includes/objectcache/SqlBagOStuff.php

   1 <?php
   2
   3 /**
   4  * Class to store objects in the database
   5  *
   6  * @ingroup Cache
   7  */
   8 class SqlBagOStuff extends BagOStuff {
   9
  10         /**
  11          * @var LoadBalancer
  12          */
  13         var $lb;
  14
  15         /**
  16          * @var DatabaseBase
  17          */
  18         var $db;
  19         var $serverInfo;
  20         var $lastExpireAll = 0;
  21         var $purgePeriod = 100;
  22         var $shards = 1;
  23         var $tableName = 'objectcache';
  24
  25         /**
  26          * Constructor. Parameters are:
  27          *   - server:   A server info structure in the format required by each
  28          *               element in $wgDBServers.
  29          *
  30          *   - purgePeriod: The average number of object cache requests in between
  31          *                  garbage collection operations, where expired entries
  32          *                  are removed from the database. Or in other words, the
  33          *                  reciprocal of the probability of purging on any given
  34          *                  request. If this is set to zero, purging will never be
  35          *                  done.
  36          *
  37          *   - tableName:   The table name to use, default is "objectcache".
  38          *
  39          *   - shards:      The number of tables to use for data storage. If this is
  40          *                  more than 1, table names will be formed in the style
  41          *                  objectcacheNNN where NNN is the shard index, between 0 and
  42          *                  shards-1. The number of digits will be the minimum number
  43          *                  required to hold the largest shard index. Data will be
  44          *                  distributed across all tables by key hash. This is for
  45          *                  MySQL bugs 61735 and 61736.
  46          *
  47          * @param $params array
  48          */
  49         public function __construct( $params ) {
  50                 if ( isset( $params['server'] ) ) {
  51                         $this->serverInfo = $params['server'];
  52                         $this->serverInfo['load'] = 1;
  53                 }
  54                 if ( isset( $params['purgePeriod'] ) ) {
  55                         $this->purgePeriod = intval( $params['purgePeriod'] );
  56                 }
  57                 if ( isset( $params['tableName'] ) ) {
  58                         $this->tableName = $params['tableName'];
  59                 }
  60                 if ( isset( $params['shards'] ) ) {
  61                         $this->shards = intval( $params['shards'] );
  62                 }
  63         }
  64
  65         /**
  66          * @return DatabaseBase
  67          */
  68         protected function getDB() {
  69                 if ( !isset( $this->db ) ) {
  70                         # If server connection info was given, use that
  71                         if ( $this->serverInfo ) {
  72                                 $this->lb = new LoadBalancer( array(
  73                                         'servers' => array( $this->serverInfo ) ) );
  74                                 $this->db = $this->lb->getConnection( DB_MASTER );
  75                                 $this->db->clearFlag( DBO_TRX );
  76                         } else {
  77                                 # We must keep a separate connection to MySQL in order to avoid deadlocks
  78                                 # However, SQLite has an opposite behaviour.
  79                                 # @todo Investigate behaviour for other databases
  80                                 if ( wfGetDB( DB_MASTER )->getType() == 'sqlite' ) {
  81                                         $this->db = wfGetDB( DB_MASTER );
  82                                 } else {
  83                                         $this->lb = wfGetLBFactory()->newMainLB();
  84                                         $this->db = $this->lb->getConnection( DB_MASTER );
  85                                         $this->db->clearFlag( DBO_TRX );
  86                                 }
  87                         }
  88                 }
  89
  90                 return $this->db;
  91         }
  92
  93         /**
  94          * Get the table name for a given key
  95          * @return string
  96          */
  97         protected function getTableByKey( $key ) {
  98                 if ( $this->shards > 1 ) {
  99                         $hash = hexdec( substr( md5( $key ), 0, 8 ) ) & 0x7fffffff;
 100                         return $this->getTableByShard( $hash % $this->shards );
 101                 } else {
 102                         return $this->tableName;
 103                 }
 104         }
 105
 106         /**
 107          * Get the table name for a given shard index
 108          * @return string
 109          */
 110         protected function getTableByShard( $index ) {
 111                 if ( $this->shards > 1 ) {
 112                         $decimals = strlen( $this->shards - 1 );
 113                         return $this->tableName .
