Last modified: 2014-09-30 17:11:47 UTC

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Bug 71461 - [hhvm] MemcachedPeclBagOStuff.php: Error at offset 0 of 6 bytes
[hhvm] MemcachedPeclBagOStuff.php: Error at offset 0 of 6 bytes
Status: RESOLVED DUPLICATE of bug 70747
Product: MediaWiki extensions
Classification: Unclassified
WikidataClient (Other open bugs)
unspecified
All All
: Unprioritized normal (vote)
: ---
Assigned To: Wikidata bugs
: hhvm
Depends on:
Blocks:
  Show dependency tree / graph
 
Reported: 2014-09-30 10:08 UTC by Aude
Modified: 2014-09-30 17:11 UTC (History)
3 users (show)

See Also:
Web browser: ---
Mobile Platform: ---
Assignee Huggle Beta Tester: ---

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Description Aude 2014-09-30 10:08:51 UTC 
There is an inconsistency in how hhvm handles / [de]serializes items (specifically statements) vs. php5.

We have test.wikidata on hhvm only

We have test2.wikipedia which has hhvm as a beta feature, so you can have hhvm or not.

If I use the property parser function on a connected page, then the entity is loaded via CachingEntityRevisionLookup (memcached).

If I am using hhvm, then it works. If I use php5 then I get a stacktrace.

If I remove the statements from the associated item, then then no stacktrace on the test2 page.

