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
24 use \MediaWiki\MediaWikiServices
;
27 * Class to store objects in the database
31 class SqlBagOStuff
extends BagOStuff
{
32 /** @var array[] (server index => server config) */
33 protected $serverInfos;
34 /** @var string[] (server index => tag/host name) */
35 protected $serverTags;
37 protected $numServers;
39 protected $lastExpireAll = 0;
41 protected $purgePeriod = 100;
43 protected $shards = 1;
45 protected $tableName = 'objectcache';
47 protected $slaveOnly = false;
49 protected $syncTimeout = 3;
51 /** @var LoadBalancer|null */
52 protected $separateMainLB;
55 /** @var array UNIX timestamps */
56 protected $connFailureTimes = [];
57 /** @var array Exceptions */
58 protected $connFailureErrors = [];
61 * Constructor. Parameters are:
62 * - server: A server info structure in the format required by each
63 * element in $wgDBServers.
65 * - servers: An array of server info structures describing a set of database servers
66 * to distribute keys to. If this is specified, the "server" option will be
67 * ignored. If string keys are used, then they will be used for consistent
68 * hashing *instead* of the host name (from the server config). This is useful
69 * when a cluster is replicated to another site (with different host names)
70 * but each server has a corresponding replica in the other cluster.
72 * - purgePeriod: The average number of object cache requests in between
73 * garbage collection operations, where expired entries
74 * are removed from the database. Or in other words, the
75 * reciprocal of the probability of purging on any given
76 * request. If this is set to zero, purging will never be
79 * - tableName: The table name to use, default is "objectcache".
81 * - shards: The number of tables to use for data storage on each server.
82 * If this is more than 1, table names will be formed in the style
83 * objectcacheNNN where NNN is the shard index, between 0 and
84 * shards-1. The number of digits will be the minimum number
85 * required to hold the largest shard index. Data will be
86 * distributed across all tables by key hash. This is for
87 * MySQL bugs 61735 and 61736.
88 * - slaveOnly: Whether to only use slave DBs and avoid triggering
89 * garbage collection logic of expired items. This only
90 * makes sense if the primary DB is used and only if get()
91 * calls will be used. This is used by ReplicatedBagOStuff.
92 * - syncTimeout: Max seconds to wait for slaves to catch up for WRITE_SYNC.
94 * @param array $params
96 public function __construct( $params ) {
97 parent
::__construct( $params );
99 $this->attrMap
[self
::ATTR_EMULATION
] = self
::QOS_EMULATION_SQL
;
101 if ( isset( $params['servers'] ) ) {
102 $this->serverInfos
= [];
103 $this->serverTags
= [];
104 $this->numServers
= count( $params['servers'] );
106 foreach ( $params['servers'] as $tag => $info ) {
107 $this->serverInfos
[$index] = $info;
108 if ( is_string( $tag ) ) {
109 $this->serverTags
[$index] = $tag;
111 $this->serverTags
[$index] = isset( $info['host'] ) ?
$info['host'] : "#$index";
115 } elseif ( isset( $params['server'] ) ) {
116 $this->serverInfos
= [ $params['server'] ];
117 $this->numServers
= count( $this->serverInfos
);
119 // Default to using the main wiki's database servers
120 $this->serverInfos
= false;
121 $this->numServers
= 1;
123 if ( isset( $params['purgePeriod'] ) ) {
124 $this->purgePeriod
= intval( $params['purgePeriod'] );
126 if ( isset( $params['tableName'] ) ) {
127 $this->tableName
= $params['tableName'];
129 if ( isset( $params['shards'] ) ) {
130 $this->shards
= intval( $params['shards'] );
132 if ( isset( $params['syncTimeout'] ) ) {
133 $this->syncTimeout
= $params['syncTimeout'];
135 $this->slaveOnly
= !empty( $params['slaveOnly'] );
138 protected function getSeparateMainLB() {
141 if ( $wgDBtype === 'mysql' && $this->usesMainDB() ) {
142 if ( !$this->separateMainLB
) {
143 // We must keep a separate connection to MySQL in order to avoid deadlocks
144 $lbFactory = MediaWikiServices
::getInstance()->getDBLoadBalancerFactory();
145 $this->separateMainLB
= $lbFactory->newMainLB();
147 return $this->separateMainLB
;
149 // However, SQLite has an opposite behavior. And PostgreSQL needs to know
150 // if we are in transaction or not (@TODO: find some PostgreSQL work-around).