 114                                 sprintf( "%0{$decimals}d", $index );
 115                 } else {
 116                         return $this->tableName;
 117                 }
 118         }
 119
 120         public function get( $key ) {
 121                 $values = $this->getBatch( array( $key ) );
 122                 return $values[$key];
 123         }
 124
 125         public function getBatch( array $keys ) {
 126                 $values = array(); // array of (key => value)
 127
 128                 $keysByTableName = array();
 129                 foreach ( $keys as $key ) {
 130                         $tableName = $this->getTableByKey( $key );
 131                         if ( !isset( $keysByTableName[$tableName] ) ) {
 132                                 $keysByTableName[$tableName] = array();
 133                         }
 134                         $keysByTableName[$tableName][] = $key;
 135                 }
 136
 137                 $db = $this->getDB();
 138                 $this->garbageCollect(); // expire old entries if any
 139
 140                 $dataRows = array();
 141                 foreach ( $keysByTableName as $tableName => $tableKeys ) {
 142                         $res = $db->select( $tableName,
 143                                 array( 'keyname', 'value', 'exptime' ),
 144                                 array( 'keyname' => $tableKeys ),
 145                                 __METHOD__ );
 146                         foreach ( $res as $row ) {
 147                                 $dataRows[$row->keyname] = $row;
 148                         }
 149                 }
 150
 151                 foreach ( $keys as $key ) {
 152                         if ( isset( $dataRows[$key] ) ) { // HIT?
 153                                 $row = $dataRows[$key];
 154                                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 155                                 if ( $this->isExpired( $row->exptime ) ) { // MISS
 156                                         $this->debug( "get: key has expired, deleting" );
 157                                         try {
 158                                                 $db->begin( __METHOD__ );
 159                                                 # Put the expiry time in the WHERE condition to avoid deleting a
 160                                                 # newly-inserted value
 161                                                 $db->delete( $this->getTableByKey( $key ),
 162                                                         array( 'keyname' => $key, 'exptime' => $row->exptime ),
 163                                                         __METHOD__ );
 164                                                 $db->commit( __METHOD__ );
 165                                         } catch ( DBQueryError $e ) {
 166                                                 $this->handleWriteError( $e );
 167                                         }
 168                                         $values[$key] = false;
 169                                 } else { // HIT
 170                                         $values[$key] = $this->unserialize( $db->decodeBlob( $row->value ) );
 171                                 }
 172                         } else { // MISS
 173                                 $values[$key] = false;
 174                                 $this->debug( 'get: no matching rows' );
 175                         }
 176                 }
 177
 178                 return $values;
 179         }
 180
 181         public function set( $key, $value, $exptime = 0 ) {
 182                 $db = $this->getDB();
 183                 $exptime = intval( $exptime );
 184
 185                 if ( $exptime < 0 ) {
 186                         $exptime = 0;
 187                 }
 188
 189                 if ( $exptime == 0 ) {
 190                         $encExpiry = $this->getMaxDateTime();
 191                 } else {
 192                         if ( $exptime < 3.16e8 ) { # ~10 years
 193                                 $exptime += time();
 194                         }
 195
 196                         $encExpiry = $db->timestamp( $exptime );
 197                 }
 198                 try {
 199                         $db->begin( __METHOD__ );
 200                         // (bug 24425) use a replace if the db supports it instead of
 201                         // delete/insert to avoid clashes with conflicting keynames
 202                         $db->replace(
 203                                 $this->getTableByKey( $key ),
 204                                 array( 'keyname' ),
 205                                 array(
 206                                         'keyname' => $key,
 207                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 208                                         'exptime' => $encExpiry
 209                                 ), __METHOD__ );
 210                         $db->commit( __METHOD__ );
 211                 } catch ( DBQueryError $e ) {
 212                         $this->handleWriteError( $e );
 213
 214                         return false;
 215                 }
 216
 217                 return true;
 218         }
 219
 220         public function delete( $key, $time = 0 ) {
 221                 $db = $this->getDB();
 222
 223                 try {
 224                         $db->begin( __METHOD__ );
 225                         $db->delete(
 226                                 $this->getTableByKey( $key ),
 227                                 array( 'keyname' => $key ),
 228                                 __METHOD__ );
 229                         $db->commit( __METHOD__ );
 230                 } catch ( DBQueryError $e ) {
 231                         $this->handleWriteError( $e );
 232
 233                         return false;
 234                 }
 235
 236                 return true;
 237         }
 238
 239         public function incr( $key, $step = 1 ) {
 240                 $db = $this->getDB();
 241                 $tableName = $this->getTableByKey( $key );
 242                 $step = intval( $step );
 243
 244                 try {
 245                         $db->begin( __METHOD__ );
