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          * @throws
  90          * @return DatabaseBase
  91          */
  92         protected function getDB() {
  93                 global $wgDebugDBTransactions;
  94
  95                 # Don't keep timing out trying to connect for each call if the DB is down
  96                 if ( $this->connFailureError && ( time() - $this->connFailureTime ) < 60 ) {
  97                         throw $this->connFailureError;
  98                 }
  99
 100                 if ( !isset( $this->db ) ) {
 101                         # If server connection info was given, use that
 102                         if ( $this->serverInfo ) {
 103                                 if ( $wgDebugDBTransactions ) {
 104                                         wfDebug( sprintf( "Using provided serverInfo for SqlBagOStuff\n" ) );
 105                                 }
 106                                 $this->lb = new LoadBalancer( array(
 107                                         'servers' => array( $this->serverInfo ) ) );
 108                                 $this->db = $this->lb->getConnection( DB_MASTER );
 109                                 $this->db->clearFlag( DBO_TRX );
 110                         } else {
 111                                 /*
 112                                  * We must keep a separate connection to MySQL in order to avoid deadlocks
 113                                  * However, SQLite has an opposite behaviour. And PostgreSQL needs to know
 114                                  * if we are in transaction or no
 115                                  */
 116                                 if ( wfGetDB( DB_MASTER )->getType() == 'mysql' ) {
 117                                         $this->lb = wfGetLBFactory()->newMainLB();
 118                                         $this->db = $this->lb->getConnection( DB_MASTER );
 119                                         $this->db->clearFlag( DBO_TRX ); // auto-commit mode
 120                                 } else {
 121                                         $this->db = wfGetDB( DB_MASTER );
 122                                 }
 123                         }
 124                         if ( $wgDebugDBTransactions ) {
 125                                 wfDebug( sprintf( "Connection %s will be used for SqlBagOStuff\n", $this->db ) );
 126                         }
 127                 }
 128
 129                 return $this->db;
 130         }
 131
 132         /**
 133          * Get the table name for a given key
 134          * @param $key string
 135          * @return string
 136          */
 137         protected function getTableByKey( $key ) {
 138                 if ( $this->shards > 1 ) {
 139                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 140                         return $this->getTableByShard( $hash % $this->shards );
 141                 } else {
 142                         return $this->tableName;
 143                 }
 144         }
 145
 146         /**
 147          * Get the table name for a given shard index
 148          * @param $index int
 149          * @return string
 150          */
 151         protected function getTableByShard( $index ) {
 152                 if ( $this->shards > 1 ) {
 153                         $decimals = strlen( $this->shards - 1 );
 154                         return $this->tableName .
 155                                 sprintf( "%0{$decimals}d", $index );
 156                 } else {
 157                         return $this->tableName;
 158                 }
 159         }
 160
 161         /**
 162          * @param $key string
 163          * @return mixed
 164          */
 165         public function get( $key ) {
 166                 $values = $this->getMulti( array( $key ) );
 167                 return array_key_exists( $key, $values ) ? $values[$key] : false;
 168         }
 169
 170         /**
 171          * @param $keys array
 172          * @return Array
 173          */
 174         public function getMulti( array $keys ) {
 175                 $values = array(); // array of (key => value)
 176
 177                 try {
 178                         $db = $this->getDB();
 179                         $keysByTableName = array();
 180                         foreach ( $keys as $key ) {
 181                                 $tableName = $this->getTableByKey( $key );
 182                                 if ( !isset( $keysByTableName[$tableName] ) ) {
 183                                         $keysByTableName[$tableName] = array();
 184                                 }
 185                                 $keysByTableName[$tableName][] = $key;
 186                         }
 187
 188                         $this->garbageCollect(); // expire old entries if any
 189
 190                         $dataRows = array();
 191                         foreach ( $keysByTableName as $tableName => $tableKeys ) {
 192                                 $res = $db->select( $tableName,
 193                                         array( 'keyname', 'value', 'exptime' ),
 194                                         array( 'keyname' => $tableKeys ),
 195                                         __METHOD__ );
 196                                 foreach ( $res as $row ) {
 197                                         $dataRows[$row->keyname] = $row;
 198                                 }
 199                         }
 200
 201                         foreach ( $keys as $key ) {
 202                                 if ( isset( $dataRows[$key] ) ) { // HIT?
