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, starting with the master.
  37  * This makes a best-effort to have transactional semantics, but since requests
  38  * may sometimes fail, the use of "autoResync" or background scripts to fix
  39  * inconsistencies is important.
  40  *
  41  * @ingroup FileBackend
  42  * @since 1.19
  43  */
  44 class FileBackendMultiWrite extends FileBackend {
  45         /** @var FileBackendStore[] Prioritized list of FileBackendStore objects */
  46         protected $backends = [];
  47
  48         /** @var int Index of master backend */
  49         protected $masterIndex = -1;
  50         /** @var int Index of read affinity backend */
  51         protected $readIndex = -1;
  52
  53         /** @var int Bitfield */
  54         protected $syncChecks = 0;
  55         /** @var string|bool */
  56         protected $autoResync = false;
  57
  58         /** @var bool */
  59         protected $asyncWrites = false;
  60
  61         /* Possible internal backend consistency checks */
  62         const CHECK_SIZE = 1;
  63         const CHECK_TIME = 2;
  64         const CHECK_SHA1 = 4;
  65
  66         /**
  67          * Construct a proxy backend that consists of several internal backends.
  68          * Locking, journaling, and read-only checks are handled by the proxy backend.
  69          *
  70          * Additional $config params include:
  71          *   - backends       : Array of backend config and multi-backend settings.
  72          *                      Each value is the config used in the constructor of a
  73          *                      FileBackendStore class, but with these additional settings:
  74          *                        - class         : The name of the backend class
  75          *                        - isMultiMaster : This must be set for one backend.
  76          *                        - readAffinity  : Use this for reads without 'latest' set.
  77          *                        - template:     : If given a backend name, this will use
  78          *                                          the config of that backend as a template.
  79          *                                          Values specified here take precedence.
  80          *   - syncChecks     : Integer bitfield of internal backend sync checks to perform.
  81          *                      Possible bits include the FileBackendMultiWrite::CHECK_* constants.
  82          *                      There are constants for SIZE, TIME, and SHA1.
  83          *                      The checks are done before allowing any file operations.
  84          *   - autoResync     : Automatically resync the clone backends to the master backend
  85          *                      when pre-operation sync checks fail. This should only be used
  86          *                      if the master backend is stable and not missing any files.
  87          *                      Use "conservative" to limit resyncing to copying newer master
  88          *                      backend files over older (or non-existing) clone backend files.
  89          *                      Cases that cannot be handled will result in operation abortion.
  90          *   - replication    : Set to 'async' to defer file operations on the non-master backends.
  91          *                      This will apply such updates post-send for web requests. Note that
  92          *                      any checks from "syncChecks" are still synchronous.
  93          *
  94          * @param array $config
  95          * @throws FileBackendError
  96          */
  97         public function __construct( array $config ) {
  98                 parent::__construct( $config );
  99                 $this->syncChecks = isset( $config['syncChecks'] )
 100                         ? $config['syncChecks']
 101                         : self::CHECK_SIZE;
 102                 $this->autoResync = isset( $config['autoResync'] )
 103                         ? $config['autoResync']
 104                         : false;
 105                 $this->asyncWrites = isset( $config['replication'] ) && $config['replication'] === 'async';
 106                 // Construct backends here rather than via registration
 107                 // to keep these backends hidden from outside the proxy.
 108                 $namesUsed = [];
 109                 foreach ( $config['backends'] as $index => $config ) {
 110                         if ( isset( $config['template'] ) ) {
 111                                 // Config is just a modified version of a registered backend's.
 112                                 // This should only be used when that config is used only by this backend.
