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          * @return string
 126          */
 127         protected function getTableByKey( $key ) {
 128                 if ( $this->shards > 1 ) {
 129                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 130                         return $this->getTableByShard( $hash % $this->shards );
 131                 } else {
 132                         return $this->tableName;
 133                 }
 134         }
 135
 136         /**
 137          * Get the table name for a given shard index
 138          * @return string
 139          */
 140         protected function getTableByShard( $index ) {
 141                 if ( $this->shards > 1 ) {
 142                         $decimals = strlen( $this->shards - 1 );
 143                         return $this->tableName .
 144                                 sprintf( "%0{$decimals}d", $index );
 145                 } else {
 146                         return $this->tableName;
 147                 }
 148         }
 149
 150         public function get( $key ) {
 151                 $values = $this->getMulti( array( $key ) );
 152                 return $values[$key];
 153         }
 154
 155         public function getMulti( array $keys ) {
 156                 $values = array(); // array of (key => value)
 157
 158                 $keysByTableName = array();
 159                 foreach ( $keys as $key ) {
 160                         $tableName = $this->getTableByKey( $key );
 161                         if ( !isset( $keysByTableName[$tableName] ) ) {
 162                                 $keysByTableName[$tableName] = array();
 163                         }
 164                         $keysByTableName[$tableName][] = $key;
 165                 }
 166
 167                 $db = $this->getDB();
 168                 $this->garbageCollect(); // expire old entries if any
 169
 170                 $dataRows = array();
 171                 foreach ( $keysByTableName as $tableName => $tableKeys ) {
 172                         $res = $db->select( $tableName,
 173                                 array( 'keyname', 'value', 'exptime' ),
 174                                 array( 'keyname' => $tableKeys ),
 175                                 __METHOD__ );
 176                         foreach ( $res as $row ) {
 177                                 $dataRows[$row->keyname] = $row;
 178                         }
 179                 }
 180
 181                 foreach ( $keys as $key ) {
 182                         if ( isset( $dataRows[$key] ) ) { // HIT?
 183                                 $row = $dataRows[$key];
 184                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 185                                 if ( $this->isExpired( $row->exptime ) ) { // MISS
 186                                         $this->debug( "get: key has expired, deleting" );
 187                                         try {
 188                                                 $db->begin( __METHOD__ );
 189                                                 # Put the expiry time in the WHERE condition to avoid deleting a
 190                                                 # newly-inserted value
 191                                                 $db->delete( $this->getTableByKey( $key ),
 192                                                         array( 'keyname' => $key, 'exptime' => $row->exptime ),
 193                                                         __METHOD__ );
 194                                                 $db->commit( __METHOD__ );
 195                                         } catch ( DBQueryError $e ) {
 196                                                 $this->handleWriteError( $e );
 197                                         }
 198                                         $values[$key] = false;
 199                                 } else { // HIT
 200                                         $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 201                                 }
 202                         } else { // MISS
 203                                 $values[$key] = false;
 204                                 $this->debug( 'get: no matching rows' );
 205                         }
 206                 }
 207
 208                 return $values;
 209         }
 210
 211         public function set( $key, $value, $exptime = 0 ) {
 212                 $db = $this->getDB();
 213                 $exptime = intval( $exptime );
 214
 215                 if ( $exptime < 0 ) {
 216                         $exptime = 0;
 217                 }
 218
 219                 if ( $exptime == 0 ) {
 220                         $encExpiry = $this->getMaxDateTime();
 221                 } else {
 222                         if ( $exptime < 3.16e8 ) { # ~10 years
 223                                 $exptime += time();
 224                         }
 225
 226                         $encExpiry = $db->timestamp( $exptime );
 227                 }
 228                 try {
 229                         $db->begin( __METHOD__ );
 230                         // (bug 24425) use a replace if the db supports it instead of
 231                         // delete/insert to avoid clashes with conflicting keynames
 232                         $db->replace(
 233                                 $this->getTableByKey( $key ),
 234                                 array( 'keyname' ),
 235                                 array(
 236                                         'keyname' => $key,
