includes/filebackend/FileBackendMultiWrite.php

   1 <?php
   2 /**
   3  * Proxy backend that mirrors writes to several internal backends.
   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 FileBackend
  22  * @author Aaron Schulz
  23  */
  24
  25 /**
  26  * @brief Proxy backend that mirrors writes to several internal backends.
  27  *
  28  * This class defines a multi-write backend. Multiple backends can be
  29  * registered to this proxy backend and it will act as a single backend.
  30  * Use this when all access to those backends is through this proxy backend.
  31  * At least one of the backends must be declared the "master" backend.
  32  *
  33  * Only use this class when transitioning from one storage system to another.
  34  *
  35  * Read operations are only done on the 'master' backend for consistency.
  36  * Write operations are performed on all backends, in the order defined.
  37  * If an operation fails on one backend it will be rolled back from the others.
  38  *
  39  * @ingroup FileBackend
  40  * @since 1.19
  41  */
  42 class FileBackendMultiWrite extends FileBackend {
  43         /** @var Array Prioritized list of FileBackendStore objects */
  44         protected $backends = array(); // array of (backend index => backends)
  45         protected $masterIndex = -1; // integer; index of master backend
  46         protected $syncChecks = 0; // integer; bitfield
  47         /** @var Array */
  48         protected $noPushDirConts = array();
  49         protected $noPushQuickOps = false; // boolean
  50
  51         /* Possible internal backend consistency checks */
  52         const CHECK_SIZE = 1;
  53         const CHECK_TIME = 2;
  54         const CHECK_SHA1 = 4;
  55
  56         /**
  57          * Construct a proxy backend that consists of several internal backends.
  58          * Locking, journaling, and read-only checks are handled by the proxy backend.
  59          *
  60          * Additional $config params include:
  61          *   - backends       : Array of backend config and multi-backend settings.
  62          *                      Each value is the config used in the constructor of a
  63          *                          FileBackendStore class, but with these additional settings:
  64          *                        - class         : The name of the backend class
  65          *                        - isMultiMaster : This must be set for one backend.
  66          *                        - template:     : If given a backend name, this will use
  67          *                                          the config of that backend as a template.
  68          *                                          Values specified here take precedence.
  69          *   - syncChecks     : Integer bitfield of internal backend sync checks to perform.
  70          *                      Possible bits include the FileBackendMultiWrite::CHECK_* constants.
  71          *                      There are constants for SIZE, TIME, and SHA1.
  72          *                      The checks are done before allowing any file operations.
  73          *   - noPushQuickOps : (hack) Only apply doQuickOperations() to the master backend.
  74          *   - noPushDirConts : (hack) Only apply directory functions to the master backend.
  75          *
  76          * @param $config Array
  77          * @throws MWException
  78          */
  79         public function __construct( array $config ) {
  80                 parent::__construct( $config );
  81                 $this->syncChecks = isset( $config['syncChecks'] )
  82                         ? $config['syncChecks']
  83                         : self::CHECK_SIZE;
  84                 $this->noPushQuickOps = isset( $config['noPushQuickOps'] )
  85                         ? $config['noPushQuickOps']
  86                         : false;
  87                 $this->noPushDirConts = isset( $config['noPushDirConts'] )
  88                         ? $config['noPushDirConts']
  89                         : array();
  90                 // Construct backends here rather than via registration
  91                 // to keep these backends hidden from outside the proxy.
  92                 $namesUsed = array();
  93                 foreach ( $config['backends'] as $index => $config ) {
  94                         if ( isset( $config['template'] ) ) {
  95                                 // Config is just a modified version of a registered backend's.
  96                                 // This should only be used when that config is used only by this backend.
