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, $relevantPaths ) {
 206                                                         wfDebugLog( 'FileOperationReplication',
 207                                                                 "'{$backend->getName()}' async replication; paths: " .
 208                                                                 FormatJson::encode( $relevantPaths ) );
 209                                                         $backend->doOperations( $realOps, $opts );
 210                                                 }
 211                                         );
 212                                 } else {
 213                                         wfDebugLog( 'FileOperationReplication',
 214                                                 "'{$backend->getName()}' sync replication; paths: " .
 215                                                 FormatJson::encode( $relevantPaths ) );
 216                                         $status->merge( $backend->doOperations( $realOps, $opts ) );
 217                                 }
 218                         }
 219                 }
 220                 // Make 'success', 'successCount', and 'failCount' fields reflect
 221                 // the overall operation, rather than all the batches for each backend.
 222                 // Do this by only using success values from the master backend's batch.
 223                 $status->success = $masterStatus->success;
 224                 $status->successCount = $masterStatus->successCount;
 225                 $status->failCount = $masterStatus->failCount;
 226
 227                 return $status;
 228         }
 229
 230         /**
 231          * Check that a set of files are consistent across all internal backends
 232          *
 233          * @param array $paths List of storage paths
 234          * @return Status
 235          */
 236         public function consistencyCheck( array $paths ) {
 237                 $status = Status::newGood();
 238                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 239                         return $status; // skip checks
 240                 }
 241
 242                 $mBackend = $this->backends[$this->masterIndex];
 243                 foreach ( $paths as $path ) {
 244                         $params = [ 'src' => $path, 'latest' => true ];
 245                         $mParams = $this->substOpPaths( $params, $mBackend );
 246                         // Stat the file on the 'master' backend
 247                         $mStat = $mBackend->getFileStat( $mParams );
 248                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 249                                 $mSha1 = $mBackend->getFileSha1Base36( $mParams );
 250                         } else {
 251                                 $mSha1 = false;
 252                         }
 253                         // Check if all clone backends agree with the master...
 254                         foreach ( $this->backends as $index => $cBackend ) {
 255                                 if ( $index === $this->masterIndex ) {
 256                                         continue; // master
 257                                 }
 258                                 $cParams = $this->substOpPaths( $params, $cBackend );
 259                                 $cStat = $cBackend->getFileStat( $cParams );
 260                                 if ( $mStat ) { // file is in master
 261                                         if ( !$cStat ) { // file should exist
 262                                                 $status->fatal( 'backend-fail-synced', $path );
 263                                                 continue;
 264                                         }
 265                                         if ( $this->syncChecks & self::CHECK_SIZE ) {
 266                                                 if ( $cStat['size'] != $mStat['size'] ) { // wrong size
 267                                                         $status->fatal( 'backend-fail-synced', $path );
 268                                                         continue;
 269                                                 }
 270                                         }
 271                                         if ( $this->syncChecks & self::CHECK_TIME ) {
 272                                                 $mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
 273                                                 $cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
 274                                                 if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
 275                                                         $status->fatal( 'backend-fail-synced', $path );
 276                                                         continue;
 277                                                 }
 278                                         }
 279                                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 280                                                 if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
 281                                                         $status->fatal( 'backend-fail-synced', $path );
 282                                                         continue;
 283                                                 }
 284                                         }
 285                                 } else { // file is not in master
 286                                         if ( $cStat ) { // file should not exist
 287                                                 $status->fatal( 'backend-fail-synced', $path );
 288                                         }
 289                                 }
 290                         }
 291                 }
 292
 293                 return $status;
 294         }
 295
 296         /**
 297          * Check that a set of file paths are usable across all internal backends
 298          *
 299          * @param array $paths List of storage paths
 300          * @return Status
 301          */
 302         public function accessibilityCheck( array $paths ) {
 303                 $status = Status::newGood();
 304                 if ( count( $this->backends ) <= 1 ) {
 305                         return $status; // skip checks
 306                 }
 307
 308                 foreach ( $paths as $path ) {
 309                         foreach ( $this->backends as $backend ) {
 310                                 $realPath = $this->substPaths( $path, $backend );
 311                                 if ( !$backend->isPathUsableInternal( $realPath ) ) {
 312                                         $status->fatal( 'backend-fail-usable', $path );
 313                                 }
 314                         }
 315                 }
 316
 317                 return $status;
 318         }
 319
 320         /**
 321          * Check that a set of files are consistent across all internal backends
 322          * and re-synchronize those files against the "multi master" if needed.
