includes/filerepo/backend/FileBackend.php

   1 <?php
   2 /**
   3  * @defgroup FileBackend File backend
   4  * @ingroup  FileRepo
   5  *
   6  * File backend is used to interact with file storage systems,
   7  * such as the local file system, NFS, or cloud storage systems.
   8  */
   9
  10 /**
  11  * Base class for all file backends.
  12  *
  13  * This program is free software; you can redistribute it and/or modify
  14  * it under the terms of the GNU General Public License as published by
  15  * the Free Software Foundation; either version 2 of the License, or
  16  * (at your option) any later version.
  17  *
  18  * This program is distributed in the hope that it will be useful,
  19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  21  * GNU General Public License for more details.
  22  *
  23  * You should have received a copy of the GNU General Public License along
  24  * with this program; if not, write to the Free Software Foundation, Inc.,
  25  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  26  * http://www.gnu.org/copyleft/gpl.html
  27  *
  28  * @file
  29  * @ingroup FileBackend
  30  * @author Aaron Schulz
  31  */
  32
  33 /**
  34  * @brief Base class for all file backend classes (including multi-write backends).
  35  *
  36  * This class defines the methods as abstract that subclasses must implement.
  37  * Outside callers can assume that all backends will have these functions.
  38  *
  39  * All "storage paths" are of the format "mwstore://<backend>/<container>/<path>".
  40  * The "<path>" portion is a relative path that uses UNIX file system (FS)
  41  * notation, though any particular backend may not actually be using a local
  42  * filesystem.
  43  * Therefore, the relative paths are only virtual.
  44  *
  45  * Backend contents are stored under wiki-specific container names by default.
  46  * For legacy reasons, this has no effect for the FS backend class, and per-wiki
  47  * segregation must be done by setting the container paths appropriately.
  48  *
  49  * FS-based backends are somewhat more restrictive due to the existence of real
  50  * directory files; a regular file cannot have the same name as a directory. Other
  51  * backends with virtual directories may not have this limitation. Callers should
  52  * store files in such a way that no files and directories are under the same path.
  53  *
  54  * Methods should avoid throwing exceptions at all costs.
  55  * As a corollary, external dependencies should be kept to a minimum.
  56  *
  57  * @ingroup FileBackend
  58  * @since 1.19
  59  */
  60 abstract class FileBackend {
  61         protected $name; // string; unique backend name
  62         protected $wikiId; // string; unique wiki name
  63         protected $readOnly; // string; read-only explanation message
  64         protected $parallelize; // string; when to do operations in parallel
  65         protected $concurrency; // integer; how many operations can be done in parallel
  66
  67         /** @var LockManager */
  68         protected $lockManager;
  69         /** @var FileJournal */
  70         protected $fileJournal;
  71
  72         /**
  73          * Create a new backend instance from configuration.
  74          * This should only be called from within FileBackendGroup.
  75          *
  76          * $config includes:
  77          *   - name        : The unique name of this backend.
  78          *                   This should consist of alphanumberic, '-', and '_' characters.
  79          *                   This name should not be changed after use.
  80          *   - wikiId      : Prefix to container names that is unique to this wiki.
  81          *                   It should only consist of alphanumberic, '-', and '_' characters.
  82          *   - lockManager : Registered name of a file lock manager to use.
  83          *   - fileJournal : File journal configuration; see FileJournal::factory().
  84          *                   Journals simply log changes to files stored in the backend.
  85          *   - readOnly    : Write operations are disallowed if this is a non-empty string.
  86          *                   It should be an explanation for the backend being read-only.
  87          *   - parallelize : When to do file operations in parallel (when possible).
  88          *                   Allowed values are "implicit", "explicit" and "off".
  89          *   - concurrency : How many file operations can be done in parallel.