156 * Get a connection to the specified database
158 * @param int $serverIndex
160 * @throws MWException
162 protected function getDB( $serverIndex ) {
163 if ( !isset( $this->conns
[$serverIndex] ) ) {
164 if ( $serverIndex >= $this->numServers
) {
165 throw new MWException( __METHOD__
. ": Invalid server index \"$serverIndex\"" );
168 # Don't keep timing out trying to connect for each call if the DB is down
169 if ( isset( $this->connFailureErrors
[$serverIndex] )
170 && ( time() - $this->connFailureTimes
[$serverIndex] ) < 60
172 throw $this->connFailureErrors
[$serverIndex];
175 # If server connection info was given, use that
176 if ( $this->serverInfos
) {
177 $info = $this->serverInfos
[$serverIndex];
178 $type = isset( $info['type'] ) ?
$info['type'] : 'mysql';
179 $host = isset( $info['host'] ) ?
$info['host'] : '[unknown]';
180 $this->logger
->debug( __CLASS__
. ": connecting to $host" );
181 // Use a blank trx profiler to ignore expections as this is a cache
182 $info['trxProfiler'] = new TransactionProfiler();
183 $db = DatabaseBase
::factory( $type, $info );
184 $db->clearFlag( DBO_TRX
);
186 $index = $this->slaveOnly ? DB_SLAVE
: DB_MASTER
;
187 if ( $this->getSeparateMainLB() ) {
188 $db = $this->getSeparateMainLB()->getConnection( $index );
189 $db->clearFlag( DBO_TRX
); // auto-commit mode
191 $db = wfGetDB( $index );
192 // Can't mess with transaction rounds (DBO_TRX) :(
195 $this->logger
->debug( sprintf( "Connection %s will be used for SqlBagOStuff", $db ) );
196 $this->conns
[$serverIndex] = $db;
199 return $this->conns
[$serverIndex];
203 * Get the server index and table name for a given key
205 * @return array Server index and table name
207 protected function getTableByKey( $key ) {
208 if ( $this->shards
> 1 ) {
209 $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
210 $tableIndex = $hash %
$this->shards
;
214 if ( $this->numServers
> 1 ) {
215 $sortedServers = $this->serverTags
;
216 ArrayUtils
::consistentHashSort( $sortedServers, $key );
217 reset( $sortedServers );
218 $serverIndex = key( $sortedServers );
222 return [ $serverIndex, $this->getTableNameByShard( $tableIndex ) ];
226 * Get the table name for a given shard index
230 protected function getTableNameByShard( $index ) {
231 if ( $this->shards
> 1 ) {
232 $decimals = strlen( $this->shards
- 1 );
233 return $this->tableName
.
234 sprintf( "%0{$decimals}d", $index );
236 return $this->tableName
;
240 protected function doGet( $key, $flags = 0 ) {
243 return $this->getWithToken( $key, $casToken, $flags );
246 protected function getWithToken( $key, &$casToken, $flags = 0 ) {
247 $values = $this->getMulti( [ $key ] );
248 if ( array_key_exists( $key, $values ) ) {
249 $casToken = $values[$key];
250 return $values[$key];
255 public function getMulti( array $keys, $flags = 0 ) {
256 $values = []; // array of (key => value)
259 foreach ( $keys as $key ) {
260 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
261 $keysByTable[$serverIndex][$tableName][] = $key;
264 $this->garbageCollect(); // expire old entries if any
267 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
269 $db = $this->getDB( $serverIndex );
270 foreach ( $serverKeys as $tableName => $tableKeys ) {
271 $res = $db->select( $tableName,
272 [ 'keyname', 'value', 'exptime' ],
273 [ 'keyname' => $tableKeys ],
275 // Approximate write-on-the-fly BagOStuff API via blocking.
276 // This approximation fails if a ROLLBACK happens (which is rare).
277 // We do not want to flush the TRX as that can break callers.
278 $db->trxLevel() ?
[ 'LOCK IN SHARE MODE' ] : []
280 if ( $res === false ) {
283 foreach ( $res as $row ) {
284 $row->serverIndex
= $serverIndex;
285 $row->tableName
= $tableName;
286 $dataRows[$row->keyname
] = $row;
289 } catch ( DBError
$e ) {
290 $this->handleReadError( $e, $serverIndex );
294 foreach ( $keys as $key ) {
295 if ( isset( $dataRows[$key] ) ) { // HIT?
