includes/objectcache/SqlBagOStuff.php

   1 <?php
   2 /**
   3  * Object caching using a SQL database.
   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  * Class to store objects in the database
  26  *
  27  * @ingroup Cache
  28  */
  29 class SqlBagOStuff extends BagOStuff {
  30
  31         /**
  32          * @var LoadBalancer
  33          */
  34         var $lb;
  35
  36         /**
  37          * @var DatabaseBase
  38          */
  39         var $db;
  40         var $serverInfo;
  41         var $lastExpireAll = 0;
  42         var $purgePeriod = 100;
  43         var $shards = 1;
  44         var $tableName = 'objectcache';
  45
  46         /**
  47          * Constructor. Parameters are:
  48          *   - server:   A server info structure in the format required by each
  49          *               element in $wgDBServers.
  50          *
  51          *   - purgePeriod: The average number of object cache requests in between
  52          *                  garbage collection operations, where expired entries
  53          *                  are removed from the database. Or in other words, the
  54          *                  reciprocal of the probability of purging on any given
  55          *                  request. If this is set to zero, purging will never be
  56          *                  done.
  57          *
  58          *   - tableName:   The table name to use, default is "objectcache".
  59          *
  60          *   - shards:      The number of tables to use for data storage. If this is
  61          *                  more than 1, table names will be formed in the style
  62          *                  objectcacheNNN where NNN is the shard index, between 0 and
  63          *                  shards-1. The number of digits will be the minimum number
  64          *                  required to hold the largest shard index. Data will be
  65          *                  distributed across all tables by key hash. This is for
  66          *                  MySQL bugs 61735 and 61736.
  67          *
  68          * @param $params array
  69          */
  70         public function __construct( $params ) {
  71                 if ( isset( $params['server'] ) ) {
  72                         $this->serverInfo = $params['server'];
  73                         $this->serverInfo['load'] = 1;
  74                 }
  75                 if ( isset( $params['purgePeriod'] ) ) {
  76                         $this->purgePeriod = intval( $params['purgePeriod'] );
  77                 }
  78                 if ( isset( $params['tableName'] ) ) {
  79                         $this->tableName = $params['tableName'];
  80                 }
  81                 if ( isset( $params['shards'] ) ) {
  82                         $this->shards = intval( $params['shards'] );
  83                 }
  84         }
  85
  86         /**
  87          * @return DatabaseBase
  88          */
  89         protected function getDB() {
  90                 global $wgDebugDBTransactions;
  91                 if ( !isset( $this->db ) ) {
  92                         # If server connection info was given, use that
  93                         if ( $this->serverInfo ) {
  94                                 if ( $wgDebugDBTransactions ) {
  95                                         wfDebug( sprintf( "Using provided serverInfo for SqlBagOStuff\n" ) );
  96                                 }
  97                                 $this->lb = new LoadBalancer( array(
  98                                         'servers' => array( $this->serverInfo ) ) );
  99                                 $this->db = $this->lb->getConnection( DB_MASTER );
 100                                 $this->db->clearFlag( DBO_TRX );
 101                         } else {
 102                                 /*
 103                                  * We must keep a separate connection to MySQL in order to avoid deadlocks
 104                                  * However, SQLite has an opposite behaviour. And PostgreSQL needs to know
 105                                  * if we are in transaction or no
 106                                  */
 107                                 if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
 108                                         $this->lb = wfGetLBFactory()->newMainLB();
 109                                         $this->db = $this->lb->getConnection( DB_MASTER );
 110                                         $this->db->clearFlag( DBO_TRX );
 111                                 } else {
 112                                         $this->db = wfGetDB( DB_MASTER );
 113                                 }
 114                         }
 115                         if ( $wgDebugDBTransactions ) {
 116                                 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $this->db ) );
 117                         }
 118                 }
 119
 120                 return $this->db;
 121         }
 122
 123         /**
 124          * Get the table name for a given key
 125          * @param $key string
 126          * @return string
 127          */
 128         protected function getTableByKey( $key ) {
 129                 if ( $this->shards > 1 ) {
 130                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 131                         return $this->getTableByShard( $hash % $this->shards );
 132                 } else {
 133                         return $this->tableName;
 134                 }
 135         }
 136
 137         /**
 138          * Get the table name for a given shard index
 139          * @param $index int
 140          * @return string
 141          */
 142         protected function getTableByShard( $index ) {
 143                 if ( $this->shards > 1 ) {
 144                         $decimals = strlen( $this->shards - 1 );
 145                         return $this->tableName .
