includes/BagOStuff.php

   1 <?php
   2 #
   3 # Copyright (C) 2003-2004 Brion Vibber <brion@pobox.com>
   4 # http://www.mediawiki.org/
   5 #
   6 # This program is free software; you can redistribute it and/or modify
   7 # it under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 2 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # This program is distributed in the hope that it will be useful,
  12 # but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  14 # GNU General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License along
  17 # with this program; if not, write to the Free Software Foundation, Inc.,
  18 # 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  19 # http://www.gnu.org/copyleft/gpl.html
  20
  21 /**
  22  * @defgroup Cache Cache
  23  *
  24  * @file
  25  * @ingroup Cache
  26  */
  27
  28 /**
  29  * interface is intended to be more or less compatible with
  30  * the PHP memcached client.
  31  *
  32  * backends for local hash array and SQL table included:
  33  * <code>
  34  *   $bag = new HashBagOStuff();
  35  *   $bag = new SqlBagOStuff(); # connect to db first
  36  * </code>
  37  *
  38  * @ingroup Cache
  39  */
  40 abstract class BagOStuff {
  41         var $debugMode = false;
  42
  43         public function set_debug( $bool ) {
  44                 $this->debugMode = $bool;
  45         }
  46
  47         /* *** THE GUTS OF THE OPERATION *** */
  48         /* Override these with functional things in subclasses */
  49
  50         /**
  51          * Get an item with the given key. Returns false if it does not exist.
  52          * @param $key string
  53          */
  54         abstract public function get( $key );
  55
  56         /**
  57          * Set an item.
  58          * @param $key string
  59          * @param $value mixed
  60          * @param $exptime int Either an interval in seconds or a unix timestamp for expiry
  61          */
  62         abstract public function set( $key, $value, $exptime = 0 );
  63
  64         /*
  65          * Delete an item.
  66          * @param $key string
  67          * @param $time int Amount of time to delay the operation (mostly memcached-specific)
  68          */
  69         abstract public function delete( $key, $time = 0 );
  70
  71         public function lock( $key, $timeout = 0 ) {
  72                 /* stub */
  73                 return true;
  74         }
  75
  76         public function unlock( $key ) {
  77                 /* stub */
  78                 return true;
  79         }
  80
  81         public function keys() {
  82                 /* stub */
  83                 return array();
  84         }
  85
  86         /* *** Emulated functions *** */
  87         /* Better performance can likely be got with custom written versions */
  88         public function get_multi( $keys ) {
  89                 $out = array();
  90
  91                 foreach ( $keys as $key ) {
  92                         $out[$key] = $this->get( $key );
  93                 }
  94
  95                 return $out;
  96         }
  97
  98         public function set_multi( $hash, $exptime = 0 ) {
  99                 foreach ( $hash as $key => $value ) {
 100                         $this->set( $key, $value, $exptime );
 101                 }
 102         }
 103
 104         public function add( $key, $value, $exptime = 0 ) {
 105                 if ( $this->get( $key ) == false ) {
 106                         $this->set( $key, $value, $exptime );
 107                         return true;
 108                 }
 109         }
 110
 111         public function add_multi( $hash, $exptime = 0 ) {
 112                 foreach ( $hash as $key => $value ) {
 113                         $this->add( $key, $value, $exptime );
 114                 }
 115         }
 116
 117         public function delete_multi( $keys, $time = 0 ) {
 118                 foreach ( $keys as $key ) {
 119                         $this->delete( $key, $time );
 120                 }
 121         }
 122
 123         public function replace( $key, $value, $exptime = 0 ) {
 124                 if ( $this->get( $key ) !== false ) {
 125                         $this->set( $key, $value, $exptime );
 126                 }
 127         }
 128
 129         public function incr( $key, $value = 1 ) {
 130                 if ( !$this->lock( $key ) ) {
 131                         return false;
 132                 }
 133                 $value = intval( $value );
 134
 135                 $n = false;
 136                 if ( ( $n = $this->get( $key ) ) !== false ) {
 137                         $n += $value;
 138                         $this->set( $key, $n ); // exptime?