 237                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 238                                         'exptime' => $encExpiry
 239                                 ), __METHOD__ );
 240                         $db->commit( __METHOD__ );
 241                 } catch ( DBQueryError $e ) {
 242                         $this->handleWriteError( $e );
 243
 244                         return false;
 245                 }
 246
 247                 return true;
 248         }
 249
 250         public function delete( $key, $time = 0 ) {
 251                 $db = $this->getDB();
 252
 253                 try {
 254                         $db->begin( __METHOD__ );
 255                         $db->delete(
 256                                 $this->getTableByKey( $key ),
 257                                 array( 'keyname' => $key ),
 258                                 __METHOD__ );
 259                         $db->commit( __METHOD__ );
 260                 } catch ( DBQueryError $e ) {
 261                         $this->handleWriteError( $e );
 262
 263                         return false;
 264                 }
 265
 266                 return true;
 267         }
 268
 269         public function incr( $key, $step = 1 ) {
 270                 $db = $this->getDB();
 271                 $tableName = $this->getTableByKey( $key );
 272                 $step = intval( $step );
 273
 274                 try {
 275                         $db->begin( __METHOD__ );
 276                         $row = $db->selectRow(
 277                                 $tableName,
 278                                 array( 'value', 'exptime' ),
 279                                 array( 'keyname' => $key ),
 280                                 __METHOD__,
 281                                 array( 'FOR UPDATE' ) );
 282                         if ( $row === false ) {
 283                                 // Missing
 284                                 $db->commit( __METHOD__ );
 285
 286                                 return null;
 287                         }
 288                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 289                         if ( $this->isExpired( $row->exptime ) ) {
 290                                 // Expired, do not reinsert
 291                                 $db->commit( __METHOD__ );
 292
 293                                 return null;
 294                         }
 295
 296                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 297                         $newValue = $oldValue + $step;
 298                         $db->insert( $tableName,
 299                                 array(
 300                                         'keyname' => $key,
 301                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 302                                         'exptime' => $row->exptime
 303                                 ), __METHOD__, 'IGNORE' );
 304
 305                         if ( $db->affectedRows() == 0 ) {
 306                                 // Race condition. See bug 28611
 307                                 $newValue = null;
 308                         }
 309                         $db->commit( __METHOD__ );
 310                 } catch ( DBQueryError $e ) {
 311                         $this->handleWriteError( $e );
 312
 313                         return null;
 314                 }
 315
 316                 return $newValue;
 317         }
 318
 319         public function keys() {
 320                 $db = $this->getDB();
 321                 $result = array();
 322
 323                 for ( $i = 0; $i < $this->shards; $i++ ) {
 324                         $res = $db->select( $this->getTableByShard( $i ),
 325                                 array( 'keyname' ), false, __METHOD__ );
 326                         foreach ( $res as $row ) {
 327                                 $result[] = $row->keyname;
 328                         }
 329                 }
 330
 331                 return $result;
 332         }
 333
 334         protected function isExpired( $exptime ) {
 335                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 336         }
 337
 338         protected function getMaxDateTime() {
 339                 if ( time() > 0x7fffffff ) {
 340                         return $this->getDB()->timestamp( 1 << 62 );
 341                 } else {
 342                         return $this->getDB()->timestamp( 0x7fffffff );
 343                 }
 344         }
 345
 346         protected function garbageCollect() {
 347                 if ( !$this->purgePeriod ) {
 348                         // Disabled
 349                         return;
 350                 }
 351                 // Only purge on one in every $this->purgePeriod requests.
 352                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 353                         return;
 354                 }
 355                 $now = time();
 356                 // Avoid repeating the delete within a few seconds
 357                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 358                         $this->lastExpireAll = $now;
 359                         $this->expireAll();
 360                 }
 361         }
 362
 363         public function expireAll() {
 364                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 365         }
 366
 367         /**
 368          * Delete objects from the database which expire before a certain date.