296 $row = $dataRows[$key];
297 $this->debug( "get: retrieved data; expiry time is " . $row->exptime
);
300 $db = $this->getDB( $row->serverIndex
);
301 if ( $this->isExpired( $db, $row->exptime
) ) { // MISS
302 $this->debug( "get: key has expired" );
304 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value
) );
306 } catch ( DBQueryError
$e ) {
307 $this->handleWriteError( $e, $db, $row->serverIndex
);
310 $this->debug( 'get: no matching rows' );
317 public function setMulti( array $data, $expiry = 0 ) {
319 foreach ( $data as $key => $value ) {
320 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
321 $keysByTable[$serverIndex][$tableName][] = $key;
324 $this->garbageCollect(); // expire old entries if any
327 $exptime = (int)$expiry;
328 foreach ( $keysByTable as $serverIndex => $serverKeys ) {
331 $db = $this->getDB( $serverIndex );
332 } catch ( DBError
$e ) {
333 $this->handleWriteError( $e, $db, $serverIndex );
338 if ( $exptime < 0 ) {
342 if ( $exptime == 0 ) {
343 $encExpiry = $this->getMaxDateTime( $db );
345 $exptime = $this->convertExpiry( $exptime );
346 $encExpiry = $db->timestamp( $exptime );
348 foreach ( $serverKeys as $tableName => $tableKeys ) {
350 foreach ( $tableKeys as $key ) {
353 'value' => $db->encodeBlob( $this->serialize( $data[$key] ) ),
354 'exptime' => $encExpiry,
365 } catch ( DBError
$e ) {
366 $this->handleWriteError( $e, $db, $serverIndex );
377 public function set( $key, $value, $exptime = 0, $flags = 0 ) {
378 $ok = $this->setMulti( [ $key => $value ], $exptime );
379 if ( ( $flags & self
::WRITE_SYNC
) == self
::WRITE_SYNC
) {
380 $ok = $ok && $this->waitForSlaves();
386 protected function cas( $casToken, $key, $value, $exptime = 0 ) {
387 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
390 $db = $this->getDB( $serverIndex );
391 $exptime = intval( $exptime );
393 if ( $exptime < 0 ) {
397 if ( $exptime == 0 ) {
398 $encExpiry = $this->getMaxDateTime( $db );
400 $exptime = $this->convertExpiry( $exptime );
401 $encExpiry = $db->timestamp( $exptime );
403 // (bug 24425) use a replace if the db supports it instead of
404 // delete/insert to avoid clashes with conflicting keynames
409 'value' => $db->encodeBlob( $this->serialize( $value ) ),
410 'exptime' => $encExpiry
414 'value' => $db->encodeBlob( $this->serialize( $casToken ) )
418 } catch ( DBQueryError
$e ) {
419 $this->handleWriteError( $e, $db, $serverIndex );
424 return (bool)$db->affectedRows();
427 public function delete( $key ) {
428 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
431 $db = $this->getDB( $serverIndex );
434 [ 'keyname' => $key ],
436 } catch ( DBError
$e ) {
437 $this->handleWriteError( $e, $db, $serverIndex );
444 public function incr( $key, $step = 1 ) {
445 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
448 $db = $this->getDB( $serverIndex );
449 $step = intval( $step );
450 $row = $db->selectRow(
452 [ 'value', 'exptime' ],
453 [ 'keyname' => $key ],
456 if ( $row === false ) {
461 $db->delete( $tableName, [ 'keyname' => $key ], __METHOD__
);
462 if ( $this->isExpired( $db, $row->exptime
) ) {
463 // Expired, do not reinsert
468 $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value
) ) );
469 $newValue = $oldValue +
$step;
470 $db->insert( $tableName,
473 'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
474 'exptime' => $row->exptime
475 ], __METHOD__
, 'IGNORE' );
477 if ( $db->affectedRows() == 0 ) {
478 // Race condition. See bug 28611
481 } catch ( DBError
$e ) {
482 $this->handleWriteError( $e, $db, $serverIndex );
489 public function merge( $key, callable
$callback, $exptime = 0, $attempts = 10, $flags = 0 ) {
490 $ok = $this->mergeViaCas( $key, $callback, $exptime, $attempts );
491 if ( ( $flags & self
::WRITE_SYNC
) == self
::WRITE_SYNC
) {
492 $ok = $ok && $this->waitForSlaves();
498 public function changeTTL( $key, $expiry = 0 ) {
499 list( $serverIndex, $tableName ) = $this->getTableByKey( $key );
502 $db = $this->getDB( $serverIndex );
505 [ 'exptime' => $db->timestamp( $this->convertExpiry( $expiry ) ) ],
506 [ 'keyname' => $key, 'exptime > ' . $db->addQuotes( $db->timestamp( time() ) ) ],
509 if ( $db->affectedRows() == 0 ) {
512 } catch ( DBError
$e ) {
513 $this->handleWriteError( $e, $db, $serverIndex );
521 * @param IDatabase $db
522 * @param string $exptime
525 protected function isExpired( $db, $exptime ) {
526 return $exptime != $this->getMaxDateTime( $db ) && wfTimestamp( TS_UNIX
, $exptime ) < time();
530 * @param IDatabase $db
533 protected function getMaxDateTime( $db ) {
534 if ( time() > 0x7fffffff ) {
535 return $db->timestamp( 1 << 62 );
537 return $db->timestamp( 0x7fffffff );
541 protected function garbageCollect() {
542 if ( !$this->purgePeriod ||
$this->slaveOnly
) {
546 // Only purge on one in every $this->purgePeriod requests.