 323          *
 324          * @param array $paths List of storage paths
 325          * @return Status
 326          */
 327         public function resyncFiles( array $paths ) {
 328                 $status = Status::newGood();
 329
 330                 $mBackend = $this->backends[$this->masterIndex];
 331                 foreach ( $paths as $path ) {
 332                         $mPath = $this->substPaths( $path, $mBackend );
 333                         $mSha1 = $mBackend->getFileSha1Base36( [ 'src' => $mPath, 'latest' => true ] );
 334                         $mStat = $mBackend->getFileStat( [ 'src' => $mPath, 'latest' => true ] );
 335                         if ( $mStat === null || ( $mSha1 !== false && !$mStat ) ) { // sanity
 336                                 $status->fatal( 'backend-fail-internal', $this->name );
 337                                 wfDebugLog( 'FileOperation', __METHOD__
 338                                         . ': File is not available on the master backend' );
 339                                 continue; // file is not available on the master backend...
 340                         }
 341                         // Check of all clone backends agree with the master...
 342                         foreach ( $this->backends as $index => $cBackend ) {
 343                                 if ( $index === $this->masterIndex ) {
 344                                         continue; // master
 345                                 }
 346                                 $cPath = $this->substPaths( $path, $cBackend );
 347                                 $cSha1 = $cBackend->getFileSha1Base36( [ 'src' => $cPath, 'latest' => true ] );
 348                                 $cStat = $cBackend->getFileStat( [ 'src' => $cPath, 'latest' => true ] );
 349                                 if ( $cStat === null || ( $cSha1 !== false && !$cStat ) ) { // sanity
 350                                         $status->fatal( 'backend-fail-internal', $cBackend->getName() );
 351                                         wfDebugLog( 'FileOperation', __METHOD__ .
 352                                                 ': File is not available on the clone backend' );
 353                                         continue; // file is not available on the clone backend...
 354                                 }
 355                                 if ( $mSha1 === $cSha1 ) {
 356                                         // already synced; nothing to do
 357                                 } elseif ( $mSha1 !== false ) { // file is in master
 358                                         if ( $this->autoResync === 'conservative'
 359                                                 && $cStat && $cStat['mtime'] > $mStat['mtime']
 360                                         ) {
 361                                                 $status->fatal( 'backend-fail-synced', $path );
 362                                                 continue; // don't rollback data
 363                                         }
 364                                         $fsFile = $mBackend->getLocalReference(
 365                                                 [ 'src' => $mPath, 'latest' => true ] );
 366                                         $status->merge( $cBackend->quickStore(
 367                                                 [ 'src' => $fsFile->getPath(), 'dst' => $cPath ]
 368                                         ) );
 369                                 } elseif ( $mStat === false ) { // file is not in master
 370                                         if ( $this->autoResync === 'conservative' ) {
 371                                                 $status->fatal( 'backend-fail-synced', $path );
 372                                                 continue; // don't delete data
 373                                         }
 374                                         $status->merge( $cBackend->quickDelete( [ 'src' => $cPath ] ) );
 375                                 }
 376                         }
 377                 }
 378
 379                 return $status;
 380         }
 381
 382         /**
 383          * Get a list of file storage paths to read or write for a list of operations
 384          *
 385          * @param array $ops Same format as doOperations()
 386          * @return array List of storage paths to files (does not include directories)
 387          */
 388         protected function fileStoragePathsForOps( array $ops ) {
 389                 $paths = [];
 390                 foreach ( $ops as $op ) {
 391                         if ( isset( $op['src'] ) ) {
 392                                 // For things like copy/move/delete with "ignoreMissingSource" and there
 393                                 // is no source file, nothing should happen and there should be no errors.
