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          * @var LoadBalancer
  32          */
  33         var $lb;
  34
  35         /**
  36          * @var DatabaseBase
  37          */
  38         var $db;
  39         var $serverInfo;
  40         var $lastExpireAll = 0;
  41         var $purgePeriod = 100;
  42         var $shards = 1;
  43         var $tableName = 'objectcache';
  44
  45         protected $connFailureTime = 0; // UNIX timestamp
  46         protected $connFailureError; // exception
  47
  48         /**
  49          * Constructor. Parameters are:
  50          *   - server:   A server info structure in the format required by each
  51          *               element in $wgDBServers.
  52          *
  53          *   - purgePeriod: The average number of object cache requests in between
  54          *                  garbage collection operations, where expired entries
  55          *                  are removed from the database. Or in other words, the
  56          *                  reciprocal of the probability of purging on any given
  57          *                  request. If this is set to zero, purging will never be
  58          *                  done.
  59          *
  60          *   - tableName:   The table name to use, default is "objectcache".
  61          *
  62          *   - shards:      The number of tables to use for data storage. If this is
  63          *                  more than 1, table names will be formed in the style
  64          *                  objectcacheNNN where NNN is the shard index, between 0 and
  65          *                  shards-1. The number of digits will be the minimum number
  66          *                  required to hold the largest shard index. Data will be
  67          *                  distributed across all tables by key hash. This is for
  68          *                  MySQL bugs 61735 and 61736.
  69          *
  70          * @param $params array
  71          */
  72         public function __construct( $params ) {
  73                 if ( isset( $params['server'] ) ) {
  74                         $this->serverInfo = $params['server'];
  75                         $this->serverInfo['load'] = 1;
  76                 }
  77                 if ( isset( $params['purgePeriod'] ) ) {
  78                         $this->purgePeriod = intval( $params['purgePeriod'] );
  79                 }
  80                 if ( isset( $params['tableName'] ) ) {
  81                         $this->tableName = $params['tableName'];
  82                 }
  83                 if ( isset( $params['shards'] ) ) {
  84                         $this->shards = intval( $params['shards'] );
  85                 }
  86         }
  87
  88         /**
  89          * @return DatabaseBase
  90          */
  91         protected function getDB() {
  92                 global $wgDebugDBTransactions;
  93
  94                 # Don't keep timing out trying to connect for each call if the DB is down
  95                 if ( $this->connFailureError && ( time() - $this->connFailureTime ) < 60 ) {
  96                         throw $this->connFailureError;
  97                 }
  98
  99                 if ( !isset( $this->db ) ) {
 100                         # If server connection info was given, use that
 101                         if ( $this->serverInfo ) {
 102                                 if ( $wgDebugDBTransactions ) {
 103                                         wfDebug( sprintf( "Using provided serverInfo for SqlBagOStuff\n" ) );
 104                                 }
 105                                 $this->lb = new LoadBalancer( array(
 106                                         'servers' => array( $this->serverInfo ) ) );
 107                                 $this->db = $this->lb->getConnection( DB_MASTER );
 108                                 $this->db->clearFlag( DBO_TRX );
 109                         } else {
 110                                 /*
 111                                  * We must keep a separate connection to MySQL in order to avoid deadlocks
 112                                  * However, SQLite has an opposite behaviour. And PostgreSQL needs to know
 113                                  * if we are in transaction or no
 114                                  */
 115                                 if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
 116                                         $this->lb = wfGetLBFactory()->newMainLB();
 117                                         $this->db = $this->lb->getConnection( DB_MASTER );
 118                                         $this->db->clearFlag( DBO_TRX ); // auto-commit mode
 119                                 } else {
 120                                         $this->db = wfGetDB( DB_MASTER );
 121                                 }
 122                         }
 123                         if ( $wgDebugDBTransactions ) {
 124                                 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $this->db ) );
 125                         }
 126                 }
 127
 128                 return $this->db;
 129         }
 130
 131         /**
 132          * Get the table name for a given key
 133          * @param $key string
 134          * @return string
 135          */
 136         protected function getTableByKey( $key ) {
 137                 if ( $this->shards > 1 ) {
 138                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 139                         return $this->getTableByShard( $hash % $this->shards );
 140                 } else {
 141                         return $this->tableName;
 142                 }
 143         }
 144
 145         /**
 146          * Get the table name for a given shard index
 147          * @param $index int
 148          * @return string
 149          */
 150         protected function getTableByShard( $index ) {
 151                 if ( $this->shards > 1 ) {
 152                         $decimals = strlen( $this->shards - 1 );
 153                         return $this->tableName .