  97                                 $config = $config + FileBackendGroup::singleton()->config( $config['template'] );
  98                         }
  99                         $name = $config['name'];
 100                         if ( isset( $namesUsed[$name] ) ) { // don't break FileOp predicates
 101                                 throw new MWException( "Two or more backends defined with the name $name." );
 102                         }
 103                         $namesUsed[$name] = 1;
 104                         // Alter certain sub-backend settings for sanity
 105                         unset( $config['readOnly'] ); // use proxy backend setting
 106                         unset( $config['fileJournal'] ); // use proxy backend journal
 107                         $config['wikiId'] = $this->wikiId; // use the proxy backend wiki ID
 108                         $config['lockManager'] = 'nullLockManager'; // lock under proxy backend
 109                         if ( !empty( $config['isMultiMaster'] ) ) {
 110                                 if ( $this->masterIndex >= 0 ) {
 111                                         throw new MWException( 'More than one master backend defined.' );
 112                                 }
 113                                 $this->masterIndex = $index; // this is the "master"
 114                                 $config['fileJournal'] = $this->fileJournal; // log under proxy backend
 115                         }
 116                         // Create sub-backend object
 117                         if ( !isset( $config['class'] ) ) {
 118                                 throw new MWException( 'No class given for a backend config.' );
 119                         }
 120                         $class = $config['class'];
 121                         $this->backends[$index] = new $class( $config );
 122                 }
 123                 if ( $this->masterIndex < 0 ) { // need backends and must have a master
 124                         throw new MWException( 'No master backend defined.' );
 125                 }
 126         }
 127
 128         /**
 129          * @see FileBackend::doOperationsInternal()
 130          * @return Status
 131          */
 132         final protected function doOperationsInternal( array $ops, array $opts ) {
 133                 $status = Status::newGood();
 134
 135                 $mbe = $this->backends[$this->masterIndex]; // convenience
 136
 137                 // Get the paths to lock from the master backend
 138                 $realOps = $this->substOpBatchPaths( $ops, $mbe );
 139                 $paths = $mbe->getPathsToLockForOpsInternal( $mbe->getOperationsInternal( $realOps ) );
 140                 // Get the paths under the proxy backend's name
 141                 $paths['sh'] = $this->unsubstPaths( $paths['sh'] );
 142                 $paths['ex'] = $this->unsubstPaths( $paths['ex'] );
 143                 // Try to lock those files for the scope of this function...
 144                 if ( empty( $opts['nonLocking'] ) ) {
 145                         // Try to lock those files for the scope of this function...
 146                         $scopeLockS = $this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status );
 147                         $scopeLockE = $this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status );
 148                         if ( !$status->isOK() ) {
 149                                 return $status; // abort
 150                         }
 151                 }
 152                 // Clear any cache entries (after locks acquired)
 153                 $this->clearCache();
 154                 // Do a consistency check to see if the backends agree
 155                 $status->merge( $this->consistencyCheck( $this->fileStoragePathsForOps( $ops ) ) );
 156                 if ( !$status->isOK() ) {
 157                         return $status; // abort
 158                 }
 159                 // Actually attempt the operation batch on the master backend...
 160                 $masterStatus = $mbe->doOperations( $realOps, $opts );
 161                 $status->merge( $masterStatus );
 162                 // Propagate the operations to the clone backends...
 163                 foreach ( $this->backends as $index => $backend ) {
 164                         if ( $index !== $this->masterIndex ) { // not done already
 165                                 $realOps = $this->substOpBatchPaths( $ops, $backend );
 166                                 $status->merge( $backend->doOperations( $realOps, $opts ) );
 167                         }
 168                 }
 169                 // Make 'success', 'successCount', and 'failCount' fields reflect
 170                 // the overall operation, rather than all the batches for each backend.
 171                 // Do this by only using success values from the master backend's batch.
