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 ( $this->autoResync === false
 182                                 || !$this->resyncFiles( $relevantPaths, $this->autoResync )->isOK()
 183                         ) {
 184                                 $status->merge( $syncStatus );
 185
 186                                 return $status; // abort
 187                         }
 188                 }
 189                 // Actually attempt the operation batch on the master backend...
 190                 $realOps = $this->substOpBatchPaths( $ops, $mbe );
 191                 $masterStatus = $mbe->doOperations( $realOps, $opts );
 192                 $status->merge( $masterStatus );
 193                 // Propagate the operations to the clone backends if there were no unexpected errors
 194                 // and if there were either no expected errors or if the 'force' option was used.
 195                 // However, if nothing succeeded at all, then don't replicate any of the operations.
 196                 // If $ops only had one operation, this might avoid backend sync inconsistencies.
 197                 if ( $masterStatus->isOK() && $masterStatus->successCount > 0 ) {
 198                         foreach ( $this->backends as $index => $backend ) {
 199                                 if ( $index === $this->masterIndex ) {
 200                                         continue; // done already
 201                                 }
 202
 203                                 $realOps = $this->substOpBatchPaths( $ops, $backend );
 204                                 if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 205                                         // Bind $scopeLock to the callback to preserve locks
 206                                         DeferredUpdates::addCallableUpdate(
 207                                                 function() use ( $backend, $realOps, $opts, $scopeLock, $relevantPaths ) {
 208                                                         wfDebugLog( 'FileOperationReplication',
 209                                                                 "'{$backend->getName()}' async replication; paths: " .
 210                                                                 FormatJson::encode( $relevantPaths ) );
 211                                                         $backend->doOperations( $realOps, $opts );
 212                                                 }
 213                                         );
 214                                 } else {
 215                                         wfDebugLog( 'FileOperationReplication',
 216                                                 "'{$backend->getName()}' sync replication; paths: " .
 217                                                 FormatJson::encode( $relevantPaths ) );
 218                                         $status->merge( $backend->doOperations( $realOps, $opts ) );
 219                                 }
 220                         }
 221                 }
 222                 // Make 'success', 'successCount', and 'failCount' fields reflect
 223                 // the overall operation, rather than all the batches for each backend.
 224                 // Do this by only using success values from the master backend's batch.
 225                 $status->success = $masterStatus->success;
 226                 $status->successCount = $masterStatus->successCount;
 227                 $status->failCount = $masterStatus->failCount;
 228
 229                 return $status;
 230         }
 231
 232         /**
 233          * Check that a set of files are consistent across all internal backends
 234          *
 235          * @param array $paths List of storage paths
 236          * @return Status
 237          */
 238         public function consistencyCheck( array $paths ) {
 239                 $status = Status::newGood();
 240                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 241                         return $status; // skip checks
 242                 }
 243
 244                 // Preload all of the stat info in as few round trips as possible...
 245                 foreach ( $this->backends as $backend ) {
 246                         $realPaths = $this->substPaths( $paths, $backend );
 247                         $backend->preloadFileStat( [ 'srcs' => $realPaths, 'latest' => true ] );
 248                 }
 249
 250                 $mBackend = $this->backends[$this->masterIndex];
 251                 foreach ( $paths as $path ) {
 252                         $params = [ 'src' => $path, 'latest' => true ];
 253                         $mParams = $this->substOpPaths( $params, $mBackend );
 254                         // Stat the file on the 'master' backend
 255                         $mStat = $mBackend->getFileStat( $mParams );
 256                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 257                                 $mSha1 = $mBackend->getFileSha1Base36( $mParams );
 258                         } else {
 259                                 $mSha1 = false;
 260                         }
 261                         // Check if all clone backends agree with the master...
