includes/libs/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  */
  23
  24 /**
  25  * @brief Proxy backend that mirrors writes to several internal backends.
  26  *
  27  * This class defines a multi-write backend. Multiple backends can be
  28  * registered to this proxy backend and it will act as a single backend.
  29  * Use this when all access to those backends is through this proxy backend.
  30  * At least one of the backends must be declared the "master" backend.
  31  *
  32  * Only use this class when transitioning from one storage system to another.
  33  *
  34  * Read operations are only done on the 'master' backend for consistency.
  35  * Write operations are performed on all backends, starting with the master.
  36  * This makes a best-effort to have transactional semantics, but since requests
  37  * may sometimes fail, the use of "autoResync" or background scripts to fix
  38  * inconsistencies is important.
  39  *
  40  * @ingroup FileBackend
  41  * @since 1.19
  42  */
  43 class FileBackendMultiWrite extends FileBackend {
  44         /** @var FileBackendStore[] Prioritized list of FileBackendStore objects */
  45         protected $backends = [];
  46
  47         /** @var int Index of master backend */
  48         protected $masterIndex = -1;
  49         /** @var int Index of read affinity backend */
  50         protected $readIndex = -1;
  51
  52         /** @var int Bitfield */
  53         protected $syncChecks = 0;
  54         /** @var string|bool */
  55         protected $autoResync = false;
  56
  57         /** @var bool */
  58         protected $asyncWrites = false;
  59
  60         /* Possible internal backend consistency checks */
  61         const CHECK_SIZE = 1;
  62         const CHECK_TIME = 2;
  63         const CHECK_SHA1 = 4;
  64
  65         /**
  66          * Construct a proxy backend that consists of several internal backends.
  67          * Locking, journaling, and read-only checks are handled by the proxy backend.
  68          *
  69          * Additional $config params include:
  70          *   - backends       : Array of backend config and multi-backend settings.
  71          *                      Each value is the config used in the constructor of a
  72          *                      FileBackendStore class, but with these additional settings:
  73          *                        - class         : The name of the backend class
  74          *                        - isMultiMaster : This must be set for one backend.
  75          *                        - readAffinity  : Use this for reads without 'latest' set.
  76          *   - syncChecks     : Integer bitfield of internal backend sync checks to perform.
  77          *                      Possible bits include the FileBackendMultiWrite::CHECK_* constants.
  78          *                      There are constants for SIZE, TIME, and SHA1.
  79          *                      The checks are done before allowing any file operations.
  80          *   - autoResync     : Automatically resync the clone backends to the master backend
  81          *                      when pre-operation sync checks fail. This should only be used
  82          *                      if the master backend is stable and not missing any files.
  83          *                      Use "conservative" to limit resyncing to copying newer master
  84          *                      backend files over older (or non-existing) clone backend files.
  85          *                      Cases that cannot be handled will result in operation abortion.
  86          *   - replication    : Set to 'async' to defer file operations on the non-master backends.
  87          *                      This will apply such updates post-send for web requests. Note that
  88          *                      any checks from "syncChecks" are still synchronous.
  89          *
  90          * Bogus warning
  91          * @suppress PhanAccessMethodProtected
  92          *
  93          * @param array $config
  94          * @throws FileBackendError
  95          */
  96         public function __construct( array $config ) {
  97                 parent::__construct( $config );
  98                 $this->syncChecks = isset( $config['syncChecks'] )
  99                         ? $config['syncChecks']
 100                         : self::CHECK_SIZE;
 101                 $this->autoResync = isset( $config['autoResync'] )
 102                         ? $config['autoResync']
 103                         : false;
 104                 $this->asyncWrites = isset( $config['replication'] ) && $config['replication'] === 'async';
 105                 // Construct backends here rather than via registration
 106                 // to keep these backends hidden from outside the proxy.