 139                 }
 140                 $this->unlock( $key );
 141                 return $n;
 142         }
 143
 144         public function decr( $key, $value = 1 ) {
 145                 return $this->incr( $key, - $value );
 146         }
 147
 148         public function debug( $text ) {
 149                 if ( $this->debugMode )
 150                         wfDebug( "BagOStuff debug: $text\n" );
 151         }
 152
 153         /**
 154          * Convert an optionally relative time to an absolute time
 155          */
 156         protected function convertExpiry( $exptime ) {
 157                 if ( ( $exptime != 0 ) && ( $exptime < 3600 * 24 * 30 ) ) {
 158                         return time() + $exptime;
 159                 } else {
 160                         return $exptime;
 161                 }
 162         }
 163 }
 164
 165 /**
 166  * Functional versions!
 167  * This is a test of the interface, mainly. It stores things in an associative
 168  * array, which is not going to persist between program runs.
 169  *
 170  * @ingroup Cache
 171  */
 172 class HashBagOStuff extends BagOStuff {
 173         var $bag;
 174
 175         function __construct() {
 176                 $this->bag = array();
 177         }
 178
 179         protected function expire( $key ) {
 180                 $et = $this->bag[$key][1];
 181                 if ( ( $et == 0 ) || ( $et > time() ) ) {
 182                         return false;
 183                 }
 184                 $this->delete( $key );
 185                 return true;
 186         }
 187
 188         function get( $key ) {
 189                 if ( !isset( $this->bag[$key] ) ) {
 190                         return false;
 191                 }
 192                 if ( $this->expire( $key ) ) {
 193                         return false;
 194                 }
 195                 return $this->bag[$key][0];
 196         }
 197
 198         function set( $key, $value, $exptime = 0 ) {
 199                 $this->bag[$key] = array( $value, $this->convertExpiry( $exptime ) );
 200         }
 201
 202         function delete( $key, $time = 0 ) {
 203                 if ( !isset( $this->bag[$key] ) ) {
 204                         return false;
 205                 }
 206                 unset( $this->bag[$key] );
 207                 return true;
 208         }
 209
 210         function keys() {
 211                 return array_keys( $this->bag );
 212         }
 213 }
 214
 215 /**
 216  * Class to store objects in the database
 217  *
 218  * @ingroup Cache
 219  */
 220 class SqlBagOStuff extends BagOStuff {
 221         var $lb, $db;
 222         var $lastExpireAll = 0;
 223
 224         protected function getDB() {
 225                 global $wgDBtype;
 226                 if ( !isset( $this->db ) ) {
 227                         /* We must keep a separate connection to MySQL in order to avoid deadlocks
 228                          * However, SQLite has an opposite behaviour.
 229                          * @todo Investigate behaviour for other databases
 230                          */
 231                         if ( $wgDBtype == 'sqlite' ) {
 232                                 $this->db = wfGetDB( DB_MASTER );
 233                         } else {
 234                                 $this->lb = wfGetLBFactory()->newMainLB();
 235                                 $this->db = $this->lb->getConnection( DB_MASTER );
 236                                 $this->db->clearFlag( DBO_TRX );
 237                         }
 238                 }
 239                 return $this->db;
 240         }
 241
 242         public function get( $key ) {
 243                 # expire old entries if any
 244                 $this->garbageCollect();
 245                 $db = $this->getDB();
 246                 $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
 247                         array( 'keyname' => $key ), __METHOD__ );
 248                 if ( !$row ) {
 249                         $this->debug( 'get: no matching rows' );
 250                         return false;
 251                 }
 252
 253                 $this->debug( "get: retrieved data; expiry time is " . $row->exptime );
 254                 if ( $this->isExpired( $row->exptime ) ) {
 255                         $this->debug( "get: key has expired, deleting" );
 256                         try {
 257                                 $db->begin();
 258                                 # Put the expiry time in the WHERE condition to avoid deleting a
 259                                 # newly-inserted value
 260                                 $db->delete( 'objectcache',
 261                                         array(
 262                                                 'keyname' => $key,
 263                                                 'exptime' => $row->exptime
 264                                         ), __METHOD__ );
 265                                 $db->commit();
 266                         } catch ( DBQueryError $e ) {
 267                                 $this->handleWriteError( $e );
 268                         }
 269                         return false;
 270                 }
 271                 return $this->unserialize( $db->decodeBlob( $row->value ) );
 272         }
 273
 274         public function set( $key, $value, $exptime = 0 ) {
 275                 $db = $this->getDB();
 276                 $exptime = intval( $exptime );
 277                 if ( $exptime < 0 ) $exptime = 0;
 278                 if ( $exptime == 0 ) {
 279                         $encExpiry = $this->getMaxDateTime();
 280                 } else {
 281                         if ( $exptime < 3.16e8 ) # ~10 years
 282                                 $exptime += time();
