?
• Use WordPress Playground for more stability
  • Just for context, this was something that @dmsnell brought up, most recently in this Slack message
  • We could simulate different I/O latencies and intercept every DB and file operation
  • wp-now has some design problems that make it less favorable for testing (needs some refactoring first?)

More thoughts:

• Test more combinations (e.g. Multisite, object cache enabled)
  • Expand performance tests setup wordpress-develop#6515

Adoption

Let's start with directly reaching out to some top plugins that we think could benefit from performance testing but don't leverage that yet. Find out why, figure out what's missing, and help them get started.

The main points I've heard so far in various discussions:

• They use a different testing setup (Codeception, Cypress, Puppeteer, k6) or CI (Bitbucket, GitLab)
• Lack of tests setup in general (e.g. not even unit tests in place)
• Focus is more on backend performance rather than frontend performance
• Lack of resources for implementing additional kinds of testing
• No testing strategy, e.g. even if they had the whole setup, they wouldn't know where to start
• Metrics stability concerns
  • Makes it especially difficult to tie metrics change to specific code change

Mentioned above:

• GitHub Action
  • Great, but lack of setup step for plugins
    • Add blueprint support so that plugins can easily prepare their testing environment
      • Blueprint support swissspidy/wp-performance-action#71
      • @adamziel Curious to hear your thoughts on that one
    • Concern: wp-now appears to be unsuitable for testing like this :( (see above)
  • Once this is in place we can think about further blog posts
• All-in-one npm package for running tests & doing comparisons
  • Does it make sense? Usually not advisable to run tests on your own machine vs. a dedicate one