 246                         $row = $db->selectRow(
 247                                 $tableName,
 248                                 array( 'value', 'exptime' ),
 249                                 array( 'keyname' => $key ),
 250                                 __METHOD__,
 251                                 array( 'FOR UPDATE' ) );
 252                         if ( $row === false ) {
 253                                 // Missing
 254                                 $db->commit( __METHOD__ );
 255
 256                                 return null;
 257                         }
 258                         $db->delete( $tableName, array( 'keyname' => $key ), __METHOD__ );
 259                         if ( $this->isExpired( $row->exptime ) ) {
 260                                 // Expired, do not reinsert
 261                                 $db->commit( __METHOD__ );
 262
 263                                 return null;
 264                         }
 265
 266                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 267                         $newValue = $oldValue + $step;
 268                         $db->insert( $tableName,
 269                                 array(
 270                                         'keyname' => $key,
 271                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 272                                         'exptime' => $row->exptime
 273                                 ), __METHOD__, 'IGNORE' );
 274
 275                         if ( $db->affectedRows() == 0 ) {
 276                                 // Race condition. See bug 28611
 277                                 $newValue = null;
 278                         }
 279                         $db->commit( __METHOD__ );
 280                 } catch ( DBQueryError $e ) {
 281                         $this->handleWriteError( $e );
 282
 283                         return null;
 284                 }
 285
 286                 return $newValue;
 287         }
 288
 289         public function keys() {
 290                 $db = $this->getDB();
 291                 $result = array();
 292
 293                 for ( $i = 0; $i < $this->shards; $i++ ) {
 294                         $res = $db->select( $this->getTableByShard( $i ),
 295                                 array( 'keyname' ), false, __METHOD__ );
 296                         foreach ( $res as $row ) {
 297                                 $result[] = $row->keyname;
 298                         }
 299                 }
 300
 301                 return $result;
 302         }
 303
 304         protected function isExpired( $exptime ) {
 305                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 306         }
 307
 308         protected function getMaxDateTime() {
 309                 if ( time() > 0x7fffffff ) {
 310                         return $this->getDB()->timestamp( 1 << 62 );
 311                 } else {
 312                         return $this->getDB()->timestamp( 0x7fffffff );
 313                 }
 314         }
 315
 316         protected function garbageCollect() {
 317                 if ( !$this->purgePeriod ) {
 318                         // Disabled
 319                         return;
 320                 }
 321                 // Only purge on one in every $this->purgePeriod requests.
 322                 if ( $this->purgePeriod !== 1 && mt_rand( 0, $this->purgePeriod - 1 ) ) {
 323                         return;
 324                 }
 325                 $now = time();
 326                 // Avoid repeating the delete within a few seconds
 327                 if ( $now > ( $this->lastExpireAll + 1 ) ) {
 328                         $this->lastExpireAll = $now;
 329                         $this->expireAll();
 330                 }
 331         }
 332
 333         public function expireAll() {
 334                 $this->deleteObjectsExpiringBefore( wfTimestampNow() );
 335         }
 336
 337         /**
 338          * Delete objects from the database which expire before a certain date.
 339          * @return bool
 340          */
 341         public function deleteObjectsExpiringBefore( $timestamp, $progressCallback = false ) {
 342                 $db = $this->getDB();
 343                 $dbTimestamp = $db->timestamp( $timestamp );
 344                 $totalSeconds = false;
 345                 $baseConds = array( 'exptime < ' . $db->addQuotes( $dbTimestamp ) );
 346
 347                 try {
 348                         for ( $i = 0; $i < $this->shards; $i++ ) {
 349                                 $maxExpTime = false;
 350                                 while ( true ) {
 351                                         $conds = $baseConds;
 352                                         if ( $maxExpTime !== false ) {
 353                                                 $conds[] = 'exptime > ' . $db->addQuotes( $maxExpTime );
 354                                         }
 355                                         $rows = $db->select(
 356                                                 $this->getTableByShard( $i ),
 357                                                 array( 'keyname', 'exptime' ),
 358                                                 $conds,
 359                                                 __METHOD__,
 360                                                 array( 'LIMIT' => 100, 'ORDER BY' => 'exptime' ) );
 361                                         if ( !$rows->numRows() ) {
 362                                                 break;
 363                                         }
 364                                         $keys = array();
 365                                         $row = $rows->current();
 366                                         $minExpTime = $row->exptime;
 367                                         if ( $totalSeconds === false ) {
 368                                                 $totalSeconds = wfTimestamp( TS_UNIX, $timestamp )
 369                                                         - wfTimestamp( TS_UNIX, $minExpTime );
 370                                         }
 371                                         foreach ( $rows as $row ) {