 203                                         $row = $dataRows[$key];
 204                                         $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 205                                         if ( $this->isExpired( $row->exptime ) ) { // MISS
 206                                                 $this->debug( "get: key has expired, deleting" );
 207                                                 try {
 208                                                         $db->begin( __METHOD__ );
 209                                                         # Put the expiry time in the WHERE condition to avoid deleting a
 210                                                         # newly-inserted value
 211                                                         $db->delete( $this->getTableByKey( $key ),
 212                                                                 array( 'keyname' => $key, 'exptime' => $row->exptime ),
 213                                                                 __METHOD__ );
 214                                                         $db->commit( __METHOD__ );
 215                                                 } catch ( DBQueryError $e ) {
 216                                                         $this->handleWriteError( $e );
 217                                                 }
 218                                                 $values[$key] = false;
 219                                         } else { // HIT
 220                                                 $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 221                                         }
 222                                 } else { // MISS
 223                                         $values[$key] = false;
 224                                         $this->debug( 'get: no matching rows' );
 225                                 }
 226                         }
 227                 } catch ( DBError $e ) {
 228                         $this->handleReadError( $e );
 229                 };
 230
 231                 return $values;
 232         }
 233
 234         /**
 235          * @param $key string
 236          * @param $value mixed
 237          * @param $exptime int
 238          * @return bool
 239          */
 240         public function set( $key, $value, $exptime = 0 ) {
 241                 try {
 242                         $db = $this->getDB();
 243                         $exptime = intval( $exptime );
 244
 245                         if ( $exptime < 0 ) {
 246                                 $exptime = 0;
 247                         }
 248
 249                         if ( $exptime == 0 ) {
 250                                 $encExpiry = $this->getMaxDateTime();
 251                         } else {
 252                                 if ( $exptime < 3.16e8 ) { # ~10 years
 253                                         $exptime += time();
 254                                 }
 255
 256                                 $encExpiry = $db->timestamp( $exptime );
 257                         }
 258                         $db->begin( __METHOD__ );
 259                         // (bug 24425) use a replace if the db supports it instead of
 260                         // delete/insert to avoid clashes with conflicting keynames
 261                         $db->replace(
 262                                 $this->getTableByKey( $key ),
 263                                 array( 'keyname' ),
 264                                 array(
 265                                         'keyname' => $key,
 266                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 267                                         'exptime' => $encExpiry
 268                                 ), __METHOD__ );
 269                         $db->commit( __METHOD__ );
 270                 } catch ( DBError $e ) {
 271                         $this->handleWriteError( $e );
 272                         return false;
 273                 }
 274
 275                 return true;
 276         }
 277
 278         /**
 279          * @param $key string
 280          * @param $time int
 281          * @return bool
 282          */
 283         public function delete( $key, $time = 0 ) {
 284                 try {
 285                         $db = $this->getDB();
 286                         $db->begin( __METHOD__ );
 287                         $db->delete(
 288                                 $this->getTableByKey( $key ),
 289                                 array( 'keyname' => $key ),
 290                                 __METHOD__ );
 291                         $db->commit( __METHOD__ );
 292                 } catch ( DBError $e ) {
 293                         $this->handleWriteError( $e );
 294                         return false;
 295                 }
 296
 297                 return true;
 298         }
 299
 300         /**
 301          * @param $key string
 302          * @param $step int
 303          * @return int|null
 304          */
 305         public function incr( $key, $step = 1 ) {
 306                 try {
 307                         $db = $this->getDB();
 308                         $tableName = $this->getTableByKey( $key );
 309                         $step = intval( $step );
 310                         $db->begin( __METHOD__ );
 311                         $row = $db->selectRow(
 312                                 $tableName,
 313                                 array( 'value', 'exptime' ),
 314                                 array( 'keyname' => $key ),
 315                                 __METHOD__,
 316                                 array( 'FOR UPDATE' ) );
 317                         if ( $row === false ) {
 318                                 // Missing
 319                                 $db->commit( __METHOD__ );
 320
 321                                 return null;
 322                         }
 323                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 324                         if ( $this->isExpired( $row->exptime ) ) {
 325                                 // Expired, do not reinsert
 326                                 $db->commit( __METHOD__ );
 327
 328                                 return null;
 329                         }
 330
 331                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 332                         $newValue = $oldValue + $step;
 333                         $db->insert( $tableName,
 334                                 array(
 335                                         'keyname' => $key,
 336                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 337                                         'exptime' => $row->exptime
 338                                 ), __METHOD__, 'IGNORE' );
 339
 340                         if ( $db->affectedRows() == 0 ) {
 341                                 // Race condition. See bug 28611
 342                                 $newValue = null;
 343                         }
 344                         $db->commit( __METHOD__ );
 345                 } catch ( DBError $e ) {
 346                         $this->handleWriteError( $e );
 347                         return null;
 348                 }
 349
 350                 return $newValue;
 351         }
 352
 353         /**
 354          * @return Array
 355          */
 356         public function keys() {
 357                 $result = array();
 358
