includes/libs/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: A numbered array of either ObjectFactory::getObjectFromSpec
  45          *      arrays yeilding BagOStuff objects or direct BagOStuff objects.
  46          *      If using the former, the 'args' field *must* be set.
  47          *      The first cache is the primary one, being the first to
  48          *      be read in the fallback chain. Writes happen to all stores
  49          *      in the order they are defined. However, lock()/unlock() calls
  50          *      only use the primary store.
  51          *   - replication: Either 'sync' or 'async'. This controls whether writes
  52          *      to secondary stores are deferred when possible. Async writes
  53          *      require setting 'asyncHandler'. HHVM register_postsend_function() function.
  54          *      Async writes can increase the chance of some race conditions
  55          *      or cause keys to expire seconds later than expected. It is
  56          *      safe to use for modules when cached values: are immutable,
  57          *      invalidation uses logical TTLs, invalidation uses etag/timestamp
  58          *      validation against the DB, or merge() is used to handle races.
  59          * @param array $params
  60          * @throws InvalidArgumentException
  61          */
  62         public function __construct( $params ) {
  63                 parent::__construct( $params );
  64
  65                 if ( empty( $params['caches'] ) || !is_array( $params['caches'] ) ) {
  66                         throw new InvalidArgumentException(
  67                                 __METHOD__ . ': "caches" parameter must be an array of caches'
  68                         );
  69                 }
  70
  71                 $this->caches = [];
  72                 foreach ( $params['caches'] as $cacheInfo ) {
  73                         if ( $cacheInfo instanceof BagOStuff ) {
  74                                 $this->caches[] = $cacheInfo;
  75                         } else {
  76                                 if ( !isset( $cacheInfo['args'] ) ) {
  77                                         // B/C for when $cacheInfo was for ObjectCache::newFromParams().
  78                                         // Callers intenting this to be for ObjectFactory::getObjectFromSpec
  79                                         // should have set "args" per the docs above. Doings so avoids extra
  80                                         // (likely harmless) params (factory/class/calls) ending up in "args".
  81                                         $cacheInfo['args'] = [ $cacheInfo ];
  82                                 }
  83                                 $this->caches[] = ObjectFactory::getObjectFromSpec( $cacheInfo );
  84                         }
  85                 }
  86
  87                 $this->asyncWrites = (
  88                         isset( $params['replication'] ) &&
  89                         $params['replication'] === 'async' &&
  90                         is_callable( $this->asyncHandler )
  91                 );
  92         }
  93
  94         public function setDebug( $debug ) {
  95                 foreach ( $this->caches as $cache ) {
  96                         $cache->setDebug( $debug );
  97                 }
  98         }
  99
 100         protected function doGet( $key, $flags = 0 ) {
 101                 if ( ( $flags & self::READ_LATEST ) == self::READ_LATEST ) {
 102                         // If the latest write was a delete(), we do NOT want to fallback
 103                         // to the other tiers and possibly see the old value. Also, this
 104                         // is used by mergeViaLock(), which only needs to hit the primary.
 105                         return $this->caches[0]->get( $key, $flags );
 106                 }
 107
 108                 $misses = 0; // number backends checked
 109                 $value = false;
 110                 foreach ( $this->caches as $cache ) {
 111                         $value = $cache->get( $key, $flags );
 112                         if ( $value !== false ) {
 113                                 break;
 114                         }
 115                         ++$misses;
 116                 }
 117
 118                 if ( $value !== false
 119                         && $misses > 0
 120                         && ( $flags & self::READ_VERIFIED ) == self::READ_VERIFIED
 121                 ) {
 122                         $this->doWrite( $misses, $this->asyncWrites, 'set', $key, $value, self::UPGRADE_TTL );
 123                 }
 124
 125                 return $value;
 126         }
 127
 128         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 129                 $asyncWrites = ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC )
 130                         ? false
 131                         : $this->asyncWrites;
 132
 133                 return $this->doWrite( self::ALL, $asyncWrites, 'set', $key, $value, $exptime );
 134         }
 135
 136         public function delete( $key ) {
 137                 return $this->doWrite( self::ALL, $this->asyncWrites, 'delete', $key );
 138         }
 139
 140         public function add( $key, $value, $exptime = 0 ) {
 141                 return $this->doWrite( self::ALL, $this->asyncWrites, 'add', $key, $value, $exptime );
 142         }
 143
 144         public function incr( $key, $value = 1 ) {
 145                 return $this->doWrite( self::ALL, $this->asyncWrites, 'incr', $key, $value );
 146         }
 147
 148         public function decr( $key, $value = 1 ) {
 149                 return $this->doWrite( self::ALL, $this->asyncWrites, 'decr', $key, $value );
 150         }
 151
 152         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 153                 // Only need to lock the first cache; also avoids deadlocks
 154                 return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
 155         }
 156
 157         public function unlock( $key ) {
 158                 // Only the first cache is locked
 159                 return $this->caches[0]->unlock( $key );
 160         }
 161
 162         public function getLastError() {
 163                 return $this->caches[0]->getLastError();
 164         }
 165
 166         public function clearLastError() {
 167                 $this->caches[0]->clearLastError();
 168         }
 169
 170         /**
 171          * Apply a write method to the first $count backing caches
 172          *
 173          * @param integer $count
 174          * @param bool $asyncWrites
 175          * @param string $method
 176          * @param mixed ...
 177          * @return bool
 178          */
 179         protected function doWrite( $count, $asyncWrites, $method /*, ... */ ) {
 180                 $ret = true;
 181                 $args = array_slice( func_get_args(), 3 );
 182
 183                 foreach ( $this->caches as $i => $cache ) {
 184                         if ( $i >= $count ) {
 185                                 break; // ignore the lower tiers
 186                         }
 187
 188                         if ( $i == 0 || !$asyncWrites ) {
 189                                 // First store or in sync mode: write now and get result
 190                                 if ( !call_user_func_array( [ $cache, $method ], $args ) ) {
 191                                         $ret = false;
 192                                 }
 193                         } else {
 194                                 // Secondary write in async mode: do not block this HTTP request
 195                                 $logger = $this->logger;
 196                                 call_user_func(
 197                                         $this->asyncHandler,
 198                                         function () use ( $cache, $method, $args, $logger ) {
 199                                                 if ( !call_user_func_array( [ $cache, $method ], $args ) ) {
 200                                                         $logger->warning( "Async $method op failed" );
 201                                                 }
 202                                         }
 203                                 );
 204                         }
 205                 }
 206
 207                 return $ret;
 208         }
 209
 210         /**
 211          * Delete objects expiring before a certain date.
 212          *
 213          * Succeed if any of the child caches succeed.
 214          * @param string $date
 215          * @param bool|callable $progressCallback
 216          * @return bool
 217          */
 218         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 219                 $ret = false;
 220                 foreach ( $this->caches as $cache ) {
 221                         if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
 222                                 $ret = true;
 223                         }
 224                 }
 225
 226                 return $ret;
 227         }
 228 }