Earlier today I successfully deployed a trivial config change: https://gerrit.wikimedia.org/r/#/c/operations/mediawiki-config/+/545779/
And now I'm seeing that the startup module randomly picks up the change (appearing, then disappearing), depending on which app server generates the startup module:
```
~/Downloads $ curl -s "https://ru.wikipedia.org/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector" | grep perceived
(generated by mw1331.eqiad.wmnet)
~/Downloads $ curl -s "https://ru.wikipedia.org/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector" | grep perceived
"ext.quicksurveys.survey.reader-demographics-ru","mmmma"],["ext.quicksurveys.survey.perceived-performance-survey","8wwz6"]]);mw.config.set({"debug":!1,"skin":"vector","stylepath":"/w/skins","wgUrlProtocols":"bitcoin\\:|ftp\\:\\/\\/|ftps\\:\\/\\/|geo\\:|git\\:\\/\\/|gopher\\:\\/\\/|http\\:\\/\\/|https\\:\\/\\/|irc\\:\\/\\/|ircs\\:\\/\\/|magnet\\:|mailto\\:|mms\\:\\/\\/|news\\:|nntp\\:\\/\\/|redis\\:\\/\\/|sftp\\:\\/\\/|sip\\:|sips\\:|sms\\:|ssh\\:\\/\\/|svn\\:\\/\\/|tel\\:|telnet\\:\\/\\/|urn\\:|worldwind\\:\\/\\/|xmpp\\:|\\/\\/","wgArticlePath":"/wiki/$1","wgScriptPath":"/w","wgScript":"/w/index.php","wgSearchType":"CirrusSearch","wgVariantArticlePath":!1,"wgActionPaths":{},"wgServer":"//ru.wikipedia.org","wgServerName":"ru.wikipedia.org","wgUserLanguage":"en","wgContentLanguage":"ru","wgTranslateNumerals":!0,"wgVersion":"1.35.0-wmf.2","wgEnableAPI":!0,"wgEnableWriteAPI":!0,"wgFormattedNamespaces":{"-2":"Медиа","-1":"Служебная","0":"","1":
"link":"Reader-demographics-2-link","instanceTokenParameterName":"entry.1791119923","isInsecure":!1},{"audience":[],"name":"perceived-performance-survey","question":"ext-quicksurveys-performance-internal-survey-question","description":null,"module":"ext.quicksurveys.survey.perceived-performance-survey","coverage":0,"platforms":{"desktop":["stable"]},"privacyPolicy":"ext-quicksurveys-performance-internal-survey-privacy-policy","type":"internal","answers":["ext-quicksurveys-example-internal-survey-answer-positive","ext-quicksurveys-example-internal-survey-answer-neutral","ext-quicksurveys-example-internal-survey-answer-negative"],"shuffleAnswersDisplay":!0,"freeformTextLabel":null}],"wgCentralNoticeActiveBannerDispatcher":"//meta.wikimedia.org/w/index.php?title=Special:BannerLoader","wgCentralSelectedBannerDispatcher":"//meta.wikimedia.org/w/index.php?title=Special:BannerLoader","wgCentralBannerRecorder":"//ru.wikipedia.org/beacon/impression","wgCentralNoticeSampleRate":0.01,
(generated by mw1239.eqiad.wmnet)
~/Downloads $ curl -s "https://ru.wikipedia.org/w/load.php?lang=en&modules=startup&only=scripts&raw=1&skin=vector" | grep perceived
(generated by mw1262.eqiad.wmnet)
```
I went on the actual web servers and could see that InitialiseSettings.php has the up-to-date content:
```
gilles@mw1262:~$ cat /srv/mediawiki/wmf-config/InitialiseSettings.php | grep T187299
// T187299
// T187299
// T187299
// T187299
// T187299
gilles@mw1262:~$
```
This feels like a caching issue at the PHP level, where it doesn't reliably pick up the updated config file.