3 * Object caching using DBA backend.
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.
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.
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
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.
30 * On construction you can pass array( 'dir' => '/some/path' ); as a parameter
31 * to override the default DBA files directory (wfTempDir()).
35 class DBABagOStuff
extends BagOStuff
{
36 var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
39 * @param $params array
41 public function __construct( $params ) {
44 if ( !isset( $params['dir'] ) ) {
45 $params['dir'] = wfTempDir();
48 $this->mFile
= $params['dir'] . '/mw-cache-' . wfWikiID() . '.db';
49 wfDebug( __CLASS__
. ": using cache file {$this->mFile}\n" );
50 $this->mHandler
= $wgDBAhandler;
54 * Encode value and expiry for storage
60 protected function encode( $value, $expiry ) {
61 # Convert to absolute time
62 $expiry = $this->convertExpiry( $expiry );
64 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
69 * @return array list containing value first and expiry second
71 protected function decode( $blob ) {
72 if ( !is_string( $blob ) ) {
73 return array( false, 0 );
76 unserialize( substr( $blob, 11 ) ),
77 intval( substr( $blob, 0, 10 ) )
85 protected function getReader() {
86 if ( file_exists( $this->mFile
) ) {
87 $handle = dba_open( $this->mFile
, 'rl', $this->mHandler
);
89 $handle = $this->getWriter();
93 wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
102 protected function getWriter() {
103 $handle = dba_open( $this->mFile
, 'cl', $this->mHandler
);
106 wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
114 * @param $casToken[optional] mixed
117 public function get( $key, &$casToken = null ) {
118 wfProfileIn( __METHOD__
);
119 wfDebug( __METHOD__
. "($key)\n" );
121 $handle = $this->getReader();
123 wfProfileOut( __METHOD__
);
127 $val = dba_fetch( $key, $handle );
128 list( $val, $expiry ) = $this->decode( $val );
130 # Must close ASAP because locks are held
131 dba_close( $handle );
133 if ( $val !== false && $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" );
144 wfProfileOut( __METHOD__
);
151 * @param $value mixed
152 * @param $exptime int
155 public function set( $key, $value, $exptime = 0 ) {
156 wfProfileIn( __METHOD__
);
157 wfDebug( __METHOD__
. "($key)\n" );
159 $blob = $this->encode( $value, $exptime );
161 $handle = $this->getWriter();
163 wfProfileOut( __METHOD__
);
167 $ret = dba_replace( $key, $blob, $handle );
168 dba_close( $handle );
170 wfProfileOut( __METHOD__
);
175 * @param $casToken mixed
177 * @param $value mixed
178 * @param $exptime int
181 public function cas( $casToken, $key, $value, $exptime = 0 ) {
182 wfProfileIn( __METHOD__
);
183 wfDebug( __METHOD__
. "($key)\n" );
185 $blob = $this->encode( $value, $exptime );
187 $handle = $this->getWriter();
189 wfProfileOut( __METHOD__
);
193 // DBA is locked to any other write connection, so we can safely
194 // compare the current & previous value before saving new value
195 $val = dba_fetch( $key, $handle );
196 list( $val, $exptime ) = $this->decode( $val );
197 if ( $casToken !== $val ) {
198 dba_close( $handle );
202 $ret = dba_replace( $key, $blob, $handle );
203 dba_close( $handle );
205 wfProfileOut( __METHOD__
);
214 public function delete( $key, $time = 0 ) {
215 wfProfileIn( __METHOD__
);
216 wfDebug( __METHOD__
. "($key)\n" );
218 $handle = $this->getWriter();
220 wfProfileOut( __METHOD__
);
224 $ret = !dba_exists( $key, $handle ) ||
dba_delete( $key, $handle );
225 dba_close( $handle );
227 wfProfileOut( __METHOD__
);
233 * @param $value mixed
234 * @param $exptime int
237 public function add( $key, $value, $exptime = 0 ) {
238 wfProfileIn( __METHOD__
);
240 $blob = $this->encode( $value, $exptime );
242 $handle = $this->getWriter();
245 wfProfileOut( __METHOD__
);
249 $ret = dba_insert( $key, $blob, $handle );
251 # Insert failed, check to see if it failed due to an expired key
253 list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
255 if ( $expiry && $expiry < time() ) {
256 # Yes expired, delete and try again
257 dba_delete( $key, $handle );
258 $ret = dba_insert( $key, $blob, $handle );
259 # This time if it failed then it will be handled by the caller like any other race
263 dba_close( $handle );
265 wfProfileOut( __METHOD__
);
271 * @param $step integer
272 * @return integer|bool
274 public function incr( $key, $step = 1 ) {
275 wfProfileIn( __METHOD__
);
277 $handle = $this->getWriter();
280 wfProfileOut( __METHOD__
);
284 list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
285 if ( $value !== false ) {
286 if ( $expiry && $expiry < time() ) {
287 # Key is expired, delete it
288 dba_delete( $key, $handle );
289 wfDebug( __METHOD__
. ": $key expired\n" );
293 $blob = $this->encode( $value, $expiry );
295 $ret = dba_replace( $key, $blob, $handle );
296 $value = $ret ?
$value : false;
300 dba_close( $handle );
302 wfProfileOut( __METHOD__
);
304 return ( $value === false ) ?
false : (int)$value;
308 $reader = $this->getReader();
309 $k1 = dba_firstkey( $reader );
317 $key = dba_nextkey( $reader );
320 $key = dba_nextkey( $reader );