 146                                 sprintf( "%0{$decimals}d", $index );
 147                 } else {
 148                         return $this->tableName;
 149                 }
 150         }
 151
 152         /**
 153          * @param $key string
 154          * @return mixed
 155          */
 156         public function get( $key ) {
 157                 $values = $this->getMulti( array( $key ) );
 158                 return $values[$key];
 159         }
 160
 161         /**
 162          * @param $keys array
 163          * @return Array
 164          */
 165         public function getMulti( array $keys ) {
 166                 $values = array(); // array of (key => value)
 167
 168                 $keysByTableName = array();
 169                 foreach ( $keys as $key ) {
 170                         $tableName = $this->getTableByKey( $key );
 171                         if ( !isset( $keysByTableName[$tableName] ) ) {
 172                                 $keysByTableName[$tableName] = array();
 173                         }
 174                         $keysByTableName[$tableName][] = $key;
 175                 }
 176
 177                 $db = $this->getDB();
 178                 $this->garbageCollect(); // expire old entries if any
 179
 180                 $dataRows = array();
 181                 foreach ( $keysByTableName as $tableName => $tableKeys ) {
 182                         $res = $db->select( $tableName,
 183                                 array( 'keyname', 'value', 'exptime' ),
 184                                 array( 'keyname' => $tableKeys ),
 185                                 __METHOD__ );
 186                         foreach ( $res as $row ) {
 187                                 $dataRows[$row->keyname] = $row;
 188                         }
 189                 }
 190
 191                 foreach ( $keys as $key ) {
 192                         if ( isset( $dataRows[$key] ) ) { // HIT?
 193                                 $row = $dataRows[$key];
 194                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 195                                 if ( $this->isExpired( $row->exptime ) ) { // MISS
 196                                         $this->debug( "get: key has expired, deleting" );
 197                                         try {
 198                                                 $db->begin( __METHOD__ );
 199                                                 # Put the expiry time in the WHERE condition to avoid deleting a
 200                                                 # newly-inserted value
 201                                                 $db->delete( $this->getTableByKey( $key ),
 202                                                         array( 'keyname' => $key, 'exptime' => $row->exptime ),
 203                                                         __METHOD__ );
 204                                                 $db->commit( __METHOD__ );
 205                                         } catch ( DBQueryError $e ) {
 206                                                 $this->handleWriteError( $e );
 207                                         }
 208                                         $values[$key] = false;
 209                                 } else { // HIT
 210                                         $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 211                                 }
 212                         } else { // MISS
 213                                 $values[$key] = false;
 214                                 $this->debug( 'get: no matching rows' );
 215                         }
 216                 }
 217
 218                 return $values;
 219         }
 220
 221         /**
 222          * @param $key string
 223          * @param $value mixed
 224          * @param $exptime int
 225          * @return bool
 226          */
 227         public function set( $key, $value, $exptime = 0 ) {
 228                 $db = $this->getDB();
 229                 $exptime = intval( $exptime );
 230
 231                 if ( $exptime < 0 ) {
 232                         $exptime = 0;
 233                 }
 234
 235                 if ( $exptime == 0 ) {
 236                         $encExpiry = $this->getMaxDateTime();
 237                 } else {
 238                         if ( $exptime < 3.16e8 ) { # ~10 years
 239                                 $exptime += time();
 240                         }
 241
 242                         $encExpiry = $db->timestamp( $exptime );
 243                 }
 244                 try {
 245                         $db->begin( __METHOD__ );
 246                         // (bug 24425) use a replace if the db supports it instead of
 247                         // delete/insert to avoid clashes with conflicting keynames
 248                         $db->replace(
 249                                 $this->getTableByKey( $key ),
 250                                 array( 'keyname' ),
 251                                 array(
 252                                         'keyname' => $key,
 253                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 254                                         'exptime' => $encExpiry
 255                                 ), __METHOD__ );
 256                         $db->commit( __METHOD__ );
 257                 } catch ( DBQueryError $e ) {
 258                         $this->handleWriteError( $e );
 259
 260                         return false;
 261                 }
 262