 283                         $encExpiry = $db->timestamp( $exptime );
 284                 }
 285                 try {
 286                         $db->begin();
 287                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 288                         $db->insert( 'objectcache',
 289                                 array(
 290                                         'keyname' => $key,
 291                                         'value' => $db->encodeBlob( $this->serialize( $value ) ),
 292                                         'exptime' => $encExpiry
 293                                 ), __METHOD__ );
 294                         $db->commit();
 295                 } catch ( DBQueryError $e ) {
 296                         $this->handleWriteError( $e );
 297                         return false;
 298                 }
 299                 return true;
 300         }
 301
 302         public function delete( $key, $time = 0 ) {
 303                 $db = $this->getDB();
 304                 try {
 305                         $db->begin();
 306                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 307                         $db->commit();
 308                 } catch ( DBQueryError $e ) {
 309                         $this->handleWriteError( $e );
 310                         return false;
 311                 }
 312                 return true;
 313         }
 314
 315         public function incr( $key, $step = 1 ) {
 316                 $db = $this->getDB();
 317                 $step = intval( $step );
 318
 319                 try {
 320                         $db->begin();
 321                         $row = $db->selectRow( 'objectcache', array( 'value', 'exptime' ),
 322                                 array( 'keyname' => $key ), __METHOD__, array( 'FOR UPDATE' ) );
 323                         if ( $row === false ) {
 324                                 // Missing
 325                                 $db->commit();
 326                                 return false;
 327                         }
 328                         $db->delete( 'objectcache', array( 'keyname' => $key ), __METHOD__ );
 329                         if ( $this->isExpired( $row->exptime ) ) {
 330                                 // Expired, do not reinsert
 331                                 $db->commit();
 332                                 return false;
 333                         }
 334
 335                         $oldValue = intval( $this->unserialize( $db->decodeBlob( $row->value ) ) );
 336                         $newValue = $oldValue + $step;
 337                         $db->insert( 'objectcache',
 338                                 array(
 339                                         'keyname' => $key,
 340                                         'value' => $db->encodeBlob( $this->serialize( $newValue ) ),
 341                                         'exptime' => $row->exptime
 342                                 ), __METHOD__ );
 343                         $db->commit();
 344                 } catch ( DBQueryError $e ) {
 345                         $this->handleWriteError( $e );
 346                         return false;
 347                 }
 348                 return $newValue;
 349         }
 350
 351         public function keys() {
 352                 $db = $this->getDB();
 353                 $res = $db->select( 'objectcache', array( 'keyname' ), false, __METHOD__ );
 354                 $result = array();
 355                 foreach ( $res as $row ) {
 356                         $result[] = $row->keyname;
 357                 }
 358                 return $result;
 359         }
 360
 361         protected function isExpired( $exptime ) {
 362                 return $exptime != $this->getMaxDateTime() && wfTimestamp( TS_UNIX, $exptime ) < time();
 363         }
 364
 365         protected function getMaxDateTime() {
 366                 if ( time() > 0x7fffffff ) {
 367                         return $this->getDB()->timestamp( 1 << 62 );
 368                 } else {
 369                         return $this->getDB()->timestamp( 0x7fffffff );
 370                 }
 371         }
 372
 373         protected function garbageCollect() {
 374                 /* Ignore 99% of requests */
 375                 if ( !mt_rand( 0, 100 ) ) {
 376                         $now = time();
 377                         /* Avoid repeating the delete within a few seconds */
 378                         if ( $now > ( $this->lastExpireAll + 1 ) ) {
 379                                 $this->lastExpireAll = $now;
 380                                 $this->expireAll();
 381                         }
 382                 }
 383         }
 384
 385         public function expireAll() {
 386                 $db = $this->getDB();
 387                 $now = $db->timestamp();
 388                 try {
 389                         $db->begin();
 390                         $db->delete( 'objectcache', array( 'exptime < ' . $db->addQuotes( $now ) ), __METHOD__ );
 391                         $db->commit();
 392                 } catch ( DBQueryError $e ) {
 393                         $this->handleWriteError( $e );
 394                 }
 395         }
 396
 397         public function deleteAll() {
 398                 $db = $this->getDB();
 399                 try {
 400                         $db->begin();
 401                         $db->delete( 'objectcache', '*', __METHOD__ );
 402                         $db->commit();
 403                 } catch ( DBQueryError $e ) {
 404                         $this->handleWriteError( $e );
 405                 }
 406         }
 407
 408         /**
 409          * Serialize an object and, if possible, compress the representation.
