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exception: Tolerate no service container when trying DB rollback

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If the exception handler gets triggered before a service container is
available, it should not attempt a DB rollback. Attempting to access
the DBLoadBalancerFactory service object would cause a secondary error,
obscuring the original issue.

This might happen when the exception handler is triggered during
bootstrapping or in the installer.

Change-Id: I644bd0953aa5e690fea16d9fc11ca3f24cb3f104
This commit is contained in:
daniel 2022-09-26 15:10:41 +02:00 committed by Krinkle
parent c4a818d5e7
commit 085b9d18c6
1 changed files with 38 additions and 18 deletions
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56
includes/exception/MWExceptionHandler.php
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@ -138,6 +138,43 @@ class MWExceptionHandler {
}
}
/**
* Roll back any open database transactions
*
* This method is used to attempt to recover from exceptions
*/
private static function rollbackPrimaryChanges() {
if ( !MediaWikiServices::hasInstance() ) {
// MediaWiki isn't fully initialized yet, it's not safe to access services.
// This also means that there's nothing to roll back yet.
return;
}
$services = MediaWikiServices::getInstance();
if ( $services->isServiceDisabled( 'DBLoadBalancerFactory' ) ) {
// The DBLoadBalancerFactory is disabled, possibly because we are in the installer,
// or we are in the process of shutting MediaWiki. At this point, any DB transactions
// would already have been committed or rolled back.
return;
}
// Roll back DBs to avoid transaction notices. This might fail
// to roll back some databases due to connection issues or exceptions.
// However, any sensible DB driver will roll back implicitly anyway.
try {
$lbFactory = $services->getDBLoadBalancerFactory();
$lbFactory->rollbackPrimaryChanges( __METHOD__ );
$lbFactory->flushPrimarySessions( __METHOD__ );
} catch ( DBError $e ) {
// If the DB is unreachable, rollback() will throw an error
// and the error report() method might need messages from the DB,
// which would result in an exception loop. PHP may escalate such
// errors to "Exception thrown without a stack frame" fatals, but
// it's better to be explicit here.
self::logException( $e, self::CAUGHT_BY_HANDLER );
}
}
/**
* Roll back any open database transactions and log the stack trace of the throwable
*
@ -151,24 +188,7 @@ class MWExceptionHandler {
Throwable $e,
$catcher = self::CAUGHT_BY_OTHER
) {
$services = MediaWikiServices::getInstance();
if ( !$services->isServiceDisabled( 'DBLoadBalancerFactory' ) ) {
// Rollback DBs to avoid transaction notices. This might fail
// to rollback some databases due to connection issues or exceptions.
// However, any sensible DB driver will rollback implicitly anyway.
try {
$lbFactory = $services->getDBLoadBalancerFactory();
$lbFactory->rollbackPrimaryChanges( __METHOD__ );
$lbFactory->flushPrimarySessions( __METHOD__ );
} catch ( DBError $e2 ) {
// If the DB is unreachable, rollback() will throw an error
// and the error report() method might need messages from the DB,
// which would result in an exception loop. PHP may escalate such
// errors to "Exception thrown without a stack frame" fatals, but
// it's better to be explicit here.
self::logException( $e2, $catcher );
}
}
self::rollbackPrimaryChanges();
self::logException( $e, $catcher );
}