includes/objectcache/MultiWriteBagOStuff.php

   1 <?php
   2 /**
   3  * Wrapper for object caching in different caches.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup Cache
  22  */
  23
  24 /**
  25  * A cache class that replicates all writes to multiple child caches. Reads
  26  * are implemented by reading from the caches in the order they are given in
  27  * the configuration until a cache gives a positive result.
  28  *
  29  * @ingroup Cache
  30  */
  31 class MultiWriteBagOStuff extends BagOStuff {
  32         /** @var BagOStuff[] */
  33         protected $caches;
  34         /** @var bool Use async secondary writes */
  35         protected $asyncReplication = false;
  36         /** @var array[] */
  37         protected $asyncWrites = array();
  38
  39         /**
  40          * $params include:
  41          *   - caches:      This should have a numbered array of cache parameter
  42          *                  structures, in the style required by $wgObjectCaches. See
  43          *                  the documentation of $wgObjectCaches for more detail.
  44          *                  BagOStuff objects can also be used as values.
  45          *                  The first cache is the primary one, being the first to
  46          *                  be read in the fallback chain. Writes happen to all stores
  47          *                  in the order they are defined. However, lock()/unlock() calls
  48          *                  only use the primary store.
  49          *   - replication: Either 'sync' or 'async'. This controls whether writes to
  50          *                  secondary stores are deferred when possible. Async writes
  51          *                  require the HHVM register_postsend_function() function.
  52          *                  Async writes can increase the chance of some race conditions
  53          *                  or cause keys to expire seconds later than expected. It is
  54          *                  safe to use for modules when cached values: are immutable,
  55          *                  invalidation uses logical TTLs, invalidation uses etag/timestamp
  56          *                  validation against the DB, or merge() is used to handle races.
  57          *
  58          * @param array $params
  59          * @throws InvalidArgumentException
  60          */
  61         public function __construct( $params ) {
  62                 parent::__construct( $params );
  63
  64                 if ( !isset( $params['caches'] ) ) {
  65                         throw new InvalidArgumentException( __METHOD__ . ': "caches" parameter required' );
  66                 }
  67
  68                 $this->caches = array();
  69                 foreach ( $params['caches'] as $cacheInfo ) {
  70                         $this->caches[] = ( $cacheInfo instanceof BagOStuff )
  71                                 ? $cacheInfo
  72                                 : ObjectCache::newFromParams( $cacheInfo );
  73                 }
  74
  75                 if ( isset( $params['replication'] ) && $params['replication'] === 'async' ) {
  76                         $this->asyncReplication = true;
  77                 }
  78         }
  79
  80         /**
  81          * @param bool $debug
  82          */
  83         public function setDebug( $debug ) {
  84                 $this->doWrite( 'setDebug', $debug );
  85         }
  86
  87         public function get( $key, &$casToken = null, $flags = 0 ) {
  88                 foreach ( $this->caches as $cache ) {
  89                         $value = $cache->get( $key, $casToken, $flags );
  90                         if ( $value !== false ) {
  91                                 return $value;
  92                         }
  93                 }
  94                 return false;
  95         }
  96
  97         /**
  98          * @param string $key
  99          * @param mixed $value
 100          * @param int $exptime
 101          * @return bool
 102          */
 103         public function set( $key, $value, $exptime = 0 ) {
 104                 return $this->doWrite( 'set', $key, $value, $exptime );
 105         }
 106
 107         /**
 108          * @param string $key
 109          * @return bool
 110          */
 111         public function delete( $key ) {
 112                 return $this->doWrite( 'delete', $key );
 113         }
 114
 115         /**
 116          * @param string $key
 117          * @param mixed $value
 118          * @param int $exptime
 119          * @return bool
 120          */
 121         public function add( $key, $value, $exptime = 0 ) {
 122                 return $this->doWrite( 'add', $key, $value, $exptime );
 123         }
 124
 125         /**
 126          * @param string $key
 127          * @param int $value
 128          * @return bool|null
 129          */
 130         public function incr( $key, $value = 1 ) {
 131                 return $this->doWrite( 'incr', $key, $value );
 132         }
 133
 134         /**
 135          * @param string $key
 136          * @param int $value
 137          * @return bool
 138          */
 139         public function decr( $key, $value = 1 ) {
 140                 return $this->doWrite( 'decr', $key, $value );
 141         }
 142
 143         /**
 144          * @param string $key
 145          * @param int $timeout
 146          * @param int $expiry
 147          * @param string $rclass
 148          * @return bool
 149          */
 150         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 151                 // Lock only the first cache, to avoid deadlocks
 152                 if ( isset( $this->caches[0] ) ) {
 153                         return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
 154                 } else {
 155                         return true;
 156                 }
 157         }
 158
 159         /**
 160          * @param string $key
 161          * @return bool
 162          */
 163         public function unlock( $key ) {
 164                 if ( isset( $this->caches[0] ) ) {
 165                         return $this->caches[0]->unlock( $key );
 166                 } else {
 167                         return true;
 168                 }
 169         }
 170
 171         /**
 172          * @param string $key
 173          * @param callable $callback Callback method to be executed
 174          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 175          * @param int $attempts The amount of times to attempt a merge in case of failure
 176          * @return bool Success
 177          */
 178         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 179                 return $this->doWrite( 'merge', $key, $callback, $exptime );
 180         }
 181
 182         public function getLastError() {
 183                 return isset( $this->caches[0] ) ? $this->caches[0]->getLastError() : self::ERR_NONE;
 184         }
 185
 186         public function clearLastError() {
 187                 if ( isset( $this->caches[0] ) ) {
 188                         $this->caches[0]->clearLastError();
 189                 }
 190         }
 191
 192         /**
 193          * @param string $method
 194          * @return bool
 195          */
 196         protected function doWrite( $method /*, ... */ ) {
 197                 $ret = true;
 198                 $args = func_get_args();
 199                 array_shift( $args );
 200
 201                 foreach ( $this->caches as $i => $cache ) {
 202                         if ( $i == 0 || !$this->asyncReplication ) {
 203                                 // First store or in sync mode: write now and get result
 204                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 205                                         $ret = false;
 206                                 }
 207                         } else {
 208                                 // Secondary write in async mode: do not block this HTTP request
 209                                 $logger = $this->logger;
 210                                 DeferredUpdates::addCallableUpdate(
 211                                         function() use ( $cache, $method, $args, $logger ) {
 212                                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 213                                                         $logger->warning( "Async $method op failed" );
 214                                                 }
 215                                         }
 216                                 );
 217                         }
 218                 }
 219
 220                 return $ret;
 221         }
 222
 223         /**
 224          * Delete objects expiring before a certain date.
 225          *
 226          * Succeed if any of the child caches succeed.
 227          * @param string $date
 228          * @param bool|callable $progressCallback
 229          * @return bool
 230          */
 231         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 232                 $ret = false;
 233                 foreach ( $this->caches as $cache ) {
 234                         if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
 235                                 $ret = true;
 236                         }
 237                 }
 238
 239                 return $ret;
 240         }
 241 }