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                 $this->mergeFlagMaps( $this->caches );
  87
  88                 $this->asyncWrites = (
  89                         isset( $params['replication'] ) &&
  90                         $params['replication'] === 'async' &&
  91                         is_callable( $this->asyncHandler )
  92                 );
  93         }
  94
  95         public function setDebug( $debug ) {
  96                 foreach ( $this->caches as $cache ) {
  97                         $cache->setDebug( $debug );
  98                 }
  99         }
 100
 101         protected function doGet( $key, $flags = 0 ) {
 102                 if ( ( $flags & self::READ_LATEST ) == self::READ_LATEST ) {
 103                         // If the latest write was a delete(), we do NOT want to fallback
 104                         // to the other tiers and possibly see the old value. Also, this
 105                         // is used by mergeViaLock(), which only needs to hit the primary.
 106                         return $this->caches[0]->get( $key, $flags );
 107                 }
 108
 109                 $misses = 0; // number backends checked
 110                 $value = false;
 111                 foreach ( $this->caches as $cache ) {
 112                         $value = $cache->get( $key, $flags );
 113                         if ( $value !== false ) {
 114                                 break;
 115                         }
 116                         ++$misses;
 117                 }
 118
 119                 if ( $value !== false
 120                         && $misses > 0
 121                         && ( $flags & self::READ_VERIFIED ) == self::READ_VERIFIED
 122                 ) {
 123                         $this->doWrite( $misses, $this->asyncWrites, 'set', $key, $value, self::UPGRADE_TTL );
 124                 }
 125
 126                 return $value;
 127         }
 128
 129         public function set( $key, $value, $exptime = 0, $flags = 0 ) {
 130                 $asyncWrites = ( ( $flags & self::WRITE_SYNC ) == self::WRITE_SYNC )
 131                         ? false
 132                         : $this->asyncWrites;
 133
 134                 return $this->doWrite( self::ALL, $asyncWrites, 'set', $key, $value, $exptime );
 135         }
 136
 137         public function delete( $key ) {
 138                 return $this->doWrite( self::ALL, $this->asyncWrites, 'delete', $key );
 139         }
 140
 141         public function add( $key, $value, $exptime = 0 ) {
 142                 return $this->doWrite( self::ALL, $this->asyncWrites, 'add', $key, $value, $exptime );
 143         }
 144
 145         public function incr( $key, $value = 1 ) {
 146                 return $this->doWrite( self::ALL, $this->asyncWrites, 'incr', $key, $value );
 147         }
 148
 149         public function decr( $key, $value = 1 ) {
 150                 return $this->doWrite( self::ALL, $this->asyncWrites, 'decr', $key, $value );
 151         }
 152
 153         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 154                 // Only need to lock the first cache; also avoids deadlocks
 155                 return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
 156         }
 157
 158         public function unlock( $key ) {
 159                 // Only the first cache is locked
 160                 return $this->caches[0]->unlock( $key );
 161         }
 162
 163         public function getLastError() {
 164                 return $this->caches[0]->getLastError();
 165         }
 166
 167         public function clearLastError() {
 168                 $this->caches[0]->clearLastError();
 169         }
 170
 171         /**
 172          * Apply a write method to the first $count backing caches
 173          *
 174          * @param int $count
 175          * @param bool $asyncWrites
 176          * @param string $method
 177          * @param mixed $args,...
 178          * @return bool
 179          */
 180         protected function doWrite( $count, $asyncWrites, $method /*, ... */ ) {
 181                 $ret = true;
 182                 $args = array_slice( func_get_args(), 3 );
 183
 184                 if ( $count > 1 && $asyncWrites ) {
 185                         // Deep-clone $args to prevent misbehavior when something writes an
 186                         // object to the BagOStuff then modifies it afterwards, e.g. T168040.
 187                         $args = unserialize( serialize( $args ) );
 188                 }
 189
 190                 foreach ( $this->caches as $i => $cache ) {
 191                         if ( $i >= $count ) {
 192                                 break; // ignore the lower tiers
 193                         }
 194
 195                         if ( $i == 0 || !$asyncWrites ) {
 196                                 // First store or in sync mode: write now and get result
 197                                 if ( !call_user_func_array( [ $cache, $method ], $args ) ) {
 198                                         $ret = false;
 199                                 }
 200                         } else {
 201                                 // Secondary write in async mode: do not block this HTTP request
 202                                 $logger = $this->logger;
 203                                 call_user_func(
 204                                         $this->asyncHandler,
 205                                         function () use ( $cache, $method, $args, $logger ) {
 206                                                 if ( !call_user_func_array( [ $cache, $method ], $args ) ) {
 207                                                         $logger->warning( "Async $method op failed" );
 208                                                 }
 209                                         }
 210                                 );
 211                         }
 212                 }
 213
 214                 return $ret;
 215         }
 216
 217         /**
 218          * Delete objects expiring before a certain date.
 219          *
 220          * Succeed if any of the child caches succeed.
 221          * @param string $date
 222          * @param bool|callable $progressCallback
 223          * @return bool
 224          */
 225         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 226                 $ret = false;
 227                 foreach ( $this->caches as $cache ) {
 228                         if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
 229                                 $ret = true;
 230                         }
 231                 }
 232
 233                 return $ret;
 234         }
 235
 236         public function makeKey( $class, $component = null ) {
 237                 return call_user_func_array( [ $this->caches[0], __FUNCTION__ ], func_get_args() );
 238         }
 239
 240         public function makeGlobalKey( $class, $component = null ) {
 241                 return call_user_func_array( [ $this->caches[0], __FUNCTION__ ], func_get_args() );
 242         }
 243 }