 262                         foreach ( $this->backends as $index => $cBackend ) {
 263                                 if ( $index === $this->masterIndex ) {
 264                                         continue; // master
 265                                 }
 266                                 $cParams = $this->substOpPaths( $params, $cBackend );
 267                                 $cStat = $cBackend->getFileStat( $cParams );
 268                                 if ( $mStat ) { // file is in master
 269                                         if ( !$cStat ) { // file should exist
 270                                                 $status->fatal( 'backend-fail-synced', $path );
 271                                                 continue;
 272                                         }
 273                                         if ( $this->syncChecks & self::CHECK_SIZE ) {
 274                                                 if ( $cStat['size'] != $mStat['size'] ) { // wrong size
 275                                                         $status->fatal( 'backend-fail-synced', $path );
 276                                                         continue;
 277                                                 }
 278                                         }
 279                                         if ( $this->syncChecks & self::CHECK_TIME ) {
 280                                                 $mTs = wfTimestamp( TS_UNIX, $mStat['mtime'] );
 281                                                 $cTs = wfTimestamp( TS_UNIX, $cStat['mtime'] );
 282                                                 if ( abs( $mTs - $cTs ) > 30 ) { // outdated file somewhere
 283                                                         $status->fatal( 'backend-fail-synced', $path );
 284                                                         continue;
 285                                                 }
 286                                         }
 287                                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 288                                                 if ( $cBackend->getFileSha1Base36( $cParams ) !== $mSha1 ) { // wrong SHA1
 289                                                         $status->fatal( 'backend-fail-synced', $path );
 290                                                         continue;
 291                                                 }
 292                                         }
 293                                 } else { // file is not in master
 294                                         if ( $cStat ) { // file should not exist
 295                                                 $status->fatal( 'backend-fail-synced', $path );
 296                                         }
 297                                 }
 298                         }
 299                 }
 300
 301                 return $status;
 302         }
 303
 304         /**
 305          * Check that a set of file paths are usable across all internal backends
 306          *
 307          * @param array $paths List of storage paths
 308          * @return Status
 309          */
 310         public function accessibilityCheck( array $paths ) {
 311                 $status = Status::newGood();
 312                 if ( count( $this->backends ) <= 1 ) {
 313                         return $status; // skip checks
 314                 }
 315
 316                 foreach ( $paths as $path ) {
 317                         foreach ( $this->backends as $backend ) {
 318                                 $realPath = $this->substPaths( $path, $backend );
 319                                 if ( !$backend->isPathUsableInternal( $realPath ) ) {
 320                                         $status->fatal( 'backend-fail-usable', $path );
 321                                 }
 322                         }
 323                 }
 324
 325                 return $status;
 326         }
 327
 328         /**
 329          * Check that a set of files are consistent across all internal backends
 330          * and re-synchronize those files against the "multi master" if needed.
 331          *
 332          * @param array $paths List of storage paths
 333          * @param string|bool $resyncMode False, True, or "conservative"; see __construct()
 334          * @return Status
 335          */
 336         public function resyncFiles( array $paths, $resyncMode = true ) {
 337                 $status = Status::newGood();
 338
 339                 $mBackend = $this->backends[$this->masterIndex];
 340                 foreach ( $paths as $path ) {
 341                         $mPath = $this->substPaths( $path, $mBackend );
 342                         $mSha1 = $mBackend->getFileSha1Base36( [ 'src' => $mPath, 'latest' => true ] );
 343                         $mStat = $mBackend->getFileStat( [ 'src' => $mPath, 'latest' => true ] );
 344                         if ( $mStat === null || ( $mSha1 !== false && !$mStat ) ) { // sanity
 345                                 $status->fatal( 'backend-fail-internal', $this->name );
 346                                 wfDebugLog( 'FileOperation', __METHOD__
 347                                         . ': File is not available on the master backend' );
 348                                 continue; // file is not available on the master backend...
 349                         }
 350                         // Check of all clone backends agree with the master...
 351                         foreach ( $this->backends as $index => $cBackend ) {
 352                                 if ( $index === $this->masterIndex ) {
 353                                         continue; // master
 354                                 }
 355                                 $cPath = $this->substPaths( $path, $cBackend );
 356                                 $cSha1 = $cBackend->getFileSha1Base36( [ 'src' => $cPath, 'latest' => true ] );
 357                                 $cStat = $cBackend->getFileStat( [ 'src' => $cPath, 'latest' => true ] );
 358                                 if ( $cStat === null || ( $cSha1 !== false && !$cStat ) ) { // sanity
 359                                         $status->fatal( 'backend-fail-internal', $cBackend->getName() );
 360                                         wfDebugLog( 'FileOperation', __METHOD__ .
 361                                                 ': File is not available on the clone backend' );
 362                                         continue; // file is not available on the clone backend...