 107                 $namesUsed = [];
 108                 foreach ( $config['backends'] as $index => $config ) {
 109                         $name = $config['name'];
 110                         if ( isset( $namesUsed[$name] ) ) { // don't break FileOp predicates
 111                                 throw new LogicException( "Two or more backends defined with the name $name." );
 112                         }
 113                         $namesUsed[$name] = 1;
 114                         // Alter certain sub-backend settings for sanity
 115                         unset( $config['readOnly'] ); // use proxy backend setting
 116                         unset( $config['fileJournal'] ); // use proxy backend journal
 117                         unset( $config['lockManager'] ); // lock under proxy backend
 118                         $config['domainId'] = $this->domainId; // use the proxy backend wiki ID
 119                         if ( !empty( $config['isMultiMaster'] ) ) {
 120                                 if ( $this->masterIndex >= 0 ) {
 121                                         throw new LogicException( 'More than one master backend defined.' );
 122                                 }
 123                                 $this->masterIndex = $index; // this is the "master"
 124                                 $config['fileJournal'] = $this->fileJournal; // log under proxy backend
 125                         }
 126                         if ( !empty( $config['readAffinity'] ) ) {
 127                                 $this->readIndex = $index; // prefer this for reads
 128                         }
 129                         // Create sub-backend object
 130                         if ( !isset( $config['class'] ) ) {
 131                                 throw new InvalidArgumentException( 'No class given for a backend config.' );
 132                         }
 133                         $class = $config['class'];
 134                         $this->backends[$index] = new $class( $config );
 135                 }
 136                 if ( $this->masterIndex < 0 ) { // need backends and must have a master
 137                         throw new LogicException( 'No master backend defined.' );
 138                 }
 139                 if ( $this->readIndex < 0 ) {
 140                         $this->readIndex = $this->masterIndex; // default
 141                 }
 142         }
 143
 144         final protected function doOperationsInternal( array $ops, array $opts ) {
 145                 $status = $this->newStatus();
 146
 147                 $mbe = $this->backends[$this->masterIndex]; // convenience
 148
 149                 // Try to lock those files for the scope of this function...
 150                 $scopeLock = null;
 151                 if ( empty( $opts['nonLocking'] ) ) {
 152                         // Try to lock those files for the scope of this function...
 153                         /** @noinspection PhpUnusedLocalVariableInspection */
 154                         $scopeLock = $this->getScopedLocksForOps( $ops, $status );
 155                         if ( !$status->isOK() ) {
 156                                 return $status; // abort
 157                         }
 158                 }
 159                 // Clear any cache entries (after locks acquired)
 160                 $this->clearCache();
 161                 $opts['preserveCache'] = true; // only locked files are cached
 162                 // Get the list of paths to read/write...
 163                 $relevantPaths = $this->fileStoragePathsForOps( $ops );
 164                 // Check if the paths are valid and accessible on all backends...
 165                 $status->merge( $this->accessibilityCheck( $relevantPaths ) );
 166                 if ( !$status->isOK() ) {
 167                         return $status; // abort
 168                 }
 169                 // Do a consistency check to see if the backends are consistent...
 170                 $syncStatus = $this->consistencyCheck( $relevantPaths );
 171                 if ( !$syncStatus->isOK() ) {
 172                         wfDebugLog( 'FileOperation', static::class .
 173                                 " failed sync check: " . FormatJson::encode( $relevantPaths ) );
 174                         // Try to resync the clone backends to the master on the spot...
 175                         if ( $this->autoResync === false
 176                                 || !$this->resyncFiles( $relevantPaths, $this->autoResync )->isOK()
 177                         ) {
 178                                 $status->merge( $syncStatus );
 179
 180                                 return $status; // abort
 181                         }
 182                 }
 183                 // Actually attempt the operation batch on the master backend...
 184                 $realOps = $this->substOpBatchPaths( $ops, $mbe );
 185                 $masterStatus = $mbe->doOperations( $realOps, $opts );
 186                 $status->merge( $masterStatus );
 187                 // Propagate the operations to the clone backends if there were no unexpected errors
 188                 // and if there were either no expected errors or if the 'force' option was used.
 189                 // However, if nothing succeeded at all, then don't replicate any of the operations.
 190                 // If $ops only had one operation, this might avoid backend sync inconsistencies.
