3 * Object caching using a SQL database.
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 * Class to store objects in the database
29 class SqlBagOStuff
extends BagOStuff
{
30 protected $serverInfos;
33 protected $serverNames;
36 protected $numServers;
42 protected $lastExpireAll = 0;
45 protected $purgePeriod = 100;
48 protected $shards = 1;
51 protected $tableName = 'objectcache';
53 /** @var array UNIX timestamps */
54 protected $connFailureTimes = array();
56 /** @var array Exceptions */
57 protected $connFailureErrors = array();
60 * Constructor. Parameters are:
61 * - server: A server info structure in the format required by each
62 * element in $wgDBServers.
64 * - servers: An array of server info structures describing a set of
65 * database servers to distribute keys to. If this is
66 * specified, the "server" option will be ignored.
68 * - purgePeriod: The average number of object cache requests in between
69 * garbage collection operations, where expired entries
70 * are removed from the database. Or in other words, the
71 * reciprocal of the probability of purging on any given
72 * request. If this is set to zero, purging will never be
75 * - tableName: The table name to use, default is "objectcache".
77 * - shards: The number of tables to use for data storage on each server.
78 * If this is more than 1, table names will be formed in the style
79 * objectcacheNNN where NNN is the shard index, between 0 and
80 * shards-1. The number of digits will be the minimum number
81 * required to hold the largest shard index. Data will be
82 * distributed across all tables by key hash. This is for
83 * MySQL bugs 61735 and 61736.
85 * @param array $params
87 public function __construct( $params ) {
88 if ( isset( $params['servers'] ) ) {
89 $this->serverInfos
= $params['servers'];
90 $this->numServers
= count( $this->serverInfos
);
91 $this->serverNames
= array();
92 foreach ( $this->serverInfos
as $i => $info ) {
93 $this->serverNames
[$i] = isset( $info['host'] ) ?
$info['host'] : "#$i";
95 } elseif ( isset( $params['server'] ) ) {
96 $this->serverInfos
= array( $params['server'] );
97 $this->numServers
= count( $this->serverInfos
);
99 $this->serverInfos
= false;
100 $this->numServers
= 1;
102 if ( isset( $params['purgePeriod'] ) ) {
103 $this->purgePeriod
= intval( $params['purgePeriod'] );
105 if ( isset( $params['tableName'] ) ) {
106 $this->tableName
= $params['tableName'];
108 if ( isset( $params['shards'] ) ) {
109 $this->shards
= intval( $params['shards'] );
114 * Get a connection to the specified database
116 * @param int $serverIndex
117 * @return DatabaseBase
119 protected function getDB( $serverIndex ) {
120 global $wgDebugDBTransactions;
122 if ( !isset( $this->conns
[$serverIndex] ) ) {
123 if ( $serverIndex >= $this->numServers
) {
124 throw new MWException( __METHOD__
. ": Invalid server index \"$serverIndex\"" );
127 # Don't keep timing out trying to connect for each call if the DB is down
128 if ( isset( $this->connFailureErrors
[$serverIndex] )
129 && ( time() - $this->connFailureTimes
[$serverIndex] ) < 60
131 throw $this->connFailureErrors
[$serverIndex];
134 # If server connection info was given, use that
135 if ( $this->serverInfos
) {
136 if ( $wgDebugDBTransactions ) {
137 wfDebug( "Using provided serverInfo for SqlBagOStuff\n" );
139 $info = $this->serverInfos
[$serverIndex];
140 $type = isset( $info['type'] ) ?
$info['type'] : 'mysql';
141 $host = isset( $info['host'] ) ?
$info['host'] : '[unknown]';
142 wfDebug( __CLASS__
. ": connecting to $host\n" );
143 $db = DatabaseBase
::factory( $type, $info );
144 $db->clearFlag( DBO_TRX
);
146 // We must keep a separate connection to MySQL in order to avoid deadlocks
147 // However, SQLite has an opposite behavior.
148 // @TODO: get this trick to work on PostgreSQL too
149 if ( wfGetDB( DB_MASTER
)->getType() == 'mysql' ) {
150 $lb = wfGetLBFactory()->newMainLB();
151 $db = $lb->getConnection( DB_MASTER
);
152 $db->clearFlag( DBO_TRX
); // auto-commit mode
154 $db = wfGetDB( DB_MASTER
);
157 if ( $wgDebugDBTransactions ) {
158 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $db ) );
160 $this->conns
[$serverIndex] = $db;
163 return $this->conns
[$serverIndex];
167 * Get the server index and table name for a given key
169 * @return array Server index and table name
171 protected function getTableByKey( $key ) {
172 if ( $this->shards
> 1 ) {
173 $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
174 $tableIndex = $hash %
$this->shards
;
178 if ( $this->numServers
> 1 ) {
179 $sortedServers = $this->serverNames
;
180 ArrayUtils
::consistentHashSort( $sortedServers, $key );
181 reset( $sortedServers );
182 $serverIndex = key( $sortedServers );
186 return array( $serverIndex, $this->getTableNameByShard( $tableIndex ) );
190 * Get the table name for a given shard index
194 protected function getTableNameByShard( $index ) {
195 if ( $this->shards
> 1 ) {
196 $decimals = strlen( $this->shards
- 1 );
197 return $this->tableName
.
