includes/libs/filebackend/FileBackendMultiWrite.php

   1 <?php
   2 /**
   3  * Proxy backend that mirrors writes to several internal backends.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  * @ingroup FileBackend
  22  */
  23
  24 use Wikimedia\Timestamp\ConvertibleTimestamp;
  25
  26 /**
  27  * @brief Proxy backend that mirrors writes to several internal backends.
  28  *
  29  * This class defines a multi-write backend. Multiple backends can be
  30  * registered to this proxy backend and it will act as a single backend.
  31  * Use this when all access to those backends is through this proxy backend.
  32  * At least one of the backends must be declared the "master" backend.
  33  *
  34  * Only use this class when transitioning from one storage system to another.
  35  *
  36  * Read operations are only done on the 'master' backend for consistency.
  37  * Write operations are performed on all backends, starting with the master.
  38  * This makes a best-effort to have transactional semantics, but since requests
  39  * may sometimes fail, the use of "autoResync" or background scripts to fix
  40  * inconsistencies is important.
  41  *
  42  * @ingroup FileBackend
  43  * @since 1.19
  44  */
  45 class FileBackendMultiWrite extends FileBackend {
  46         /** @var FileBackendStore[] Prioritized list of FileBackendStore objects */
  47         protected $backends = [];
  48
  49         /** @var int Index of master backend */
  50         protected $masterIndex = -1;
  51         /** @var int Index of read affinity backend */
  52         protected $readIndex = -1;
  53
  54         /** @var int Bitfield */
  55         protected $syncChecks = 0;
  56         /** @var string|bool */
  57         protected $autoResync = false;
  58
  59         /** @var bool */
  60         protected $asyncWrites = false;
  61
  62         /** @var int Compare file sizes among backends */
  63         const CHECK_SIZE = 1;
  64         /** @var int Compare file mtimes among backends */
  65         const CHECK_TIME = 2;
  66         /** @var int Compare file hashes among backends */
  67         const CHECK_SHA1 = 4;
  68
  69         /**
  70          * Construct a proxy backend that consists of several internal backends.
  71          * Locking, journaling, and read-only checks are handled by the proxy backend.
  72          *
  73          * Additional $config params include:
  74          *   - backends       : Array of backend config and multi-backend settings.
  75          *                      Each value is the config used in the constructor of a
  76          *                      FileBackendStore class, but with these additional settings:
  77          *                        - class         : The name of the backend class
  78          *                        - isMultiMaster : This must be set for one backend.
  79          *                        - readAffinity  : Use this for reads without 'latest' set.
  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 LogicException
  96          */
  97         public function __construct( array $config ) {
  98                 parent::__construct( $config );
  99                 $this->syncChecks = $config['syncChecks'] ?? self::CHECK_SIZE;
 100                 $this->autoResync = $config['autoResync'] ?? false;
 101                 $this->asyncWrites = isset( $config['replication'] ) && $config['replication'] === 'async';
 102                 // Construct backends here rather than via registration
 103                 // to keep these backends hidden from outside the proxy.
