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 (wfTempDir()).
  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                         $params['dir'] = wfTempDir();
  43                 }
  44
  45                 $this->mFile = $params['dir']."/mw-cache-" . wfWikiID();
  46                 $this->mFile .= '.db';
  47                 wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
  48                 $this->mHandler = $wgDBAhandler;
  49         }
  50
  51         /**
  52          * Encode value and expiry for storage
  53          * @param $value
  54          * @param $expiry
  55          *
  56          * @return string
  57          */
  58         function encode( $value, $expiry ) {
  59                 # Convert to absolute time
  60                 $expiry = $this->convertExpiry( $expiry );
  61
  62                 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
  63         }
  64
  65         /**
  66          * @return array list containing value first and expiry second
  67          */
  68         function decode( $blob ) {
  69                 if ( !is_string( $blob ) ) {
  70                         return array( null, 0 );
  71                 } else {
  72                         return array(
  73                                 unserialize( substr( $blob, 11 ) ),
  74                                 intval( substr( $blob, 0, 10 ) )
  75                         );
  76                 }
  77         }
  78
  79         function getReader() {
  80                 if ( file_exists( $this->mFile ) ) {
  81                         $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
  82                 } else {
  83                         $handle = $this->getWriter();
  84                 }
  85
  86                 if ( !$handle ) {
  87                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
  88                 }
  89
  90                 return $handle;
  91         }
  92
  93         function getWriter() {
  94                 $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
  95
  96                 if ( !$handle ) {
  97                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
  98                 }
  99
 100                 return $handle;
 101         }
 102
 103         function get( $key ) {
 104                 wfProfileIn( __METHOD__ );
 105                 wfDebug( __METHOD__ . "($key)\n" );
 106
 107                 $handle = $this->getReader();
 108                 if ( !$handle ) {
 109                         wfProfileOut( __METHOD__ );
 110                         return null;
 111                 }
 112
 113                 $val = dba_fetch( $key, $handle );
 114                 list( $val, $expiry ) = $this->decode( $val );
 115
 116                 # Must close ASAP because locks are held
 117                 dba_close( $handle );
 118
 119                 if ( !is_null( $val ) && $expiry && $expiry < time() ) {
 120                         # Key is expired, delete it
 121                         $handle = $this->getWriter();
 122                         dba_delete( $key, $handle );
 123                         dba_close( $handle );
 124                         wfDebug( __METHOD__ . ": $key expired\n" );
 125                         $val = null;
 126                 }
 127
 128                 wfProfileOut( __METHOD__ );
 129                 return $val;
 130         }
 131
 132         function set( $key, $value, $exptime = 0 ) {
 133                 wfProfileIn( __METHOD__ );
 134                 wfDebug( __METHOD__ . "($key)\n" );
 135
 136                 $blob = $this->encode( $value, $exptime );
 137
 138                 $handle = $this->getWriter();
 139                 if ( !$handle ) {
 140                         wfProfileOut( __METHOD__ );
 141                         return false;
 142                 }
 143
 144                 $ret = dba_replace( $key, $blob, $handle );
 145                 dba_close( $handle );
 146
 147                 wfProfileOut( __METHOD__ );
 148                 return $ret;
 149         }
 150
 151         function delete( $key, $time = 0 ) {
 152                 wfProfileIn( __METHOD__ );
 153                 wfDebug( __METHOD__ . "($key)\n" );
 154
 155                 $handle = $this->getWriter();
 156                 if ( !$handle ) {
 157                         wfProfileOut( __METHOD__ );
 158                         return false;
 159                 }
 160
 161                 $ret = dba_delete( $key, $handle );
 162                 dba_close( $handle );
 163
 164                 wfProfileOut( __METHOD__ );
 165                 return $ret;
 166         }
 167
 168         function add( $key, $value, $exptime = 0 ) {
 169                 wfProfileIn( __METHOD__ );
 170
 171                 $blob = $this->encode( $value, $exptime );
 172
 173                 $handle = $this->getWriter();
 174
 175                 if ( !$handle ) {
 176                         wfProfileOut( __METHOD__ );
 177                         return false;
 178                 }
 179
 180                 $ret = dba_insert( $key, $blob, $handle );
 181
 182                 # Insert failed, check to see if it failed due to an expired key
 183                 if ( !$ret ) {
 184                         list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
 185
 186                         if ( $expiry < time() ) {
 187                                 # Yes expired, delete and try again
 188                                 dba_delete( $key, $handle );
 189                                 $ret = dba_insert( $key, $blob, $handle );
 190                                 # This time if it failed then it will be handled by the caller like any other race
 191                         }
 192                 }
 193
 194                 dba_close( $handle );
 195
 196                 wfProfileOut( __METHOD__ );
 197                 return $ret;
 198         }
 199
 200         function keys() {
 201                 $reader = $this->getReader();
 202                 $k1 = dba_firstkey( $reader );
 203
 204                 if ( !$k1 ) {
 205                         return array();
 206                 }
 207
 208                 $result[] = $k1;
 209
 210                 $key = dba_nextkey( $reader );
 211                 while ( $key ) {
 212                         $result[] = $key;
 213                         $key = dba_nextkey( $reader );
 214                 }
 215
 216                 return $result;
 217         }
 218 }
 219