 191                 if ( $masterStatus->isOK() && $masterStatus->successCount > 0 ) {
 192                         foreach ( $this->backends as $index => $backend ) {
 193                                 if ( $index === $this->masterIndex ) {
 194                                         continue; // done already
 195                                 }
 196
 197                                 $realOps = $this->substOpBatchPaths( $ops, $backend );
 198                                 if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 199                                         // Bind $scopeLock to the callback to preserve locks
 200                                         DeferredUpdates::addCallableUpdate(
 201                                                 function () use ( $backend, $realOps, $opts, $scopeLock, $relevantPaths ) {
 202                                                         wfDebugLog( 'FileOperationReplication',
 203                                                                 "'{$backend->getName()}' async replication; paths: " .
 204                                                                 FormatJson::encode( $relevantPaths ) );
 205                                                         $backend->doOperations( $realOps, $opts );
 206                                                 }
 207                                         );
 208                                 } else {
 209                                         wfDebugLog( 'FileOperationReplication',
 210                                                 "'{$backend->getName()}' sync replication; paths: " .
 211                                                 FormatJson::encode( $relevantPaths ) );
 212                                         $status->merge( $backend->doOperations( $realOps, $opts ) );
 213                                 }
 214                         }
 215                 }
 216                 // Make 'success', 'successCount', and 'failCount' fields reflect
 217                 // the overall operation, rather than all the batches for each backend.
 218                 // Do this by only using success values from the master backend's batch.
 219                 $status->success = $masterStatus->success;
 220                 $status->successCount = $masterStatus->successCount;
 221                 $status->failCount = $masterStatus->failCount;
 222
 223                 return $status;
 224         }
 225
 226         /**
 227          * Check that a set of files are consistent across all internal backends
 228          *
 229          * @param array $paths List of storage paths
 230          * @return StatusValue
 231          */
 232         public function consistencyCheck( array $paths ) {
 233                 $status = $this->newStatus();
 234                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 235                         return $status; // skip checks
 236                 }
 237
 238                 // Preload all of the stat info in as few round trips as possible...
 239                 foreach ( $this->backends as $backend ) {
 240                         $realPaths = $this->substPaths( $paths, $backend );
 241                         $backend->preloadFileStat( [ 'srcs' => $realPaths, 'latest' => true ] );
 242                 }
 243
 244                 $mBackend = $this->backends[$this->masterIndex];
 245                 foreach ( $paths as $path ) {
 246                         $params = [ 'src' => $path, 'latest' => true ];
 247                         $mParams = $this->substOpPaths( $params, $mBackend );
 248                         // Stat the file on the 'master' backend
 249                         $mStat = $mBackend->getFileStat( $mParams );
 250                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 251                                 $mSha1 = $mBackend->getFileSha1Base36( $mParams );
 252                         } else {
 253                                 $mSha1 = false;
 254                         }
 255                         // Check if all clone backends agree with the master...
 256                         foreach ( $this->backends as $index => $cBackend ) {
 257                                 if ( $index === $this->masterIndex ) {
 258                                         continue; // master
 259                                 }
 260                                 $cParams = $this->substOpPaths( $params, $cBackend );
 261                                 $cStat = $cBackend->getFileStat( $cParams );
 262                                 if ( $mStat ) { // file is in master
 263                                         if ( !$cStat ) { // file should exist
 264                                                 $status->fatal( 'backend-fail-synced', $path );
 265                                                 continue;
 266                                         }
 267                                         if ( $this->syncChecks & self::CHECK_SIZE ) {
 268                                                 if ( $cStat['size'] != $mStat['size'] ) { // wrong size
 269                                                         $status->fatal( 'backend-fail-synced', $path );
 270                                                         continue;
 271                                                 }
 272                                         }
 273                                         if ( $this->syncChecks & self::CHECK_TIME ) {
 274                                                 $mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
 275                                                 $cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
 276                                                 if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
 277                                                         $status->fatal( 'backend-fail-synced', $path );
 278                                                         continue;
 279                                                 }
 280                                         }
 281                                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 282                                                 if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
 283                                                         $status->fatal( 'backend-fail-synced', $path );
 284                                                         continue;
 285                                                 }
 286                                         }
 287                                 } else { // file is not in master
 288                                         if ( $cStat ) { // file should not exist
 289                                                 $status->fatal( 'backend-fail-synced', $path );
 290                                         }
 291                                 }
 292                         }
 293                 }
 294
 295                 return $status;
 296         }
 297
 298         /**
 299          * Check that a set of file paths are usable across all internal backends
 300          *
 301          * @param array $paths List of storage paths
 302          * @return StatusValue
 303          */
 304         public function accessibilityCheck( array $paths ) {
 305                 $status = $this->newStatus();
 306                 if ( count( $this->backends ) <= 1 ) {
 307                         return $status; // skip checks
 308                 }
 309
 310                 foreach ( $paths as $path ) {
 311                         foreach ( $this->backends as $backend ) {
 312                                 $realPath = $this->substPaths( $path, $backend );
 313                                 if ( !$backend->isPathUsableInternal( $realPath ) ) {
 314                                         $status->fatal( 'backend-fail-usable', $path );
 315                                 }
 316                         }
 317                 }
 318
 319                 return $status;
 320         }
 321
 322         /**
 323          * Check that a set of files are consistent across all internal backends
 324          * and re-synchronize those files against the "multi master" if needed.