 154                                 sprintf( "%0{$decimals}d", $index );
 155                 } else {
 156                         return $this->tableName;
 157                 }
 158         }
 159
 160         /**
 161          * @param $key string
 162          * @return mixed
 163          */
 164         public function get( $key ) {
 165                 $values = $this->getMulti( array( $key ) );
 166                 return array_key_exists( $key, $values ) ? $values[$key] : false;
 167         }
 168
 169         /**
 170          * @param $keys array
 171          * @return Array
 172          */
 173         public function getMulti( array $keys ) {
 174                 $values = array(); // array of (key => value)
 175
 176                 try {
 177                         $db = $this->getDB();
 178                         $keysByTableName = array();
 179                         foreach ( $keys as $key ) {
 180                                 $tableName = $this->getTableByKey( $key );
 181                                 if ( !isset( $keysByTableName[$tableName] ) ) {
 182                                         $keysByTableName[$tableName] = array();
 183                                 }
 184                                 $keysByTableName[$tableName][] = $key;
 185                         }
 186
 187                         $this->garbageCollect(); // expire old entries if any
 188
 189                         $dataRows = array();
 190                         foreach ( $keysByTableName as $tableName => $tableKeys ) {
 191                                 $res = $db->select( $tableName,
 192                                         array( 'keyname', 'value', 'exptime' ),
 193                                         array( 'keyname' => $tableKeys ),
 194                                         __METHOD__ );
 195                                 foreach ( $res as $row ) {
 196                                         $dataRows[$row->keyname] = $row;
 197                                 }
 198                         }
 199
 200                         foreach ( $keys as $key ) {
 201                                 if ( isset( $dataRows[$key] ) ) { // HIT?
 202                                         $row = $dataRows[$key];
 203                                         $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 204                                         if ( $this->isExpired( $row->exptime ) ) { // MISS
 205                                                 $this->debug( "get: key has expired, deleting" );
 206                                                 try {
 207                                                         $db->begin( __METHOD__ );
 208                                                         # Put the expiry time in the WHERE condition to avoid deleting a
 209                                                         # newly-inserted value
 210                                                         $db->delete( $this->getTableByKey( $key ),
 211                                                                 array( 'keyname' => $key, 'exptime' => $row->exptime ),
 212                                                                 __METHOD__ );
 213                                                         $db->commit( __METHOD__ );
 214                                                 } catch ( DBQueryError $e ) {
 215                                                         $this->handleWriteError( $e );
 216                                                 }
 217                                                 $values[$key] = false;
 218                                         } else { // HIT
 219                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 220                                         }
 221                                 } else { // MISS
 222                                         $values[$key] = false;
 223                                         $this->debug( 'get: no matching rows' );
 224                                 }
 225                         }
 226                 } catch ( DBError $e ) {
 227                         $this->handleReadError( $e );
 228                 };
 229
 230                 return $values;
 231         }
 232
 233         /**
 234          * @param $key string
 235          * @param $value mixed
 236          * @param $exptime int
 237          * @return bool
 238          */
 239         public function set( $key, $value, $exptime = 0 ) {
 240                 try {
 241                         $db = $this->getDB();
 242                         $exptime = intval( $exptime );
 243
 244                         if ( $exptime < 0 ) {
 245                                 $exptime = 0;
 246                         }
 247
 248                         if ( $exptime == 0 ) {
 249                                 $encExpiry = $this->getMaxDateTime();
 250                         } else {
 251                                 if ( $exptime < 3.16e8 ) { # ~10 years
 252                                         $exptime += time();
 253                                 }
 254
 255                                 $encExpiry = $db->timestamp( $exptime );
 256                         }
 257                         $db->begin( __METHOD__ );
 258                         // (bug 24425) use a replace if the db supports it instead of
 259                         // delete/insert to avoid clashes with conflicting keynames
 260                         $db->replace(
 261                                 $this->getTableByKey( $key ),
 262                                 array( 'keyname' ),
 263                                 array(
 264                                         'keyname' => $key,
 265                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 266                                         'exptime' => $encExpiry
 267                                 ), __METHOD__ );
 268                         $db->commit( __METHOD__ );