 394                                 if ( empty( $op['ignoreMissingSource'] )
 395                                         || $this->fileExists( [ 'src' => $op['src'] ] )
 396                                 ) {
 397                                         $paths[] = $op['src'];
 398                                 }
 399                         }
 400                         if ( isset( $op['srcs'] ) ) {
 401                                 $paths = array_merge( $paths, $op['srcs'] );
 402                         }
 403                         if ( isset( $op['dst'] ) ) {
 404                                 $paths[] = $op['dst'];
 405                         }
 406                 }
 407
 408                 return array_values( array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) ) );
 409         }
 410
 411         /**
 412          * Substitute the backend name in storage path parameters
 413          * for a set of operations with that of a given internal backend.
 414          *
 415          * @param array $ops List of file operation arrays
 416          * @param FileBackendStore $backend
 417          * @return array
 418          */
 419         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 420                 $newOps = []; // operations
 421                 foreach ( $ops as $op ) {
 422                         $newOp = $op; // operation
 423                         foreach ( [ 'src', 'srcs', 'dst', 'dir' ] as $par ) {
 424                                 if ( isset( $newOp[$par] ) ) { // string or array
 425                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 426                                 }
 427                         }
 428                         $newOps[] = $newOp;
 429                 }
 430
 431                 return $newOps;
 432         }
 433
 434         /**
 435          * Same as substOpBatchPaths() but for a single operation
 436          *
 437          * @param array $ops File operation array
 438          * @param FileBackendStore $backend
 439          * @return array
 440          */
 441         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 442                 $newOps = $this->substOpBatchPaths( [ $ops ], $backend );
 443
 444                 return $newOps[0];
 445         }
 446
 447         /**
 448          * Substitute the backend of storage paths with an internal backend's name
 449          *
 450          * @param array|string $paths List of paths or single string path
 451          * @param FileBackendStore $backend
 452          * @return array|string
 453          */
 454         protected function substPaths( $paths, FileBackendStore $backend ) {
 455                 return preg_replace(
 456                         '!^mwstore://' . preg_quote( $this->name, '!' ) . '/!',
 457                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 458                         $paths // string or array
 459                 );
 460         }
 461
 462         /**
 463          * Substitute the backend of internal storage paths with the proxy backend's name
 464          *
 465          * @param array|string $paths List of paths or single string path
 466          * @return array|string
 467          */
 468         protected function unsubstPaths( $paths ) {
 469                 return preg_replace(
 470                         '!^mwstore://([^/]+)!',
 471                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
 472                         $paths // string or array
 473                 );
 474         }
 475
 476         /**
 477          * @param array $ops File operations for FileBackend::doOperations()
 478          * @return bool Whether there are file path sources with outside lifetime/ownership
 479          */
 480         protected function hasVolatileSources( array $ops ) {
 481                 foreach ( $ops as $op ) {
 482                         if ( $op['op'] === 'store' && !isset( $op['srcRef'] ) ) {
 483                                 return true; // source file might be deleted anytime after do*Operations()
 484                         }
 485                 }
 486
 487                 return false;
 488         }
 489
 490         protected function doQuickOperationsInternal( array $ops ) {
 491                 $status = Status::newGood();
 492                 // Do the operations on the master backend; setting Status fields...
 493                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 494                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 495                 $status->merge( $masterStatus );
 496                 // Propagate the operations to the clone backends...
 497                 foreach ( $this->backends as $index => $backend ) {
 498                         if ( $index === $this->masterIndex ) {
 499                                 continue; // done already
 500                         }
 501
 502                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 503                         if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 504                                 DeferredUpdates::addCallableUpdate(
 505                                         function() use ( $backend, $realOps ) {
 506                                                 $backend->doQuickOperations( $realOps );
 507                                         }
 508                                 );
 509                         } else {
 510                                 $status->merge( $backend->doQuickOperations( $realOps ) );
 511                         }
 512                 }
 513                 // Make 'success', 'successCount', and 'failCount' fields reflect
 514                 // the overall operation, rather than all the batches for each backend.
