includes/objectcache/DBABagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using DBA backend.
   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  * Cache that uses DBA as a backend.
  26  * Slow due to the need to constantly open and close the file to avoid holding
  27  * writer locks. Intended for development use only,  as a memcached workalike
  28  * for systems that don't have it.
  29  *
  30  * On construction you can pass array( 'dir' => '/some/path' ); as a parameter
  31  * to override the default DBA files directory (wgTmpDirectory).
  32  *
  33  * @ingroup Cache
  34  */
  35 class DBABagOStuff extends BagOStuff {
  36         var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
  37
  38         public function __construct( $params ) {
  39                 global $wgDBAhandler;
  40
  41                 if ( !isset( $params['dir'] ) ) {
  42                         global $wgTmpDirectory;
  43                         $params['dir'] = $wgTmpDirectory;
  44                 }
  45
  46                 $this->mFile = $params['dir']."/mw-cache-" . wfWikiID();
  47                 $this->mFile .= '.db';
  48                 wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
  49                 $this->mHandler = $wgDBAhandler;
  50         }
  51
  52         /**
  53          * Encode value and expiry for storage
  54          * @param $value
  55          * @param $expiry
  56          *
  57          * @return string
  58          */
  59         function encode( $value, $expiry ) {
  60                 # Convert to absolute time
  61                 $expiry = $this->convertExpiry( $expiry );
  62
  63                 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
  64         }
  65
  66         /**
  67          * @return array list containing value first and expiry second
  68          */
  69         function decode( $blob ) {
  70                 if ( !is_string( $blob ) ) {
  71                         return array( null, 0 );
  72                 } else {
  73                         return array(
  74                                 unserialize( substr( $blob, 11 ) ),
  75                                 intval( substr( $blob, 0, 10 ) )
  76                         );
  77                 }
  78         }
  79
  80         function getReader() {
  81                 if ( file_exists( $this->mFile ) ) {
  82                         $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
  83                 } else {
  84                         $handle = $this->getWriter();
  85                 }
  86
  87                 if ( !$handle ) {
  88                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
  89                 }
  90
  91                 return $handle;
  92         }
  93
  94         function getWriter() {
  95                 $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
  96
  97                 if ( !$handle ) {
  98                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
  99                 }
 100
 101                 return $handle;
 102         }
 103
 104         function get( $key ) {
 105                 wfProfileIn( __METHOD__ );
 106                 wfDebug( __METHOD__ . "($key)\n" );
 107
 108                 $handle = $this->getReader();
 109                 if ( !$handle ) {
 110                         wfProfileOut( __METHOD__ );
 111                         return null;
 112                 }
 113
 114                 $val = dba_fetch( $key, $handle );
 115                 list( $val, $expiry ) = $this->decode( $val );
 116
 117                 # Must close ASAP because locks are held
 118                 dba_close( $handle );
 119
 120                 if ( !is_null( $val ) && $expiry && $expiry < time() ) {
 121                         # Key is expired, delete it
 122                         $handle = $this->getWriter();
 123                         dba_delete( $key, $handle );
 124                         dba_close( $handle );
 125                         wfDebug( __METHOD__ . ": $key expired\n" );
 126                         $val = null;
 127                 }
 128
 129                 wfProfileOut( __METHOD__ );
 130                 return $val;
 131         }
 132
 133         function set( $key, $value, $exptime = 0 ) {
 134                 wfProfileIn( __METHOD__ );
 135                 wfDebug( __METHOD__ . "($key)\n" );
 136
 137                 $blob = $this->encode( $value, $exptime );
 138
 139                 $handle = $this->getWriter();
 140                 if ( !$handle ) {
 141                         wfProfileOut( __METHOD__ );
 142                         return false;
 143                 }
 144
 145                 $ret = dba_replace( $key, $blob, $handle );
 146                 dba_close( $handle );
 147
 148                 wfProfileOut( __METHOD__ );
 149                 return $ret;
 150         }
 151
 152         function delete( $key, $time = 0 ) {
 153                 wfProfileIn( __METHOD__ );
 154                 wfDebug( __METHOD__ . "($key)\n" );
 155
 156                 $handle = $this->getWriter();
 157                 if ( !$handle ) {
 158                         wfProfileOut( __METHOD__ );
 159                         return false;
 160                 }
 161
 162                 $ret = dba_delete( $key, $handle );
 163                 dba_close( $handle );
 164
 165                 wfProfileOut( __METHOD__ );
 166                 return $ret;
 167         }
 168
 169         function add( $key, $value, $exptime = 0 ) {
 170                 wfProfileIn( __METHOD__ );
 171
 172                 $blob = $this->encode( $value, $exptime );
 173
 174                 $handle = $this->getWriter();
 175
 176                 if ( !$handle ) {
 177                         wfProfileOut( __METHOD__ );
 178                         return false;
 179                 }
 180
 181                 $ret = dba_insert( $key, $blob, $handle );
 182
 183                 # Insert failed, check to see if it failed due to an expired key
 184                 if ( !$ret ) {
 185                         list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
 186
 187                         if ( $expiry < time() ) {
 188                                 # Yes expired, delete and try again
 189                                 dba_delete( $key, $handle );
 190                                 $ret = dba_insert( $key, $blob, $handle );
 191                                 # This time if it failed then it will be handled by the caller like any other race
 192                         }
 193                 }
 194
 195                 dba_close( $handle );
 196
 197                 wfProfileOut( __METHOD__ );
 198                 return $ret;
 199         }
 200
 201         function keys() {
 202                 $reader = $this->getReader();
 203                 $k1 = dba_firstkey( $reader );
 204
 205                 if ( !$k1 ) {
 206                         return array();
 207                 }
 208
 209                 $result[] = $k1;
 210
 211                 $key = dba_nextkey( $reader );
 212                 while ( $key ) {
 213                         $result[] = $key;
 214                         $key = dba_nextkey( $reader );
 215                 }
 216
 217                 return $result;
 218         }
 219 }
 220