 104                 $namesUsed = [];
 105                 foreach ( $config['backends'] as $index => $config ) {
 106                         $name = $config['name'];
 107                         if ( isset( $namesUsed[$name] ) ) { // don't break FileOp predicates
 108                                 throw new LogicException( "Two or more backends defined with the name $name." );
 109                         }
 110                         $namesUsed[$name] = 1;
 111                         // Alter certain sub-backend settings for sanity
 112                         unset( $config['readOnly'] ); // use proxy backend setting
 113                         unset( $config['fileJournal'] ); // use proxy backend journal
 114                         unset( $config['lockManager'] ); // lock under proxy backend
 115                         $config['domainId'] = $this->domainId; // use the proxy backend wiki ID
 116                         if ( !empty( $config['isMultiMaster'] ) ) {
 117                                 if ( $this->masterIndex >= 0 ) {
 118                                         throw new LogicException( 'More than one master backend defined.' );
 119                                 }
 120                                 $this->masterIndex = $index; // this is the "master"
 121                                 $config['fileJournal'] = $this->fileJournal; // log under proxy backend
 122                         }
 123                         if ( !empty( $config['readAffinity'] ) ) {
 124                                 $this->readIndex = $index; // prefer this for reads
 125                         }
 126                         // Create sub-backend object
 127                         if ( !isset( $config['class'] ) ) {
 128                                 throw new InvalidArgumentException( 'No class given for a backend config.' );
 129                         }
 130                         $class = $config['class'];
 131                         $this->backends[$index] = new $class( $config );
 132                 }
 133                 if ( $this->masterIndex < 0 ) { // need backends and must have a master
 134                         throw new LogicException( 'No master backend defined.' );
 135                 }
 136                 if ( $this->readIndex < 0 ) {
 137                         $this->readIndex = $this->masterIndex; // default
 138                 }
 139         }
 140
 141         final protected function doOperationsInternal( array $ops, array $opts ) {
 142                 $status = $this->newStatus();
 143
 144                 $mbe = $this->backends[$this->masterIndex]; // convenience
 145
 146                 // Acquire any locks as needed
 147                 if ( empty( $opts['nonLocking'] ) ) {
 148                         /** @noinspection PhpUnusedLocalVariableInspection */
 149                         $scopeLock = $this->getScopedLocksForOps( $ops, $status );
 150                         if ( !$status->isOK() ) {
 151                                 return $status; // abort
 152                         }
 153                 }
 154                 // Clear any cache entries (after locks acquired)
 155                 $this->clearCache();
 156                 $opts['preserveCache'] = true; // only locked files are cached
 157                 // Get the list of paths to read/write
 158                 $relevantPaths = $this->fileStoragePathsForOps( $ops );
 159                 // Check if the paths are valid and accessible on all backends
 160                 $status->merge( $this->accessibilityCheck( $relevantPaths ) );
 161                 if ( !$status->isOK() ) {
 162                         return $status; // abort
 163                 }
 164                 // Do a consistency check to see if the backends are consistent
 165                 $syncStatus = $this->consistencyCheck( $relevantPaths );
 166                 if ( !$syncStatus->isOK() ) {
 167                         $this->logger->error(
 168                                 __METHOD__ . ": failed sync check: " . FormatJson::encode( $relevantPaths )
 169                         );
 170                         // Try to resync the clone backends to the master on the spot
 171                         if (
 172                                 $this->autoResync === false ||
 173                                 !$this->resyncFiles( $relevantPaths, $this->autoResync )->isOK()
 174                         ) {
 175                                 $status->merge( $syncStatus );
 176
 177                                 return $status; // abort
 178                         }
 179                 }
 180                 // Actually attempt the operation batch on the master backend
 181                 $realOps = $this->substOpBatchPaths( $ops, $mbe );
 182                 $masterStatus = $mbe->doOperations( $realOps, $opts );
 183                 $status->merge( $masterStatus );
 184                 // Propagate the operations to the clone backends if there were no unexpected errors
 185                 // and everything didn't fail due to predicted errors. If $ops only had one operation,
 186                 // this might avoid backend sync inconsistencies.
 187                 if ( $masterStatus->isOK() && $masterStatus->successCount > 0 ) {
 188                         foreach ( $this->backends as $index => $backend ) {
 189                                 if ( $index === $this->masterIndex ) {
 190                                         continue; // done already
 191                                 }
 192
 193                                 $realOps = $this->substOpBatchPaths( $ops, $backend );
 194                                 if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 195                                         // Bind $scopeLock to the callback to preserve locks
 196                                         DeferredUpdates::addCallableUpdate(
 197                                                 function () use ( $backend, $realOps, $opts, $scopeLock, $relevantPaths ) {
 198                                                         $this->logger->error(
 199                                                                 "'{$backend->getName()}' async replication; paths: " .
 200                                                                 FormatJson::encode( $relevantPaths )
 201                                                         );
 202                                                         $backend->doOperations( $realOps, $opts );
 203                                                 }
 204                                         );
 205                                 } else {
 206                                         $this->logger->error(
 207                                                 "'{$backend->getName()}' sync replication; paths: " .