 515                 // Do this by only using success values from the master backend's batch.
 516                 $status->success = $masterStatus->success;
 517                 $status->successCount = $masterStatus->successCount;
 518                 $status->failCount = $masterStatus->failCount;
 519
 520                 return $status;
 521         }
 522
 523         protected function doPrepare( array $params ) {
 524                 return $this->doDirectoryOp( 'prepare', $params );
 525         }
 526
 527         protected function doSecure( array $params ) {
 528                 return $this->doDirectoryOp( 'secure', $params );
 529         }
 530
 531         protected function doPublish( array $params ) {
 532                 return $this->doDirectoryOp( 'publish', $params );
 533         }
 534
 535         protected function doClean( array $params ) {
 536                 return $this->doDirectoryOp( 'clean', $params );
 537         }
 538
 539         /**
 540          * @param string $method One of (doPrepare,doSecure,doPublish,doClean)
 541          * @param array $params Method arguments
 542          * @return Status
 543          */
 544         protected function doDirectoryOp( $method, array $params ) {
 545                 $status = Status::newGood();
 546
 547                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 548                 $masterStatus = $this->backends[$this->masterIndex]->$method( $realParams );
 549                 $status->merge( $masterStatus );
 550
 551                 foreach ( $this->backends as $index => $backend ) {
 552                         if ( $index === $this->masterIndex ) {
 553                                 continue; // already done
 554                         }
 555
 556                         $realParams = $this->substOpPaths( $params, $backend );
 557                         if ( $this->asyncWrites ) {
 558                                 DeferredUpdates::addCallableUpdate(
 559                                         function() use ( $backend, $method, $realParams ) {
 560                                                 $backend->$method( $realParams );
 561                                         }
 562                                 );
 563                         } else {
 564                                 $status->merge( $backend->$method( $realParams ) );
 565                         }
 566                 }
 567
 568                 return $status;
 569         }
 570
 571         public function concatenate( array $params ) {
 572                 // We are writing to an FS file, so we don't need to do this per-backend
 573                 $index = $this->getReadIndexFromParams( $params );
 574                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 575
 576                 return $this->backends[$index]->concatenate( $realParams );
 577         }
 578
 579         public function fileExists( array $params ) {
 580                 $index = $this->getReadIndexFromParams( $params );
 581                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 582
 583                 return $this->backends[$index]->fileExists( $realParams );
 584         }
 585
 586         public function getFileTimestamp( array $params ) {
 587                 $index = $this->getReadIndexFromParams( $params );
 588                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 589
 590                 return $this->backends[$index]->getFileTimestamp( $realParams );
 591         }
 592
 593         public function getFileSize( array $params ) {
 594                 $index = $this->getReadIndexFromParams( $params );
 595                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 596
 597                 return $this->backends[$index]->getFileSize( $realParams );
 598         }
 599
 600         public function getFileStat( array $params ) {
 601                 $index = $this->getReadIndexFromParams( $params );
 602                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 603
 604                 return $this->backends[$index]->getFileStat( $realParams );
 605         }
 606
 607         public function getFileXAttributes( array $params ) {
 608                 $index = $this->getReadIndexFromParams( $params );
 609                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 610
 611                 return $this->backends[$index]->getFileXAttributes( $realParams );
 612         }
 613
 614         public function getFileContentsMulti( array $params ) {
 615                 $index = $this->getReadIndexFromParams( $params );
 616                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 617
 618                 $contentsM = $this->backends[$index]->getFileContentsMulti( $realParams );
 619
 620                 $contents = []; // (path => FSFile) mapping using the proxy backend's name
 621                 foreach ( $contentsM as $path => $data ) {
 622                         $contents[$this->unsubstPaths( $path )] = $data;
 623                 }
 624
 625                 return $contents;
 626         }
 627
 628         public function getFileSha1Base36( array $params ) {
 629                 $index = $this->getReadIndexFromParams( $params );
 630                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 631
