includes/deferred/WANCacheReapUpdate.php

   1 <?php
   2
   3 use MediaWiki\Linker\LinkTarget;
   4 use MediaWiki\MediaWikiServices;
   5 use Psr\Log\LoggerInterface;
   6 use Wikimedia\Rdbms\IDatabase;
   7
   8 /**
   9  * Class for fixing stale WANObjectCache keys using a purge event source
  10  *
  11  * This is useful for expiring keys that missed fire-and-forget purges. This uses the
  12  * recentchanges table as a reliable stream to make certain keys reach consistency
  13  * as soon as the underlying replica database catches up. These means that critical
  14  * keys will not escape getting purged simply due to brief hiccups in the network,
  15  * which are more prone to happen across datacenters.
  16  *
  17  * ----
  18  * "I was trying to cheat death. I was only trying to surmount for a little while the
  19  * darkness that all my life I surely knew was going to come rolling in on me some day
  20  * and obliterate me. I was only to stay alive a little brief while longer, after I was
  21  * already gone. To stay in the light, to be with the living, a little while past my time."
  22  *   -- Notes for "Blues of a Lifetime", by [[Cornell Woolrich]]
  23  *
  24  * @since 1.28
  25  */
  26 class WANCacheReapUpdate implements DeferrableUpdate {
  27         /** @var IDatabase */
  28         private $db;
  29         /** @var LoggerInterface */
  30         private $logger;
  31
  32         /**
  33          * @param IDatabase $db
  34          * @param LoggerInterface $logger
  35          */
  36         public function __construct( IDatabase $db, LoggerInterface $logger ) {
  37                 $this->db = $db;
  38                 $this->logger = $logger;
  39         }
  40
  41         public function doUpdate() {
  42                 $reaper = new WANObjectCacheReaper(
  43                         MediaWikiServices::getInstance()->getMainWANObjectCache(),
  44                         ObjectCache::getLocalClusterInstance(),
  45                         [ $this, 'getTitleChangeEvents' ],
  46                         [ $this, 'getEventAffectedKeys' ],
  47                         [
  48                                 'channel' => 'table:recentchanges:' . $this->db->getDomainID(),
  49                                 'logger' => $this->logger
  50                         ]
  51                 );
  52
  53                 $reaper->invoke( 100 );
  54         }
  55
  56         /**
  57          * @see WANObjectCacheRepear
  58          *
  59          * @param int $start
  60          * @param int $id
  61          * @param int $end
  62          * @param int $limit
  63          * @return TitleValue[]
  64          */
  65         public function getTitleChangeEvents( $start, $id, $end, $limit ) {
  66                 $db = $this->db;
  67                 $encStart = $db->addQuotes( $db->timestamp( $start ) );
  68                 $encEnd = $db->addQuotes( $db->timestamp( $end ) );
  69                 $id = (int)$id; // cast NULL => 0 since rc_id is an integer
  70
  71                 $res = $db->select(
  72                         'recentchanges',
  73                         [ 'rc_namespace', 'rc_title', 'rc_timestamp', 'rc_id' ],
  74                         [
  75                                 $db->makeList( [
  76                                         "rc_timestamp > $encStart",
  77                                         "rc_timestamp = $encStart AND rc_id > " . $db->addQuotes( $id )
  78                                 ], LIST_OR ),
  79                                 "rc_timestamp < $encEnd"
  80                         ],
  81                         __METHOD__,
  82                         [ 'ORDER BY' => [ 'rc_timestamp ASC', 'rc_id ASC' ], 'LIMIT' => $limit ]
  83                 );
  84
  85                 $events = [];
  86                 foreach ( $res as $row ) {
  87                         $events[] = [
  88                                 'id' => (int)$row->rc_id,
  89                                 'pos' => (int)wfTimestamp( TS_UNIX, $row->rc_timestamp ),
  90                                 'item' => new TitleValue( (int)$row->rc_namespace, $row->rc_title )
  91                         ];
  92                 }
  93
  94                 return $events;
  95         }
  96
  97         /**
  98          * Gets a list of important cache keys associated with a title
  99          *
 100          * @see WANObjectCacheRepear
 101          * @param WANObjectCache $cache
 102          * @param LinkTarget $t
 103          * @return string[]
 104          */
 105         public function getEventAffectedKeys( WANObjectCache $cache, LinkTarget $t ) {
 106                 /** @var WikiPage[]|LocalFile[]|User[] $entities */
 107                 $entities = [];
 108
 109                 // You can't create a WikiPage for special pages (-1) or other virtual
 110                 // namespaces, but special pages do appear in RC sometimes, e.g. for logs
 111                 // of AbuseFilter filter changes.
 112                 if ( $t->getNamespace() >= 0 ) {
 113                         $entities[] = WikiPage::factory( Title::newFromLinkTarget( $t ) );
 114                 }
 115
 116                 if ( $t->inNamespace( NS_FILE ) ) {
 117                         $entities[] = MediaWikiServices::getInstance()->getRepoGroup()->getLocalRepo()
 118                                 ->newFile( $t->getText() );
 119                 }
 120                 if ( $t->inNamespace( NS_USER ) ) {
 121                         $entities[] = User::newFromName( $t->getText(), false );
 122                 }
 123
 124                 $keys = [];
 125                 foreach ( $entities as $entity ) {
 126                         if ( $entity ) {
 127                                 $keys = array_merge( $keys, $entity->getMutableCacheKeys( $cache ) );
 128                         }
 129                 }
 130                 if ( $keys ) {
 131                         $this->logger->debug( __CLASS__ . ': got key(s) ' . implode( ', ', $keys ) );
 132                 }
 133
 134                 return $keys;
 135         }
 136 }