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 $asyncWrites = false;
  36
  37         /** Idiom for "write to all backends" */
  38         const ALL = INF;
  39
  40         const UPGRADE_TTL = 3600; // TTL when a key is copied to a higher cache tier
  41
  42         /**
  43          * $params include:
  44          *   - caches:      This should have a numbered array of cache parameter
  45          *                  structures, in the style required by $wgObjectCaches. See
  46          *                  the documentation of $wgObjectCaches for more detail.
  47          *                  BagOStuff objects can also be used as values.
  48          *                  The first cache is the primary one, being the first to
  49          *                  be read in the fallback chain. Writes happen to all stores
  50          *                  in the order they are defined. However, lock()/unlock() calls
  51          *                  only use the primary store.
  52          *   - replication: Either 'sync' or 'async'. This controls whether writes to
  53          *                  secondary stores are deferred when possible. Async writes
  54          *                  require the HHVM register_postsend_function() function.
  55          *                  Async writes can increase the chance of some race conditions
  56          *                  or cause keys to expire seconds later than expected. It is
  57          *                  safe to use for modules when cached values: are immutable,
  58          *                  invalidation uses logical TTLs, invalidation uses etag/timestamp
  59          *                  validation against the DB, or merge() is used to handle races.
  60          *
  61          * @param array $params
  62          * @throws InvalidArgumentException
  63          */
  64         public function __construct( $params ) {
  65                 parent::__construct( $params );
  66
  67                 if ( empty( $params['caches'] ) || !is_array( $params['caches'] ) ) {
  68                         throw new InvalidArgumentException(
  69                                 __METHOD__ . ': "caches" parameter must be an array of caches'
  70                         );
  71                 }
  72
  73                 $this->caches = array();
  74                 foreach ( $params['caches'] as $cacheInfo ) {
  75                         $this->caches[] = ( $cacheInfo instanceof BagOStuff )
  76                                 ? $cacheInfo
  77                                 : ObjectCache::newFromParams( $cacheInfo );
  78                 }
  79
  80                 $this->asyncWrites = isset( $params['replication'] ) && $params['replication'] === 'async';
  81         }
  82
  83         /**
  84          * @param bool $debug
  85          */
  86         public function setDebug( $debug ) {
  87                 $this->doWrite( self::ALL, 'setDebug', $debug );
  88         }
  89
  90         protected function doGet( $key, $flags = 0 ) {
  91                 $misses = 0; // number backends checked
  92                 $value = false;
  93                 foreach ( $this->caches as $cache ) {
  94                         $value = $cache->get( $key, $flags );
  95                         if ( $value !== false ) {
  96                                 break;
  97                         }
  98                         ++$misses;
  99                 }
 100
 101                 if ( $value !== false
 102                         && $misses > 0
 103                         && ( $flags & self::READ_VERIFIED ) == self::READ_VERIFIED
 104                 ) {
 105                         $this->doWrite( $misses, 'set', $key, $value, self::UPGRADE_TTL );
 106                 }
 107
 108                 return $value;
 109         }
 110
 111         /**
 112          * @param string $key
 113          * @param mixed $value
 114          * @param int $exptime
 115          * @return bool
 116          */
 117         public function set( $key, $value, $exptime = 0 ) {
 118                 return $this->doWrite( self::ALL, 'set', $key, $value, $exptime );
 119         }
 120
 121         /**
 122          * @param string $key
 123          * @return bool
 124          */
 125         public function delete( $key ) {
 126                 return $this->doWrite( self::ALL, 'delete', $key );
 127         }
 128
 129         /**
 130          * @param string $key
 131          * @param mixed $value
 132          * @param int $exptime
 133          * @return bool
 134          */
 135         public function add( $key, $value, $exptime = 0 ) {
 136                 return $this->doWrite( self::ALL, 'add', $key, $value, $exptime );
 137         }
 138
 139         /**
 140          * @param string $key
 141          * @param int $value
 142          * @return bool|null
 143          */
 144         public function incr( $key, $value = 1 ) {
 145                 return $this->doWrite( self::ALL, 'incr', $key, $value );
 146         }
 147
 148         /**
 149          * @param string $key
 150          * @param int $value
 151          * @return bool
 152          */
 153         public function decr( $key, $value = 1 ) {
 154                 return $this->doWrite( self::ALL, 'decr', $key, $value );
 155         }
 156
 157         /**
 158          * @param string $key
 159          * @param int $timeout
 160          * @param int $expiry
 161          * @param string $rclass
 162          * @return bool
 163          */
 164         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 165                 // Lock only the first cache, to avoid deadlocks
 166                 return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
 167         }
 168
 169         /**
 170          * @param string $key
 171          * @return bool
 172          */
 173         public function unlock( $key ) {
 174                 return $this->caches[0]->unlock( $key );
 175         }
 176
 177         /**
 178          * @param string $key
 179          * @param callable $callback Callback method to be executed
 180          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 181          * @param int $attempts The amount of times to attempt a merge in case of failure
 182          * @return bool Success
 183          */
 184         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 185                 return $this->doWrite( self::ALL, 'merge', $key, $callback, $exptime );
 186         }
 187
 188         public function getLastError() {
 189                 return $this->caches[0]->getLastError();
 190         }
 191
 192         public function clearLastError() {
 193                 $this->caches[0]->clearLastError();
 194         }
 195
 196         /**
 197          * Apply a write method to the first $count backing caches
 198          *
 199          * @param integer $count
 200          * @param string $method
 201          * @param mixed ...
 202          * @return bool
 203          */
 204         protected function doWrite( $count, $method /*, ... */ ) {
 205                 $ret = true;
 206                 $args = array_slice( func_get_args(), 2 );
 207
 208                 foreach ( $this->caches as $i => $cache ) {
 209                         if ( $i >= $count ) {
 210                                 break; // ignore the lower tiers
 211                         }
 212
 213                         if ( $i == 0 || !$this->asyncWrites ) {
 214                                 // First store or in sync mode: write now and get result
 215                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 216                                         $ret = false;
 217                                 }
 218                         } else {
 219                                 // Secondary write in async mode: do not block this HTTP request
 220                                 $logger = $this->logger;
 221                                 DeferredUpdates::addCallableUpdate(
 222                                         function () use ( $cache, $method, $args, $logger ) {
 223                                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 224                                                         $logger->warning( "Async $method op failed" );
 225                                                 }
 226                                         }
 227                                 );
 228                         }
 229                 }
 230
 231                 return $ret;
 232         }
 233
 234         /**
 235          * Delete objects expiring before a certain date.
 236          *
 237          * Succeed if any of the child caches succeed.
 238          * @param string $date
 239          * @param bool|callable $progressCallback
 240          * @return bool
 241          */
 242         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 243                 $ret = false;
 244                 foreach ( $this->caches as $cache ) {
 245                         if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
 246                                 $ret = true;
 247                         }
 248                 }
 249
 250                 return $ret;
 251         }
 252 }