198 sprintf( "%0{$decimals}d", $index );
200 return $this->tableName
;
206 * @param mixed $casToken [optional]
209 public function get( $key, &$casToken = null ) {
210 $values = $this->getMulti( array( $key ) );
211 if ( array_key_exists( $key, $values ) ) {
212 $casToken = $values[$key];
213 return $values[$key];
222 public function getMulti( array $keys ) {
223 $values = array(); // array of (key => value)
225 $keysByTable = array();
226 foreach ( $keys as $key ) {
227 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
228 $keysByTable[$serverIndex][$tableName][] = $key;
231 $this->garbageCollect(); // expire old entries if any
234 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
236 $db = $this->getDB( $serverIndex );
237 foreach ( $serverKeys as $tableName => $tableKeys ) {
238 $res = $db->select( $tableName,
239 array( 'keyname', 'value', 'exptime' ),
240 array( 'keyname' => $tableKeys ),
242 foreach ( $res as $row ) {
243 $row->serverIndex
= $serverIndex;
244 $row->tableName
= $tableName;
245 $dataRows[$row->keyname
] = $row;
248 } catch ( DBError
$e ) {
249 $this->handleReadError( $e, $serverIndex );
253 foreach ( $keys as $key ) {
254 if ( isset( $dataRows[$key] ) ) { // HIT?
255 $row = $dataRows[$key];
256 $this->debug( "get: retrieved data; expiry time is " . $row->exptime
);
258 $db = $this->getDB( $row->serverIndex
);
259 if ( $this->isExpired( $db, $row->exptime
) ) { // MISS
260 $this->debug( "get: key has expired, deleting" );
261 $db->commit( __METHOD__
, 'flush' );
262 # Put the expiry time in the WHERE condition to avoid deleting a
263 # newly-inserted value
264 $db->delete( $row->tableName
,
265 array( 'keyname' => $key, 'exptime' => $row->exptime
),
267 $db->commit( __METHOD__
, 'flush' );
269 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value
) );
271 } catch ( DBQueryError
$e ) {
272 $this->handleWriteError( $e, $row->serverIndex
);
275 $this->debug( 'get: no matching rows' );
287 public function setMulti( array $data, $expiry = 0 ) {
288 $keysByTable = array();
289 foreach ( $data as $key => $value ) {
290 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
291 $keysByTable[$serverIndex][$tableName][] = $key;
294 $this->garbageCollect(); // expire old entries if any
297 $exptime = (int)$expiry;
298 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
300 $db = $this->getDB( $serverIndex );
301 } catch ( DBError
$e ) {
302 $this->handleWriteError( $e, $serverIndex );
307 if ( $exptime < 0 ) {
311 if ( $exptime == 0 ) {
312 $encExpiry = $this->getMaxDateTime( $db );
314 if ( $exptime < 3.16e8
) { # ~10 years
317 $encExpiry = $db->timestamp( $exptime );
319 foreach ( $serverKeys as $tableName => $tableKeys ) {
321 foreach ( $tableKeys as $key ) {
324 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
325 'exptime' => $encExpiry,
330 $db->commit( __METHOD__
, 'flush' );
337 $db->commit( __METHOD__
, 'flush' );
338 } catch ( DBError
$e ) {
339 $this->handleWriteError( $e, $serverIndex );
354 * @param mixed $value
355 * @param int $exptime
358 public function set( $key, $value, $exptime = 0 ) {
359 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
361 $db = $this->getDB( $serverIndex );
362 $exptime = intval( $exptime );
364 if ( $exptime < 0 ) {
368 if ( $exptime == 0 ) {
369 $encExpiry = $this->getMaxDateTime( $db );
371 if ( $exptime < 3.16e8
) { # ~10 years
375 $encExpiry = $db->timestamp( $exptime );
377 $db->commit( __METHOD__
, 'flush' );
378 // (bug 24425) use a replace if the db supports it instead of
379 // delete/insert to avoid clashes with conflicting keynames
385 'value' => $db->encodeBlob( $this->serialize( $value ) ),
386 'exptime' => $encExpiry
388 $db->commit( __METHOD__
, 'flush' );
389 } catch ( DBError
$e ) {
390 $this->handleWriteError( $e, $serverIndex );
398 * @param mixed $casToken
400 * @param mixed $value
401 * @param int $exptime
404 public function cas( $casToken, $key, $value, $exptime = 0 ) {
405 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
407 $db = $this->getDB( $serverIndex );
408 $exptime = intval( $exptime );
410 if ( $exptime < 0 ) {
414 if ( $exptime == 0 ) {
415 $encExpiry = $this->getMaxDateTime( $db );
417 if ( $exptime < 3.16e8
) { # ~10 years
420 $encExpiry = $db->timestamp( $exptime );
422 $db->commit( __METHOD__
, 'flush' );
423 // (bug 24425) use a replace if the db supports it instead of
424 // delete/insert to avoid clashes with conflicting keynames
429 'value' => $db->encodeBlob( $this->serialize( $value ) ),
430 'exptime' => $encExpiry
434 'value' => $db->encodeBlob( $this->serialize( $casToken ) )
438 $db->commit( __METHOD__
, 'flush' );
