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:      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 to
  52          *                  secondary stores are deferred when possible. Async writes
  53          *                  require the 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          *
  60          * @param array $params
  61          * @throws InvalidArgumentException
  62          */
  63         public function __construct( $params ) {
  64                 parent::__construct( $params );
  65
  66                 if ( empty( $params['caches'] ) || !is_array( $params['caches'] ) ) {
  67                         throw new InvalidArgumentException(
  68                                 __METHOD__ . ': "caches" parameter must be an array of caches'
  69                         );
  70                 }
  71
  72                 $this->caches = array();
  73                 foreach ( $params['caches'] as $cacheInfo ) {
  74                         if ( $cacheInfo instanceof BagOStuff ) {
  75                                 $this->caches[] = $cacheInfo;
  76                         } else {
  77                                 if ( !isset( $cacheInfo['args'] ) ) {
  78                                         // B/C for when $cacheInfo was for ObjectCache::newFromParams().
  79                                         // Callers intenting this to be for ObjectFactory::getObjectFromSpec
  80                                         // should have set "args" per the docs above. Doings so avoids extra
  81                                         // (likely harmless) params (factory/class/calls) ending up in "args".
  82                                         $cacheInfo['args'] = array( $cacheInfo );
  83                                 }
  84                                 $this->caches[] = ObjectFactory::getObjectFromSpec( $cacheInfo );
  85                         }
  86                 }
  87
  88                 $this->asyncWrites = isset( $params['replication'] ) && $params['replication'] === 'async';
  89         }
  90
  91         /**
  92          * @param bool $debug
  93          */
  94         public function setDebug( $debug ) {
  95                 $this->doWrite( self::ALL, 'setDebug', $debug );
  96         }
  97
  98         protected function doGet( $key, $flags = 0 ) {
  99                 $misses = 0; // number backends checked
 100                 $value = false;
 101                 foreach ( $this->caches as $cache ) {
 102                         $value = $cache->get( $key, $flags );
 103                         if ( $value !== false ) {
 104                                 break;
 105                         }
 106                         ++$misses;
 107                 }
 108
 109                 if ( $value !== false
 110                         && $misses > 0
 111                         && ( $flags & self::READ_VERIFIED ) == self::READ_VERIFIED
 112                 ) {
 113                         $this->doWrite( $misses, 'set', $key, $value, self::UPGRADE_TTL );
 114                 }
 115
 116                 return $value;
 117         }
 118
 119         /**
 120          * @param string $key
 121          * @param mixed $value
 122          * @param int $exptime
 123          * @return bool
 124          */
 125         public function set( $key, $value, $exptime = 0 ) {
 126                 return $this->doWrite( self::ALL, 'set', $key, $value, $exptime );
 127         }
 128
 129         /**
 130          * @param string $key
 131          * @return bool
 132          */
 133         public function delete( $key ) {
 134                 return $this->doWrite( self::ALL, 'delete', $key );
 135         }
 136
 137         /**
 138          * @param string $key
 139          * @param mixed $value
 140          * @param int $exptime
 141          * @return bool
 142          */
 143         public function add( $key, $value, $exptime = 0 ) {
 144                 return $this->doWrite( self::ALL, 'add', $key, $value, $exptime );
 145         }
 146
 147         /**
 148          * @param string $key
 149          * @param int $value
 150          * @return bool|null
 151          */
 152         public function incr( $key, $value = 1 ) {
 153                 return $this->doWrite( self::ALL, 'incr', $key, $value );
 154         }
 155
 156         /**
 157          * @param string $key
 158          * @param int $value
 159          * @return bool
 160          */
 161         public function decr( $key, $value = 1 ) {
 162                 return $this->doWrite( self::ALL, 'decr', $key, $value );
 163         }
 164
 165         /**
 166          * @param string $key
 167          * @param int $timeout
 168          * @param int $expiry
 169          * @param string $rclass
 170          * @return bool
 171          */
 172         public function lock( $key, $timeout = 6, $expiry = 6, $rclass = '' ) {
 173                 // Lock only the first cache, to avoid deadlocks
 174                 return $this->caches[0]->lock( $key, $timeout, $expiry, $rclass );
 175         }
 176
 177         /**
 178          * @param string $key
 179          * @return bool
 180          */
 181         public function unlock( $key ) {
 182                 return $this->caches[0]->unlock( $key );
 183         }
 184
 185         /**
 186          * @param string $key
 187          * @param callable $callback Callback method to be executed
 188          * @param int $exptime Either an interval in seconds or a unix timestamp for expiry
 189          * @param int $attempts The amount of times to attempt a merge in case of failure
 190          * @return bool Success
 191          */
 192         public function merge( $key, $callback, $exptime = 0, $attempts = 10 ) {
 193                 return $this->doWrite( self::ALL, 'merge', $key, $callback, $exptime );
 194         }
 195
 196         public function getLastError() {
 197                 return $this->caches[0]->getLastError();
 198         }
 199
 200         public function clearLastError() {
 201                 $this->caches[0]->clearLastError();
 202         }
 203
 204         /**
 205          * Apply a write method to the first $count backing caches
 206          *
 207          * @param integer $count
 208          * @param string $method
 209          * @param mixed ...
 210          * @return bool
 211          */
 212         protected function doWrite( $count, $method /*, ... */ ) {
 213                 $ret = true;
 214                 $args = array_slice( func_get_args(), 2 );
 215
 216                 foreach ( $this->caches as $i => $cache ) {
 217                         if ( $i >= $count ) {
 218                                 break; // ignore the lower tiers
 219                         }
 220
 221                         if ( $i == 0 || !$this->asyncWrites ) {
 222                                 // First store or in sync mode: write now and get result
 223                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 224                                         $ret = false;
 225                                 }
 226                         } else {
 227                                 // Secondary write in async mode: do not block this HTTP request
 228                                 $logger = $this->logger;
 229                                 DeferredUpdates::addCallableUpdate(
 230                                         function () use ( $cache, $method, $args, $logger ) {
 231                                                 if ( !call_user_func_array( array( $cache, $method ), $args ) ) {
 232                                                         $logger->warning( "Async $method op failed" );
 233                                                 }
 234                                         }
 235                                 );
 236                         }
 237                 }
 238
 239                 return $ret;
 240         }
 241
 242         /**
 243          * Delete objects expiring before a certain date.
 244          *
 245          * Succeed if any of the child caches succeed.
 246          * @param string $date
 247          * @param bool|callable $progressCallback
 248          * @return bool
 249          */
 250         public function deleteObjectsExpiringBefore( $date, $progressCallback = false ) {
 251                 $ret = false;
 252                 foreach ( $this->caches as $cache ) {
 253                         if ( $cache->deleteObjectsExpiringBefore( $date, $progressCallback ) ) {
 254                                 $ret = true;
 255                         }
 256                 }
 257
 258                 return $ret;
 259         }
 260 }