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 MediumSpecificBagOStuff {
  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                 foreach ( $args as &$arg ) {
  53                         $arg = strtr( $arg, ' ', '_' );
  54
  55                         // Make sure %, #, and non-ASCII chars are escaped
  56                         $arg = preg_replace_callback(
  57                                 '/[^\x21-\x22\x24\x26-\x39\x3b-\x7e]+/',
  58                                 function ( $m ) {
  59                                         return rawurlencode( $m[0] );
  60                                 },
  61                                 $arg
  62                         );
  63
  64                         // 33 = 32 characters for the MD5 + 1 for the '#' prefix.
  65                         if ( $charsLeft > 33 && strlen( $arg ) > $charsLeft ) {
  66                                 $arg = '#' . md5( $arg );
  67                         }
  68
  69                         $charsLeft -= strlen( $arg );
  70                 }
  71
  72                 if ( $charsLeft < 0 ) {
  73                         return $keyspace . ':BagOStuff-long-key:##' . md5( implode( ':', $args ) );
  74                 }
  75
  76                 return $keyspace . ':' . implode( ':', $args );
  77         }
  78
  79         /**
  80          * Ensure that a key is safe to use (contains no control characters and no
  81          * characters above the ASCII range.)
  82          *
  83          * @param string $key
  84          * @return string
  85          * @throws Exception
  86          */
  87         public function validateKeyEncoding( $key ) {
  88                 if ( preg_match( '/[^\x21-\x7e]+/', $key ) ) {
  89                         throw new Exception( "Key contains invalid characters: $key" );
  90                 }
  91                 return $key;
  92         }
  93
  94         /**
  95          * @param int|float $exptime
  96          * @return int
  97          */
  98         protected function fixExpiry( $exptime ) {
  99                 if ( $exptime < 0 ) {
 100                         // The PECL driver does not seem to like negative relative values
 101                         $expiresAt = $this->getCurrentTime() + $exptime;
 102                 } elseif ( $this->isRelativeExpiration( $exptime ) ) {
 103                         // TTLs higher than 30 days will be detected as absolute TTLs
 104                         // (UNIX timestamps), and will result in the cache entry being
 105                         // discarded immediately because the expiry is in the past.
 106                         // Clamp expires >30d at 30d, unless they're >=1e9 in which
 107                         // case they are likely to really be absolute (1e9 = 2011-09-09)
 108                         $expiresAt = min( $exptime, self::TTL_MONTH );
 109                 } else {
 110                         $expiresAt = $exptime;
 111                 }
 112
 113                 return (int)$expiresAt;
 114         }
 115 }