 113                                 $config = $config + FileBackendGroup::singleton()->config( $config['template'] );
 114                         }
 115                         $name = $config['name'];
 116                         if ( isset( $namesUsed[$name] ) ) { // don't break FileOp predicates
 117                                 throw new FileBackendError( "Two or more backends defined with the name $name." );
 118                         }
 119                         $namesUsed[$name] = 1;
 120                         // Alter certain sub-backend settings for sanity
 121                         unset( $config['readOnly'] ); // use proxy backend setting
 122                         unset( $config['fileJournal'] ); // use proxy backend journal
 123                         unset( $config['lockManager'] ); // lock under proxy backend
 124                         $config['wikiId'] = $this->wikiId; // use the proxy backend wiki ID
 125                         if ( !empty( $config['isMultiMaster'] ) ) {
 126                                 if ( $this->masterIndex >= 0 ) {
 127                                         throw new FileBackendError( 'More than one master backend defined.' );
 128                                 }
 129                                 $this->masterIndex = $index; // this is the "master"
 130                                 $config['fileJournal'] = $this->fileJournal; // log under proxy backend
 131                         }
 132                         if ( !empty( $config['readAffinity'] ) ) {
 133                                 $this->readIndex = $index; // prefer this for reads
 134                         }
 135                         // Create sub-backend object
 136                         if ( !isset( $config['class'] ) ) {
 137                                 throw new FileBackendError( 'No class given for a backend config.' );
 138                         }
 139                         $class = $config['class'];
 140                         $this->backends[$index] = new $class( $config );
 141                 }
 142                 if ( $this->masterIndex < 0 ) { // need backends and must have a master
 143                         throw new FileBackendError( 'No master backend defined.' );
 144                 }
 145                 if ( $this->readIndex < 0 ) {
 146                         $this->readIndex = $this->masterIndex; // default
 147                 }
 148         }
 149
 150         final protected function doOperationsInternal( array $ops, array $opts ) {
 151                 $status = Status::newGood();
 152
 153                 $mbe = $this->backends[$this->masterIndex]; // convenience
 154
 155                 // Try to lock those files for the scope of this function...
 156                 $scopeLock = null;
 157                 if ( empty( $opts['nonLocking'] ) ) {
 158                         // Try to lock those files for the scope of this function...
 159                         /** @noinspection PhpUnusedLocalVariableInspection */
 160                         $scopeLock = $this->getScopedLocksForOps( $ops, $status );
 161                         if ( !$status->isOK() ) {
 162                                 return $status; // abort
 163                         }
 164                 }
 165                 // Clear any cache entries (after locks acquired)
 166                 $this->clearCache();
 167                 $opts['preserveCache'] = true; // only locked files are cached
 168                 // Get the list of paths to read/write...
 169                 $relevantPaths = $this->fileStoragePathsForOps( $ops );
 170                 // Check if the paths are valid and accessible on all backends...
 171                 $status->merge( $this->accessibilityCheck( $relevantPaths ) );
 172                 if ( !$status->isOK() ) {
 173                         return $status; // abort
 174                 }
 175                 // Do a consistency check to see if the backends are consistent...
 176                 $syncStatus = $this->consistencyCheck( $relevantPaths );
 177                 if ( !$syncStatus->isOK() ) {
 178                         wfDebugLog( 'FileOperation', get_class( $this ) .
 179                                 " failed sync check: " . FormatJson::encode( $relevantPaths ) );
 180                         // Try to resync the clone backends to the master on the spot...
 181                         if ( !$this->autoResync || !$this->resyncFiles( $relevantPaths )->isOK() ) {
 182                                 $status->merge( $syncStatus );
 183
 184                                 return $status; // abort
 185                         }
 186                 }
 187                 // Actually attempt the operation batch on the master backend...
 188                 $realOps = $this->substOpBatchPaths( $ops, $mbe );
 189                 $masterStatus = $mbe->doOperations( $realOps, $opts );
 190                 $status->merge( $masterStatus );
 191                 // Propagate the operations to the clone backends if there were no unexpected errors
 192                 // and if there were either no expected errors or if the 'force' option was used.
 193                 // However, if nothing succeeded at all, then don't replicate any of the operations.
 194                 // If $ops only had one operation, this might avoid backend sync inconsistencies.
