Quibble supervisord memcached confusion
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	tstarling
	Jun 25 2025, 6:12 AM

Description

Trying to reproduce a CI Selenium failure locally, I ran Quibble under docker. Many Selenium tests failed with login errors. Inspecting the screenshots and debug logs, I found that MW was trying to store sessions in memcached, but memcached was not running, leading to a "session loss" error.

I was following the instructions at https://doc.wikimedia.org/quibble/ but it didn't have the critical detail: the default entrypoint in the quibble docker images is now broken, and it's necessary to override it with --entrypoint=quibble-with-supervisord. Then supervisord will start memcached.

I don't understand why supervisord is needed at all. Quibble has its backend.py and does a reasonable job of managing MySQL and Chrome. Why not add memcached, php-fpm and Apache there?

Pretty much as soon as I manually started memcached, I hit a bug due to sharing of memcached data between one run and another. Memcached needs to have the same lifetime as MySQL.

It would be convenient for users of Quibble if it worked as documented and didn't require external services.

Details

Related Changes in Gerrit:

Subject	Repo	Branch	Lines +/-
Add support to spawn Memcached as a backend	integration/quibble	master	+90 -6
Fix semantic for Quibble injected PHP constants	integration/quibble	master	+13 -14
jjb: update Quibble jobs for supervisord improvements	integration/config	master	+31 -31
dockerfiles: rebuild Quibble images for supervisord	integration/config	master	+80 -0
dockerfiles: quibble-bullseye: improve supervisord configuration	integration/config	master	+8 -5
dockerfiles: quibble-bullseye: fix run as different user	integration/config	master	+5 -5

Customize query in gerrit

Related Objects

Mentioned In: Quibble (Phase out supervisord)
T418233: Selenium tests fail when targeting Quibble
Mentioned Here: T225218: Consider httpd for quibble instead of php built-in server
T300340: Use Memcached with Quibble

Event Timeline

tstarling created this task.Jun 25 2025, 6:12 AM

tstarling added a subscriber: kostajh.

The task which added Memcached is T300340. The issue is MediaWiki is configured to use Memcached whenever the extension is loaded regardless of whether a Memcached server is available.

The initial code was introduced by https://gerrit.wikimedia.org/r/c/integration/quibble/+/757844/5/quibble/mediawiki/local_settings.php.tpl and today looks like:

// Caching settings.
if ( extension_loaded( 'memcached' ) ) {
    $wgMainCacheType = CACHE_MEMCACHED;
    $wgMemCachedServers = [ '127.0.0.1:11211' ];
    $wgMemCachedPersistent = true;
}

It should probably only be configured when one uses quibble --memcached 127.0.0.1:11211 (and the CI job and/or quibble-with-supervisord should then do it).

The Quibble images should most probably default to use quibble-with-supervisord as an entrypoint. It takes care of spinning up backend services that can be used by different test suites.

zeljkofilipin added a project: Browser Test Platform.Feb 25 2026, 10:26 AM

zeljkofilipin subscribed.

zeljkofilipin added a project: User-zeljkofilipin.Feb 25 2026, 10:30 AM

zeljkofilipin moved this task from Backlog 🪒 to Sprint 🏃‍➡️ on the User-zeljkofilipin board.

I did not act on that task because on CI that is hardcoded to use quibble-with-supervisord as an entry point and frankly I forgot about it.

Introducing Supervisord was to have it drive Apache / php-fpm, support parallel requests and because it is faster than php -S T225218. It was not necessarily doable with Quibble backend.php, or maybe I haven't tried hard.

That definitely causes confusion to have two systems in parallel and @zeljkofilipin encountered the same issue when running Selenium tests, there were bunch of memcached errors because the image entrypoint invokes Quibble rather than supervisord.

So I guess a quick fix is to change the image entrypoint.

Memcached should probably be driven by Quibble itself and removed from Supervisord, that sounds easy to do.

zeljkofilipin moved this task from Sprint 🏃‍➡️ to Waiting 🏹 on the User-zeljkofilipin board.Feb 27 2026, 9:58 AM

zeljkofilipin mentioned this in T418233: Selenium tests fail when targeting Quibble.Feb 27 2026, 1:37 PM

Change #1251084 had a related patch set uploaded (by Hashar; author: Hashar):

[integration/config@master] dockerfiles: quibble-bullseye: fix run as different user

https://gerrit.wikimedia.org/r/1251084

gerritbot added a project: Patch-For-Review.Mar 12 2026, 1:42 PM

Change #1251122 had a related patch set uploaded (by Hashar; author: Hashar):

[integration/config@master] dockerfiles: quibble-bullseye: improve supervisord

https://gerrit.wikimedia.org/r/1251122

hashar mentioned this in Quibble (Phase out supervisord).Apr 11 2026, 1:46 PM