 263                 return true;
 264         }
 265
 266         /**
 267          * @param $key string
 268          * @param $time int
 269          * @return bool
 270          */
 271         public function delete( $key, $time = 0 ) {
 272                 $db = $this->getDB();
 273
 274                 try {
 275                         $db->begin( __METHOD__ );
 276                         $db->delete(
 277                                 $this->getTableByKey( $key ),
 278                                 array( 'keyname' => $key ),
 279                                 __METHOD__ );
 280                         $db->commit( __METHOD__ );
 281                 } catch ( DBQueryError $e ) {
 282                         $this->handleWriteError( $e );
 283
 284                         return false;
 285                 }
 286
 287                 return true;
 288         }
 289
 290         /**
 291          * @param $key string
 292          * @param $step int
 293          * @return int|null
 294          */
 295         public function incr( $key, $step = 1 ) {
 296                 $db = $this->getDB();
 297                 $tableName = $this->getTableByKey( $key );
 298                 $step = intval( $step );
 299
 300                 try {
 301                         $db->begin( __METHOD__ );
 302                         $row = $db->selectRow(
 303                                 $tableName,
 304                                 array( 'value', 'exptime' ),
 305                                 array( 'keyname' => $key ),
 306                                 __METHOD__,
 307                                 array( 'FOR UPDATE' ) );
 308                         if ( $row === false ) {
 309                                 // Missing
 310                                 $db->commit( __METHOD__ );
 311
 312                                 return null;
 313                         }
 314                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 315                         if ( $this->isExpired( $row->exptime ) ) {
 316                                 // Expired, do not reinsert
 317                                 $db->commit( __METHOD__ );
 318
 319                                 return null;
 320                         }
 321
 322                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 323                         $newValue = $oldValue + $step;
 324                         $db->insert( $tableName,
 325                                 array(
 326                                         'keyname' => $key,
 327                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 328                                         'exptime' => $row->exptime
 329                                 ), __METHOD__, 'IGNORE' );
 330
 331                         if ( $db->affectedRows() == 0 ) {
 332                                 // Race condition. See bug 28611
 333                                 $newValue = null;
 334                         }
 335                         $db->commit( __METHOD__ );
 336                 } catch ( DBQueryError $e ) {
 337                         $this->handleWriteError( $e );
 338
 339                         return null;
 340                 }
 341
 342                 return $newValue;
 343         }
 344
 345         /**
 346          * @return Array
 347          */
 348         public function keys() {
 349                 $db = $this->getDB();
 350                 $result = array();
 351
 352                 for ( $i = 0; $i < $this->shards; $i++ ) {
 353                         $res = $db->select( $this->getTableByShard( $i ),
 354                                 array( 'keyname' ), false, __METHOD__ );
 355                         foreach ( $res as $row ) {
 356                                 $result[] = $row->keyname;
 357                         }
 358                 }
 359
 360                 return $result;
 361         }
 362
 363         /**
 364          * @param $exptime string
 365          * @return bool
 366          */
 367         protected function isExpired( $exptime ) {
 368                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 369         }
 370
 371         /**
 372          * @return string
 373          */
 374         protected function getMaxDateTime() {
 375                 if ( time() > 0x7fffffff ) {
 376                         return $this->getDB()->timestamp( 1 << 62 );
 377                 } else {
 378                         return $this->getDB()->timestamp( 0x7fffffff );
 379                 }
 380         }
 381
 382         protected function garbageCollect() {
 383                 if ( !$this->purgePeriod ) {
 384                         // Disabled
 385                         return;
 386                 }
 387                 // Only purge on one in every $this->purgePeriod requests.
 388                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 389                         return;
 390                 }
 391                 $now = time();
 392                 // Avoid repeating the delete within a few seconds
 393                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 394                         $this->lastExpireAll = $now;
 395                         $this->expireAll();
 396                 }
 397         }
 398
 399         public function expireAll() {
 400                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 401         }
 402
 403         /**
 404          * Delete objects from the database which expire before a certain date.