 195                 if ( $masterStatus->isOK() && $masterStatus->successCount > 0 ) {
 196                         foreach ( $this->backends as $index => $backend ) {
 197                                 if ( $index === $this->masterIndex ) {
 198                                         continue; // done already
 199                                 }
 200
 201                                 $realOps = $this->substOpBatchPaths( $ops, $backend );
 202                                 if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 203                                         // Bind $scopeLock to the callback to preserve locks
 204                                         DeferredUpdates::addCallableUpdate(
 205                                                 function() use ( $backend, $realOps, $opts, $scopeLock ) {
 206                                                         $backend->doOperations( $realOps, $opts );
 207                                                 }
 208                                         );
 209                                 } else {
 210                                         $status->merge( $backend->doOperations( $realOps, $opts ) );
 211                                 }
 212                         }
 213                 }
 214                 // Make 'success', 'successCount', and 'failCount' fields reflect
 215                 // the overall operation, rather than all the batches for each backend.
 216                 // Do this by only using success values from the master backend's batch.
 217                 $status->success = $masterStatus->success;
 218                 $status->successCount = $masterStatus->successCount;
 219                 $status->failCount = $masterStatus->failCount;
 220
 221                 return $status;
 222         }
 223
 224         /**
 225          * Check that a set of files are consistent across all internal backends
 226          *
 227          * @param array $paths List of storage paths
 228          * @return Status
 229          */
 230         public function consistencyCheck( array $paths ) {
 231                 $status = Status::newGood();
 232                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 233                         return $status; // skip checks
 234                 }
 235
 236                 $mBackend = $this->backends[$this->masterIndex];
 237                 foreach ( $paths as $path ) {
 238                         $params = [ 'src' => $path, 'latest' => true ];
 239                         $mParams = $this->substOpPaths( $params, $mBackend );
 240                         // Stat the file on the 'master' backend
 241                         $mStat = $mBackend->getFileStat( $mParams );
 242                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 243                                 $mSha1 = $mBackend->getFileSha1Base36( $mParams );
 244                         } else {
 245                                 $mSha1 = false;
 246                         }
 247                         // Check if all clone backends agree with the master...
 248                         foreach ( $this->backends as $index => $cBackend ) {
 249                                 if ( $index === $this->masterIndex ) {
 250                                         continue; // master
 251                                 }
 252                                 $cParams = $this->substOpPaths( $params, $cBackend );
 253                                 $cStat = $cBackend->getFileStat( $cParams );
 254                                 if ( $mStat ) { // file is in master
 255                                         if ( !$cStat ) { // file should exist
 256                                                 $status->fatal( 'backend-fail-synced', $path );
 257                                                 continue;
 258                                         }
 259                                         if ( $this->syncChecks & self::CHECK_SIZE ) {
 260                                                 if ( $cStat['size'] != $mStat['size'] ) { // wrong size
 261                                                         $status->fatal( 'backend-fail-synced', $path );
 262                                                         continue;
 263                                                 }
 264                                         }
 265                                         if ( $this->syncChecks & self::CHECK_TIME ) {
 266                                                 $mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
 267                                                 $cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
 268                                                 if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
 269                                                         $status->fatal( 'backend-fail-synced', $path );
 270                                                         continue;
 271                                                 }
 272                                         }
 273                                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 274                                                 if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
 275                                                         $status->fatal( 'backend-fail-synced', $path );
 276                                                         continue;
 277                                                 }
 278                                         }
 279                                 } else { // file is not in master
 280                                         if ( $cStat ) { // file should not exist
 281                                                 $status->fatal( 'backend-fail-synced', $path );
 282                                         }
 283                                 }
 284                         }
 285                 }
 286
 287                 return $status;
 288         }
 289
 290         /**
 291          * Check that a set of file paths are usable across all internal backends
 292          *
 293          * @param array $paths List of storage paths
 294          * @return Status
 295          */
 296         public function accessibilityCheck( array $paths ) {
 297                 $status = Status::newGood();
 298                 if ( count( $this->backends ) <= 1 ) {
 299                         return $status; // skip checks
 300                 }
 301
 302                 foreach ( $paths as $path ) {
 303                         foreach ( $this->backends as $backend ) {
 304                                 $realPath = $this->substPaths( $path, $backend );
 305                                 if ( !$backend->isPathUsableInternal( $realPath ) ) {
 306                                         $status->fatal( 'backend-fail-usable', $path );
 307                                 }
 308                         }
 309                 }
 310
 311                 return $status;
 312         }
 313
 314         /**
 315          * Check that a set of files are consistent across all internal backends
 316          * and re-synchronize those files against the "multi master" if needed.