 172                 $status->success = $masterStatus->success;
 173                 $status->successCount = $masterStatus->successCount;
 174                 $status->failCount = $masterStatus->failCount;
 175
 176                 return $status;
 177         }
 178
 179         /**
 180          * Check that a set of files are consistent across all internal backends
 181          *
 182          * @param $paths Array List of storage paths
 183          * @return Status
 184          */
 185         public function consistencyCheck( array $paths ) {
 186                 $status = Status::newGood();
 187                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 188                         return $status; // skip checks
 189                 }
 190
 191                 $mBackend = $this->backends[$this->masterIndex];
 192                 foreach ( array_unique( $paths ) as $path ) {
 193                         $params = array( 'src' => $path, 'latest' => true );
 194                         $mParams = $this->substOpPaths( $params, $mBackend );
 195                         // Stat the file on the 'master' backend
 196                         $mStat = $mBackend->getFileStat( $mParams );
 197                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 198                                 $mSha1 = $mBackend->getFileSha1Base36( $mParams );
 199                         } else {
 200                                 $mSha1 = false;
 201                         }
 202                         $mUsable = $mBackend->isPathUsableInternal( $mParams['src'] );
 203                         // Check of all clone backends agree with the master...
 204                         foreach ( $this->backends as $index => $cBackend ) {
 205                                 if ( $index === $this->masterIndex ) {
 206                                         continue; // master
 207                                 }
 208                                 $cParams = $this->substOpPaths( $params, $cBackend );
 209                                 $cStat = $cBackend->getFileStat( $cParams );
 210                                 if ( $mStat ) { // file is in master
 211                                         if ( !$cStat ) { // file should exist
 212                                                 $status->fatal( 'backend-fail-synced', $path );
 213                                                 continue;
 214                                         }
 215                                         if ( $this->syncChecks & self::CHECK_SIZE ) {
 216                                                 if ( $cStat['size'] != $mStat['size'] ) { // wrong size
 217                                                         $status->fatal( 'backend-fail-synced', $path );
 218                                                         continue;
 219                                                 }
 220                                         }
 221                                         if ( $this->syncChecks & self::CHECK_TIME ) {
 222                                                 $mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
 223                                                 $cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
 224                                                 if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
 225                                                         $status->fatal( 'backend-fail-synced', $path );
 226                                                         continue;
 227                                                 }
 228                                         }
 229                                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 230                                                 if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
 231                                                         $status->fatal( 'backend-fail-synced', $path );
 232                                                         continue;
 233                                                 }
 234                                         }
 235                                 } else { // file is not in master
 236                                         if ( $cStat ) { // file should not exist
 237                                                 $status->fatal( 'backend-fail-synced', $path );
 238                                         }
 239                                 }
 240                                 if ( $mUsable !== $cBackend->isPathUsableInternal( $cParams['src'] ) ) {
 241                                         $status->fatal( 'backend-fail-synced', $path );
 242                                 }
 243                         }
 244                 }
 245
 246                 return $status;
 247         }
 248
 249         /**
 250          * Check that a set of files are consistent across all internal backends
 251          * and re-synchronize those files againt the "multi master" if needed.
 252          *
 253          * @param $paths Array List of storage paths
 254          * @return Status
 255          */
 256         public function resyncFiles( array $paths ) {
 257                 $status = Status::newGood();
 258
 259                 $mBackend = $this->backends[$this->masterIndex];
 260                 foreach ( $paths as $path ) {
 261                         $mPath  = $this->substPaths( $path, $mBackend );
 262                         $mSha1  = $mBackend->getFileSha1Base36( array( 'src' => $mPath ) );
 263                         $mExist = $mBackend->fileExists( array( 'src' => $mPath ) );
 264                         // Check of all clone backends agree with the master...
