A large proportion of the warnings in T267945: Increase in DBPerformance warnings since 1.36.0-wmf.13 are coming from special page GET requests that check user blocks.
Summary
When PermissionManager::checkUserBlock is called with PermissionManager::RIGOR_SECURE, the primary database is always used, due to the following line:
$useReplica = ( $rigor !== self::RIGOR_SECURE );
Many special pages are calling this method on GET requests, either by passing PermissionManager::RIGOR_SECURE directly, or by not passing anything and using the default rigor level.
These special pages can either execute on GET or POST, and they simply do the same checks on both. Example with Special:MovePage:
- Displaying the Special:MovePage form is a GET request
- Posting the form is a POST request
- They both do the same block check
- But the primary database should only be checked for the POST request
Details
About 500,000 warnings in the last 24 hours (at the time of writing) satisfy the following filters:
- normalized_message.keyword: Expectation (masterConns <=) 0 by MediaWiki::main not met (actual: {actual}): {query}
- http_method: GET
- exception.trace: SpecialPage->run
- exception.trace: MediaWiki\Permissions\PermissionManager->checkUserBlock
99% of these are related to account creation, with a stack trace like this:
from /srv/mediawiki/php-1.37.0-wmf.5/includes/libs/rdbms/TransactionProfiler.php(432)
#0 /srv/mediawiki/php-1.37.0-wmf.5/includes/libs/rdbms/TransactionProfiler.php(212): Wikimedia\Rdbms\TransactionProfiler->reportExpectationViolated(string, string, integer)
#1 /srv/mediawiki/php-1.37.0-wmf.5/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1010): Wikimedia\Rdbms\TransactionProfiler->recordConnection(string, string, boolean)
#2 /srv/mediawiki/php-1.37.0-wmf.5/includes/libs/rdbms/loadbalancer/LoadBalancer.php(964): Wikimedia\Rdbms\LoadBalancer->getServerConnection(integer, string, integer)
#3 /srv/mediawiki/php-1.37.0-wmf.5/includes/libs/rdbms/loadbalancer/LoadBalancer.php(1130): Wikimedia\Rdbms\LoadBalancer->getConnection(integer, array, string, integer)
#4 /srv/mediawiki/php-1.37.0-wmf.5/includes/GlobalFunctions.php(2307): Wikimedia\Rdbms\LoadBalancer->getMaintenanceConnectionRef(integer, array, string)
#5 /srv/mediawiki/php-1.37.0-wmf.5/includes/block/DatabaseBlock.php(283): wfGetDB(integer)
#6 /srv/mediawiki/php-1.37.0-wmf.5/includes/block/DatabaseBlock.php(936): MediaWiki\Block\DatabaseBlock::newLoad(User, integer, boolean, string)
#7 /srv/mediawiki/php-1.37.0-wmf.5/includes/block/BlockManager.php(145): MediaWiki\Block\DatabaseBlock::newListFromTarget(User, string, boolean)
#8 /srv/mediawiki/php-1.37.0-wmf.5/includes/user/User.php(1641): MediaWiki\Block\BlockManager->getUserBlock(User, WebRequest, boolean, boolean)
#9 /srv/mediawiki/php-1.37.0-wmf.5/includes/user/User.php(1936): User->getBlockedStatus(boolean, boolean)
#10 /srv/mediawiki/php-1.37.0-wmf.5/includes/Permissions/PermissionManager.php(725): User->getBlock(boolean)
#11 /srv/mediawiki/php-1.37.0-wmf.5/includes/Permissions/PermissionManager.php(460): MediaWiki\Permissions\PermissionManager->checkUserBlock(string, User, array, string, boolean, Title)
#12 /srv/mediawiki/php-1.37.0-wmf.5/includes/Permissions/PermissionManager.php(310): MediaWiki\Permissions\PermissionManager->getPermissionErrorsInternal(string, User, Title, string)
#13 /srv/mediawiki/php-1.37.0-wmf.5/includes/Permissions/UserAuthority.php(254): MediaWiki\Permissions\PermissionManager->getPermissionErrors(string, User, Title, string)
#14 /srv/mediawiki/php-1.37.0-wmf.5/includes/Permissions/UserAuthority.php(226): MediaWiki\Permissions\UserAuthority->internalCan(string, string, Title, MediaWiki\Permissions\PermissionStatus)
#15 /srv/mediawiki/php-1.37.0-wmf.5/includes/user/User.php(4406): MediaWiki\Permissions\UserAuthority->authorizeWrite(string, Title, MediaWiki\Permissions\PermissionStatus)
#16 /srv/mediawiki/php-1.37.0-wmf.5/includes/auth/AuthManager.php(1057): User->authorizeWrite(string, Title, MediaWiki\Permissions\PermissionStatus)
#17 /srv/mediawiki/php-1.37.0-wmf.5/includes/specials/SpecialCreateAccount.php(75): MediaWiki\Auth\AuthManager->checkAccountCreatePermissions(User)
#18 /srv/mediawiki/php-1.37.0-wmf.5/includes/specialpage/LoginSignupSpecialPage.php(238): SpecialCreateAccount->checkPermissions()
#19 /srv/mediawiki/php-1.37.0-wmf.5/includes/specialpage/SpecialPage.php(646): LoginSignupSpecialPage->execute(NULL)
#20 /srv/mediawiki/php-1.37.0-wmf.5/includes/specialpage/SpecialPageFactory.php(1396): SpecialPage->run(NULL)
#21 /srv/mediawiki/php-1.37.0-wmf.5/includes/MediaWiki.php(313): MediaWiki\SpecialPage\SpecialPageFactory->executePath(string, RequestContext)
#22 /srv/mediawiki/php-1.37.0-wmf.5/includes/MediaWiki.php(916): MediaWiki->performRequest()
#23 /srv/mediawiki/php-1.37.0-wmf.5/includes/MediaWiki.php(550): MediaWiki->main()
#24 /srv/mediawiki/php-1.37.0-wmf.5/index.php(53): MediaWiki->run()
#25 /srv/mediawiki/php-1.37.0-wmf.5/index.php(46): wfIndexMain()
#26 /srv/mediawiki/w/index.php(3): require(string)
#27 {main}SpecialCreateAccount::checkPermissions eventually calls UserAuthority::authorizeWrite, which passes PermissionManager::RIGOR_SECURE through to PermissionManager::getPermissionErrors.
The other 1% come from various different special pages calling PermissionManager methods (getPermissionErrors, userCan, etc) directly.
Possible solutions
Change PermissionManager::checkUserBlock
A quick solution that should fix all of these cases would be to change the above line from PermissionManager::checkUserBlock to something like:
$useReplica = $rigor !== self::RIGOR_SECURE && $user->getRequest()->getMethod() !== 'GET';
PermissionManager::checkUserBlock already checks properties of the WebRequest, so if checking the HTTP request method here is undesirable, it could presumably be fixed at the same time and in the same way as checking the IP address, etc. (perhaps as part of T231930).
Change the callers
We could pass the correct rigor level from the callers. This would involve:
- Somehow calling through to UserAuthority::authorizeRead instead of UserAuthority::authorizeWrite from SpecialCreateAccount::checkPermissions
- Passing the appropriate rigor level from the special pages that call PermissionManager methods directly
Both of the above
This might be the most correct thing to do, since callers should pass the correct rigor level and PermissionManager::checkUserBlock should arguably not allow connecting to the primary database on GET requests.