 317          *
 318          * @param array $paths List of storage paths
 319          * @return Status
 320          */
 321         public function resyncFiles( array $paths ) {
 322                 $status = Status::newGood();
 323
 324                 $mBackend = $this->backends[$this->masterIndex];
 325                 foreach ( $paths as $path ) {
 326                         $mPath = $this->substPaths( $path, $mBackend );
 327                         $mSha1 = $mBackend->getFileSha1Base36( [ 'src' => $mPath, 'latest' => true ] );
 328                         $mStat = $mBackend->getFileStat( [ 'src' => $mPath, 'latest' => true ] );
 329                         if ( $mStat === null || ( $mSha1 !== false && !$mStat ) ) { // sanity
 330                                 $status->fatal( 'backend-fail-internal', $this->name );
 331                                 wfDebugLog( 'FileOperation', __METHOD__
 332                                         . ': File is not available on the master backend' );
 333                                 continue; // file is not available on the master backend...
 334                         }
 335                         // Check of all clone backends agree with the master...
 336                         foreach ( $this->backends as $index => $cBackend ) {
 337                                 if ( $index === $this->masterIndex ) {
 338                                         continue; // master
 339                                 }
 340                                 $cPath = $this->substPaths( $path, $cBackend );
 341                                 $cSha1 = $cBackend->getFileSha1Base36( [ 'src' => $cPath, 'latest' => true ] );
 342                                 $cStat = $cBackend->getFileStat( [ 'src' => $cPath, 'latest' => true ] );
 343                                 if ( $cStat === null || ( $cSha1 !== false && !$cStat ) ) { // sanity
 344                                         $status->fatal( 'backend-fail-internal', $cBackend->getName() );
 345                                         wfDebugLog( 'FileOperation', __METHOD__ .
 346                                                 ': File is not available on the clone backend' );
 347                                         continue; // file is not available on the clone backend...
 348                                 }
 349                                 if ( $mSha1 === $cSha1 ) {
 350                                         // already synced; nothing to do
 351                                 } elseif ( $mSha1 !== false ) { // file is in master
 352                                         if ( $this->autoResync === 'conservative'
 353                                                 && $cStat && $cStat['mtime'] > $mStat['mtime']
 354                                         ) {
 355                                                 $status->fatal( 'backend-fail-synced', $path );
 356                                                 continue; // don't rollback data
 357                                         }
 358                                         $fsFile = $mBackend->getLocalReference(
 359                                                 [ 'src' => $mPath, 'latest' => true ] );
 360                                         $status->merge( $cBackend->quickStore(
 361                                                 [ 'src' => $fsFile->getPath(), 'dst' => $cPath ]
 362                                         ) );
 363                                 } elseif ( $mStat === false ) { // file is not in master
 364                                         if ( $this->autoResync === 'conservative' ) {
 365                                                 $status->fatal( 'backend-fail-synced', $path );
 366                                                 continue; // don't delete data
 367                                         }
 368                                         $status->merge( $cBackend->quickDelete( [ 'src' => $cPath ] ) );
 369                                 }
 370                         }
 371                 }
 372
 373                 return $status;
 374         }
 375
 376         /**
 377          * Get a list of file storage paths to read or write for a list of operations
 378          *
 379          * @param array $ops Same format as doOperations()
 380          * @return array List of storage paths to files (does not include directories)
 381          */
 382         protected function fileStoragePathsForOps( array $ops ) {
 383                 $paths = [];
 384                 foreach ( $ops as $op ) {
 385                         if ( isset( $op['src'] ) ) {
 386                                 // For things like copy/move/delete with "ignoreMissingSource" and there
 387                                 // is no source file, nothing should happen and there should be no errors.