 265                         foreach ( $this->backends as $index => $cBackend ) {
 266                                 if ( $index === $this->masterIndex ) {
 267                                         continue; // master
 268                                 }
 269                                 $cPath = $this->substPaths( $path, $cBackend );
 270                                 $cSha1 = $cBackend->getFileSha1Base36( array( 'src' => $cPath ) );
 271                                 if ( $mSha1 === $cSha1 ) {
 272                                         // already synced; nothing to do
 273                                 } elseif ( $mSha1 ) { // file is in master
 274                                         $fsFile = $mBackend->getLocalReference( array( 'src' => $mPath ) );
 275                                         $status->merge( $cBackend->quickStore(
 276                                                 array( 'src' => $fsFile->getPath(), 'dst' => $cPath )
 277                                         ) );
 278                                 } elseif ( $mExist === false ) { // file is not in master
 279                                         $status->merge( $cBackend->quickDelete( array( 'src' => $cPath ) ) );
 280                                 }
 281                         }
 282                 }
 283
 284                 return $status;
 285         }
 286
 287         /**
 288          * Get a list of file storage paths to read or write for a list of operations
 289          *
 290          * @param $ops Array Same format as doOperations()
 291          * @return Array List of storage paths to files (does not include directories)
 292          */
 293         protected function fileStoragePathsForOps( array $ops ) {
 294                 $paths = array();
 295                 foreach ( $ops as $op ) {
 296                         if ( isset( $op['src'] ) ) {
 297                                 $paths[] = $op['src'];
 298                         }
 299                         if ( isset( $op['srcs'] ) ) {
 300                                 $paths = array_merge( $paths, $op['srcs'] );
 301                         }
 302                         if ( isset( $op['dst'] ) ) {
 303                                 $paths[] = $op['dst'];
 304                         }
 305                 }
 306                 return array_unique( $paths );
 307         }
 308
 309         /**
 310          * Substitute the backend name in storage path parameters
 311          * for a set of operations with that of a given internal backend.
 312          *
 313          * @param $ops Array List of file operation arrays
 314          * @param $backend FileBackendStore
 315          * @return Array
 316          */
 317         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 318                 $newOps = array(); // operations
 319                 foreach ( $ops as $op ) {
 320                         $newOp = $op; // operation
 321                         foreach ( array( 'src', 'srcs', 'dst', 'dir' ) as $par ) {
 322                                 if ( isset( $newOp[$par] ) ) { // string or array
 323                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 324                                 }
 325                         }
 326                         $newOps[] = $newOp;
 327                 }
 328                 return $newOps;
 329         }
 330
 331         /**
 332          * Same as substOpBatchPaths() but for a single operation
 333          *
 334          * @param $ops array File operation array
 335          * @param $backend FileBackendStore
 336          * @return Array
 337          */
 338         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 339                 $newOps = $this->substOpBatchPaths( array( $ops ), $backend );
 340                 return $newOps[0];
 341         }
 342
 343         /**
 344          * Substitute the backend of storage paths with an internal backend's name
 345          *
 346          * @param $paths Array|string List of paths or single string path
 347          * @param $backend FileBackendStore
 348          * @return Array|string
 349          */
 350         protected function substPaths( $paths, FileBackendStore $backend ) {
 351                 return preg_replace(
 352                         '!^mwstore://' . preg_quote( $this->name ) . '/!',
 353                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 354                         $paths // string or array
 355                 );
 356         }
 357
 358         /**
 359          * Substitute the backend of internal storage paths with the proxy backend's name
 360          *
 361          * @param $paths Array|string List of paths or single string path
 362          * @return Array|string
 363          */
 364         protected function unsubstPaths( $paths ) {
 365                 return preg_replace(
 366                         '!^mwstore://([^/]+)!',
 367                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
 368                         $paths // string or array
 369                 );
 370         }
 371
 372         /**
 373          * @see FileBackend::doQuickOperationsInternal()
 374          * @return Status
 375          */
 376         protected function doQuickOperationsInternal( array $ops ) {
 377                 $status = Status::newGood();
 378                 // Do the operations on the master backend; setting Status fields...
 379                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 380                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 381                 $status->merge( $masterStatus );
 382                 // Propagate the operations to the clone backends...
 383                 if ( !$this->noPushQuickOps ) {
 384                         foreach ( $this->backends as $index => $backend ) {
 385                                 if ( $index !== $this->masterIndex ) { // not done already
 386                                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 387                                         $status->merge( $backend->doQuickOperations( $realOps ) );
 388                                 }
 389                         }
 390                 }
 391                 // Make 'success', 'successCount', and 'failCount' fields reflect
 392                 // the overall operation, rather than all the batches for each backend.
 393                 // Do this by only using success values from the master backend's batch.