 372                                                 $keys[] = $row->keyname;
 373                                                 $maxExpTime = $row->exptime;
 374                                         }
 375
 376                                         $db->begin( __METHOD__ );
 377                                         $db->delete(
 378                                                 $this->getTableByShard( $i ),
 379                                                 array(
 380                                                         'exptime >= ' . $db->addQuotes( $minExpTime ),
 381                                                         'exptime < ' . $db->addQuotes( $dbTimestamp ),
 382                                                         'keyname' => $keys
 383                                                 ),
 384                                                 __METHOD__ );
 385                                         $db->commit( __METHOD__ );
 386
 387                                         if ( $progressCallback ) {
 388                                                 if ( intval( $totalSeconds ) === 0 ) {
 389                                                         $percent = 0;
 390                                                 } else {
 391                                                         $remainingSeconds = wfTimestamp( TS_UNIX, $timestamp )
 392                                                                 - wfTimestamp( TS_UNIX, $maxExpTime );
 393                                                         if ( $remainingSeconds > $totalSeconds ) {
 394                                                                 $totalSeconds = $remainingSeconds;
 395                                                         }
 396                                                         $percent = ( $i + $remainingSeconds / $totalSeconds )
 397                                                                 / $this->shards * 100;
 398                                                 }
 399                                                 call_user_func( $progressCallback, $percent );
 400                                         }
 401                                 }
 402                         }
 403                 } catch ( DBQueryError $e ) {
 404                         $this->handleWriteError( $e );
 405                 }
 406                 return true;
 407         }
 408
 409         public function deleteAll() {
 410                 $db = $this->getDB();
 411
 412                 try {
 413                         for ( $i = 0; $i < $this->shards; $i++ ) {
 414                                 $db->begin( __METHOD__ );
 415                                 $db->delete( $this->getTableByShard( $i ), '*', __METHOD__ );
 416                                 $db->commit( __METHOD__ );
 417                         }
 418                 } catch ( DBQueryError $e ) {
 419                         $this->handleWriteError( $e );
 420                 }
 421         }
 422
 423         /**
 424          * Serialize an object and, if possible, compress the representation.
 425          * On typical message and page data, this can provide a 3X decrease
 426          * in storage requirements.
 427          *
 428          * @param $data mixed
 429          * @return string
 430          */
 431         protected function serialize( &$data ) {
 432                 $serial = serialize( $data );
 433
 434                 if ( function_exists( 'gzdeflate' ) ) {
 435                         return gzdeflate( $serial );
 436                 } else {
 437                         return $serial;
 438                 }
 439         }
 440
 441         /**
 442          * Unserialize and, if necessary, decompress an object.
 443          * @param $serial string
 444          * @return mixed
 445          */
 446         protected function unserialize( $serial ) {
 447                 if ( function_exists( 'gzinflate' ) ) {
 448                         wfSuppressWarnings();
 449                         $decomp = gzinflate( $serial );
 450                         wfRestoreWarnings();
 451
 452                         if ( false !== $decomp ) {
 453                                 $serial = $decomp;
 454                         }
 455                 }
 456
 457                 $ret = unserialize( $serial );
 458
 459                 return $ret;
 460         }
 461
 462         /**
 463          * Handle a DBQueryError which occurred during a write operation.
 464          * Ignore errors which are due to a read-only database, rethrow others.
 465          */
 466         protected function handleWriteError( $exception ) {
 467                 $db = $this->getDB();
 468
 469                 if ( !$db->wasReadOnlyError() ) {
 470                         throw $exception;
 471                 }
 472
 473                 try {
 474                         $db->rollback( __METHOD__ );
 475                 } catch ( DBQueryError $e ) {
 476                 }
 477
 478                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 479                 $db->ignoreErrors( false );
 480         }
 481
 482         /**
 483          * Create shard tables. For use from eval.php.
 484          */
 485         public function createTables() {
 486                 $db = $this->getDB();
 487                 if ( $db->getType() !== 'mysql'
 488                         || version_compare( $db->getServerVersion(), '4.1.0', '<' ) )
 489                 {
 490                         throw new MWException( __METHOD__ . ' is not supported on this DB server' );
 491                 }
 492
 493                 for ( $i = 0; $i < $this->shards; $i++ ) {
 494                         $db->begin( __METHOD__ );
 495                         $db->query(
 496                                 'CREATE TABLE ' . $db->tableName( $this->getTableByShard( $i ) ) .
 497                                 ' LIKE ' . $db->tableName( 'objectcache' ),
 498                                 __METHOD__ );
 499                         $db->commit( __METHOD__ );
 500                 }
 501         }
 502 }
 503
 504 /**
 505  * Backwards compatibility alias
 506  */
 507 class MediaWikiBagOStuff extends SqlBagOStuff { }
 508