 388                                 if ( empty( $op['ignoreMissingSource'] )
 389                                         || $this->fileExists( [ 'src' => $op['src'] ] )
 390                                 ) {
 391                                         $paths[] = $op['src'];
 392                                 }
 393                         }
 394                         if ( isset( $op['srcs'] ) ) {
 395                                 $paths = array_merge( $paths, $op['srcs'] );
 396                         }
 397                         if ( isset( $op['dst'] ) ) {
 398                                 $paths[] = $op['dst'];
 399                         }
 400                 }
 401
 402                 return array_values( array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) ) );
 403         }
 404
 405         /**
 406          * Substitute the backend name in storage path parameters
 407          * for a set of operations with that of a given internal backend.
 408          *
 409          * @param array $ops List of file operation arrays
 410          * @param FileBackendStore $backend
 411          * @return array
 412          */
 413         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 414                 $newOps = []; // operations
 415                 foreach ( $ops as $op ) {
 416                         $newOp = $op; // operation
 417                         foreach ( [ 'src', 'srcs', 'dst', 'dir' ] as $par ) {
 418                                 if ( isset( $newOp[$par] ) ) { // string or array
 419                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 420                                 }
 421                         }
 422                         $newOps[] = $newOp;
 423                 }
 424
 425                 return $newOps;
 426         }
 427
 428         /**
 429          * Same as substOpBatchPaths() but for a single operation
 430          *
 431          * @param array $ops File operation array
 432          * @param FileBackendStore $backend
 433          * @return array
 434          */
 435         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 436                 $newOps = $this->substOpBatchPaths( [ $ops ], $backend );
 437
 438                 return $newOps[0];
 439         }
 440
 441         /**
 442          * Substitute the backend of storage paths with an internal backend's name
 443          *
 444          * @param array|string $paths List of paths or single string path
 445          * @param FileBackendStore $backend
 446          * @return array|string
 447          */
 448         protected function substPaths( $paths, FileBackendStore $backend ) {
 449                 return preg_replace(
 450                         '!^mwstore://' . preg_quote( $this->name, '!' ) . '/!',
 451                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 452                         $paths // string or array
 453                 );
 454         }
 455
 456         /**
 457          * Substitute the backend of internal storage paths with the proxy backend's name
 458          *
 459          * @param array|string $paths List of paths or single string path
 460          * @return array|string
 461          */
 462         protected function unsubstPaths( $paths ) {
 463                 return preg_replace(
 464                         '!^mwstore://([^/]+)!',
 465                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
 466                         $paths // string or array
 467                 );
 468         }
 469
 470         /**
 471          * @param array $ops File operations for FileBackend::doOperations()
 472          * @return bool Whether there are file path sources with outside lifetime/ownership
 473          */
 474         protected function hasVolatileSources( array $ops ) {
 475                 foreach ( $ops as $op ) {
 476                         if ( $op['op'] === 'store' && !isset( $op['srcRef'] ) ) {
 477                                 return true; // source file might be deleted anytime after do*Operations()
 478                         }
 479                 }
 480
 481                 return false;
 482         }
 483
 484         protected function doQuickOperationsInternal( array $ops ) {
 485                 $status = Status::newGood();
 486                 // Do the operations on the master backend; setting Status fields...
 487                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 488                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 489                 $status->merge( $masterStatus );
 490                 // Propagate the operations to the clone backends...
 491                 foreach ( $this->backends as $index => $backend ) {
 492                         if ( $index === $this->masterIndex ) {
 493                                 continue; // done already
 494                         }
 495
 496                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 497                         if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 498                                 DeferredUpdates::addCallableUpdate(
 499                                         function() use ( $backend, $realOps ) {
 500                                                 $backend->doQuickOperations( $realOps );
 501                                         }
 502                                 );
 503                         } else {
 504                                 $status->merge( $backend->doQuickOperations( $realOps ) );
 505                         }
 506                 }
 507                 // Make 'success', 'successCount', and 'failCount' fields reflect
 508                 // the overall operation, rather than all the batches for each backend.
