Automated performance monitoring in WordPress core

Gathering performance metrics automatically is a way to track performance over time and ensure that WordPress continues to improve.  Automated performance tooling will also help the coreCore Core is the set of software required to run WordPress. The Core Development Team builds WordPress. team identify issues and resolve them with less effort.

Why add automated performance testing?

Adding automated performance testing will help us monitor performance changes in WordPress core continuously. It gives us a track record to capture how core performance is being enhanced over time, and it allows us to catch regressions early and accurately identify underlying causes. Similar to our unit testunit test Code written to test a small piece of code or functionality within a larger application. Everything from themes to WordPress core have a series of unit tests. Also see regression. suite, automated performance testing would help protect core from introducing large performance regressions by catching problems immediately and tracking performance over time. Automating testing also means saving contributor effort by replacing a time consuming manual process.

The core performance team is focused on improving core performance. Examples of this work include introducing changes that reduce the number of database queries or improve caching. Each new performance team feature must show measurable gains, and each new WordPress release is performance tested by the team. In the 6.1 release cycle, this led to the discovery of some significant performance regressions, e.g. in this Gutenberg issue or this Trac ticket. Automated testing would catch this type of regressionregression A software bug that breaks or degrades something that previously worked. Regressions are often treated as critical bugs or blockers. Recent regressions may be given higher priorities. A "3.6 regression" would be a bug in 3.6 that worked as intended in 3.5. as soon as it was introduced, making it much easier to resolve.

It is worth noting that GutenbergGutenberg The Gutenberg project is the new Editor Interface for WordPress. The editor improves the process and experience of creating new content, making writing rich content much simpler. It uses ‘blocks’ to add richness rather than shortcodes, custom HTML etc. has already done extensive work on performance, tracking metrics with each commit and publicizing details with each release.  

What automated performance testing would do in core

Similar to Gutenberg, WordPress core would gather a set of automated performance metrics along with the existing test runs (e.g. unit tests, coding standards) we already have for each new commit. These metrics can be used to identify the exact point a performance regression is introduced into core. At milestones like a major releasemajor release A release, identified by the first two numbers (3.6), which is the focus of a full release cycle and feature development. WordPress uses decimaling count for major release versions, so 2.8, 2.9, 3.0, and 3.1 are sequential and comparable in scope., the metrics can be compared against the previous release to gauge progress.

Goals for the initial version

The scope of the  initial version of automated performance testing is intentionally kept limited so we can deliver more quickly, then we can iterate. 

The initial version will include the following features:

  • For each core commit a GitHubGitHub GitHub is a website that offers online implementation of git repositories that can easily be shared, copied and modified by other developers. Public repositories are free to host, private repositories require a paid subscription. GitHub introduced the concept of the ‘pull request’ where code changes done in branches by contributors can be reviewed and discussed before being merged be the repository owner. action will run a set of automated performance tests, collecting key data points about how WordPress is performing (such as total load time and total query time) on blockBlock Block is the abstract term used to describe units of markup that, composed together, form the content or layout of a webpage using the WordPress editor. The idea combines concepts of what in the past may have achieved with shortcodes, custom HTML, and embed discovery into a single consistent API and user experience. and classic themes. 
  • The system will collect server timing metrics using the standard WordPress environment and current recommended version of PHPPHP The web scripting language in which WordPress is primarily architected. WordPress requires PHP 5.6.20 or higher.  

Future Enhancements

Several areas of work are considered out of scope for the initial implementation, primarily to keep the focus limited for the initial release — not because they aren’t good ideas! Once we build a solid foundation for tests and are confident in the metrics we are collecting, we can consider additional improvements.

  • Collecting additional metrics: initially we will focus on key server timing metrics
  • Collecting metrics for other contexts: initial metrics will only measure the home page of the latest core block and classic themes with their default demo content.
  • SlackSlack Slack is a Collaborative Group Chat Platform The WordPress community has its own Slack Channel at or ticketticket Created for both bug reports and feature development on the bug tracker. reporting: initial work will focus only on collecting and recording metrics at each commit. 


Will the data be stable enough to be useful?

Performance results can vary in a CI environment, making regressions harder to detect. To mitigate this, the system will run several iterations and use the median value.

What metrics will be collected exactly?

Initially we will only collect a few key metrics to keep the dashboard simple, focused on the total load time. Once we have established the new tool, we can consider including additional metrics, or adding hooksHooks In WordPress theme and development, hooks are functions that can be applied to an action or a Filter in WordPress. Actions are functions performed when a certain event occurs in WordPress. Filters allow you to modify certain functions. Arguments used to hook both filters and actions look the same. to make the test runs extensibleExtensible This is the ability to add additional functionality to the code. Plugins extend the WordPress core software..

What about testing older PHP versions?

To reduce the time/cost associated with running these tests, they will be limited to the current recommended version of PHP. Unlike unit tests, performance tests are unlikely to produce significantly different deltas for different PHP versions: regressions are likely to be across PHP versions.

Why not test wp-adminadmin (and super admin) or more routes?

In order to keep the time and cost of running these tests low, and the dashboard simplified, initial testing is intentionally being kept somewhat minimal. In the future it would be good to consider adding other common routes such as the wp-admin dashboard and single post page.

Thanks to @tweetythierry @flixos90 @joemcgill @mukesh27 for reviewing this post and to @youknowriad for the inspiration (and foundation) of the Gutenberg performance metrics.

#core-performance, #performance, #testing