 208                                                 FormatJson::encode( $relevantPaths )
 209                                         );
 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          * This method should only be called if the files are locked or the backend
 228          * is in read-only mode
 229          *
 230          * @param array $paths List of storage paths
 231          * @return StatusValue
 232          */
 233         public function consistencyCheck( array $paths ) {
 234                 $status = $this->newStatus();
 235                 if ( $this->syncChecks == 0 || count( $this->backends ) <= 1 ) {
 236                         return $status; // skip checks
 237                 }
 238
 239                 // Preload all of the stat info in as few round trips as possible
 240                 foreach ( $this->backends as $backend ) {
 241                         $realPaths = $this->substPaths( $paths, $backend );
 242                         $backend->preloadFileStat( [ 'srcs' => $realPaths, 'latest' => true ] );
 243                 }
 244
 245                 foreach ( $paths as $path ) {
 246                         $params = [ 'src' => $path, 'latest' => true ];
 247                         // Get the state of the file on the master backend
 248                         $masterBackend = $this->backends[$this->masterIndex];
 249                         $masterParams = $this->substOpPaths( $params, $masterBackend );
 250                         $masterStat = $masterBackend->getFileStat( $masterParams );
 251                         if ( $masterStat === self::STAT_ERROR ) {
 252                                 $status->fatal( 'backend-fail-stat', $path );
 253                                 continue;
 254                         }
 255                         if ( $this->syncChecks & self::CHECK_SHA1 ) {
 256                                 $masterSha1 = $masterBackend->getFileSha1Base36( $masterParams );
 257                                 if ( ( $masterSha1 !== false ) !== (bool)$masterStat ) {
 258                                         $status->fatal( 'backend-fail-hash', $path );
 259                                         continue;
 260                                 }
 261                         } else {
 262                                 $masterSha1 = null; // unused
 263                         }
 264
 265                         // Check if all clone backends agree with the master...
 266                         foreach ( $this->backends as $index => $cloneBackend ) {
 267                                 if ( $index === $this->masterIndex ) {
 268                                         continue; // master
 269                                 }
 270
 271                                 // Get the state of the file on the clone backend
 272                                 $cloneParams = $this->substOpPaths( $params, $cloneBackend );
 273                                 $cloneStat = $cloneBackend->getFileStat( $cloneParams );
 274
 275                                 if ( $masterStat ) {
 276                                         // File exists in the master backend
 277                                         if ( !$cloneStat ) {
 278                                                 // File is missing from the clone backend
 279                                                 $status->fatal( 'backend-fail-synced', $path );
 280                                         } elseif (
 281                                                 ( $this->syncChecks & self::CHECK_SIZE ) &&
 282                                                 $cloneStat['size'] !== $masterStat['size']
 283                                         ) {
 284                                                 // File in the clone backend is different
 285                                                 $status->fatal( 'backend-fail-synced', $path );
 286                                         } elseif (
 287                                                 ( $this->syncChecks & self::CHECK_TIME ) &&
 288                                                 abs(
 289                                                         ConvertibleTimestamp::convert( TS_UNIX, $masterStat['mtime'] ) -
 290                                                         ConvertibleTimestamp::convert( TS_UNIX, $cloneStat['mtime'] )
 291                                                 ) > 30
 292                                         ) {
 293                                                 // File in the clone backend is significantly newer or older
 294                                                 $status->fatal( 'backend-fail-synced', $path );
 295                                         } elseif (
 296                                                 ( $this->syncChecks & self::CHECK_SHA1 ) &&
 297                                                 $cloneBackend->getFileSha1Base36( $cloneParams ) !== $masterSha1
 298                                         ) {
 299                                                 // File in the clone backend is different
 300                                                 $status->fatal( 'backend-fail-synced', $path );
 301                                         }
 302                                 } else {
 303                                         // File does not exist in the master backend
 304                                         if ( $cloneStat ) {
 305                                                 // Stray file exists in the clone backend
 306                                                 $status->fatal( 'backend-fail-synced', $path );
 307                                         }
 308                                 }
 309                         }
 310                 }
 311
 312                 return $status;
 313         }
 314
 315         /**
 316          * Check that a set of file paths are usable across all internal backends
 317          *
 318          * @param array $paths List of storage paths
 319          * @return StatusValue
 320          */
 321         public function accessibilityCheck( array $paths ) {
 322                 $status = $this->newStatus();
 323                 if ( count( $this->backends ) <= 1 ) {
 324                         return $status; // skip checks
 325                 }
 326
 327                 foreach ( $paths as $path ) {
 328                         foreach ( $this->backends as $backend ) {
 329                                 $realPath = $this->substPaths( $path, $backend );
 330                                 if ( !$backend->isPathUsableInternal( $realPath ) ) {
 331                                         $status->fatal( 'backend-fail-usable', $path );
 332                                 }
 333                         }
 334                 }
 335
 336                 return $status;
 337         }
 338
 339         /**
 340          * Check that a set of files are consistent across all internal backends
 341          * and re-synchronize those files against the "multi master" if needed.
