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 );
129 list( $val, $expiry ) = $this->decode( $val );
131 # Must close ASAP because locks are held
132 dba_close( $handle );
134 if ( $val !== false && $expiry && $expiry < time() ) {
135 # Key is expired, delete it
136 $handle = $this->getWriter();
137 dba_delete( $key, $handle );
138 dba_close( $handle );
139 wfDebug( __METHOD__
. ": $key expired\n" );
143 wfProfileOut( __METHOD__
);
150 * @param $value mixed
151 * @param $exptime int
154 public function set( $key, $value, $exptime = 0 ) {
155 wfProfileIn( __METHOD__
);
156 wfDebug( __METHOD__
. "($key)\n" );
158 $blob = $this->encode( $value, $exptime );
160 $handle = $this->getWriter();
162 wfProfileOut( __METHOD__
);
166 $ret = dba_replace( $key, $blob, $handle );
167 dba_close( $handle );
169 wfProfileOut( __METHOD__
);
174 * @param $casToken mixed
176 * @param $value mixed
177 * @param $exptime int
180 public function cas( $casToken, $key, $value, $exptime = 0 ) {
181 wfProfileIn( __METHOD__
);
182 wfDebug( __METHOD__
. "($key)\n" );
184 $blob = $this->encode( $value, $exptime );
186 $handle = $this->getWriter();
188 wfProfileOut( __METHOD__
);
192 // DBA is locked to any other write connection, so we can safely
193 // compare the current & previous value before saving new value
194 $val = dba_fetch( $key, $handle );
195 if ( $casToken !== $val ) {
196 dba_close( $handle );
197 wfProfileOut( __METHOD__
);
201 $ret = dba_replace( $key, $blob, $handle );
202 dba_close( $handle );
204 wfProfileOut( __METHOD__
);
213 public function delete( $key, $time = 0 ) {
214 wfProfileIn( __METHOD__
);
215 wfDebug( __METHOD__
. "($key)\n" );
217 $handle = $this->getWriter();
219 wfProfileOut( __METHOD__
);
223 $ret = !dba_exists( $key, $handle ) ||
dba_delete( $key, $handle );
224 dba_close( $handle );
226 wfProfileOut( __METHOD__
);
232 * @param $value mixed
233 * @param $exptime int
236 public function add( $key, $value, $exptime = 0 ) {
237 wfProfileIn( __METHOD__
);
239 $blob = $this->encode( $value, $exptime );
241 $handle = $this->getWriter();
244 wfProfileOut( __METHOD__
);
248 $ret = dba_insert( $key, $blob, $handle );
250 # Insert failed, check to see if it failed due to an expired key
252 list( , $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
254 if ( $expiry && $expiry < time() ) {
255 # Yes expired, delete and try again
256 dba_delete( $key, $handle );
257 $ret = dba_insert( $key, $blob, $handle );
258 # This time if it failed then it will be handled by the caller like any other race
262 dba_close( $handle );
264 wfProfileOut( __METHOD__
);
270 * @param $step integer
271 * @return integer|bool
273 public function incr( $key, $step = 1 ) {
274 wfProfileIn( __METHOD__
);
276 $handle = $this->getWriter();
279 wfProfileOut( __METHOD__
);
283 list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
284 if ( $value !== false ) {
285 if ( $expiry && $expiry < time() ) {
286 # Key is expired, delete it
287 dba_delete( $key, $handle );
288 wfDebug( __METHOD__
. ": $key expired\n" );
292 $blob = $this->encode( $value, $expiry );
294 $ret = dba_replace( $key, $blob, $handle );
295 $value = $ret ?
$value : false;
299 dba_close( $handle );
301 wfProfileOut( __METHOD__
);
303 return ( $value === false ) ?
false : (int)$value;