, agent: ) */ protected $client; /** @var bool Whether to no-op all method calls */ protected $enabled = true; /** @var bool Whether to check and wait on positions */ protected $wait = true; /** @var bool Whether the client data was loaded */ protected $initialized = false; /** @var DBMasterPos[] Map of (DB master name => position) */ protected $startupPositions = []; /** @var DBMasterPos[] Map of (DB master name => position) */ protected $shutdownPositions = []; /** * @param BagOStuff $store * @param array $client Map of (ip: , agent: ) * @since 1.27 */ public function __construct( BagOStuff $store, array $client ) { $this->store = $store; $this->client = $client; $this->key = $store->makeGlobalKey( 'ChronologyProtector', md5( $client['ip'] . "\n" . $client['agent'] ) ); } /** * @param bool $enabled Whether to no-op all method calls * @since 1.27 */ public function setEnabled( $enabled ) { $this->enabled = $enabled; } /** * @param bool $enabled Whether to check and wait on positions * @since 1.27 */ public function setWaitEnabled( $enabled ) { $this->wait = $enabled; } /** * Initialise a LoadBalancer to give it appropriate chronology protection. * * If the stash has a previous master position recorded, this will try to * make sure that the next query to a slave of that master will see changes up * to that position by delaying execution. The delay may timeout and allow stale * data if no non-lagged slaves are available. * * @param LoadBalancer $lb * @return void */ public function initLB( LoadBalancer $lb ) { if ( !$this->enabled || $lb->getServerCount() <= 1 ) { return; // non-replicated setup or disabled } $this->initPositions(); $masterName = $lb->getServerName( $lb->getWriterIndex() ); if ( !empty( $this->startupPositions[$masterName] ) ) { $info = $lb->parentInfo(); $pos = $this->startupPositions[$masterName]; wfDebugLog( 'replication', __METHOD__ . ": LB '" . $info['id'] . "' waiting for master pos $pos\n" ); $lb->waitFor( $pos ); } } /** * Notify the ChronologyProtector that the LoadBalancer is about to shut * down. Saves replication positions. * * @param LoadBalancer $lb * @return void */ public function shutdownLB( LoadBalancer $lb ) { if ( !$this->enabled || $lb->getServerCount() <= 1 ) { return; // non-replicated setup or disabled } $info = $lb->parentInfo(); $masterName = $lb->getServerName( $lb->getWriterIndex() ); // Only save the position if writes have been done on the connection $db = $lb->getAnyOpenConnection( $lb->getWriterIndex() ); if ( !$db || !$db->doneWrites() ) { wfDebugLog( 'replication', __METHOD__ . ": LB {$info['id']}, no writes done\n" ); return; // nothing to do } $pos = $db->getMasterPos(); wfDebugLog( 'replication', __METHOD__ . ": LB {$info['id']} has master pos $pos\n" ); $this->shutdownPositions[$masterName] = $pos; } /** * Notify the ChronologyProtector that the LBFactory is done calling shutdownLB() for now. * May commit chronology data to persistent storage. * * @return array Empty on success; returns the (db name => position) map on failure */ public function shutdown() { if ( !$this->enabled || !count( $this->shutdownPositions ) ) { return true; // nothing to save } wfDebugLog( 'replication', __METHOD__ . ": saving master pos for " . implode( ', ', array_keys( $this->shutdownPositions ) ) . "\n" ); $shutdownPositions = $this->shutdownPositions; $ok = $this->store->merge( $this->key, function ( $store, $key, $curValue ) use ( $shutdownPositions ) { /** @var $curPositions DBMasterPos[] */ if ( $curValue === false ) { $curPositions = $shutdownPositions; } else { $curPositions = $curValue['positions']; // Use the newest positions for each DB master foreach ( $shutdownPositions as $db => $pos ) { if ( !isset( $curPositions[$db] ) || $pos->asOfTime() > $curPositions[$db]->asOfTime() ) { $curPositions[$db] = $pos; } } } return [ 'positions' => $curPositions ]; }, BagOStuff::TTL_MINUTE, 10, BagOStuff::WRITE_SYNC // visible in all datacenters ); if ( !$ok ) { // Raced out too many times or stash is down wfDebugLog( 'replication', __METHOD__ . ": failed to save master pos for " . implode( ', ', array_keys( $this->shutdownPositions ) ) . "\n" ); return $this->shutdownPositions; } return []; } /** * Load in previous master positions for the client */ protected function initPositions() { if ( $this->initialized ) { return; } $this->initialized = true; if ( $this->wait ) { $data = $this->store->get( $this->key ); $this->startupPositions = $data ? $data['positions'] : []; wfDebugLog( 'replication', __METHOD__ . ": key is {$this->key} (read)\n" ); } else { $this->startupPositions = []; wfDebugLog( 'replication', __METHOD__ . ": key is {$this->key} (unread)\n" ); } } }