 359                 try {
 360                         $db = $this->getDB();
 361                         for ( $i = 0; $i < $this->shards; $i++ ) {
 362                                 $res = $db->select( $this->getTableByShard( $i ),
 363                                         array( 'keyname' ), false, __METHOD__ );
 364                                 foreach ( $res as $row ) {
 365                                         $result[] = $row->keyname;
 366                                 }
 367                         }
 368                 } catch ( DBError $e ) {
 369                         $this->handleReadError( $e );
 370                 }
 371
 372                 return $result;
 373         }
 374
 375         /**
 376          * @param $exptime string
 377          * @return bool
 378          */
 379         protected function isExpired( $exptime ) {
 380                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 381         }
 382
 383         /**
 384          * @return string
 385          */
 386         protected function getMaxDateTime() {
 387                 if ( time() > 0x7fffffff ) {
 388                         return $this->getDB()->timestamp( 1 << 62 );
 389                 } else {
 390                         return $this->getDB()->timestamp( 0x7fffffff );
 391                 }
 392         }
 393
 394         protected function garbageCollect() {
 395                 if ( !$this->purgePeriod ) {
 396                         // Disabled
 397                         return;
 398                 }
 399                 // Only purge on one in every $this->purgePeriod requests.
 400                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 401                         return;
 402                 }
 403                 $now = time();
 404                 // Avoid repeating the delete within a few seconds
 405                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 406                         $this->lastExpireAll = $now;
 407                         $this->expireAll();
 408                 }
 409         }
 410
 411         public function expireAll() {
 412                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 413         }
 414
 415         /**
 416          * Delete objects from the database which expire before a certain date.
 417          * @param $timestamp string
 418          * @param $progressCallback bool|callback
 419          * @return bool
 420          */
 421         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 422                 try {
 423                         $db = $this->getDB();
 424                         $dbTimestamp = $db->timestamp( $timestamp );
 425                         $totalSeconds = false;
 426                         $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 427                         for ( $i = 0; $i < $this->shards; $i++ ) {
 428                                 $maxExpTime = false;
 429                                 while ( true ) {
 430                                         $conds = $baseConds;
 431                                         if ( $maxExpTime !== false ) {
 432                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 433                                         }
 434                                         $rows = $db->select(
 435                                                 $this->getTableByShard( $i ),
 436                                                 array( 'keyname', 'exptime' ),
 437                                                 $conds,
 438                                                 __METHOD__,
 439                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 440                                         if ( !$rows->numRows() ) {
 441                                                 break;
 442                                         }
 443                                         $keys = array();
 444                                         $row = $rows->current();
 445                                         $minExpTime = $row->exptime;
 446                                         if ( $totalSeconds === false ) {
 447                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 448                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 449                                         }
 450                                         foreach ( $rows as $row ) {
 451                                                 $keys[] = $row->keyname;
 452                                                 $maxExpTime = $row->exptime;
 453                                         }
 454
 455                                         $db->begin( __METHOD__ );
 456                                         $db->delete(
 457                                                 $this->getTableByShard( $i ),
 458                                                 array(
 459                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 460                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 461                                                         'keyname' => $keys
 462                                                 ),
 463                                                 __METHOD__ );
 464                                         $db->commit( __METHOD__ );
 465
 466                                         if ( $progressCallback ) {
 467                                                 if ( intval( $totalSeconds ) === 0 ) {
 468                                                         $percent = 0;
 469                                                 } else {
 470                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 471                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 472                                                         if ( $remainingSeconds > $totalSeconds ) {
 473                                                                 $totalSeconds = $remainingSeconds;
 474                                                         }
 475                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 476                                                                 / $this->shards * 100;
 477                                                 }
 478                                                 call_user_func( $progressCallback, $percent );
 479                                         }
 480                                 }
 481                         }
 482                 } catch ( DBError $e ) {
 483                         $this->handleWriteError( $e );
 484                         return false;
 485                 }
 486
 487                 return true;
 488         }
 489
 490         public function deleteAll() {
 491                 try {
 492                         $db = $this->getDB();
 493                         for ( $i = 0; $i < $this->shards; $i++ ) {
 494                                 $db->begin( __METHOD__ );
 495                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 496                                 $db->commit( __METHOD__ );
 497                         }
 498                 } catch ( DBError $e ) {
 499                         $this->handleWriteError( $e );
 500                         return false;
 501                 }
 502
 503                 return true;
 504         }
 505
 506         /**
 507          * Serialize an object and, if possible, compress the representation.