 363                                 }
 364                                 if ( $mSha1 === $cSha1 ) {
 365                                         // already synced; nothing to do
 366                                 } elseif ( $mSha1 !== false ) { // file is in master
 367                                         if ( $resyncMode === 'conservative'
 368                                                 && $cStat && $cStat['mtime'] > $mStat['mtime']
 369                                         ) {
 370                                                 $status->fatal( 'backend-fail-synced', $path );
 371                                                 continue; // don't rollback data
 372                                         }
 373                                         $fsFile = $mBackend->getLocalReference(
 374                                                 [ 'src' => $mPath, 'latest' => true ] );
 375                                         $status->merge( $cBackend->quickStore(
 376                                                 [ 'src' => $fsFile->getPath(), 'dst' => $cPath ]
 377                                         ) );
 378                                 } elseif ( $mStat === false ) { // file is not in master
 379                                         if ( $resyncMode === 'conservative' ) {
 380                                                 $status->fatal( 'backend-fail-synced', $path );
 381                                                 continue; // don't delete data
 382                                         }
 383                                         $status->merge( $cBackend->quickDelete( [ 'src' => $cPath ] ) );
 384                                 }
 385                         }
 386                 }
 387
 388                 if ( !$status->isOK() ) {
 389                         wfDebugLog( 'FileOperation', get_class( $this ) .
 390                                 " failed to resync: " . FormatJson::encode( $paths ) );
 391                 }
 392
 393                 return $status;
 394         }
 395
 396         /**
 397          * Get a list of file storage paths to read or write for a list of operations
 398          *
 399          * @param array $ops Same format as doOperations()
 400          * @return array List of storage paths to files (does not include directories)
 401          */
 402         protected function fileStoragePathsForOps( array $ops ) {
 403                 $paths = [];
 404                 foreach ( $ops as $op ) {
 405                         if ( isset( $op['src'] ) ) {
 406                                 // For things like copy/move/delete with "ignoreMissingSource" and there
 407                                 // is no source file, nothing should happen and there should be no errors.
 408                                 if ( empty( $op['ignoreMissingSource'] )
 409                                         || $this->fileExists( [ 'src' => $op['src'] ] )
 410                                 ) {
 411                                         $paths[] = $op['src'];
 412                                 }
 413                         }
 414                         if ( isset( $op['srcs'] ) ) {
 415                                 $paths = array_merge( $paths, $op['srcs'] );
 416                         }
 417                         if ( isset( $op['dst'] ) ) {
 418                                 $paths[] = $op['dst'];
 419                         }
 420                 }
 421
 422                 return array_values( array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) ) );
 423         }
 424
 425         /**
 426          * Substitute the backend name in storage path parameters
 427          * for a set of operations with that of a given internal backend.
 428          *
 429          * @param array $ops List of file operation arrays
 430          * @param FileBackendStore $backend
 431          * @return array
 432          */
 433         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 434                 $newOps = []; // operations
 435                 foreach ( $ops as $op ) {
 436                         $newOp = $op; // operation
 437                         foreach ( [ 'src', 'srcs', 'dst', 'dir' ] as $par ) {
 438                                 if ( isset( $newOp[$par] ) ) { // string or array
 439                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 440                                 }
 441                         }
 442                         $newOps[] = $newOp;
 443                 }
 444
 445                 return $newOps;
 446         }
 447
 448         /**
 449          * Same as substOpBatchPaths() but for a single operation
 450          *
 451          * @param array $ops File operation array
 452          * @param FileBackendStore $backend
 453          * @return array
 454          */
 455         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 456                 $newOps = $this->substOpBatchPaths( [ $ops ], $backend );
 457
 458                 return $newOps[0];
 459         }
 460
 461         /**
 462          * Substitute the backend of storage paths with an internal backend's name
 463          *
 464          * @param array|string $paths List of paths or single string path
 465          * @param FileBackendStore $backend
 466          * @return array|string
 467          */
 468         protected function substPaths( $paths, FileBackendStore $backend ) {
 469                 return preg_replace(
 470                         '!^mwstore://' . preg_quote( $this->name, '!' ) . '/!',
 471                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 472                         $paths // string or array
 473                 );
 474         }
 475
 476         /**
 477          * Substitute the backend of internal storage paths with the proxy backend's name
 478          *
 479          * @param array|string $paths List of paths or single string path
 480          * @return array|string
 481          */
 482         protected function unsubstPaths( $paths ) {
 483                 return preg_replace(
 484                         '!^mwstore://([^/]+)!',
 485                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}" ),
 486                         $paths // string or array
 487                 );
 488         }
 489
 490         /**
 491          * @param array $ops File operations for FileBackend::doOperations()
 492          * @return bool Whether there are file path sources with outside lifetime/ownership
 493          */
 494         protected function hasVolatileSources( array $ops ) {
 495                 foreach ( $ops as $op ) {
 496                         if ( $op['op'] === 'store' && !isset( $op['srcRef'] ) ) {
 497                                 return true; // source file might be deleted anytime after do*Operations()
 498                         }
 499                 }
 500
 501                 return false;
 502         }
 503
 504         protected function doQuickOperationsInternal( array $ops ) {
 505                 $status = Status::newGood();
 506                 // Do the operations on the master backend; setting Status fields...