 325          *
 326          * @param array $paths List of storage paths
 327          * @param string|bool $resyncMode False, True, or "conservative"; see __construct()
 328          * @return StatusValue
 329          */
 330         public function resyncFiles( array $paths, $resyncMode = true ) {
 331                 $status = $this->newStatus();
 332
 333                 $mBackend = $this->backends[$this->masterIndex];
 334                 foreach ( $paths as $path ) {
 335                         $mPath = $this->substPaths( $path, $mBackend );
 336                         $mSha1 = $mBackend->getFileSha1Base36( [ 'src' => $mPath, 'latest' => true ] );
 337                         $mStat = $mBackend->getFileStat( [ 'src' => $mPath, 'latest' => true ] );
 338                         if ( $mStat === null || ( $mSha1 !== false && !$mStat ) ) { // sanity
 339                                 $status->fatal( 'backend-fail-internal', $this->name );
 340                                 wfDebugLog( 'FileOperation', __METHOD__
 341                                         . ': File is not available on the master backend' );
 342                                 continue; // file is not available on the master backend...
 343                         }
 344                         // Check of all clone backends agree with the master...
 345                         foreach ( $this->backends as $index => $cBackend ) {
 346                                 if ( $index === $this->masterIndex ) {
 347                                         continue; // master
 348                                 }
 349                                 $cPath = $this->substPaths( $path, $cBackend );
 350                                 $cSha1 = $cBackend->getFileSha1Base36( [ 'src' => $cPath, 'latest' => true ] );
 351                                 $cStat = $cBackend->getFileStat( [ 'src' => $cPath, 'latest' => true ] );
 352                                 if ( $cStat === null || ( $cSha1 !== false && !$cStat ) ) { // sanity
 353                                         $status->fatal( 'backend-fail-internal', $cBackend->getName() );
 354                                         wfDebugLog( 'FileOperation', __METHOD__ .
 355                                                 ': File is not available on the clone backend' );
 356                                         continue; // file is not available on the clone backend...
 357                                 }
 358                                 if ( $mSha1 === $cSha1 ) {
 359                                         // already synced; nothing to do
 360                                 } elseif ( $mSha1 !== false ) { // file is in master
 361                                         if ( $resyncMode === 'conservative'
 362                                                 && $cStat && $cStat['mtime'] > $mStat['mtime']
 363                                         ) {
 364                                                 $status->fatal( 'backend-fail-synced', $path );
 365                                                 continue; // don't rollback data
 366                                         }
 367                                         $fsFile = $mBackend->getLocalReference(
 368                                                 [ 'src' => $mPath, 'latest' => true ] );
 369                                         $status->merge( $cBackend->quickStore(
 370                                                 [ 'src' => $fsFile->getPath(), 'dst' => $cPath ]
 371                                         ) );
 372                                 } elseif ( $mStat === false ) { // file is not in master
 373                                         if ( $resyncMode === 'conservative' ) {
 374                                                 $status->fatal( 'backend-fail-synced', $path );
 375                                                 continue; // don't delete data
 376                                         }
 377                                         $status->merge( $cBackend->quickDelete( [ 'src' => $cPath ] ) );
 378                                 }
 379                         }
 380                 }
 381
 382                 if ( !$status->isOK() ) {
 383                         wfDebugLog( 'FileOperation', static::class .