 342          *
 343          * This method should only be called if the files are locked
 344          *
 345          * @param array $paths List of storage paths
 346          * @param string|bool $resyncMode False, True, or "conservative"; see __construct()
 347          * @return StatusValue
 348          */
 349         public function resyncFiles( array $paths, $resyncMode = true ) {
 350                 $status = $this->newStatus();
 351
 352                 $fname = __METHOD__;
 353                 foreach ( $paths as $path ) {
 354                         $params = [ 'src' => $path, 'latest' => true ];
 355                         // Get the state of the file on the master backend
 356                         $masterBackend = $this->backends[$this->masterIndex];
 357                         $masterParams = $this->substOpPaths( $params, $masterBackend );
 358                         $masterPath = $masterParams['src'];
 359                         $masterStat = $masterBackend->getFileStat( $masterParams );
 360                         if ( $masterStat === self::STAT_ERROR ) {
 361                                 $status->fatal( 'backend-fail-stat', $path );
 362                                 $this->logger->error( "$fname: file '$masterPath' is not available" );
 363                                 continue;
 364                         }
 365                         $masterSha1 = $masterBackend->getFileSha1Base36( $masterParams );
 366                         if ( ( $masterSha1 !== false ) !== (bool)$masterStat ) {
 367                                 $status->fatal( 'backend-fail-hash', $path );
 368                                 $this->logger->error( "$fname: file '$masterPath' hash does not match stat" );
 369                                 continue;
 370                         }
 371
 372                         // Check of all clone backends agree with the master...
 373                         foreach ( $this->backends as $index => $cloneBackend ) {
 374                                 if ( $index === $this->masterIndex ) {
 375                                         continue; // master
 376                                 }
 377
 378                                 // Get the state of the file on the clone backend
 379                                 $cloneParams = $this->substOpPaths( $params, $cloneBackend );
 380                                 $clonePath = $cloneParams['src'];
 381                                 $cloneStat = $cloneBackend->getFileStat( $cloneParams );
 382                                 if ( $cloneStat === self::STAT_ERROR ) {
 383                                         $status->fatal( 'backend-fail-stat', $path );
 384                                         $this->logger->error( "$fname: file '$clonePath' is not available" );
 385                                         continue;
 386                                 }
 387                                 $cloneSha1 = $cloneBackend->getFileSha1Base36( $cloneParams );
 388                                 if ( ( $cloneSha1 !== false ) !== (bool)$cloneStat ) {
 389                                         $status->fatal( 'backend-fail-hash', $path );
 390                                         $this->logger->error( "$fname: file '$clonePath' hash does not match stat" );
 391                                         continue;
 392                                 }
 393
 394                                 if ( $masterSha1 === $cloneSha1 ) {
 395                                         // File is either the same in both backends or absent from both backends
 396                                         $this->logger->debug( "$fname: file '$clonePath' matches '$masterPath'" );
 397                                 } elseif ( $masterSha1 !== false ) {
 398                                         // File is either missing from or different in the clone backend
 399                                         if (
