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