 384                                 " failed to resync: " . FormatJson::encode( $paths ) );
 385                 }
 386
 387                 return $status;
 388         }
 389
 390         /**
 391          * Get a list of file storage paths to read or write for a list of operations
 392          *
 393          * @param array $ops Same format as doOperations()
 394          * @return array List of storage paths to files (does not include directories)
 395          */
 396         protected function fileStoragePathsForOps( array $ops ) {
 397                 $paths = [];
 398                 foreach ( $ops as $op ) {
 399                         if ( isset( $op['src'] ) ) {
 400                                 // For things like copy/move/delete with "ignoreMissingSource" and there
 401                                 // is no source file, nothing should happen and there should be no errors.
 402                                 if ( empty( $op['ignoreMissingSource'] )
 403                                         || $this->fileExists( [ 'src' => $op['src'] ] )
 404                                 ) {
 405                                         $paths[] = $op['src'];
 406                                 }
 407                         }
 408                         if ( isset( $op['srcs'] ) ) {
 409                                 $paths = array_merge( $paths, $op['srcs'] );
 410                         }
 411                         if ( isset( $op['dst'] ) ) {
 412                                 $paths[] = $op['dst'];
 413                         }
 414                 }
 415
 416                 return array_values( array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) ) );
 417         }
 418
 419         /**
 420          * Substitute the backend name in storage path parameters
 421          * for a set of operations with that of a given internal backend.
 422          *
 423          * @param array $ops List of file operation arrays
 424          * @param FileBackendStore $backend
 425          * @return array
 426          */
 427         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 428                 $newOps = []; // operations
 429                 foreach ( $ops as $op ) {
 430                         $newOp = $op; // operation
 431                         foreach ( [ 'src', 'srcs', 'dst', 'dir' ] as $par ) {
 432                                 if ( isset( $newOp[$par] ) ) { // string or array
 433                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 434                                 }
 435                         }
 436                         $newOps[] = $newOp;
 437                 }
 438
 439                 return $newOps;
 440         }
 441
 442         /**
 443          * Same as substOpBatchPaths() but for a single operation
 444          *
 445          * @param array $ops File operation array
 446          * @param FileBackendStore $backend
 447          * @return array
 448          */
 449         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 450                 $newOps = $this->substOpBatchPaths( [ $ops ], $backend );
 451
 452                 return $newOps[0];
 453         }
 454
 455         /**
 456          * Substitute the backend of storage paths with an internal backend's name
 457          *
 458          * @param array|string $paths List of paths or single string path
 459          * @param FileBackendStore $backend
 460          * @return array|string
 461          */
 462         protected function substPaths( $paths, FileBackendStore $backend ) {
 463                 return preg_replace(
 464                         '!^mwstore://' . preg_quote( $this->name, '!' ) . '/!',
 465                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 466                         $paths // string or array
 467                 );
 468         }
 469
 470         /**
 471          * Substitute the backend of internal storage paths with the proxy backend's name
 472          *
 473          * @param array|string $paths List of paths or single string path
 474          * @return array|string
 475          */
 476         protected function unsubstPaths( $paths ) {
 477                 return preg_replace(
 478                         '!^mwstore://([^/]+)!',
 479                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
 480                         $paths // string or array
 481                 );
 482         }
 483
 484         /**
 485          * @param array $ops File operations for FileBackend::doOperations()
 486          * @return bool Whether there are file path sources with outside lifetime/ownership
 487          */
 488         protected function hasVolatileSources( array $ops ) {
 489                 foreach ( $ops as $op ) {
 490                         if ( $op['op'] === 'store' && !isset( $op['srcRef'] ) ) {
 491                                 return true; // source file might be deleted anytime after do*Operations()
 492                         }
 493                 }
 494
 495                 return false;
 496         }
 497
 498         protected function doQuickOperationsInternal( array $ops ) {
 499                 $status = $this->newStatus();
 500                 // Do the operations on the master backend; setting StatusValue fields...
 501                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 502                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 503                 $status->merge( $masterStatus );
 504                 // Propagate the operations to the clone backends...