439 } catch ( DBQueryError
$e ) {
440 $this->handleWriteError( $e, $serverIndex );
445 return (bool)$db->affectedRows();
453 public function delete( $key, $time = 0 ) {
454 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
456 $db = $this->getDB( $serverIndex );
457 $db->commit( __METHOD__
, 'flush' );
460 array( 'keyname' => $key ),
462 $db->commit( __METHOD__
, 'flush' );
463 } catch ( DBError
$e ) {
464 $this->handleWriteError( $e, $serverIndex );
476 public function incr( $key, $step = 1 ) {
477 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
479 $db = $this->getDB( $serverIndex );
480 $step = intval( $step );
481 $db->commit( __METHOD__
, 'flush' );
482 $row = $db->selectRow(
484 array( 'value', 'exptime' ),
485 array( 'keyname' => $key ),
487 array( 'FOR UPDATE' ) );
488 if ( $row === false ) {
490 $db->commit( __METHOD__
, 'flush' );
494 $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__
);
495 if ( $this->isExpired( $db, $row->exptime
) ) {
496 // Expired, do not reinsert
497 $db->commit( __METHOD__
, 'flush' );
502 $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value
) ) );
503 $newValue = $oldValue +
$step;
504 $db->insert( $tableName,
507 'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
508 'exptime' => $row->exptime
509 ), __METHOD__
, 'IGNORE' );
511 if ( $db->affectedRows() == 0 ) {
512 // Race condition. See bug 28611
515 $db->commit( __METHOD__
, 'flush' );
516 } catch ( DBError
$e ) {
517 $this->handleWriteError( $e, $serverIndex );
525 * @param string $exptime
528 protected function isExpired( $db, $exptime ) {
529 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX
, $exptime ) < time();
533 * @param DatabaseBase $db
536 protected function getMaxDateTime( $db ) {
537 if ( time() > 0x7fffffff ) {
538 return $db->timestamp( 1 << 62 );
540 return $db->timestamp( 0x7fffffff );
544 protected function garbageCollect() {
545 if ( !$this->purgePeriod
) {
549 // Only purge on one in every $this->purgePeriod requests.
550 if ( $this->purgePeriod
!== 1 && mt_rand( 0, $this->purgePeriod
- 1 ) ) {
554 // Avoid repeating the delete within a few seconds
555 if ( $now > ( $this->lastExpireAll +
1 ) ) {
556 $this->lastExpireAll
= $now;
561 public function expireAll() {
562 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
566 * Delete objects from the database which expire before a certain date.
567 * @param string $timestamp
568 * @param bool|callable $progressCallback
571 public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
572 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
574 $db = $this->getDB( $serverIndex );
575 $dbTimestamp = $db->timestamp( $timestamp );
576 $totalSeconds = false;
577 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
578 for ( $i = 0; $i < $this->shards
; $i++
) {
582 if ( $maxExpTime !== false ) {
583 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
586 $this->getTableNameByShard( $i ),
587 array( 'keyname', 'exptime' ),
590 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
591 if ( !$rows->numRows() ) {
595 $row = $rows->current();
596 $minExpTime = $row->exptime
;
597 if ( $totalSeconds === false ) {
598 $totalSeconds = wfTimestamp( TS_UNIX
, $timestamp )
599 - wfTimestamp( TS_UNIX
, $minExpTime );
601 foreach ( $rows as $row ) {
602 $keys[] = $row->keyname
;
603 $maxExpTime = $row->exptime
;
606 $db->commit( __METHOD__
, 'flush' );
608 $this->getTableNameByShard( $i ),
610 'exptime >= ' . $db->addQuotes( $minExpTime ),
611 'exptime < ' . $db->addQuotes( $dbTimestamp ),
615 $db->commit( __METHOD__
, 'flush' );
617 if ( $progressCallback ) {
618 if ( intval( $totalSeconds ) === 0 ) {
621 $remainingSeconds = wfTimestamp( TS_UNIX
, $timestamp )
622 - wfTimestamp( TS_UNIX
, $maxExpTime );
623 if ( $remainingSeconds > $totalSeconds ) {
624 $totalSeconds = $remainingSeconds;
626 $percent = ( $i +
$remainingSeconds / $totalSeconds )
627 / $this->shards
* 100;
629 $percent = ( $percent / $this->numServers
)
630 +
( $serverIndex / $this->numServers
* 100 );
631 call_user_func( $progressCallback, $percent );
635 } catch ( DBError
$e ) {
636 $this->handleWriteError( $e, $serverIndex );
643 public function deleteAll() {
644 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
646 $db = $this->getDB( $serverIndex );
647 for ( $i = 0; $i < $this->shards
; $i++
) {
648 $db->commit( __METHOD__
, 'flush' );
649 $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__
);
650 $db->commit( __METHOD__
, 'flush' );
652 } catch ( DBError
$e ) {
653 $this->handleWriteError( $e, $serverIndex );
661 * Serialize an object and, if possible, compress the representation.
