// Initialize the request object in $wgRequest
$wgRequest = RequestContext::getMain()->getRequest(); // BackCompat
-// Set user IP/agent information for causal consistency purposes
+// Set user IP/agent information for causal consistency purposes.
+// The cpPosTime cookie has no prefix and is set by MediaWiki::preOutputCommit().
+$cpPosTime = $wgRequest->getFloat( 'cpPosTime', $wgRequest->getCookie( 'cpPosTime', '' ) );
MediaWikiServices::getInstance()->getDBLoadBalancerFactory()->setRequestInfo( [
'IPAddress' => $wgRequest->getIP(),
'UserAgent' => $wgRequest->getHeader( 'User-Agent' ),
'ChronologyProtection' => $wgRequest->getHeader( 'ChronologyProtection' ),
- // The cpPosTime cookie has no prefix and is set by MediaWiki::preOutputCommit()
- 'ChronologyPositionTime' => $wgRequest->getFloat(
- 'cpPosTime',
- $wgRequest->getCookie( 'cpPosTime', '' )
- )
+ 'ChronologyPositionTime' => $cpPosTime
] );
+// Make sure that caching does not compromise the consistency improvements
+if ( $cpPosTime ) {
+ MediaWikiServices::getInstance()->getMainWANObjectCache()->useInterimHoldOffCaching( false );
+}
+unset( $cpPosTime );
// Useful debug output
if ( $wgCommandLineMode ) {
protected $logger;
/** @var StatsdDataFactoryInterface */
protected $stats;
+ /** @var bool Whether to use "interim" caching while keys are tombstoned */
+ protected $useInterimHoldOffCaching = true;
/** @var int ERR_* constant for the "last error" registry */
protected $lastRelayError = self::ERR_NONE;
* @return mixed
*/
protected function getInterimValue( $key, $versioned, $minTime, &$asOf ) {
+ if ( !$this->useInterimHoldOffCaching ) {
+ return false; // disabled
+ }
+
$wrapped = $this->cache->get( self::INTERIM_KEY_PREFIX . $key );
list( $value ) = $this->unwrap( $wrapped, $this->getCurrentTime() );
if ( $value !== false && $this->isValid( $value, $versioned, $asOf, $minTime ) ) {
$this->processCaches = [];
}
+ /**
+ * Disable the use of brief caching for tombstoned keys
+ *
+ * When a key is purged via delete(), there normally is a period where caching
+ * is hold-off limited to an extremely short time. This method will disable that
+ * caching, forcing the callback to run for any of:
+ * - WANObjectCache::getWithSetCallback()
+ * - WANObjectCache::getMultiWithSetCallback()
+ * - WANObjectCache::getMultiWithUnionSetCallback()
+ *
+ * This is useful when both:
+ * - a) the database used by the callback is known to be up-to-date enough
+ * for some particular purpose (e.g. replica DB has applied transaction X)
+ * - b) the caller needs to exploit that fact, and therefore needs to avoid the
+ * use of inherently volatile and possibly stale interim keys
+ *
+ * @see WANObjectCache::delete()
+ * @param bool $enabled Whether to enable interim caching
+ * @since 1.31
+ */
+ public function useInterimHoldOffCaching( $enabled ) {
+ $this->useInterimHoldOffCaching = $enabled;
+ }
+
/**
* @param int $flag ATTR_* class constant
* @return int QOS_* class constant
$calls = 0;
$func = function () use ( &$calls, $value, $cache, $key ) {
++$calls;
- // Immediately kill any mutex rather than waiting a second
- $cache->delete( $cache::MUTEX_KEY_PREFIX . $key );
return $value;
};
$this->assertEquals( $value, $ret );
$this->assertEquals( 1, $calls, 'Value was populated' );
- // Acquire a lock to verify that getWithSetCallback uses lockTSE properly
+ // Acquire the mutex to verify that getWithSetCallback uses lockTSE properly
$this->internalCache->add( $cache::MUTEX_KEY_PREFIX . $key, 1, 0 );
$checkKeys = [ wfRandomString() ]; // new check keys => force misses
$ret = $cache->getWithSetCallback( $key, 30, $func,
[ 'lockTSE' => 5, 'checkKeys' => $checkKeys ] );
- $this->assertEquals( $value, $ret, 'Callback was not used; used interim' );
- $this->assertEquals( 2, $calls, 'Callback was not used; used interim' );
+ $this->assertEquals( $value, $ret, 'Callback was not used; used interim (mutex failed)' );
+ $this->assertEquals( 2, $calls, 'Callback was not used; used interim (mutex failed)' );
}
/**
];
}
+ /**
+ * @covers WANObjectCache::useInterimHoldOffCaching
+ * @covers WANObjectCache::getInterimValue
+ */
+ public function testInterimHoldOffCaching() {
+ $cache = $this->cache;
+
+ $value = 'CRL-40-940';
+ $wasCalled = 0;
+ $func = function () use ( &$wasCalled, $value ) {
+ $wasCalled++;
+
+ return $value;
+ };
+
+ $cache->useInterimHoldOffCaching( true );
+
+ $key = wfRandomString( 32 );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 1, $wasCalled, 'Value cached' );
+ $cache->delete( $key );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 2, $wasCalled, 'Value regenerated (got mutex)' ); // sets interim
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 3, $wasCalled, 'Value regenerated (got mutex)' ); // sets interim
+ // Lock up the mutex so interim cache is used
+ $this->internalCache->add( $cache::MUTEX_KEY_PREFIX . $key, 1, 0 );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 3, $wasCalled, 'Value interim cached (failed mutex)' );
+ $this->internalCache->delete( $cache::MUTEX_KEY_PREFIX . $key );
+
+ $cache->useInterimHoldOffCaching( false );
+
+ $wasCalled = 0;
+ $key = wfRandomString( 32 );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 1, $wasCalled, 'Value cached' );
+ $cache->delete( $key );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 2, $wasCalled, 'Value regenerated (got mutex)' );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 3, $wasCalled, 'Value still regenerated (got mutex)' );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 4, $wasCalled, 'Value still regenerated (got mutex)' );
+ // Lock up the mutex so interim cache is used
+ $this->internalCache->add( $cache::MUTEX_KEY_PREFIX . $key, 1, 0 );
+ $v = $cache->getWithSetCallback( $key, 60, $func );
+ $this->assertEquals( 5, $wasCalled, 'Value still regenerated (failed mutex)' );
+ }
+
/**
* @covers WANObjectCache::touchCheckKey
* @covers WANObjectCache::resetCheckKey