 405          * @param $timestamp string
 406          * @param $progressCallback bool|callback
 407          * @return bool
 408          */
 409         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 410                 $db = $this->getDB();
 411                 $dbTimestamp = $db->timestamp( $timestamp );
 412                 $totalSeconds = false;
 413                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 414
 415                 try {
 416                         for ( $i = 0; $i < $this->shards; $i++ ) {
 417                                 $maxExpTime = false;
 418                                 while ( true ) {
 419                                         $conds = $baseConds;
 420                                         if ( $maxExpTime !== false ) {
 421                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 422                                         }
 423                                         $rows = $db->select(
 424                                                 $this->getTableByShard( $i ),
 425                                                 array( 'keyname', 'exptime' ),
 426                                                 $conds,
 427                                                 __METHOD__,
 428                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 429                                         if ( !$rows->numRows() ) {
 430                                                 break;
 431                                         }
 432                                         $keys = array();
 433                                         $row = $rows->current();
 434                                         $minExpTime = $row->exptime;
 435                                         if ( $totalSeconds === false ) {
 436                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 437                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 438                                         }
 439                                         foreach ( $rows as $row ) {
 440                                                 $keys[] = $row->keyname;
 441                                                 $maxExpTime = $row->exptime;
 442                                         }
 443
 444                                         $db->begin( __METHOD__ );
 445                                         $db->delete(
 446                                                 $this->getTableByShard( $i ),
 447                                                 array(
 448                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 449                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 450                                                         'keyname' => $keys
 451                                                 ),
 452                                                 __METHOD__ );
 453                                         $db->commit( __METHOD__ );
 454
 455                                         if ( $progressCallback ) {
 456                                                 if ( intval( $totalSeconds ) === 0 ) {
 457                                                         $percent = 0;
 458                                                 } else {
 459                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 460                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 461                                                         if ( $remainingSeconds > $totalSeconds ) {
 462                                                                 $totalSeconds = $remainingSeconds;
 463                                                         }
 464                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 465                                                                 / $this->shards * 100;
 466                                                 }
 467                                                 call_user_func( $progressCallback, $percent );
 468                                         }
 469                                 }
 470                         }
 471                 } catch ( DBQueryError $e ) {
 472                         $this->handleWriteError( $e );
 473                 }
 474                 return true;
 475         }
 476
 477         public function deleteAll() {
 478                 $db = $this->getDB();
 479
 480                 try {
 481                         for ( $i = 0; $i < $this->shards; $i++ ) {
 482                                 $db->begin( __METHOD__ );
 483                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 484                                 $db->commit( __METHOD__ );
 485                         }
 486                 } catch ( DBQueryError $e ) {
 487                         $this->handleWriteError( $e );
 488                 }
 489         }
 490
 491         /**
 492          * Serialize an object and, if possible, compress the representation.
 493          * On typical message and page data, this can provide a 3X decrease
 494          * in storage requirements.
 495          *
 496          * @param $data mixed
 497          * @return string
 498          */
 499         protected function serialize( &$data ) {
 500                 $serial = serialize( $data );
 501
 502                 if ( function_exists( 'gzdeflate' ) ) {
 503                         return gzdeflate( $serial );
 504                 } else {
 505                         return $serial;
 506                 }
 507         }
 508
 509         /**
 510          * Unserialize and, if necessary, decompress an object.
 511          * @param $serial string
 512          * @return mixed
 513          */
 514         protected function unserialize( $serial ) {
 515                 if ( function_exists( 'gzinflate' ) ) {
 516                         wfSuppressWarnings();
 517                         $decomp = gzinflate( $serial );
 518                         wfRestoreWarnings();
 519
 520                         if ( false !== $decomp ) {
 521                                 $serial = $decomp;
 522                         }
 523                 }
 524
 525                 $ret = unserialize( $serial );
 526
 527                 return $ret;
 528         }
 529
 530         /**
 531          * Handle a DBQueryError which occurred during a write operation.
 532          * Ignore errors which are due to a read-only database, rethrow others.
 533          */
 534         protected function handleWriteError( $exception ) {
 535                 $db = $this->getDB();
 536
 537                 if ( !$db->wasReadOnlyError() ) {
 538                         throw $exception;
 539                 }
 540
 541                 try {
 542                         $db->rollback( __METHOD__ );
 543                 } catch ( DBQueryError $e ) {
 544                 }
 545
 546                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 547                 $db->ignoreErrors( false );
 548         }
 549
 550         /**
 551          * Create shard tables. For use from eval.php.
 552          */
 553         public function createTables() {
 554                 $db = $this->getDB();
 555                 if ( $db->getType() !== 'mysql'
 556                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 557                 {
 558                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 559                 }
 560
 561                 for ( $i = 0; $i < $this->shards; $i++ ) {
 562                         $db->begin( __METHOD__ );
 563                         $db->query(
 564                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 565                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 566                                 __METHOD__ );
 567                         $db->commit( __METHOD__ );
 568                 }
 569         }
 570 }
 571
 572 /**
 573  * Backwards compatibility alias
 574  */
 575 class MediaWikiBagOStuff extends SqlBagOStuff { }
 576