547 if ( $this->purgePeriod
!== 1 && mt_rand( 0, $this->purgePeriod
- 1 ) ) {
551 // Avoid repeating the delete within a few seconds
552 if ( $now > ( $this->lastExpireAll +
1 ) ) {
553 $this->lastExpireAll
= $now;
558 public function expireAll() {
559 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
563 * Delete objects from the database which expire before a certain date.
564 * @param string $timestamp
565 * @param bool|callable $progressCallback
568 public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
569 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
572 $db = $this->getDB( $serverIndex );
573 $dbTimestamp = $db->timestamp( $timestamp );
574 $totalSeconds = false;
575 $baseConds = [ 'exptime < ' . $db->addQuotes( $dbTimestamp ) ];
576 for ( $i = 0; $i < $this->shards
; $i++
) {
580 if ( $maxExpTime !== false ) {
581 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
584 $this->getTableNameByShard( $i ),
585 [ 'keyname', 'exptime' ],
588 [ 'LIMIT' => 100, 'ORDER BY' => 'exptime' ] );
589 if ( $rows === false ||
!$rows->numRows() ) {
593 $row = $rows->current();
594 $minExpTime = $row->exptime
;
595 if ( $totalSeconds === false ) {
596 $totalSeconds = wfTimestamp( TS_UNIX
, $timestamp )
597 - wfTimestamp( TS_UNIX
, $minExpTime );
599 foreach ( $rows as $row ) {
600 $keys[] = $row->keyname
;
601 $maxExpTime = $row->exptime
;
605 $this->getTableNameByShard( $i ),
607 'exptime >= ' . $db->addQuotes( $minExpTime ),
608 'exptime < ' . $db->addQuotes( $dbTimestamp ),
613 if ( $progressCallback ) {
614 if ( intval( $totalSeconds ) === 0 ) {
617 $remainingSeconds = wfTimestamp( TS_UNIX
, $timestamp )
618 - wfTimestamp( TS_UNIX
, $maxExpTime );
619 if ( $remainingSeconds > $totalSeconds ) {
620 $totalSeconds = $remainingSeconds;
622 $processedSeconds = $totalSeconds - $remainingSeconds;
623 $percent = ( $i +
$processedSeconds / $totalSeconds )
624 / $this->shards
* 100;
626 $percent = ( $percent / $this->numServers
)
627 +
( $serverIndex / $this->numServers
* 100 );
628 call_user_func( $progressCallback, $percent );
632 } catch ( DBError
$e ) {
633 $this->handleWriteError( $e, $db, $serverIndex );
641 * Delete content of shard tables in every server.
642 * Return true if the operation is successful, false otherwise.
645 public function deleteAll() {
646 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
649 $db = $this->getDB( $serverIndex );
650 for ( $i = 0; $i < $this->shards
; $i++
) {
651 $db->delete( $this->getTableNameByShard( $i ), '*', __METHOD__
);
653 } catch ( DBError
$e ) {
654 $this->handleWriteError( $e, $db, $serverIndex );
662 * Serialize an object and, if possible, compress the representation.
663 * On typical message and page data, this can provide a 3X decrease
664 * in storage requirements.
669 protected function serialize( &$data ) {
670 $serial = serialize( $data );
672 if ( function_exists( 'gzdeflate' ) ) {
673 return gzdeflate( $serial );
680 * Unserialize and, if necessary, decompress an object.