 505                 foreach ( $this->backends as $index => $backend ) {
 506                         if ( $index === $this->masterIndex ) {
 507                                 continue; // done already
 508                         }
 509
 510                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 511                         if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 512                                 DeferredUpdates::addCallableUpdate(
 513                                         function () use ( $backend, $realOps ) {
 514                                                 $backend->doQuickOperations( $realOps );
 515                                         }
 516                                 );
 517                         } else {
 518                                 $status->merge( $backend->doQuickOperations( $realOps ) );
 519                         }
 520                 }
 521                 // Make 'success', 'successCount', and 'failCount' fields reflect
 522                 // the overall operation, rather than all the batches for each backend.
 523                 // Do this by only using success values from the master backend's batch.
 524                 $status->success = $masterStatus->success;
 525                 $status->successCount = $masterStatus->successCount;
 526                 $status->failCount = $masterStatus->failCount;
 527
 528                 return $status;
 529         }
 530
 531         protected function doPrepare( array $params ) {
 532                 return $this->doDirectoryOp( 'prepare', $params );
 533         }
 534
 535         protected function doSecure( array $params ) {
 536                 return $this->doDirectoryOp( 'secure', $params );
 537         }
 538
 539         protected function doPublish( array $params ) {
 540                 return $this->doDirectoryOp( 'publish', $params );
 541         }
 542
 543         protected function doClean( array $params ) {
 544                 return $this->doDirectoryOp( 'clean', $params );
 545         }
 546
 547         /**
 548          * @param string $method One of (doPrepare,doSecure,doPublish,doClean)
 549          * @param array $params Method arguments
 550          * @return StatusValue
 551          */
 552         protected function doDirectoryOp( $method, array $params ) {
 553                 $status = $this->newStatus();
 554
 555                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 556                 $masterStatus = $this->backends[$this->masterIndex]->$method( $realParams );
 557                 $status->merge( $masterStatus );
 558
 559                 foreach ( $this->backends as $index => $backend ) {
 560                         if ( $index === $this->masterIndex ) {
 561                                 continue; // already done
 562                         }
 563
 564                         $realParams = $this->substOpPaths( $params, $backend );
 565                         if ( $this->asyncWrites ) {
 566                                 DeferredUpdates::addCallableUpdate(
 567                                         function () use ( $backend, $method, $realParams ) {
 568                                                 $backend->$method( $realParams );
 569                                         }
 570                                 );
 571                         } else {
 572                                 $status->merge( $backend->$method( $realParams ) );
 573                         }
 574                 }
 575
 576                 return $status;
 577         }
 578
 579         public function concatenate( array $params ) {
 580                 $status = $this->newStatus();
 581                 // We are writing to an FS file, so we don't need to do this per-backend
 582                 $index = $this->getReadIndexFromParams( $params );
 583                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 584
 585                 $status->merge( $this->backends[$index]->concatenate( $realParams ) );
 586
 587                 return $status;
 588         }
 589
 590         public function fileExists( array $params ) {
 591                 $index = $this->getReadIndexFromParams( $params );
 592                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 593
 594                 return $this->backends[$index]->fileExists( $realParams );
 595         }
 596
 597         public function getFileTimestamp( array $params ) {
 598                 $index = $this->getReadIndexFromParams( $params );
 599                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 600
 601                 return $this->backends[$index]->getFileTimestamp( $realParams );
 602         }
 603
 604         public function getFileSize( array $params ) {
 605                 $index = $this->getReadIndexFromParams( $params );
 606                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 607
 608                 return $this->backends[$index]->getFileSize( $realParams );
 609         }
 610
 611         public function getFileStat( array $params ) {
 612                 $index = $this->getReadIndexFromParams( $params );
 613                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 614
 615                 return $this->backends[$index]->getFileStat( $realParams );
 616         }
 617
 618         public function getFileXAttributes( array $params ) {
 619                 $index = $this->getReadIndexFromParams( $params );
 620                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 621
 622                 return $this->backends[$index]->getFileXAttributes( $realParams );
 623         }
 624
 625         public function getFileContentsMulti( array $params ) {
 626                 $index = $this->getReadIndexFromParams( $params );
 627                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 628