 507                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 508                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 509                 $status->merge( $masterStatus );
 510                 // Propagate the operations to the clone backends...
 511                 foreach ( $this->backends as $index => $backend ) {
 512                         if ( $index === $this->masterIndex ) {
 513                                 continue; // done already
 514                         }
 515
 516                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 517                         if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 518                                 DeferredUpdates::addCallableUpdate(
 519                                         function() use ( $backend, $realOps ) {
 520                                                 $backend->doQuickOperations( $realOps );
 521                                         }
 522                                 );
 523                         } else {
 524                                 $status->merge( $backend->doQuickOperations( $realOps ) );
 525                         }
 526                 }
 527                 // Make 'success', 'successCount', and 'failCount' fields reflect
 528                 // the overall operation, rather than all the batches for each backend.
 529                 // Do this by only using success values from the master backend's batch.
 530                 $status->success = $masterStatus->success;
 531                 $status->successCount = $masterStatus->successCount;
 532                 $status->failCount = $masterStatus->failCount;
 533
 534                 return $status;
 535         }
 536
 537         protected function doPrepare( array $params ) {
 538                 return $this->doDirectoryOp( 'prepare', $params );
 539         }
 540
 541         protected function doSecure( array $params ) {
 542                 return $this->doDirectoryOp( 'secure', $params );
 543         }
 544
 545         protected function doPublish( array $params ) {
 546                 return $this->doDirectoryOp( 'publish', $params );
 547         }
 548
 549         protected function doClean( array $params ) {
 550                 return $this->doDirectoryOp( 'clean', $params );
 551         }
 552
 553         /**
 554          * @param string $method One of (doPrepare,doSecure,doPublish,doClean)
 555          * @param array $params Method arguments
 556          * @return Status
 557          */
 558         protected function doDirectoryOp( $method, array $params ) {
 559                 $status = Status::newGood();
 560
 561                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 562                 $masterStatus = $this->backends[$this->masterIndex]->$method( $realParams );
 563                 $status->merge( $masterStatus );
 564
 565                 foreach ( $this->backends as $index => $backend ) {
 566                         if ( $index === $this->masterIndex ) {
 567                                 continue; // already done
 568                         }
 569
 570                         $realParams = $this->substOpPaths( $params, $backend );
 571                         if ( $this->asyncWrites ) {
 572                                 DeferredUpdates::addCallableUpdate(
 573                                         function() use ( $backend, $method, $realParams ) {
 574                                                 $backend->$method( $realParams );
 575                                         }
 576                                 );
 577                         } else {
 578                                 $status->merge( $backend->$method( $realParams ) );
 579                         }
 580                 }
 581
 582                 return $status;
 583         }
 584
 585         public function concatenate( array $params ) {
 586                 // We are writing to an FS file, so we don't need to do this per-backend
 587                 $index = $this->getReadIndexFromParams( $params );
 588                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 589
 590                 return $this->backends[$index]->concatenate( $realParams );
 591         }
 592
 593         public function fileExists( array $params ) {
 594                 $index = $this->getReadIndexFromParams( $params );
 595                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 596
 597                 return $this->backends[$index]->fileExists( $realParams );
 598         }
 599
 600         public function getFileTimestamp( array $params ) {
 601                 $index = $this->getReadIndexFromParams( $params );
 602                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 603
 604                 return $this->backends[$index]->getFileTimestamp( $realParams );
 605         }
 606
 607         public function getFileSize( array $params ) {
 608                 $index = $this->getReadIndexFromParams( $params );
 609                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 610
 611                 return $this->backends[$index]->getFileSize( $realParams );
 612         }
 613
 614         public function getFileStat( array $params ) {
 615                 $index = $this->getReadIndexFromParams( $params );
 616                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 617
 618                 return $this->backends[$index]->getFileStat( $realParams );
 619         }
 620
 621         public function getFileXAttributes( array $params ) {
 622                 $index = $this->getReadIndexFromParams( $params );
 623                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 624
 625                 return $this->backends[$index]->getFileXAttributes( $realParams );
 626         }
 627
 628         public function getFileContentsMulti( array $params ) {
 629                 $index = $this->getReadIndexFromParams( $params );
