includes/libs/objectcache/MemcachedBagOStuff.php

   1 <?php
   2 /**
   3  * Base class for memcached clients.
   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  * Base class for memcached clients.
  26  *
  27  * @ingroup Cache
  28  */
  29 abstract class MemcachedBagOStuff extends BagOStuff {
  30         function __construct( array $params ) {
  31                 parent::__construct( $params );
  32
  33                 $this->attrMap[self::ATTR_SYNCWRITES] = self::QOS_SYNCWRITES_BE; // unreliable
  34                 $this->segmentationSize = $params['maxPreferedKeySize'] ?? 917504; // < 1MiB
  35         }
  36
  37         /**
  38          * Construct a cache key.
  39          *
  40          * @since 1.27
  41          * @param string $keyspace
  42          * @param array $args
  43          * @return string
  44          */
  45         public function makeKeyInternal( $keyspace, $args ) {
  46                 // Memcached keys have a maximum length of 255 characters. From that,
  47                 // subtract the number of characters we need for the keyspace and for
  48                 // the separator character needed for each argument. To handle some
  49                 // custom prefixes used by thing like WANObjectCache, limit to 205.
  50                 $charsLeft = 205 - strlen( $keyspace ) - count( $args );
  51
  52                 $args = array_map(
  53                         function ( $arg ) use ( &$charsLeft ) {
  54                                 $arg = strtr( $arg, ' ', '_' );
  55
  56                                 // Make sure %, #, and non-ASCII chars are escaped
  57                                 $arg = preg_replace_callback(
  58                                         '/[^\x21-\x22\x24\x26-\x39\x3b-\x7e]+/',
  59                                         function ( $m ) {
  60                                                 return rawurlencode( $m[0] );
  61                                         },
  62                                         $arg
  63                                 );
  64
  65                                 // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
  66                                 if ( $charsLeft > 33 && strlen( $arg ) > $charsLeft ) {
  67                                         $arg = '#' . md5( $arg );
  68                                 }
  69
  70                                 $charsLeft -= strlen( $arg );
  71                                 return $arg;
  72                         },
  73                         $args
  74                 );
  75
  76                 if ( $charsLeft < 0 ) {
  77                         return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $args ) );
  78                 }
  79
  80                 return $keyspace . ':' . implode( ':', $args );
  81         }
  82
  83         /**
  84          * Ensure that a key is safe to use (contains no control characters and no
  85          * characters above the ASCII range.)
  86          *
  87          * @param string $key
  88          * @return string
  89          * @throws Exception
  90          */
  91         public function validateKeyEncoding( $key ) {
  92                 if ( preg_match( '/[^\x21-\x7e]+/', $key ) ) {
  93                         throw new Exception( "Key contains invalid characters: $key" );
  94                 }
  95                 return $key;
  96         }
  97
  98         /**
  99          * TTLs higher than 30 days will be detected as absolute TTLs
 100          * (UNIX timestamps), and will result in the cache entry being
 101          * discarded immediately because the expiry is in the past.
 102          * Clamp expires >30d at 30d, unless they're >=1e9 in which
 103          * case they are likely to really be absolute (1e9 = 2011-09-09)
 104          * @param int $expiry
 105          * @return int
 106          */
 107         function fixExpiry( $expiry ) {
 108                 if ( $expiry > 2592000 && $expiry < 1000000000 ) {
 109                         $expiry = 2592000;
 110                 }
 111                 return (int)$expiry;
 112         }
 113 }