 394                 $status->success = $masterStatus->success;
 395                 $status->successCount = $masterStatus->successCount;
 396                 $status->failCount = $masterStatus->failCount;
 397                 return $status;
 398         }
 399
 400         /**
 401          * @param $path string Storage path
 402          * @return bool Path container should have dir changes pushed to all backends
 403          */
 404         protected function replicateContainerDirChanges( $path ) {
 405                 list( $b, $shortCont, $r ) = self::splitStoragePath( $path );
 406                 return !in_array( $shortCont, $this->noPushDirConts );
 407         }
 408
 409         /**
 410          * @see FileBackend::doPrepare()
 411          * @return Status
 412          */
 413         protected function doPrepare( array $params ) {
 414                 $status = Status::newGood();
 415                 $replicate = $this->replicateContainerDirChanges( $params['dir'] );
 416                 foreach ( $this->backends as $index => $backend ) {
 417                         if ( $replicate || $index == $this->masterIndex ) {
 418                                 $realParams = $this->substOpPaths( $params, $backend );
 419                                 $status->merge( $backend->doPrepare( $realParams ) );
 420                         }
 421                 }
 422                 return $status;
 423         }
 424
 425         /**
 426          * @see FileBackend::doSecure()
 427          * @param $params array
 428          * @return Status
 429          */
 430         protected function doSecure( array $params ) {
 431                 $status = Status::newGood();
 432                 $replicate = $this->replicateContainerDirChanges( $params['dir'] );
 433                 foreach ( $this->backends as $index => $backend ) {
 434                         if ( $replicate || $index == $this->masterIndex ) {
 435                                 $realParams = $this->substOpPaths( $params, $backend );
 436                                 $status->merge( $backend->doSecure( $realParams ) );
 437                         }
 438                 }
 439                 return $status;
 440         }
 441
 442         /**
 443          * @see FileBackend::doPublish()
 444          * @param $params array
 445          * @return Status
 446          */
 447         protected function doPublish( array $params ) {
 448                 $status = Status::newGood();
 449                 $replicate = $this->replicateContainerDirChanges( $params['dir'] );
 450                 foreach ( $this->backends as $index => $backend ) {
 451                         if ( $replicate || $index == $this->masterIndex ) {
 452                                 $realParams = $this->substOpPaths( $params, $backend );
 453                                 $status->merge( $backend->doPublish( $realParams ) );
 454                         }
 455                 }
 456                 return $status;
 457         }
 458
 459         /**
 460          * @see FileBackend::doClean()
 461          * @param $params array
 462          * @return Status
 463          */
 464         protected function doClean( array $params ) {
 465                 $status = Status::newGood();
 466                 $replicate = $this->replicateContainerDirChanges( $params['dir'] );
 467                 foreach ( $this->backends as $index => $backend ) {
 468                         if ( $replicate || $index == $this->masterIndex ) {
 469                                 $realParams = $this->substOpPaths( $params, $backend );
 470                                 $status->merge( $backend->doClean( $realParams ) );
 471                         }
 472                 }
 473                 return $status;
 474         }
 475
 476         /**
 477          * @see FileBackend::concatenate()
 478          * @param $params array
 479          * @return Status
 480          */
 481         public function concatenate( array $params ) {
 482                 // We are writing to an FS file, so we don't need to do this per-backend
 483                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 484                 return $this->backends[$this->masterIndex]->concatenate( $realParams );
 485         }
 486
 487         /**
 488          * @see FileBackend::fileExists()
 489          * @param $params array
 490          */
 491         public function fileExists( array $params ) {
 492                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 493                 return $this->backends[$this->masterIndex]->fileExists( $realParams );
 494         }
 495
 496         /**
 497          * @see FileBackend::getFileTimestamp()
 498          * @param $params array
 499          * @return bool|string
 500          */
 501         public function getFileTimestamp( array $params ) {
 502                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 503                 return $this->backends[$this->masterIndex]->getFileTimestamp( $realParams );
 504         }
 505
 506         /**
 507          * @see FileBackend::getFileSize()
 508          * @param $params array
 509          * @return bool|int
 510          */
 511         public function getFileSize( array $params ) {
 512                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 513                 return $this->backends[$this->masterIndex]->getFileSize( $realParams );