 630                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 631
 632                 $contentsM = $this->backends[$index]->getFileContentsMulti( $realParams );
 633
 634                 $contents = []; // (path => FSFile) mapping using the proxy backend's name
 635                 foreach ( $contentsM as $path => $data ) {
 636                         $contents[$this->unsubstPaths( $path )] = $data;
 637                 }
 638
 639                 return $contents;
 640         }
 641
 642         public function getFileSha1Base36( array $params ) {
 643                 $index = $this->getReadIndexFromParams( $params );
 644                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 645
 646                 return $this->backends[$index]->getFileSha1Base36( $realParams );
 647         }
 648
 649         public function getFileProps( array $params ) {
 650                 $index = $this->getReadIndexFromParams( $params );
 651                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 652
 653                 return $this->backends[$index]->getFileProps( $realParams );
 654         }
 655
 656         public function streamFile( array $params ) {
 657                 $index = $this->getReadIndexFromParams( $params );
 658                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 659
 660                 return $this->backends[$index]->streamFile( $realParams );
 661         }
 662
 663         public function getLocalReferenceMulti( array $params ) {
 664                 $index = $this->getReadIndexFromParams( $params );
 665                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 666
 667                 $fsFilesM = $this->backends[$index]->getLocalReferenceMulti( $realParams );
 668
 669                 $fsFiles = []; // (path => FSFile) mapping using the proxy backend's name
 670                 foreach ( $fsFilesM as $path => $fsFile ) {
 671                         $fsFiles[$this->unsubstPaths( $path )] = $fsFile;
 672                 }
 673
 674                 return $fsFiles;
 675         }
 676
 677         public function getLocalCopyMulti( array $params ) {
 678                 $index = $this->getReadIndexFromParams( $params );
 679                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 680
 681                 $tempFilesM = $this->backends[$index]->getLocalCopyMulti( $realParams );
 682
 683                 $tempFiles = []; // (path => TempFSFile) mapping using the proxy backend's name
 684                 foreach ( $tempFilesM as $path => $tempFile ) {
 685                         $tempFiles[$this->unsubstPaths( $path )] = $tempFile;
 686                 }
 687
 688                 return $tempFiles;
 689         }
 690
 691         public function getFileHttpUrl( array $params ) {
 692                 $index = $this->getReadIndexFromParams( $params );
 693                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 694
 695                 return $this->backends[$index]->getFileHttpUrl( $realParams );
 696         }
 697
 698         public function directoryExists( array $params ) {
 699                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 700
 701                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 702         }
 703
 704         public function getDirectoryList( array $params ) {
 705                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 706
 707                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 708         }
 709
 710         public function getFileList( array $params ) {
 711                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 712
 713                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 714         }
 715
 716         public function getFeatures() {
 717                 return $this->backends[$this->masterIndex]->getFeatures();
 718         }
 719
 720         public function clearCache( array $paths = null ) {
 721                 foreach ( $this->backends as $backend ) {
 722                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 723                         $backend->clearCache( $realPaths );
 724                 }
 725         }
 726
 727         public function preloadCache( array $paths ) {
 728                 $realPaths = $this->substPaths( $paths, $this->backends[$this->readIndex] );
 729                 $this->backends[$this->readIndex]->preloadCache( $realPaths );
 730         }
 731
 732         public function preloadFileStat( array $params ) {
 733                 $index = $this->getReadIndexFromParams( $params );
 734                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 735
 736                 return $this->backends[$index]->preloadFileStat( $realParams );
 737         }
 738
 739         public function getScopedLocksForOps( array $ops, Status $status ) {
 740                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 741                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $realOps );
 742                 // Get the paths to lock from the master backend
 743                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 744                 // Get the paths under the proxy backend's name
 745                 $pbPaths = [
 746                         LockManager::LOCK_UW => $this->unsubstPaths( $paths[LockManager::LOCK_UW] ),
 747                         LockManager::LOCK_EX => $this->unsubstPaths( $paths[LockManager::LOCK_EX] )
 748                 ];
 749
 750                 // Actually acquire the locks
 751                 return $this->getScopedFileLocks( $pbPaths, 'mixed', $status );
 752         }
 753
 754         /**
 755          * @param array $params
 756          * @return int The master or read affinity backend index, based on $params['latest']
 757          */
 758         protected function getReadIndexFromParams( array $params ) {
 759                 return !empty( $params['latest'] ) ? $this->masterIndex : $this->readIndex;
 760         }
 761 }