 369          * @return bool
 370          */
 371         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 372                 $db = $this->getDB();
 373                 $dbTimestamp = $db->timestamp( $timestamp );
 374                 $totalSeconds = false;
 375                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 376
 377                 try {
 378                         for ( $i = 0; $i < $this->shards; $i++ ) {
 379                                 $maxExpTime = false;
 380                                 while ( true ) {
 381                                         $conds = $baseConds;
 382                                         if ( $maxExpTime !== false ) {
 383                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 384                                         }
 385                                         $rows = $db->select(
 386                                                 $this->getTableByShard( $i ),
 387                                                 array( 'keyname', 'exptime' ),
 388                                                 $conds,
 389                                                 __METHOD__,
 390                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 391                                         if ( !$rows->numRows() ) {
 392                                                 break;
 393                                         }
 394                                         $keys = array();
 395                                         $row = $rows->current();
 396                                         $minExpTime = $row->exptime;
 397                                         if ( $totalSeconds === false ) {
 398                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 399                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 400                                         }
 401                                         foreach ( $rows as $row ) {
 402                                                 $keys[] = $row->keyname;
 403                                                 $maxExpTime = $row->exptime;
 404                                         }
 405
 406                                         $db->begin( __METHOD__ );
 407                                         $db->delete(
 408                                                 $this->getTableByShard( $i ),
 409                                                 array(
 410                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 411                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 412                                                         'keyname' => $keys
 413                                                 ),
 414                                                 __METHOD__ );
 415                                         $db->commit( __METHOD__ );
 416
 417                                         if ( $progressCallback ) {
 418                                                 if ( intval( $totalSeconds ) === 0 ) {
 419                                                         $percent = 0;
 420                                                 } else {
 421                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 422                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 423                                                         if ( $remainingSeconds > $totalSeconds ) {
 424                                                                 $totalSeconds = $remainingSeconds;
 425                                                         }
 426                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 427                                                                 / $this->shards * 100;
 428                                                 }
 429                                                 call_user_func( $progressCallback, $percent );
 430                                         }
 431                                 }
 432                         }
 433                 } catch ( DBQueryError $e ) {
 434                         $this->handleWriteError( $e );
 435                 }
 436                 return true;
 437         }
 438
 439         public function deleteAll() {
 440                 $db = $this->getDB();
 441
 442                 try {
 443                         for ( $i = 0; $i < $this->shards; $i++ ) {
 444                                 $db->begin( __METHOD__ );
 445                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 446                                 $db->commit( __METHOD__ );
 447                         }
 448                 } catch ( DBQueryError $e ) {
 449                         $this->handleWriteError( $e );
 450                 }
 451         }
 452
 453         /**
 454          * Serialize an object and, if possible, compress the representation.
 455          * On typical message and page data, this can provide a 3X decrease
 456          * in storage requirements.
 457          *
 458          * @param $data mixed
 459          * @return string
 460          */
 461         protected function serialize( &$data ) {
 462                 $serial = serialize( $data );
 463
 464                 if ( function_exists( 'gzdeflate' ) ) {
 465                         return gzdeflate( $serial );
 466                 } else {
 467                         return $serial;
 468                 }
 469         }
 470
 471         /**
 472          * Unserialize and, if necessary, decompress an object.
 473          * @param $serial string
 474          * @return mixed
 475          */
 476         protected function unserialize( $serial ) {
 477                 if ( function_exists( 'gzinflate' ) ) {
 478                         wfSuppressWarnings();
 479                         $decomp = gzinflate( $serial );
 480                         wfRestoreWarnings();
 481
 482                         if ( false !== $decomp ) {
 483                                 $serial = $decomp;
 484                         }
 485                 }
 486
 487                 $ret = unserialize( $serial );
 488
 489                 return $ret;
 490         }
 491
 492         /**
 493          * Handle a DBQueryError which occurred during a write operation.
 494          * Ignore errors which are due to a read-only database, rethrow others.
 495          */
 496         protected function handleWriteError( $exception ) {
 497                 $db = $this->getDB();
 498
 499                 if ( !$db->wasReadOnlyError() ) {
 500                         throw $exception;
 501                 }
 502
 503                 try {
 504                         $db->rollback( __METHOD__ );
 505                 } catch ( DBQueryError $e ) {
 506                 }
 507
 508                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 509                 $db->ignoreErrors( false );
 510         }
 511
 512         /**
 513          * Create shard tables. For use from eval.php.
 514          */
 515         public function createTables() {
 516                 $db = $this->getDB();
 517                 if ( $db->getType() !== 'mysql'
 518                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 519                 {
 520                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 521                 }
 522
 523                 for ( $i = 0; $i < $this->shards; $i++ ) {
 524                         $db->begin( __METHOD__ );
 525                         $db->query(
 526                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 527                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 528                                 __METHOD__ );
 529                         $db->commit( __METHOD__ );
 530                 }
 531         }
 532 }
 533
 534 /**
 535  * Backwards compatibility alias
 536  */
 537 class MediaWikiBagOStuff extends SqlBagOStuff { }
 538