 509                 // Do this by only using success values from the master backend's batch.
 510                 $status->success = $masterStatus->success;
 511                 $status->successCount = $masterStatus->successCount;
 512                 $status->failCount = $masterStatus->failCount;
 513
 514                 return $status;
 515         }
 516
 517         protected function doPrepare( array $params ) {
 518                 return $this->doDirectoryOp( 'prepare', $params );
 519         }
 520
 521         protected function doSecure( array $params ) {
 522                 return $this->doDirectoryOp( 'secure', $params );
 523         }
 524
 525         protected function doPublish( array $params ) {
 526                 return $this->doDirectoryOp( 'publish', $params );
 527         }
 528
 529         protected function doClean( array $params ) {
 530                 return $this->doDirectoryOp( 'clean', $params );
 531         }
 532
 533         /**
 534          * @param string $method One of (doPrepare,doSecure,doPublish,doClean)
 535          * @param array $params Method arguments
 536          * @return Status
 537          */
 538         protected function doDirectoryOp( $method, array $params ) {
 539                 $status = Status::newGood();
 540
 541                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 542                 $masterStatus = $this->backends[$this->masterIndex]->$method( $realParams );
 543                 $status->merge( $masterStatus );
 544
 545                 foreach ( $this->backends as $index => $backend ) {
 546                         if ( $index === $this->masterIndex ) {
 547                                 continue; // already done
 548                         }
 549
 550                         $realParams = $this->substOpPaths( $params, $backend );
 551                         if ( $this->asyncWrites ) {
 552                                 DeferredUpdates::addCallableUpdate(
 553                                         function() use ( $backend, $method, $realParams ) {
 554                                                 $backend->$method( $realParams );
 555                                         }
 556                                 );
 557                         } else {
 558                                 $status->merge( $backend->$method( $realParams ) );
 559                         }
 560                 }
 561
 562                 return $status;
 563         }
 564
 565         public function concatenate( array $params ) {
 566                 // We are writing to an FS file, so we don't need to do this per-backend
 567                 $index = $this->getReadIndexFromParams( $params );
 568                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 569
 570                 return $this->backends[$index]->concatenate( $realParams );
 571         }
 572
 573         public function fileExists( array $params ) {
 574                 $index = $this->getReadIndexFromParams( $params );
 575                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 576
 577                 return $this->backends[$index]->fileExists( $realParams );
 578         }
 579
 580         public function getFileTimestamp( array $params ) {
 581                 $index = $this->getReadIndexFromParams( $params );
 582                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 583
 584                 return $this->backends[$index]->getFileTimestamp( $realParams );
 585         }
 586
 587         public function getFileSize( array $params ) {
 588                 $index = $this->getReadIndexFromParams( $params );
 589                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 590
 591                 return $this->backends[$index]->getFileSize( $realParams );
 592         }
 593
 594         public function getFileStat( array $params ) {
 595                 $index = $this->getReadIndexFromParams( $params );
 596                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 597
 598                 return $this->backends[$index]->getFileStat( $realParams );
 599         }
 600
 601         public function getFileXAttributes( array $params ) {
 602                 $index = $this->getReadIndexFromParams( $params );
 603                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 604
 605                 return $this->backends[$index]->getFileXAttributes( $realParams );
 606         }
 607
 608         public function getFileContentsMulti( array $params ) {
 609                 $index = $this->getReadIndexFromParams( $params );
 610                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 611
 612                 $contentsM = $this->backends[$index]->getFileContentsMulti( $realParams );
 613
 614                 $contents = []; // (path => FSFile) mapping using the proxy backend's name
 615                 foreach ( $contentsM as $path => $data ) {
 616                         $contents[$this->unsubstPaths( $path )] = $data;
 617                 }
 618
 619                 return $contents;
 620         }
 621
 622         public function getFileSha1Base36( array $params ) {
 623                 $index = $this->getReadIndexFromParams( $params );
 624                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 625