 269                 } catch ( DBError $e ) {
 270                         $this->handleWriteError( $e );
 271                         return false;
 272                 }
 273
 274                 return true;
 275         }
 276
 277         /**
 278          * @param $key string
 279          * @param $time int
 280          * @return bool
 281          */
 282         public function delete( $key, $time = 0 ) {
 283                 try {
 284                         $db = $this->getDB();
 285                         $db->begin( __METHOD__ );
 286                         $db->delete(
 287                                 $this->getTableByKey( $key ),
 288                                 array( 'keyname' => $key ),
 289                                 __METHOD__ );
 290                         $db->commit( __METHOD__ );
 291                 } catch ( DBError $e ) {
 292                         $this->handleWriteError( $e );
 293                         return false;
 294                 }
 295
 296                 return true;
 297         }
 298
 299         /**
 300          * @param $key string
 301          * @param $step int
 302          * @return int|null
 303          */
 304         public function incr( $key, $step = 1 ) {
 305                 try {
 306                         $db = $this->getDB();
 307                         $tableName = $this->getTableByKey( $key );
 308                         $step = intval( $step );
 309                         $db->begin( __METHOD__ );
 310                         $row = $db->selectRow(
 311                                 $tableName,
 312                                 array( 'value', 'exptime' ),
 313                                 array( 'keyname' => $key ),
 314                                 __METHOD__,
 315                                 array( 'FOR UPDATE' ) );
 316                         if ( $row === false ) {
 317                                 // Missing
 318                                 $db->commit( __METHOD__ );
 319
 320                                 return null;
 321                         }
 322                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 323                         if ( $this->isExpired( $row->exptime ) ) {
 324                                 // Expired, do not reinsert
 325                                 $db->commit( __METHOD__ );
 326
 327                                 return null;
 328                         }
 329
 330                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 331                         $newValue = $oldValue + $step;
 332                         $db->insert( $tableName,
 333                                 array(
 334                                         'keyname' => $key,
 335                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 336                                         'exptime' => $row->exptime
 337                                 ), __METHOD__, 'IGNORE' );
 338
 339                         if ( $db->affectedRows() == 0 ) {
 340                                 // Race condition. See bug 28611
 341                                 $newValue = null;
 342                         }
 343                         $db->commit( __METHOD__ );
 344                 } catch ( DBError $e ) {
 345                         $this->handleWriteError( $e );
 346                         return null;
 347                 }
 348
 349                 return $newValue;
 350         }
 351
 352         /**
 353          * @return Array
 354          */
 355         public function keys() {
 356                 $result = array();
 357
 358                 try {
 359                         $db = $this->getDB();
 360                         for ( $i = 0; $i < $this->shards; $i++ ) {
 361                                 $res = $db->select( $this->getTableByShard( $i ),
 362                                         array( 'keyname' ), false, __METHOD__ );
 363                                 foreach ( $res as $row ) {
 364                                         $result[] = $row->keyname;
 365                                 }
 366                         }
 367                 } catch ( DBError $e ) {
 368                         $this->handleReadError( $e );
 369                 }
 370
 371                 return $result;
 372         }
 373
 374         /**
 375          * @param $exptime string
 376          * @return bool
 377          */
 378         protected function isExpired( $exptime ) {
 379                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 380         }
 381
 382         /**
 383          * @return string
 384          */
 385         protected function getMaxDateTime() {
 386                 if ( time() > 0x7fffffff ) {
 387                         return $this->getDB()->timestamp( 1 << 62 );
 388                 } else {
 389                         return $this->getDB()->timestamp( 0x7fffffff );
 390                 }
 391         }
 392
 393         protected function garbageCollect() {
 394                 if ( !$this->purgePeriod ) {
 395                         // Disabled
 396                         return;
 397                 }
 398                 // Only purge on one in every $this->purgePeriod requests.
 399                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 400                         return;
 401                 }
 402                 $now = time();
 403                 // Avoid repeating the delete within a few seconds
 404                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 405                         $this->lastExpireAll = $now;
 406                         $this->expireAll();
 407                 }
 408         }
 409
 410         public function expireAll() {
 411                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 412         }
 413
 414         /**
 415          * Delete objects from the database which expire before a certain date.