662 * On typical message and page data, this can provide a 3X decrease
663 * in storage requirements.
668 protected function serialize( &$data ) {
669 $serial = serialize( $data );
671 if ( function_exists( 'gzdeflate' ) ) {
672 return gzdeflate( $serial );
679 * Unserialize and, if necessary, decompress an object.
680 * @param string $serial
683 protected function unserialize( $serial ) {
684 if ( function_exists( 'gzinflate' ) ) {
685 wfSuppressWarnings();
686 $decomp = gzinflate( $serial );
689 if ( false !== $decomp ) {
694 $ret = unserialize( $serial );
700 * Handle a DBError which occurred during a read operation.
702 * @param DBError $exception
703 * @param int $serverIndex
705 protected function handleReadError( DBError
$exception, $serverIndex ) {
706 if ( $exception instanceof DBConnectionError
) {
707 $this->markServerDown( $exception, $serverIndex );
709 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
710 if ( $exception instanceof DBConnectionError
) {
711 $this->setLastError( BagOStuff
::ERR_UNREACHABLE
);
712 wfDebug( __METHOD__
. ": ignoring connection error\n" );
714 $this->setLastError( BagOStuff
::ERR_UNEXPECTED
);
715 wfDebug( __METHOD__
. ": ignoring query error\n" );
720 * Handle a DBQueryError which occurred during a write operation.
722 * @param DBError $exception
723 * @param int $serverIndex
725 protected function handleWriteError( DBError
$exception, $serverIndex ) {
726 if ( $exception instanceof DBConnectionError
) {
727 $this->markServerDown( $exception, $serverIndex );
729 if ( $exception->db
&& $exception->db
->wasReadOnlyError() ) {
731 $exception->db
->rollback( __METHOD__
);
732 } catch ( DBError
$e ) {
735 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
736 if ( $exception instanceof DBConnectionError
) {
737 $this->setLastError( BagOStuff
::ERR_UNREACHABLE
);
738 wfDebug( __METHOD__
. ": ignoring connection error\n" );
740 $this->setLastError( BagOStuff
::ERR_UNEXPECTED
);
741 wfDebug( __METHOD__
. ": ignoring query error\n" );
746 * Mark a server down due to a DBConnectionError exception
748 * @param DBError $exception
749 * @param int $serverIndex
751 protected function markServerDown( $exception, $serverIndex ) {
752 if ( isset( $this->connFailureTimes
[$serverIndex] ) ) {
753 if ( time() - $this->connFailureTimes
[$serverIndex] >= 60 ) {
754 unset( $this->connFailureTimes
[$serverIndex] );
755 unset( $this->connFailureErrors
[$serverIndex] );
757 wfDebug( __METHOD__
. ": Server #$serverIndex already down\n" );
762 wfDebug( __METHOD__
. ": Server #$serverIndex down until " . ( $now +
60 ) . "\n" );
763 $this->connFailureTimes
[$serverIndex] = $now;
764 $this->connFailureErrors
[$serverIndex] = $exception;
768 * Create shard tables. For use from eval.php.
770 public function createTables() {
771 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
772 $db = $this->getDB( $serverIndex );
773 if ( $db->getType() !== 'mysql' ) {
774 throw new MWException( __METHOD__
. ' is not supported on this DB server' );
777 for ( $i = 0; $i < $this->shards
; $i++
) {
778 $db->commit( __METHOD__
, 'flush' );
780 'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
781 ' LIKE ' . $db->tableName( 'objectcache' ),
783 $db->commit( __METHOD__
, 'flush' );
790 * Backwards compatibility alias
792 class MediaWikiBagOStuff
extends SqlBagOStuff
{