 632                 return $this->backends[$index]->getFileSha1Base36( $realParams );
 633         }
 634
 635         public function getFileProps( array $params ) {
 636                 $index = $this->getReadIndexFromParams( $params );
 637                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 638
 639                 return $this->backends[$index]->getFileProps( $realParams );
 640         }
 641
 642         public function streamFile( array $params ) {
 643                 $index = $this->getReadIndexFromParams( $params );
 644                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 645
 646                 return $this->backends[$index]->streamFile( $realParams );
 647         }
 648
 649         public function getLocalReferenceMulti( array $params ) {
 650                 $index = $this->getReadIndexFromParams( $params );
 651                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 652
 653                 $fsFilesM = $this->backends[$index]->getLocalReferenceMulti( $realParams );
 654
 655                 $fsFiles = []; // (path => FSFile) mapping using the proxy backend's name
 656                 foreach ( $fsFilesM as $path => $fsFile ) {
 657                         $fsFiles[$this->unsubstPaths( $path )] = $fsFile;
 658                 }
 659
 660                 return $fsFiles;
 661         }
 662
 663         public function getLocalCopyMulti( array $params ) {
 664                 $index = $this->getReadIndexFromParams( $params );
 665                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 666
 667                 $tempFilesM = $this->backends[$index]->getLocalCopyMulti( $realParams );
 668
 669                 $tempFiles = []; // (path => TempFSFile) mapping using the proxy backend's name
 670                 foreach ( $tempFilesM as $path => $tempFile ) {
 671                         $tempFiles[$this->unsubstPaths( $path )] = $tempFile;
 672                 }
 673
 674                 return $tempFiles;
 675         }
 676
 677         public function getFileHttpUrl( array $params ) {
 678                 $index = $this->getReadIndexFromParams( $params );
 679                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 680
 681                 return $this->backends[$index]->getFileHttpUrl( $realParams );
 682         }
 683
 684         public function directoryExists( array $params ) {
 685                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 686
 687                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 688         }
 689
 690         public function getDirectoryList( array $params ) {
 691                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 692
 693                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 694         }
 695
 696         public function getFileList( array $params ) {
 697                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 698
 699                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 700         }
 701
 702         public function getFeatures() {
 703                 return $this->backends[$this->masterIndex]->getFeatures();
 704         }
 705
 706         public function clearCache( array $paths = null ) {
 707                 foreach ( $this->backends as $backend ) {
 708                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 709                         $backend->clearCache( $realPaths );
 710                 }
 711         }
 712
 713         public function preloadCache( array $paths ) {
 714                 $realPaths = $this->substPaths( $paths, $this->backends[$this->readIndex] );
 715                 $this->backends[$this->readIndex]->preloadCache( $realPaths );
 716         }
 717
 718         public function preloadFileStat( array $params ) {
 719                 $index = $this->getReadIndexFromParams( $params );
 720                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 721
 722                 return $this->backends[$index]->preloadFileStat( $realParams );
 723         }
 724
 725         public function getScopedLocksForOps( array $ops, Status $status ) {
 726                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 727                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $realOps );
 728                 // Get the paths to lock from the master backend
 729                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 730                 // Get the paths under the proxy backend's name
 731                 $pbPaths = [
 732                         LockManager::LOCK_UW => $this->unsubstPaths( $paths[LockManager::LOCK_UW] ),
 733                         LockManager::LOCK_EX => $this->unsubstPaths( $paths[LockManager::LOCK_EX] )
 734                 ];
 735
 736                 // Actually acquire the locks
 737                 return $this->getScopedFileLocks( $pbPaths, 'mixed', $status );
 738         }
 739
 740         /**
 741          * @param array $params
 742          * @return int The master or read affinity backend index, based on $params['latest']
 743          */
 744         protected function getReadIndexFromParams( array $params ) {
 745                 return !empty( $params['latest'] ) ? $this->masterIndex : $this->readIndex;
 746         }
 747 }