We saw this when the job that dumps metadata for all revisions was running for this wiki; This is the only wiki impacted so far

The page at issue has the title Json:World-110m, it used to be in the Data: namespace, i.e. with the full title Data:Json:World-110m but that namespace was removed sometime between the April 1st dump run and the beginning of the April 20th run.

I guess this is likely related: https://gerrit.wikimedia.org/r/c/operations/mediawiki-config/+/909603

Pinging @Zabe for more info.

Aha, this’ll be why – the Json.JsonConfig namespace content model is, confusingly, not added by JsonConfig itself, but in CommonSettings.php:

	if ( $wmgUseGraphWithJsonNamespace ) {
		$wgJsonConfigModels['Json.JsonConfig'] = null;
		$wgJsonConfigs['Json.JsonConfig'] = [
			'namespace' => 486,
			'nsName' => 'Data',
			'isLocal' => true,
			'pattern' => '/^Json:./',
		];
	}

And all this is in if ( $wmgUseGraph ) {, which remains disabled, despite @Zabe reenabling JsonConfig on its own earlier.

In T335130#8796272, @Lucas_Werkmeister_WMDE wrote:

	if ( $wmgUseGraphWithJsonNamespace ) {
		$wgJsonConfigModels['Json.JsonConfig'] = null;
		$wgJsonConfigs['Json.JsonConfig'] = [
			'namespace' => 486,
			'nsName' => 'Data',
			'isLocal' => true,
			'pattern' => '/^Json:./',
		];
	}

I think it should be fine to move this block outside of the $wmgUseGraph check, so that it runs on wikis with $wmgUseGraphWithJsonNamespace = true even when Graph is disabled? (collabwiki is the only such wiki left anyways, “To be removed as per T124748”, mediawikiwiki having been removed earlier today incidentally.)

Change 910479 had a related patch set uploaded (by Lucas Werkmeister (WMDE); author: Lucas Werkmeister (WMDE)):

[operations/mediawiki-config@master] Make $wmgUseGraphWithJsonNamespace depend on $wmgUseJsonConfig

https://gerrit.wikimedia.org/r/910479

I think it should be fine to move this block outside of the $wmgUseGraph check, so that it runs on wikis with $wmgUseGraphWithJsonNamespace = true even when Graph is disabled?

On second thought, let’s move it into the $wmgUseJsonConfig block instead. I missed earlier that this assigns to $wgJsonConfigModels and $wgJsonConfigs, not e.g. $wgContentHandlers, so I assume it wouldn’t have any effect if JsonConfig wasn’t loaded.

Change 910479 merged by jenkins-bot:

[operations/mediawiki-config@master] Make $wmgUseGraphWithJsonNamespace depend on $wmgUseJsonConfig

https://gerrit.wikimedia.org/r/910479

Mentioned in SAL (#wikimedia-operations) [2023-04-20T14:42:41Z] <lucaswerkmeister-wmde@deploy2002> Started scap: Backport for [[gerrit:910479|Make $wmgUseGraphWithJsonNamespace depend on $wmgUseJsonConfig (T335130)]]

Mentioned in SAL (#wikimedia-operations) [2023-04-20T14:43:56Z] <lucaswerkmeister-wmde@deploy2002> lucaswerkmeister-wmde: Backport for [[gerrit:910479|Make $wmgUseGraphWithJsonNamespace depend on $wmgUseJsonConfig (T335130)]] synced to the testservers: mwdebug1002.eqiad.wmnet, mwdebug1001.eqiad.wmnet, mwdebug2001.codfw.wmnet, mwdebug2002.codfw.wmnet

Mentioned in SAL (#wikimedia-operations) [2023-04-20T14:50:22Z] <lucaswerkmeister-wmde@deploy2002> Finished scap: Backport for [[gerrit:910479|Make $wmgUseGraphWithJsonNamespace depend on $wmgUseJsonConfig (T335130)]] (duration: 07m 40s)

Change 910780 had a related patch set uploaded (by Lucas Werkmeister (WMDE); author: Lucas Werkmeister (WMDE)):

[operations/mediawiki-config@master] Set wmgUseGraphWithJsonNamespace = true for mediawikiwiki

https://gerrit.wikimedia.org/r/910780

Change 910780 merged by jenkins-bot:

[operations/mediawiki-config@master] Set wmgUseGraphWithJsonNamespace = true for mediawikiwiki

https://gerrit.wikimedia.org/r/910780

Mentioned in SAL (#wikimedia-operations) [2023-04-21T15:47:13Z] <lucaswerkmeister-wmde@deploy2002> Started scap: Backport for [[gerrit:910780|Set wmgUseGraphWithJsonNamespace = true for mediawikiwiki (T124748 T335130)]]

Mentioned in SAL (#wikimedia-operations) [2023-04-21T15:48:48Z] <lucaswerkmeister-wmde@deploy2002> lucaswerkmeister-wmde: Backport for [[gerrit:910780|Set wmgUseGraphWithJsonNamespace = true for mediawikiwiki (T124748 T335130)]] synced to the testservers: mwdebug1002.eqiad.wmnet, mwdebug2001.codfw.wmnet, mwdebug1001.eqiad.wmnet, mwdebug2002.codfw.wmnet

Mentioned in SAL (#wikimedia-operations) [2023-04-21T15:57:15Z] <lucaswerkmeister-wmde@deploy2002> Finished scap: Backport for [[gerrit:910780|Set wmgUseGraphWithJsonNamespace = true for mediawikiwiki (T124748 T335130)]] (duration: 10m 01s)

A note just to say that the mediawiki metadata dumps ran successfully after this patch was deployed. Thanks!

I am not sure if it's relevant here, but in case it's useful: The is a way to keep page histories and diffs workign after a content model has been removed from a wiki. That's the job of FallbackContentHandler. Just register it for the relevant content model, e.g.:

$wgContentHandlers['Json.JsonConfig'] = FallbackContentHandler::class;

In T335130#8804384, @daniel wrote:

I am not sure if it's relevant here, but in case it's useful: The is a way to keep page histories and diffs workign after a content model has been removed from a wiki. That's the job of FallbackContentHandler. Just register it for the relevant content model, e.g.:

$wgContentHandlers['Json.JsonConfig'] = FallbackContentHandler::class;

Yeah, we have a set of shims for otherwise-removed extensions/code in WikimediaMessages; perhaps it should be put there if the code shouldn't be in the Graph extension any more?