 400                                                 $resyncMode === 'conservative' &&
 401                                                 $cloneStat &&
 402                                                 $cloneStat['mtime'] > $masterStat['mtime']
 403                                         ) {
 404                                                 // Do not replace files with older ones; reduces the risk of data loss
 405                                                 $status->fatal( 'backend-fail-synced', $path );
 406                                         } else {
 407                                                 // Copy the master backend file to the clone backend in overwrite mode
 408                                                 $fsFile = $masterBackend->getLocalReference( $masterParams );
 409                                                 $status->merge( $cloneBackend->quickStore( [
 410                                                         'src' => $fsFile,
 411                                                         'dst' => $clonePath
 412                                                 ] ) );
 413                                         }
 414                                 } elseif ( $masterStat === false ) {
 415                                         // Stray file exists in the clone backend
 416                                         if ( $resyncMode === 'conservative' ) {
 417                                                 // Do not delete stray files; reduces the risk of data loss
 418                                                 $status->fatal( 'backend-fail-synced', $path );
 419                                         } else {
 420                                                 // Delete the stay file from the clone backend
 421                                                 $status->merge( $cloneBackend->quickDelete( [ 'src' => $clonePath ] ) );
 422                                         }
 423                                 }
 424                         }
 425                 }
 426
 427                 if ( !$status->isOK() ) {
 428                         $this->logger->error( "$fname: failed to resync: " . FormatJson::encode( $paths ) );
 429                 }
 430
 431                 return $status;
 432         }
 433
 434         /**
 435          * Get a list of file storage paths to read or write for a list of operations
 436          *
 437          * @param array $ops Same format as doOperations()
 438          * @return array List of storage paths to files (does not include directories)
 439          */
 440         protected function fileStoragePathsForOps( array $ops ) {
 441                 $paths = [];
 442                 foreach ( $ops as $op ) {
 443                         if ( isset( $op['src'] ) ) {
 444                                 // For things like copy/move/delete with "ignoreMissingSource" and there
 445                                 // is no source file, nothing should happen and there should be no errors.
 446                                 if ( empty( $op['ignoreMissingSource'] )
 447                                         || $this->fileExists( [ 'src' => $op['src'] ] )
 448                                 ) {
 449                                         $paths[] = $op['src'];
 450                                 }
 451                         }
 452                         if ( isset( $op['srcs'] ) ) {
 453                                 $paths = array_merge( $paths, $op['srcs'] );
 454                         }
 455                         if ( isset( $op['dst'] ) ) {
 456                                 $paths[] = $op['dst'];
 457                         }
 458                 }
 459
 460                 return array_values( array_unique( array_filter( $paths, 'FileBackend::isStoragePath' ) ) );
 461         }
 462
 463         /**
 464          * Substitute the backend name in storage path parameters
 465          * for a set of operations with that of a given internal backend.