 410          * On typical message and page data, this can provide a 3X decrease
 411          * in storage requirements.
 412          *
 413          * @param $data mixed
 414          * @return string
 415          */
 416         protected function serialize( &$data ) {
 417                 $serial = serialize( $data );
 418                 if ( function_exists( 'gzdeflate' ) ) {
 419                         return gzdeflate( $serial );
 420                 } else {
 421                         return $serial;
 422                 }
 423         }
 424
 425         /**
 426          * Unserialize and, if necessary, decompress an object.
 427          * @param $serial string
 428          * @return mixed
 429          */
 430         protected function unserialize( $serial ) {
 431                 if ( function_exists( 'gzinflate' ) ) {
 432                         $decomp = @gzinflate( $serial );
 433                         if ( false !== $decomp ) {
 434                                 $serial = $decomp;
 435                         }
 436                 }
 437                 $ret = unserialize( $serial );
 438                 return $ret;
 439         }
 440
 441         /**
 442          * Handle a DBQueryError which occurred during a write operation.
 443          * Ignore errors which are due to a read-only database, rethrow others.
 444          */
 445         protected function handleWriteError( $exception ) {
 446                 $db = $this->getDB();
 447                 if ( !$db->wasReadOnlyError() ) {
 448                         throw $exception;
 449                 }
 450                 try {
 451                         $db->rollback();
 452                 } catch ( DBQueryError $e ) {
 453                 }
 454                 wfDebug( __METHOD__ . ": ignoring query error\n" );
 455                 $db->ignoreErrors( false );
 456         }
 457 }
 458
 459 /**
 460  * Backwards compatibility alias
 461  */
 462 class MediaWikiBagOStuff extends SqlBagOStuff { }
 463
 464 /**
 465  * This is a wrapper for Turck MMCache's shared memory functions.
 466  *
 467  * You can store objects with mmcache_put() and mmcache_get(), but Turck seems
 468  * to use a weird custom serializer that randomly segfaults. So we wrap calls
 469  * with serialize()/unserialize().
 470  *
 471  * The thing I noticed about the Turck serialized data was that unlike ordinary
 472  * serialize(), it contained the names of methods, and judging by the amount of
 473  * binary data, perhaps even the bytecode of the methods themselves. It may be
 474  * that Turck's serializer is faster, so a possible future extension would be
 475  * to use it for arrays but not for objects.
 476  *
 477  * @ingroup Cache
 478  */
 479 class TurckBagOStuff extends BagOStuff {
 480         public function get( $key ) {
 481                 $val = mmcache_get( $key );
 482                 if ( is_string( $val ) ) {
 483                         $val = unserialize( $val );
 484                 }
 485                 return $val;
 486         }
 487
 488         public function set( $key, $value, $exptime = 0 ) {
 489                 mmcache_put( $key, serialize( $value ), $exptime );
 490                 return true;
 491         }
 492
 493         public function delete( $key, $time = 0 ) {
 494                 mmcache_rm( $key );
 495                 return true;
 496         }
 497
 498         public function lock( $key, $waitTimeout = 0 ) {
 499                 mmcache_lock( $key );
 500                 return true;
 501         }
 502
 503         public function unlock( $key ) {
 504                 mmcache_unlock( $key );
 505                 return true;
 506         }
 507 }
 508
 509 /**
 510  * This is a wrapper for APC's shared memory functions
 511  *
 512  * @ingroup Cache
 513  */
 514 class APCBagOStuff extends BagOStuff {
 515         public function get( $key ) {
 516                 $val = apc_fetch( $key );
 517                 if ( is_string( $val ) ) {
 518                         $val = unserialize( $val );
 519                 }
 520                 return $val;
 521         }
 522
 523         public function set( $key, $value, $exptime = 0 ) {
 524                 apc_store( $key, serialize( $value ), $exptime );
 525                 return true;
 526         }
 527
 528         public function delete( $key, $time = 0 ) {
 529                 apc_delete( $key );
 530                 return true;
 531         }
 532
 533         public function keys() {
 534                 $info = apc_cache_info( 'user' );
 535                 $list = $info['cache_list'];
 536                 $keys = array();
 537                 foreach ( $list as $entry ) {
 538                         $keys[] = $entry['info'];
 539                 }
 540                 return $keys;
 541         }
 542 }
 543
 544 /**
 545  * This is a wrapper for eAccelerator's shared memory functions.