 508          * On typical message and page data, this can provide a 3X decrease
 509          * in storage requirements.
 510          *
 511          * @param $data mixed
 512          * @return string
 513          */
 514         protected function serialize( &$data ) {
 515                 $serial = serialize( $data );
 516
 517                 if ( function_exists( 'gzdeflate' ) ) {
 518                         return gzdeflate( $serial );
 519                 } else {
 520                         return $serial;
 521                 }
 522         }
 523
 524         /**
 525          * Unserialize and, if necessary, decompress an object.
 526          * @param $serial string
 527          * @return mixed
 528          */
 529         protected function unserialize( $serial ) {
 530                 if ( function_exists( 'gzinflate' ) ) {
 531                         wfSuppressWarnings();
 532                         $decomp = gzinflate( $serial );
 533                         wfRestoreWarnings();
 534
 535                         if ( false !== $decomp ) {
 536                                 $serial = $decomp;
 537                         }
 538                 }
 539
 540                 $ret = unserialize( $serial );
 541
 542                 return $ret;
 543         }
 544
 545         /**
 546          * Handle a DBError which occurred during a read operation.
 547          */
 548         protected function handleReadError( DBError $exception ) {
 549                 if ( $exception instanceof DBConnectionError ) {
 550                         $this->connFailureTime  = time();
 551                         $this->connFailureError = $exception;
 552                 }
 553                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 554                 if ( $this->db ) {
 555                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 556                 } else {
 557                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 558                 }
 559         }
 560
 561         /**
 562          * Handle a DBQueryError which occurred during a write operation.
 563          */
 564         protected function handleWriteError( DBError $exception ) {
 565                 if ( $exception instanceof DBConnectionError ) {
 566                         $this->connFailureTime  = time();
 567                         $this->connFailureError = $exception;
 568                 }
 569                 if ( $this->db && $this->db->wasReadOnlyError() ) {
 570                         try {
 571                                 $this->db->rollback( __METHOD__ );
 572                         } catch ( DBError $e ) {}
 573                 }
 574                 wfDebugLog( 'SQLBagOStuff', "DBError: {$exception->getMessage()}" );
 575                 if ( $this->db ) {
 576                         wfDebug( __METHOD__ . ": ignoring query error\n" );
 577                 } else {
 578                         wfDebug( __METHOD__ . ": ignoring connection error\n" );
 579                 }
 580         }
 581
 582         /**
 583          * Create shard tables. For use from eval.php.
 584          */
 585         public function createTables() {
 586                 $db = $this->getDB();
 587                 if ( $db->getType() !== 'mysql'
 588                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 589                 {
 590                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 591                 }
 592
 593                 for ( $i = 0; $i < $this->shards; $i++ ) {
 594                         $db->begin( __METHOD__ );
 595                         $db->query(
 596                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 597                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 598                                 __METHOD__ );
 599                         $db->commit( __METHOD__ );
 600                 }
 601         }
 602 }
 603
 604 /**
 605  * Backwards compatibility alias
 606  */
 607 class MediaWikiBagOStuff extends SqlBagOStuff { }
 608