 466          *
 467          * @param array $ops List of file operation arrays
 468          * @param FileBackendStore $backend
 469          * @return array
 470          */
 471         protected function substOpBatchPaths( array $ops, FileBackendStore $backend ) {
 472                 $newOps = []; // operations
 473                 foreach ( $ops as $op ) {
 474                         $newOp = $op; // operation
 475                         foreach ( [ 'src', 'srcs', 'dst', 'dir' ] as $par ) {
 476                                 if ( isset( $newOp[$par] ) ) { // string or array
 477                                         $newOp[$par] = $this->substPaths( $newOp[$par], $backend );
 478                                 }
 479                         }
 480                         $newOps[] = $newOp;
 481                 }
 482
 483                 return $newOps;
 484         }
 485
 486         /**
 487          * Same as substOpBatchPaths() but for a single operation
 488          *
 489          * @param array $ops File operation array
 490          * @param FileBackendStore $backend
 491          * @return array
 492          */
 493         protected function substOpPaths( array $ops, FileBackendStore $backend ) {
 494                 $newOps = $this->substOpBatchPaths( [ $ops ], $backend );
 495
 496                 return $newOps[0];
 497         }
 498
 499         /**
 500          * Substitute the backend of storage paths with an internal backend's name
 501          *
 502          * @param array|string $paths List of paths or single string path
 503          * @param FileBackendStore $backend
 504          * @return string[]|string
 505          */
 506         protected function substPaths( $paths, FileBackendStore $backend ) {
 507                 return preg_replace(
 508                         '!^mwstore://' . preg_quote( $this->name, '!' ) . '/!',
 509                         StringUtils::escapeRegexReplacement( "mwstore://{$backend->getName()}/" ),
 510                         $paths // string or array
 511                 );
 512         }
 513
 514         /**
 515          * Substitute the backend of internal storage paths with the proxy backend's name
 516          *
 517          * @param array|string $paths List of paths or single string path
 518          * @param FileBackendStore $backend internal storage backend
 519          * @return string[]|string
 520          */
 521         protected function unsubstPaths( $paths, FileBackendStore $backend ) {
 522                 return preg_replace(
 523                         '!^mwstore://' . preg_quote( $backend->getName(), '!' ) . '/!',
 524                         StringUtils::escapeRegexReplacement( "mwstore://{$this->name}/" ),
 525                         $paths // string or array
 526                 );
 527         }
 528
 529         /**
 530          * @param array $ops File operations for FileBackend::doOperations()
 531          * @return bool Whether there are file path sources with outside lifetime/ownership
 532          */
 533         protected function hasVolatileSources( array $ops ) {
 534                 foreach ( $ops as $op ) {
 535                         if ( $op['op'] === 'store' && !isset( $op['srcRef'] ) ) {
 536                                 return true; // source file might be deleted anytime after do*Operations()
 537                         }
 538                 }
 539
 540                 return false;
 541         }
 542
 543         protected function doQuickOperationsInternal( array $ops ) {
 544                 $status = $this->newStatus();
 545                 // Do the operations on the master backend; setting StatusValue fields
 546                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 547                 $masterStatus = $this->backends[$this->masterIndex]->doQuickOperations( $realOps );
 548                 $status->merge( $masterStatus );
 549                 // Propagate the operations to the clone backends...
 550                 foreach ( $this->backends as $index => $backend ) {
 551                         if ( $index === $this->masterIndex ) {
 552                                 continue; // done already
 553                         }
 554
 555                         $realOps = $this->substOpBatchPaths( $ops, $backend );
 556                         if ( $this->asyncWrites && !$this->hasVolatileSources( $ops ) ) {
 557                                 DeferredUpdates::addCallableUpdate(
 558                                         function () use ( $backend, $realOps ) {
 559                                                 $backend->doQuickOperations( $realOps );
 560                                         }
 561                                 );
 562                         } else {
 563                                 $status->merge( $backend->doQuickOperations( $realOps ) );
 564                         }
 565                 }
 566                 // Make 'success', 'successCount', and 'failCount' fields reflect
 567                 // the overall operation, rather than all the batches for each backend.
 568                 // Do this by only using success values from the master backend's batch.