Unexpected non-MediaWiki exception encountered, of type "UnexpectedValueException"
[b084b1ad] /wiki/Kitten Exception from line 124 of /srv/mediawiki/php-1.25wmf1/includes/objectcache/MemcachedPeclBagOStuff.php: Error at offset 0 of 6 bytes
Backtrace:
#0 [internal function]: SplObjectStorage->unserialize(string)
#1 /srv/mediawiki/php-1.25wmf1/includes/objectcache/MemcachedPeclBagOStuff.php(124): Memcached->get(string, NULL, NULL)
#2 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/CachingEntityRevisionLookup.php(107): MemcachedPeclBagOStuff->get(string)
#3 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/CachingEntityRevisionLookup.php(146): Wikibase\Lib\Store\CachingEntityRevisionLookup->getEntityRevision(Wikibase\DataModel\Entity\ItemId, integer)
#4 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/CachingEntityRevisionLookup.php(126): Wikibase\Lib\Store\CachingEntityRevisionLookup->fetchEntityRevision(Wikibase\DataModel\Entity\ItemId, integer)
#5 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/RevisionBasedEntityLookup.php(41): Wikibase\Lib\Store\CachingEntityRevisionLookup->getEntityRevision(Wikibase\DataModel\Entity\ItemId)
#6 [internal function]: Wikibase\Lib\Store\RevisionBasedEntityLookup->getEntity(Wikibase\DataModel\Entity\ItemId)
#7 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/EntityRedirectResolvingDecorator.php(79): call_user_func_array(array, array)
#8 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/RedirectResolvingEntityLookup.php(50): Wikibase\Lib\Store\EntityRedirectResolvingDecorator->__call(string, array)
#9 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/lib/includes/store/RedirectResolvingEntityLookup.php(50): Wikibase\Lib\Store\EntityRedirectResolvingDecorator->getEntity(Wikibase\DataModel\Entity\ItemId)
#10 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/DataAccess/PropertyParserFunction/SnaksFinder.php(55): Wikibase\Lib\Store\RedirectResolvingEntityLookup->getEntity(Wikibase\DataModel\Entity\ItemId)
#11 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/DataAccess/PropertyParserFunction/LanguageAwareRenderer.php(107): Wikibase\DataAccess\PropertyParserFunction\SnaksFinder->findSnaks(Wikibase\DataModel\Entity\ItemId, string, string)
#12 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/DataAccess/PropertyParserFunction/LanguageAwareRenderer.php(49): Wikibase\DataAccess\PropertyParserFunction\LanguageAwareRenderer->getStatus(Wikibase\DataModel\Entity\ItemId, string)
#13 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/DataAccess/PropertyParserFunction/Runner.php(73): Wikibase\DataAccess\PropertyParserFunction\LanguageAwareRenderer->render(Wikibase\DataModel\Entity\ItemId, string)
#14 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/DataAccess/PropertyParserFunction/Runner.php(120): Wikibase\DataAccess\PropertyParserFunction\Runner->runPropertyParserFunction(Parser, string)
#15 /srv/mediawiki/php-1.25wmf1/extensions/Wikidata/extensions/Wikibase/client/includes/hooks/ParserFunctionRegistrant.php(46): Wikibase\DataAccess\PropertyParserFunction\Runner::render(Parser, string)
#16 [internal function]: Wikibase\Client\Hooks\{closure}(Parser, string)
#17 /srv/mediawiki/php-1.25wmf1/includes/parser/Parser.php(3768): call_user_func_array(Closure, array)
#18 /srv/mediawiki/php-1.25wmf1/includes/parser/Parser.php(3486): Parser->callParserFunction(PPFrame_DOM, string, array)
#19 /srv/mediawiki/php-1.25wmf1/includes/parser/Preprocessor_DOM.php(1179): Parser->braceSubstitution(array, PPFrame_DOM)
#20 /srv/mediawiki/php-1.25wmf1/includes/parser/Parser.php(3296): PPFrame_DOM->expand(PPNode_DOM, integer)
#21 /srv/mediawiki/php-1.25wmf1/includes/parser/Parser.php(1254): Parser->replaceVariables(string)
#22 /srv/mediawiki/php-1.25wmf1/includes/parser/Parser.php(420): Parser->internalParse(string)
#23 /srv/mediawiki/php-1.25wmf1/includes/content/WikitextContent.php(338): Parser->parse(string, Title, ParserOptions, boolean, boolean, integer)
#24 /srv/mediawiki/php-1.25wmf1/includes/content/AbstractContent.php(490): WikitextContent->fillParserOutput(Title, integer, ParserOptions, boolean, ParserOutput)
#25 /srv/mediawiki/php-1.25wmf1/includes/poolcounter/PoolWorkArticleView.php(139): AbstractContent->getParserOutput(Title, integer, ParserOptions)
#26 /srv/mediawiki/php-1.25wmf1/includes/poolcounter/PoolCounterWork.php(123): PoolWorkArticleView->doWork()
#27 /srv/mediawiki/php-1.25wmf1/includes/page/Article.php(688): PoolCounterWork->execute()
#28 /srv/mediawiki/php-1.25wmf1/includes/actions/ViewAction.php(44): Article->view()
#29 /srv/mediawiki/php-1.25wmf1/includes/MediaWiki.php(414): ViewAction->show()
#30 /srv/mediawiki/php-1.25wmf1/includes/MediaWiki.php(282): MediaWiki->performAction(Article, Title)
#31 /srv/mediawiki/php-1.25wmf1/includes/MediaWiki.php(584): MediaWiki->performRequest()
#32 /srv/mediawiki/php-1.25wmf1/includes/MediaWiki.php(435): MediaWiki->main()
#33 /srv/mediawiki/php-1.25wmf1/index.php(46): MediaWiki->run()
#34 /srv/mediawiki/w/index.php(3): require(string)
Comment 1 Aude 2014-09-30 10:09:49 UTC 
also, this was not a problem before we switched to DataModel 1.0
Comment 2 Daniel Kinzler 2014-09-30 11:36:16 UTC 
We actually put full EntityRevision objects into memcached, including the contained Entity objects. I can very well imagine that hhvm's implementation of "native" object serialization differs from vanilla php's.

For further analysis, it would be useful to get our hands on the actual blob.

However, I fear native serialization will remain a problem if fundamentally different versions of php keep sharing a memcached instance. This may mean we have to serialize/unserialize explicitly.
Comment 3 Gerrit Notification Bot 2014-09-30 13:29:05 UTC 
Change 163842 had a related patch set uploaded by Hoo man:
Split Wikibase's entity cache for HHVM/Zend

https://gerrit.wikimedia.org/r/163842
Comment 4 Gerrit Notification Bot 2014-09-30 15:06:10 UTC 
Change 163842 merged by jenkins-bot:
Split Wikibase's entity cache for HHVM/Zend

https://gerrit.wikimedia.org/r/163842
Comment 5 Ori Livneh 2014-09-30 17:11:47 UTC 
Dupe of 70747, which contains an actual blob, too.

*** This bug has been marked as a duplicate of bug 70747 ***
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