 626                 return $this->backends[$index]->getFileSha1Base36( $realParams );
 627         }
 628
 629         public function getFileProps( array $params ) {
 630                 $index = $this->getReadIndexFromParams( $params );
 631                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 632
 633                 return $this->backends[$index]->getFileProps( $realParams );
 634         }
 635
 636         public function streamFile( array $params ) {
 637                 $index = $this->getReadIndexFromParams( $params );
 638                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 639
 640                 return $this->backends[$index]->streamFile( $realParams );
 641         }
 642
 643         public function getLocalReferenceMulti( array $params ) {
 644                 $index = $this->getReadIndexFromParams( $params );
 645                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 646
 647                 $fsFilesM = $this->backends[$index]->getLocalReferenceMulti( $realParams );
 648
 649                 $fsFiles = []; // (path => FSFile) mapping using the proxy backend's name
 650                 foreach ( $fsFilesM as $path => $fsFile ) {
 651                         $fsFiles[$this->unsubstPaths( $path )] = $fsFile;
 652                 }
 653
 654                 return $fsFiles;
 655         }
 656
 657         public function getLocalCopyMulti( array $params ) {
 658                 $index = $this->getReadIndexFromParams( $params );
 659                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 660
 661                 $tempFilesM = $this->backends[$index]->getLocalCopyMulti( $realParams );
 662
 663                 $tempFiles = []; // (path => TempFSFile) mapping using the proxy backend's name
 664                 foreach ( $tempFilesM as $path => $tempFile ) {
 665                         $tempFiles[$this->unsubstPaths( $path )] = $tempFile;
 666                 }
 667
 668                 return $tempFiles;
 669         }
 670
 671         public function getFileHttpUrl( array $params ) {
 672                 $index = $this->getReadIndexFromParams( $params );
 673                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 674
 675                 return $this->backends[$index]->getFileHttpUrl( $realParams );
 676         }
 677
 678         public function directoryExists( array $params ) {
 679                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 680
 681                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 682         }
 683
 684         public function getDirectoryList( array $params ) {
 685                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 686
 687                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 688         }
 689
 690         public function getFileList( array $params ) {
 691                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 692
 693                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 694         }
 695
 696         public function getFeatures() {
 697                 return $this->backends[$this->masterIndex]->getFeatures();
 698         }
 699
 700         public function clearCache( array $paths = null ) {
 701                 foreach ( $this->backends as $backend ) {
 702                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 703                         $backend->clearCache( $realPaths );
 704                 }
 705         }
 706
 707         public function preloadCache( array $paths ) {
 708                 $realPaths = $this->substPaths( $paths, $this->backends[$this->readIndex] );
 709                 $this->backends[$this->readIndex]->preloadCache( $realPaths );
 710         }
 711
 712         public function preloadFileStat( array $params ) {
 713                 $index = $this->getReadIndexFromParams( $params );
 714                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 715
 716                 return $this->backends[$index]->preloadFileStat( $realParams );
 717         }
 718
 719         public function getScopedLocksForOps( array $ops, Status $status ) {
 720                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 721                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $realOps );
 722                 // Get the paths to lock from the master backend
 723                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 724                 // Get the paths under the proxy backend's name
 725                 $pbPaths = [
 726                         LockManager::LOCK_UW => $this->unsubstPaths( $paths[LockManager::LOCK_UW] ),
 727                         LockManager::LOCK_EX => $this->unsubstPaths( $paths[LockManager::LOCK_EX] )
 728                 ];
 729
 730                 // Actually acquire the locks
 731                 return $this->getScopedFileLocks( $pbPaths, 'mixed', $status );
 732         }
 733
 734         /**
 735          * @param array $params
 736          * @return int The master or read affinity backend index, based on $params['latest']
 737          */
 738         protected function getReadIndexFromParams( array $params ) {
 739                 return !empty( $params['latest'] ) ? $this->masterIndex : $this->readIndex;
 740         }
 741 }