 546  *
 547  * This is basically identical to the Turck MMCache version,
 548  * mostly because eAccelerator is based on Turck MMCache.
 549  *
 550  * @ingroup Cache
 551  */
 552 class eAccelBagOStuff extends BagOStuff {
 553         public function get( $key ) {
 554                 $val = eaccelerator_get( $key );
 555                 if ( is_string( $val ) ) {
 556                         $val = unserialize( $val );
 557                 }
 558                 return $val;
 559         }
 560
 561         public function set( $key, $value, $exptime = 0 ) {
 562                 eaccelerator_put( $key, serialize( $value ), $exptime );
 563                 return true;
 564         }
 565
 566         public function delete( $key, $time = 0 ) {
 567                 eaccelerator_rm( $key );
 568                 return true;
 569         }
 570
 571         public function lock( $key, $waitTimeout = 0 ) {
 572                 eaccelerator_lock( $key );
 573                 return true;
 574         }
 575
 576         public function unlock( $key ) {
 577                 eaccelerator_unlock( $key );
 578                 return true;
 579         }
 580 }
 581
 582 /**
 583  * Wrapper for XCache object caching functions; identical interface
 584  * to the APC wrapper
 585  *
 586  * @ingroup Cache
 587  */
 588 class XCacheBagOStuff extends BagOStuff {
 589
 590         /**
 591          * Get a value from the XCache object cache
 592          *
 593          * @param $key String: cache key
 594          * @return mixed
 595          */
 596         public function get( $key ) {
 597                 $val = xcache_get( $key );
 598                 if ( is_string( $val ) )
 599                         $val = unserialize( $val );
 600                 return $val;
 601         }
 602
 603         /**
 604          * Store a value in the XCache object cache
 605          *
 606          * @param $key String: cache key
 607          * @param $value Mixed: object to store
 608          * @param $expire Int: expiration time
 609          * @return bool
 610          */
 611         public function set( $key, $value, $expire = 0 ) {
 612                 xcache_set( $key, serialize( $value ), $expire );
 613                 return true;
 614         }
 615
 616         /**
 617          * Remove a value from the XCache object cache
 618          *
 619          * @param $key String: cache key
 620          * @param $time Int: not used in this implementation
 621          * @return bool
 622          */
 623         public function delete( $key, $time = 0 ) {
 624                 xcache_unset( $key );
 625                 return true;
 626         }
 627 }
 628
 629 /**
 630  * Cache that uses DBA as a backend.
 631  * Slow due to the need to constantly open and close the file to avoid holding
 632  * writer locks. Intended for development use only,  as a memcached workalike
 633  * for systems that don't have it.