 416          * @param $timestamp string
 417          * @param $progressCallback bool|callback
 418          * @return bool
 419          */
 420         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 421                 try {
 422                         $db = $this->getDB();
 423                         $dbTimestamp = $db->timestamp( $timestamp );
 424                         $totalSeconds = false;
 425                         $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 426                         for ( $i = 0; $i < $this->shards; $i++ ) {
 427                                 $maxExpTime = false;
 428                                 while ( true ) {
 429                                         $conds = $baseConds;
 430                                         if ( $maxExpTime !== false ) {
 431                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 432                                         }
 433                                         $rows = $db->select(
 434                                                 $this->getTableByShard( $i ),
 435                                                 array( 'keyname', 'exptime' ),
 436                                                 $conds,
 437                                                 __METHOD__,
 438                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 439                                         if ( !$rows->numRows() ) {
 440                                                 break;
 441                                         }
 442                                         $keys = array();
 443                                         $row = $rows->current();
 444                                         $minExpTime = $row->exptime;
 445                                         if ( $totalSeconds === false ) {
 446                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 447                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 448                                         }
 449                                         foreach ( $rows as $row ) {
 450                                                 $keys[] = $row->keyname;
 451                                                 $maxExpTime = $row->exptime;
 452                                         }
 453
 454                                         $db->begin( __METHOD__ );
 455                                         $db->delete(
 456                                                 $this->getTableByShard( $i ),
 457                                                 array(
 458                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 459                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 460                                                         'keyname' => $keys
 461                                                 ),
 462                                                 __METHOD__ );
 463                                         $db->commit( __METHOD__ );
 464
 465                                         if ( $progressCallback ) {
 466                                                 if ( intval( $totalSeconds ) === 0 ) {
 467                                                         $percent = 0;
 468                                                 } else {
 469                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 470                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 471                                                         if ( $remainingSeconds > $totalSeconds ) {
 472                                                                 $totalSeconds = $remainingSeconds;
 473                                                         }
 474                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 475                                                                 / $this->shards * 100;
 476                                                 }
 477                                                 call_user_func( $progressCallback, $percent );
 478                                         }
 479                                 }
 480                         }
 481                 } catch ( DBError $e ) {
 482                         $this->handleWriteError( $e );
 483                         return false;
 484                 }
 485
 486                 return true;
 487         }
 488
 489         public function deleteAll() {
 490                 try {
 491                         $db = $this->getDB();
 492                         for ( $i = 0; $i < $this->shards; $i++ ) {
 493                                 $db->begin( __METHOD__ );
 494                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 495                                 $db->commit( __METHOD__ );
 496                         }
 497                 } catch ( DBError $e ) {
 498                         $this->handleWriteError( $e );
 499                         return false;
 500                 }
 501
 502                 return true;
 503         }
 504
 505         /**
 506          * Serialize an object and, if possible, compress the representation.
 507          * On typical message and page data, this can provide a 3X decrease
 508          * in storage requirements.
 509          *
 510          * @param $data mixed
 511          * @return string
 512          */
 513         protected function serialize( &$data ) {
 514                 $serial = serialize( $data );
 515
 516                 if ( function_exists( 'gzdeflate' ) ) {
 517                         return gzdeflate( $serial );
 518                 } else {
 519                         return $serial;
 520                 }
 521         }
 522
 523         /**
 524          * Unserialize and, if necessary, decompress an object.
 525          * @param $serial string
 526          * @return mixed
 527          */
 528         protected function unserialize( $serial ) {
 529                 if ( function_exists( 'gzinflate' ) ) {
 530                         wfSuppressWarnings();
 531                         $decomp = gzinflate( $serial );
 532                         wfRestoreWarnings();
 533
 534                         if ( false !== $decomp ) {
 535                                 $serial = $decomp;
 536                         }
 537                 }
 538
 539                 $ret = unserialize( $serial );
 540
 541                 return $ret;
 542         }
 543
 544         /**
 545          * Handle a DBError which occurred during a read operation.
 546          */
 547         protected function handleReadError( DBError $exception ) {
 548                 if ( $exception instanceof DBConnectionError ) {
 549                         $this->connFailureTime  = time();
 550                         $this->connFailureError = $exception;
 551                 }
 552                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 553                 if ( $this->db ) {
 554                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 555                 } else {
 556                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 557                 }
 558         }
 559
 560         /**
 561          * Handle a DBQueryError which occurred during a write operation.
 562          */
 563         protected function handleWriteError( DBError $exception ) {
 564                 if ( $exception instanceof DBConnectionError ) {
 565                         $this->connFailureTime  = time();
 566                         $this->connFailureError = $exception;
 567                 }
 568                 if ( $this->db && $this->db->wasReadOnlyError() ) {
 569                         try {
 570                                 $this->db->rollback( __METHOD__ );
 571                         } catch ( DBError $e ) {}
 572                 }
 573                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 574                 if ( $this->db ) {
 575                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 576                 } else {
 577                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 578                 }
 579         }
 580
 581         /**
 582          * Create shard tables. For use from eval.php.
 583          */
 584         public function createTables() {
 585                 $db = $this->getDB();
 586                 if ( $db->getType() !== 'mysql'
 587                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 588                 {
 589                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 590                 }
 591
 592                 for ( $i = 0; $i < $this->shards; $i++ ) {
 593                         $db->begin( __METHOD__ );
 594                         $db->query(
 595                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 596                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 597                                 __METHOD__ );
 598                         $db->commit( __METHOD__ );
 599                 }
 600         }
 601 }
 602
 603 /**
 604  * Backwards compatibility alias
 605  */
 606 class MediaWikiBagOStuff extends SqlBagOStuff { }
 607