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         /**
  39          * @param $params array
  40          */
  41         public function __construct( $params ) {
  42                 global $wgDBAhandler;
  43
  44                 if ( !isset( $params['dir'] ) ) {
  45                         $params['dir'] = wfTempDir();
  46                 }
  47
  48                 $this->mFile = $params['dir']."/mw-cache-" . wfWikiID();
  49                 $this->mFile .= '.db';
  50                 wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
  51                 $this->mHandler = $wgDBAhandler;
  52         }
  53
  54         /**
  55          * Encode value and expiry for storage
  56          * @param $value
  57          * @param $expiry
  58          *
  59          * @return string
  60          */
  61         function encode( $value, $expiry ) {
  62                 # Convert to absolute time
  63                 $expiry = $this->convertExpiry( $expiry );
  64
  65                 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
  66         }
  67
  68         /**
  69          * @param $blob string
  70          * @return array list containing value first and expiry second
  71          */
  72         function decode( $blob ) {
  73                 if ( !is_string( $blob ) ) {
  74                         return array( null, 0 );
  75                 } else {
  76                         return array(
  77                                 unserialize( substr( $blob, 11 ) ),
  78                                 intval( substr( $blob, 0, 10 ) )
  79                         );
  80                 }
  81         }
  82
  83         /**
  84          * @return resource
  85          */
  86         function getReader() {
  87                 if ( file_exists( $this->mFile ) ) {
  88                         $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
  89                 } else {
  90                         $handle = $this->getWriter();
  91                 }
  92
  93                 if ( !$handle ) {
  94                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
  95                 }
  96
  97                 return $handle;
  98         }
  99
 100         /**
 101          * @return resource
 102          */
 103         function getWriter() {
 104                 $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
 105
 106                 if ( !$handle ) {
 107                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
 108                 }
 109
 110                 return $handle;
 111         }
 112
 113         /**
 114          * @param $key string
 115          * @return mixed|null|string
 116          */
 117         function get( $key ) {
 118                 wfProfileIn( __METHOD__ );
 119                 wfDebug( __METHOD__ . "($key)\n" );
 120
 121                 $handle = $this->getReader();
 122                 if ( !$handle ) {
 123                         wfProfileOut( __METHOD__ );
 124                         return null;
 125                 }
 126
 127                 $val = dba_fetch( $key, $handle );
 128                 list( $val, $expiry ) = $this->decode( $val );
 129
 130                 # Must close ASAP because locks are held
 131                 dba_close( $handle );
 132
 133                 if ( !is_null( $val ) && $expiry && $expiry < time() ) {
 134                         # Key is expired, delete it
 135                         $handle = $this->getWriter();
 136                         dba_delete( $key, $handle );
 137                         dba_close( $handle );
 138                         wfDebug( __METHOD__ . ": $key expired\n" );
 139                         $val = null;
 140                 }
 141
 142                 wfProfileOut( __METHOD__ );
 143                 return $val;
 144         }
 145
 146         /**
 147          * @param $key string
 148          * @param $value mixed
 149          * @param $exptime int
 150          * @return bool
 151          */
 152         function set( $key, $value, $exptime = 0 ) {
 153                 wfProfileIn( __METHOD__ );
 154                 wfDebug( __METHOD__ . "($key)\n" );
 155
 156                 $blob = $this->encode( $value, $exptime );
 157
 158                 $handle = $this->getWriter();
 159                 if ( !$handle ) {
 160                         wfProfileOut( __METHOD__ );
 161                         return false;
 162                 }
 163
 164                 $ret = dba_replace( $key, $blob, $handle );
 165                 dba_close( $handle );
 166
 167                 wfProfileOut( __METHOD__ );
 168                 return $ret;
 169         }
 170
 171         /**
 172          * @param $key string
 173          * @param $time int
 174          * @return bool
 175          */
 176         function delete( $key, $time = 0 ) {
 177                 wfProfileIn( __METHOD__ );
 178                 wfDebug( __METHOD__ . "($key)\n" );
 179
 180                 $handle = $this->getWriter();
 181                 if ( !$handle ) {
 182                         wfProfileOut( __METHOD__ );
 183                         return false;
 184                 }
 185
 186                 $ret = dba_delete( $key, $handle );
 187                 dba_close( $handle );
 188
 189                 wfProfileOut( __METHOD__ );
 190                 return $ret;
 191         }
 192
 193         /**
 194          * @param $key string
 195          * @param $value mixed
 196          * @param $exptime int
 197          * @return bool
 198          */
 199         function add( $key, $value, $exptime = 0 ) {
 200                 wfProfileIn( __METHOD__ );
 201
 202                 $blob = $this->encode( $value, $exptime );
 203
 204                 $handle = $this->getWriter();
 205
 206                 if ( !$handle ) {
 207                         wfProfileOut( __METHOD__ );
 208                         return false;
 209                 }
 210
 211                 $ret = dba_insert( $key, $blob, $handle );
 212
 213                 # Insert failed, check to see if it failed due to an expired key
 214                 if ( !$ret ) {
 215                         list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
 216
 217                         if ( $expiry < time() ) {
 218                                 # Yes expired, delete and try again
 219                                 dba_delete( $key, $handle );
 220                                 $ret = dba_insert( $key, $blob, $handle );
 221                                 # This time if it failed then it will be handled by the caller like any other race
 222                         }
 223                 }
 224
 225                 dba_close( $handle );
 226
 227                 wfProfileOut( __METHOD__ );
 228                 return $ret;
 229         }
 230
 231         /**
 232          * @return Array
 233          */
 234         function keys() {
 235                 $reader = $this->getReader();
 236                 $k1 = dba_firstkey( $reader );
 237
 238                 if ( !$k1 ) {
 239                         return array();
 240                 }
 241
 242                 $result[] = $k1;
 243
 244                 $key = dba_nextkey( $reader );
 245                 while ( $key ) {
 246                         $result[] = $key;
 247                         $key = dba_nextkey( $reader );
 248                 }
 249
 250                 return $result;
 251         }
 252 }
 253