 634  *
 635  * @ingroup Cache
 636  */
 637 class DBABagOStuff extends BagOStuff {
 638         var $mHandler, $mFile, $mReader, $mWriter, $mDisabled;
 639
 640         public function __construct( $dir = false ) {
 641                 global $wgDBAhandler;
 642                 if ( $dir === false ) {
 643                         global $wgTmpDirectory;
 644                         $dir = $wgTmpDirectory;
 645                 }
 646                 $this->mFile = "$dir/mw-cache-" . wfWikiID();
 647                 $this->mFile .= '.db';
 648                 wfDebug( __CLASS__ . ": using cache file {$this->mFile}\n" );
 649                 $this->mHandler = $wgDBAhandler;
 650         }
 651
 652         /**
 653          * Encode value and expiry for storage
 654          */
 655         function encode( $value, $expiry ) {
 656                 # Convert to absolute time
 657                 $expiry = $this->convertExpiry( $expiry );
 658                 return sprintf( '%010u', intval( $expiry ) ) . ' ' . serialize( $value );
 659         }
 660
 661         /**
 662          * @return list containing value first and expiry second
 663          */
 664         function decode( $blob ) {
 665                 if ( !is_string( $blob ) ) {
 666                         return array( null, 0 );
 667                 } else {
 668                         return array(
 669                                 unserialize( substr( $blob, 11 ) ),
 670                                 intval( substr( $blob, 0, 10 ) )
 671                         );
 672                 }
 673         }
 674
 675         function getReader() {
 676                 if ( file_exists( $this->mFile ) ) {
 677                         $handle = dba_open( $this->mFile, 'rl', $this->mHandler );
 678                 } else {
 679                         $handle = $this->getWriter();
 680                 }
 681                 if ( !$handle ) {
 682                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
 683                 }
 684                 return $handle;
 685         }
 686
 687         function getWriter() {
 688                 $handle = dba_open( $this->mFile, 'cl', $this->mHandler );
 689                 if ( !$handle ) {
 690                         wfDebug( "Unable to open DBA cache file {$this->mFile}\n" );
 691                 }
 692                 return $handle;
 693         }
 694
 695         function get( $key ) {
 696                 wfProfileIn( __METHOD__ );
 697                 wfDebug( __METHOD__ . "($key)\n" );
 698                 $handle = $this->getReader();
 699                 if ( !$handle ) {
 700                         return null;
 701                 }
 702                 $val = dba_fetch( $key, $handle );
 703                 list( $val, $expiry ) = $this->decode( $val );
 704                 # Must close ASAP because locks are held
 705                 dba_close( $handle );
 706
 707                 if ( !is_null( $val ) && $expiry && $expiry < time() ) {
 708                         # Key is expired, delete it
 709                         $handle = $this->getWriter();
 710                         dba_delete( $key, $handle );
 711                         dba_close( $handle );
 712                         wfDebug( __METHOD__ . ": $key expired\n" );
 713                         $val = null;
 714                 }
 715                 wfProfileOut( __METHOD__ );
 716                 return $val;
 717         }
 718
 719         function set( $key, $value, $exptime = 0 ) {
 720                 wfProfileIn( __METHOD__ );
 721                 wfDebug( __METHOD__ . "($key)\n" );
 722                 $blob = $this->encode( $value, $exptime );
 723                 $handle = $this->getWriter();
 724                 if ( !$handle ) {
 725                         return false;
 726                 }
 727                 $ret = dba_replace( $key, $blob, $handle );
 728                 dba_close( $handle );
 729                 wfProfileOut( __METHOD__ );
 730                 return $ret;
 731         }
 732
 733         function delete( $key, $time = 0 ) {
 734                 wfProfileIn( __METHOD__ );
 735                 wfDebug( __METHOD__ . "($key)\n" );
 736                 $handle = $this->getWriter();
 737                 if ( !$handle ) {
 738                         return false;
 739                 }
 740                 $ret = dba_delete( $key, $handle );
 741                 dba_close( $handle );
 742                 wfProfileOut( __METHOD__ );
 743                 return $ret;
 744         }
 745
 746         function add( $key, $value, $exptime = 0 ) {
 747                 wfProfileIn( __METHOD__ );
 748                 $blob = $this->encode( $value, $exptime );
 749                 $handle = $this->getWriter();
 750                 if ( !$handle ) {
 751                         return false;
 752                 }
 753                 $ret = dba_insert( $key, $blob, $handle );
 754                 # Insert failed, check to see if it failed due to an expired key
 755                 if ( !$ret ) {
 756                         list( $value, $expiry ) = $this->decode( dba_fetch( $key, $handle ) );
 757                         if ( $expiry < time() ) {
 758                                 # Yes expired, delete and try again
 759                                 dba_delete( $key, $handle );
 760                                 $ret = dba_insert( $key, $blob, $handle );
 761                                 # This time if it failed then it will be handled by the caller like any other race
 762                         }
 763                 }
 764
 765                 dba_close( $handle );
 766                 wfProfileOut( __METHOD__ );
 767                 return $ret;
 768         }
 769
 770         function keys() {
 771                 $reader = $this->getReader();
 772                 $k1 = dba_firstkey( $reader );
 773                 if ( !$k1 ) {
 774                         return array();
 775                 }
 776                 $result[] = $k1;
 777                 while ( $key = dba_nextkey( $reader ) ) {
 778                         $result[] = $key;
 779                 }
 780                 return $result;
 781         }
 782 }