 629                 $contentsM = $this->backends[$index]->getFileContentsMulti( $realParams );
 630
 631                 $contents = []; // (path => FSFile) mapping using the proxy backend's name
 632                 foreach ( $contentsM as $path => $data ) {
 633                         $contents[$this->unsubstPaths( $path )] = $data;
 634                 }
 635
 636                 return $contents;
 637         }
 638
 639         public function getFileSha1Base36( array $params ) {
 640                 $index = $this->getReadIndexFromParams( $params );
 641                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 642
 643                 return $this->backends[$index]->getFileSha1Base36( $realParams );
 644         }
 645
 646         public function getFileProps( array $params ) {
 647                 $index = $this->getReadIndexFromParams( $params );
 648                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 649
 650                 return $this->backends[$index]->getFileProps( $realParams );
 651         }
 652
 653         public function streamFile( array $params ) {
 654                 $index = $this->getReadIndexFromParams( $params );
 655                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 656
 657                 return $this->backends[$index]->streamFile( $realParams );
 658         }
 659
 660         public function getLocalReferenceMulti( array $params ) {
 661                 $index = $this->getReadIndexFromParams( $params );
 662                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 663
 664                 $fsFilesM = $this->backends[$index]->getLocalReferenceMulti( $realParams );
 665
 666                 $fsFiles = []; // (path => FSFile) mapping using the proxy backend's name
 667                 foreach ( $fsFilesM as $path => $fsFile ) {
 668                         $fsFiles[$this->unsubstPaths( $path )] = $fsFile;
 669                 }
 670
 671                 return $fsFiles;
 672         }
 673
 674         public function getLocalCopyMulti( array $params ) {
 675                 $index = $this->getReadIndexFromParams( $params );
 676                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 677
 678                 $tempFilesM = $this->backends[$index]->getLocalCopyMulti( $realParams );
 679
 680                 $tempFiles = []; // (path => TempFSFile) mapping using the proxy backend's name
 681                 foreach ( $tempFilesM as $path => $tempFile ) {
 682                         $tempFiles[$this->unsubstPaths( $path )] = $tempFile;
 683                 }
 684
 685                 return $tempFiles;
 686         }
 687
 688         public function getFileHttpUrl( array $params ) {
 689                 $index = $this->getReadIndexFromParams( $params );
 690                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 691
 692                 return $this->backends[$index]->getFileHttpUrl( $realParams );
 693         }
 694
 695         public function directoryExists( array $params ) {
 696                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 697
 698                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 699         }
 700
 701         public function getDirectoryList( array $params ) {
 702                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 703
 704                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 705         }
 706
 707         public function getFileList( array $params ) {
 708                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 709
 710                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 711         }
 712
 713         public function getFeatures() {
 714                 return $this->backends[$this->masterIndex]->getFeatures();
 715         }
 716
 717         public function clearCache( array $paths = null ) {
 718                 foreach ( $this->backends as $backend ) {
 719                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 720                         $backend->clearCache( $realPaths );
 721                 }
 722         }
 723
 724         public function preloadCache( array $paths ) {
 725                 $realPaths = $this->substPaths( $paths, $this->backends[$this->readIndex] );
 726                 $this->backends[$this->readIndex]->preloadCache( $realPaths );
 727         }
 728
 729         public function preloadFileStat( array $params ) {
 730                 $index = $this->getReadIndexFromParams( $params );
 731                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 732
 733                 return $this->backends[$index]->preloadFileStat( $realParams );
 734         }
 735
 736         public function getScopedLocksForOps( array $ops, StatusValue $status ) {
 737                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 738                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $realOps );
 739                 // Get the paths to lock from the master backend
 740                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 741                 // Get the paths under the proxy backend's name
 742                 $pbPaths = [
 743                         LockManager::LOCK_UW => $this->unsubstPaths( $paths[LockManager::LOCK_UW] ),
 744                         LockManager::LOCK_EX => $this->unsubstPaths( $paths[LockManager::LOCK_EX] )
 745                 ];
 746
 747                 // Actually acquire the locks
 748                 return $this->getScopedFileLocks( $pbPaths, 'mixed', $status );
 749         }
 750
 751         /**
 752          * @param array $params
 753          * @return int The master or read affinity backend index, based on $params['latest']
 754          */
 755         protected function getReadIndexFromParams( array $params ) {
 756                 return !empty( $params['latest'] ) ? $this->masterIndex : $this->readIndex;
 757         }
 758 }