includes/deferred/WANCacheReapUpdate.php

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