681 * @param string $serial
684 protected function unserialize( $serial ) {
685 if ( function_exists( 'gzinflate' ) ) {
686 MediaWiki\
suppressWarnings();
687 $decomp = gzinflate( $serial );
688 MediaWiki\restoreWarnings
();
690 if ( false !== $decomp ) {
695 $ret = unserialize( $serial );
701 * Handle a DBError which occurred during a read operation.
703 * @param DBError $exception
704 * @param int $serverIndex
706 protected function handleReadError( DBError
$exception, $serverIndex ) {
707 if ( $exception instanceof DBConnectionError
) {
708 $this->markServerDown( $exception, $serverIndex );
710 $this->logger
->error( "DBError: {$exception->getMessage()}" );
711 if ( $exception instanceof DBConnectionError
) {
712 $this->setLastError( BagOStuff
::ERR_UNREACHABLE
);
713 $this->logger
->debug( __METHOD__
. ": ignoring connection error" );
715 $this->setLastError( BagOStuff
::ERR_UNEXPECTED
);
716 $this->logger
->debug( __METHOD__
. ": ignoring query error" );
721 * Handle a DBQueryError which occurred during a write operation.
723 * @param DBError $exception
724 * @param IDatabase|null $db DB handle or null if connection failed
725 * @param int $serverIndex
728 protected function handleWriteError( DBError
$exception, IDatabase
$db = null, $serverIndex ) {
730 $this->markServerDown( $exception, $serverIndex );
731 } elseif ( $db->wasReadOnlyError() ) {
732 if ( $db->trxLevel() && $this->usesMainDB() ) {
733 // Errors like deadlocks and connection drops already cause rollback.
734 // For consistency, we have no choice but to throw an error and trigger
735 // complete rollback if the main DB is also being used as the cache DB.
740 $this->logger
->error( "DBError: {$exception->getMessage()}" );
741 if ( $exception instanceof DBConnectionError
) {
742 $this->setLastError( BagOStuff
::ERR_UNREACHABLE
);
743 $this->logger
->debug( __METHOD__
. ": ignoring connection error" );
745 $this->setLastError( BagOStuff
::ERR_UNEXPECTED
);
746 $this->logger
->debug( __METHOD__
. ": ignoring query error" );
751 * Mark a server down due to a DBConnectionError exception
753 * @param DBError $exception
754 * @param int $serverIndex
756 protected function markServerDown( DBError
$exception, $serverIndex ) {
757 unset( $this->conns
[$serverIndex] ); // bug T103435
759 if ( isset( $this->connFailureTimes
[$serverIndex] ) ) {
760 if ( time() - $this->connFailureTimes
[$serverIndex] >= 60 ) {
761 unset( $this->connFailureTimes
[$serverIndex] );
762 unset( $this->connFailureErrors
[$serverIndex] );
764 $this->logger
->debug( __METHOD__
. ": Server #$serverIndex already down" );
769 $this->logger
->info( __METHOD__
. ": Server #$serverIndex down until " . ( $now +
60 ) );
770 $this->connFailureTimes
[$serverIndex] = $now;
771 $this->connFailureErrors
[$serverIndex] = $exception;
775 * Create shard tables. For use from eval.php.
777 public function createTables() {
778 for ( $serverIndex = 0; $serverIndex < $this->numServers
; $serverIndex++
) {
779 $db = $this->getDB( $serverIndex );
780 if ( $db->getType() !== 'mysql' ) {
781 throw new MWException( __METHOD__
. ' is not supported on this DB server' );
784 for ( $i = 0; $i < $this->shards
; $i++
) {
786 'CREATE TABLE ' . $db->tableName( $this->getTableNameByShard( $i ) ) .
787 ' LIKE ' . $db->tableName( 'objectcache' ),
794 * @return bool Whether the main DB is used, e.g. wfGetDB( DB_MASTER )
796 protected function usesMainDB() {
797 return !$this->serverInfos
;
800 protected function waitForSlaves() {
801 if ( $this->usesMainDB() ) {
802 $lb = $this->getSeparateMainLB()
803 ?
: MediaWikiServices
::getInstance()->getDBLoadBalancer();
804 // Main LB is used; wait for any slaves to catch up
806 $pos = $lb->getMasterPos();
808 return $lb->waitForAll( $pos, 3 );
810 } catch ( DBReplicationWaitError
$e ) {
815 // Custom DB server list; probably doesn't use replication