 569                 $status->success = $masterStatus->success;
 570                 $status->successCount = $masterStatus->successCount;
 571                 $status->failCount = $masterStatus->failCount;
 572
 573                 return $status;
 574         }
 575
 576         protected function doPrepare( array $params ) {
 577                 return $this->doDirectoryOp( 'prepare', $params );
 578         }
 579
 580         protected function doSecure( array $params ) {
 581                 return $this->doDirectoryOp( 'secure', $params );
 582         }
 583
 584         protected function doPublish( array $params ) {
 585                 return $this->doDirectoryOp( 'publish', $params );
 586         }
 587
 588         protected function doClean( array $params ) {
 589                 return $this->doDirectoryOp( 'clean', $params );
 590         }
 591
 592         /**
 593          * @param string $method One of (doPrepare,doSecure,doPublish,doClean)
 594          * @param array $params Method arguments
 595          * @return StatusValue
 596          */
 597         protected function doDirectoryOp( $method, array $params ) {
 598                 $status = $this->newStatus();
 599
 600                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 601                 $masterStatus = $this->backends[$this->masterIndex]->$method( $realParams );
 602                 $status->merge( $masterStatus );
 603
 604                 foreach ( $this->backends as $index => $backend ) {
 605                         if ( $index === $this->masterIndex ) {
 606                                 continue; // already done
 607                         }
 608
 609                         $realParams = $this->substOpPaths( $params, $backend );
 610                         if ( $this->asyncWrites ) {
 611                                 DeferredUpdates::addCallableUpdate(
 612                                         function () use ( $backend, $method, $realParams ) {
 613                                                 $backend->$method( $realParams );
 614                                         }
 615                                 );
 616                         } else {
 617                                 $status->merge( $backend->$method( $realParams ) );
 618                         }
 619                 }
 620
 621                 return $status;
 622         }
 623
 624         public function concatenate( array $params ) {
 625                 $status = $this->newStatus();
 626                 // We are writing to an FS file, so we don't need to do this per-backend
 627                 $index = $this->getReadIndexFromParams( $params );
 628                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 629
 630                 $status->merge( $this->backends[$index]->concatenate( $realParams ) );
 631
 632                 return $status;
 633         }
 634
 635         public function fileExists( array $params ) {
 636                 $index = $this->getReadIndexFromParams( $params );
 637                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 638
 639                 return $this->backends[$index]->fileExists( $realParams );
 640         }
 641
 642         public function getFileTimestamp( array $params ) {
 643                 $index = $this->getReadIndexFromParams( $params );
 644                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 645
 646                 return $this->backends[$index]->getFileTimestamp( $realParams );
 647         }
 648
 649         public function getFileSize( array $params ) {
 650                 $index = $this->getReadIndexFromParams( $params );
 651                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 652
 653                 return $this->backends[$index]->getFileSize( $realParams );
 654         }
 655
 656         public function getFileStat( array $params ) {
 657                 $index = $this->getReadIndexFromParams( $params );
 658                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 659
 660                 return $this->backends[$index]->getFileStat( $realParams );
 661         }
 662
 663         public function getFileXAttributes( array $params ) {
 664                 $index = $this->getReadIndexFromParams( $params );
 665                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 666
 667                 return $this->backends[$index]->getFileXAttributes( $realParams );
 668         }
 669
 670         public function getFileContentsMulti( array $params ) {
 671                 $index = $this->getReadIndexFromParams( $params );
 672                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 673
 674                 $contentsM = $this->backends[$index]->getFileContentsMulti( $realParams );
 675
 676                 $contents = []; // (path => FSFile) mapping using the proxy backend's name
 677                 foreach ( $contentsM as $path => $data ) {
 678                         $contents[$this->unsubstPaths( $path, $this->backends[$index] )] = $data;
 679                 }
 680
 681                 return $contents;
 682         }
 683
 684         public function getFileSha1Base36( array $params ) {
 685                 $index = $this->getReadIndexFromParams( $params );
 686                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 687
 688                 return $this->backends[$index]->getFileSha1Base36( $realParams );
 689         }
 690
 691         public function getFileProps( array $params ) {
 692                 $index = $this->getReadIndexFromParams( $params );
