[{reqId}] {exception_url} PHP Warning: Undefined array key "active_experiments"Followed by:
in_array(): Argument #2 ($haystack) must be of type array, null given
Both from /srv/mediawiki/php-1.45.0-wmf.13/extensions/MetricsPlatform/includes/XLab/ExperimentManager.php:44
| Status | Subtype | Assigned | Task | ||
|---|---|---|---|---|---|
| Resolved | Release | hashar | T396374 1.45.0-wmf.13 deployment blockers | ||
| Resolved | PRODUCTION ERROR | phuedx | T401294 PHP Warning: Undefined array key "active_experiments" |
Change #1176194 had a related patch set uploaded (by Phuedx; author: Phuedx):
[mediawiki/extensions/MetricsPlatform@master] ExperimentManager: Fix #getExperiment() when uninitialized
Change #1176195 had a related patch set uploaded (by Hashar; author: Phuedx):
[mediawiki/extensions/MetricsPlatform@wmf/1.45.0-wmf.13] ExperimentManager: Fix #getExperiment() when uninitialized
Change #1176195 merged by jenkins-bot:
[mediawiki/extensions/MetricsPlatform@wmf/1.45.0-wmf.13] ExperimentManager: Fix #getExperiment() when uninitialized
Mentioned in SAL (#wikimedia-operations) [2025-08-06T09:45:55Z] <hashar@deploy1003> Started scap sync-world: Backport for [[gerrit:1176195|ExperimentManager: Fix #getExperiment() when uninitialized (T401294)]]
Mentioned in SAL (#wikimedia-operations) [2025-08-06T09:47:44Z] <hashar@deploy1003> hashar: Backport for [[gerrit:1176195|ExperimentManager: Fix #getExperiment() when uninitialized (T401294)]] synced to the testservers (see https://wikitech.wikimedia.org/wiki/Mwdebug). Changes can now be verified there.
Change #1176194 merged by jenkins-bot:
[mediawiki/extensions/MetricsPlatform@master] ExperimentManager: Fix #getExperiment() when uninitialized
Mentioned in SAL (#wikimedia-operations) [2025-08-06T09:54:15Z] <hashar@deploy1003> Finished scap sync-world: Backport for [[gerrit:1176195|ExperimentManager: Fix #getExperiment() when uninitialized (T401294)]] (duration: 08m 20s)
This bug has existed since the creation of the ExperimentManager class in {86850b4630e1c8b6c330050729bd987e7e6fb9d2}.
The bug itself is that ExperimentManager#getExperiment() expects ExperimentManager#$enrollmentResult to always have an active_experiments entry. However, this will only be the case when ExperimentManager#initialize() has been called. Currently, ExperimentManager#initialize() is called when the BeforeInitialize hook is run.
The reason that the bug has only just started to be triggered is that up until now, no code has been running in production that calls ExperimentManager#getExperiment() in a context when the BeforeInitialize hook hasn't run (and therefore ExperimentMananger#initialize() hasn't been called), i.e. a MediaWiki Action API request.