 514         }
 515
 516         /**
 517          * @see FileBackend::getFileStat()
 518          * @param $params array
 519          * @return Array|bool|null
 520          */
 521         public function getFileStat( array $params ) {
 522                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 523                 return $this->backends[$this->masterIndex]->getFileStat( $realParams );
 524         }
 525
 526         /**
 527          * @see FileBackend::getFileContents()
 528          * @param $params array
 529          * @return bool|string
 530          */
 531         public function getFileContents( array $params ) {
 532                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 533                 return $this->backends[$this->masterIndex]->getFileContents( $realParams );
 534         }
 535
 536         /**
 537          * @see FileBackend::getFileSha1Base36()
 538          * @param $params array
 539          * @return bool|string
 540          */
 541         public function getFileSha1Base36( array $params ) {
 542                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 543                 return $this->backends[$this->masterIndex]->getFileSha1Base36( $realParams );
 544         }
 545
 546         /**
 547          * @see FileBackend::getFileProps()
 548          * @param $params array
 549          * @return Array
 550          */
 551         public function getFileProps( array $params ) {
 552                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 553                 return $this->backends[$this->masterIndex]->getFileProps( $realParams );
 554         }
 555
 556         /**
 557          * @see FileBackend::streamFile()
 558          * @param $params array
 559          * @return \Status
 560          */
 561         public function streamFile( array $params ) {
 562                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 563                 return $this->backends[$this->masterIndex]->streamFile( $realParams );
 564         }
 565
 566         /**
 567          * @see FileBackend::getLocalReference()
 568          * @param $params array
 569          * @return FSFile|null
 570          */
 571         public function getLocalReference( array $params ) {
 572                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 573                 return $this->backends[$this->masterIndex]->getLocalReference( $realParams );
 574         }
 575
 576         /**
 577          * @see FileBackend::getLocalCopy()
 578          * @param $params array
 579          * @return null|TempFSFile
 580          */
 581         public function getLocalCopy( array $params ) {
 582                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 583                 return $this->backends[$this->masterIndex]->getLocalCopy( $realParams );
 584         }
 585
 586         /**
 587          * @see FileBackend::directoryExists()
 588          * @param $params array
 589          * @return bool|null
 590          */
 591         public function directoryExists( array $params ) {
 592                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 593                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 594         }
 595
 596         /**
 597          * @see FileBackend::getSubdirectoryList()
 598          * @param $params array
 599          * @return Array|null|Traversable
 600          */
 601         public function getDirectoryList( array $params ) {
 602                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 603                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 604         }
 605
 606         /**
 607          * @see FileBackend::getFileList()
 608          * @param $params array
 609          * @return Array|null|\Traversable
 610          */
 611         public function getFileList( array $params ) {
 612                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 613                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 614         }
 615
 616         /**
 617          * @see FileBackend::clearCache()
 618          */
 619         public function clearCache( array $paths = null ) {
 620                 foreach ( $this->backends as $backend ) {
 621                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 622                         $backend->clearCache( $realPaths );
 623                 }
 624         }
 625
 626         /**
 627          * @see FileBackend::getScopedLocksForOps()
 628          */
 629         public function getScopedLocksForOps( array $ops, Status $status ) {
 630                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $ops );
 631                 // Get the paths to lock from the master backend
 632                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 633                 // Get the paths under the proxy backend's name
 634                 $paths['sh'] = $this->unsubstPaths( $paths['sh'] );
 635                 $paths['ex'] = $this->unsubstPaths( $paths['ex'] );
 636                 return array(
 637                         $this->getScopedFileLocks( $paths['sh'], LockManager::LOCK_UW, $status ),
 638                         $this->getScopedFileLocks( $paths['ex'], LockManager::LOCK_EX, $status )
 639                 );
 640         }
 641 }