 693                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 694
 695                 return $this->backends[$index]->getFileProps( $realParams );
 696         }
 697
 698         public function streamFile( array $params ) {
 699                 $index = $this->getReadIndexFromParams( $params );
 700                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 701
 702                 return $this->backends[$index]->streamFile( $realParams );
 703         }
 704
 705         public function getLocalReferenceMulti( array $params ) {
 706                 $index = $this->getReadIndexFromParams( $params );
 707                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 708
 709                 $fsFilesM = $this->backends[$index]->getLocalReferenceMulti( $realParams );
 710
 711                 $fsFiles = []; // (path => FSFile) mapping using the proxy backend's name
 712                 foreach ( $fsFilesM as $path => $fsFile ) {
 713                         $fsFiles[$this->unsubstPaths( $path, $this->backends[$index] )] = $fsFile;
 714                 }
 715
 716                 return $fsFiles;
 717         }
 718
 719         public function getLocalCopyMulti( array $params ) {
 720                 $index = $this->getReadIndexFromParams( $params );
 721                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 722
 723                 $tempFilesM = $this->backends[$index]->getLocalCopyMulti( $realParams );
 724
 725                 $tempFiles = []; // (path => TempFSFile) mapping using the proxy backend's name
 726                 foreach ( $tempFilesM as $path => $tempFile ) {
 727                         $tempFiles[$this->unsubstPaths( $path, $this->backends[$index] )] = $tempFile;
 728                 }
 729
 730                 return $tempFiles;
 731         }
 732
 733         public function getFileHttpUrl( array $params ) {
 734                 $index = $this->getReadIndexFromParams( $params );
 735                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 736
 737                 return $this->backends[$index]->getFileHttpUrl( $realParams );
 738         }
 739
 740         public function directoryExists( array $params ) {
 741                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 742
 743                 return $this->backends[$this->masterIndex]->directoryExists( $realParams );
 744         }
 745
 746         public function getDirectoryList( array $params ) {
 747                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 748
 749                 return $this->backends[$this->masterIndex]->getDirectoryList( $realParams );
 750         }
 751
 752         public function getFileList( array $params ) {
 753                 $realParams = $this->substOpPaths( $params, $this->backends[$this->masterIndex] );
 754
 755                 return $this->backends[$this->masterIndex]->getFileList( $realParams );
 756         }
 757
 758         public function getFeatures() {
 759                 return $this->backends[$this->masterIndex]->getFeatures();
 760         }
 761
 762         public function clearCache( array $paths = null ) {
 763                 foreach ( $this->backends as $backend ) {
 764                         $realPaths = is_array( $paths ) ? $this->substPaths( $paths, $backend ) : null;
 765                         $backend->clearCache( $realPaths );
 766                 }
 767         }
 768
 769         public function preloadCache( array $paths ) {
 770                 $realPaths = $this->substPaths( $paths, $this->backends[$this->readIndex] );
 771                 $this->backends[$this->readIndex]->preloadCache( $realPaths );
 772         }
 773
 774         public function preloadFileStat( array $params ) {
 775                 $index = $this->getReadIndexFromParams( $params );
 776                 $realParams = $this->substOpPaths( $params, $this->backends[$index] );
 777
 778                 return $this->backends[$index]->preloadFileStat( $realParams );
 779         }
 780
 781         public function getScopedLocksForOps( array $ops, StatusValue $status ) {
 782                 $realOps = $this->substOpBatchPaths( $ops, $this->backends[$this->masterIndex] );
 783                 $fileOps = $this->backends[$this->masterIndex]->getOperationsInternal( $realOps );
 784                 // Get the paths to lock from the master backend
 785                 $paths = $this->backends[$this->masterIndex]->getPathsToLockForOpsInternal( $fileOps );
 786                 // Get the paths under the proxy backend's name
 787                 $pbPaths = [
 788                         LockManager::LOCK_UW => $this->unsubstPaths(
 789                                 $paths[LockManager::LOCK_UW],
 790                                 $this->backends[$this->masterIndex]
 791                         ),
 792                         LockManager::LOCK_EX => $this->unsubstPaths(
 793                                 $paths[LockManager::LOCK_EX],
 794                                 $this->backends[$this->masterIndex]
 795                         )
 796                 ];
 797
 798                 // Actually acquire the locks
 799                 return $this->getScopedFileLocks( $pbPaths, 'mixed', $status );
 800         }
 801
 802         /**
 803          * @param array $params
 804          * @return int The master or read affinity backend index, based on $params['latest']
 805          */
 806         protected function getReadIndexFromParams( array $params ) {
 807                 return !empty( $params['latest'] ) ? $this->masterIndex : $this->readIndex;
 808         }
 809 }