  90          *
  91          * @param $config Array
  92          * @throws MWException
  93          */
  94         public function __construct( array $config ) {
  95                 $this->name = $config['name'];
  96                 if ( !preg_match( '!^[a-zA-Z0-9-_]{1,255}$!', $this->name ) ) {
  97                         throw new MWException( "Backend name `{$this->name}` is invalid." );
  98                 }
  99                 $this->wikiId = isset( $config['wikiId'] )
 100                         ? $config['wikiId']
 101                         : wfWikiID(); // e.g. "my_wiki-en_"
 102                 $this->lockManager = ( $config['lockManager'] instanceof LockManager )
 103                         ? $config['lockManager']
 104                         : LockManagerGroup::singleton()->get( $config['lockManager'] );
 105                 $this->fileJournal = isset( $config['fileJournal'] )
 106                         ? ( ( $config['fileJournal'] instanceof FileJournal )
 107                                 ? $config['fileJournal']
 108                                 : FileJournal::factory( $config['fileJournal'], $this->name ) )
 109                         : FileJournal::factory( array( 'class' => 'NullFileJournal' ), $this->name );
 110                 $this->readOnly = isset( $config['readOnly'] )
 111                         ? (string)$config['readOnly']
 112                         : '';
 113                 $this->parallelize = isset( $config['parallelize'] )
 114                         ? (string)$config['parallelize']
 115                         : 'off';
 116                 $this->concurrency = isset( $config['concurrency'] )
 117                         ? (int)$config['concurrency']
 118                         : 50;
 119         }
 120
 121         /**
 122          * Get the unique backend name.
 123          * We may have multiple different backends of the same type.
 124          * For example, we can have two Swift backends using different proxies.
 125          *
 126          * @return string
 127          */
 128         final public function getName() {
 129                 return $this->name;
 130         }
 131
 132         /**
 133          * Check if this backend is read-only
 134          *
 135          * @return bool
 136          */
 137         final public function isReadOnly() {
 138                 return ( $this->readOnly != '' );
 139         }
 140
 141         /**
 142          * Get an explanatory message if this backend is read-only
 143          *
 144          * @return string|bool Returns false if the backend is not read-only
 145          */
 146         final public function getReadOnlyReason() {
 147                 return ( $this->readOnly != '' ) ? $this->readOnly : false;
 148         }
 149
 150         /**
 151          * This is the main entry point into the backend for write operations.
 152          * Callers supply an ordered list of operations to perform as a transaction.
 153          * Files will be locked, the stat cache cleared, and then the operations attempted.
 154          * If any serious errors occur, all attempted operations will be rolled back.
 155          *
 156          * $ops is an array of arrays. The outer array holds a list of operations.
 157          * Each inner array is a set of key value pairs that specify an operation.
 158          *
 159          * Supported operations and their parameters. The supported actions are:
 160          *  - create
 161          *  - store
 162          *  - copy
 163          *  - move
 164          *  - delete
 165          *  - null
 166          *
 167          * a) Create a new file in storage with the contents of a string
 168          * @code
 169          *     array(
 170          *         'op'                  => 'create',
 171          *         'dst'                 => <storage path>,
 172          *         'content'             => <string of new file contents>,
 173          *         'overwrite'           => <boolean>,
 174          *         'overwriteSame'       => <boolean>
 175          *     );
 176          * @endcode
 177          *
 178          * b) Copy a file system file into storage
 179          * @code
 180          *     array(
 181          *         'op'                  => 'store',
 182          *         'src'                 => <file system path>,
 183          *         'dst'                 => <storage path>,
 184          *         'overwrite'           => <boolean>,
 185          *         'overwriteSame'       => <boolean>
 186          *     )
 187          * @endcode
 188          *
 189          * c) Copy a file within storage
 190          * @code
 191          *     array(
 192          *         'op'                  => 'copy',
 193          *         'src'                 => <storage path>,
 194          *         'dst'                 => <storage path>,
 195          *         'overwrite'           => <boolean>,
 196          *         'overwriteSame'       => <boolean>
 197          *     )
 198          * @endcode
 199          *
 200          * d) Move a file within storage
 201          * @code
 202          *     array(
 203          *         'op'                  => 'move',
 204          *         'src'                 => <storage path>,
 205          *         'dst'                 => <storage path>,
 206          *         'overwrite'           => <boolean>,
 207          *         'overwriteSame'       => <boolean>
 208          *     )
 209          * @endcode
 210          *
 211          * e) Delete a file within storage
 212          * @code
 213          *     array(
 214          *         'op'                  => 'delete',
 215          *         'src'                 => <storage path>,
 216          *         'ignoreMissingSource' => <boolean>
 217          *     )
 218          * @endcode
 219          *
 220          * f) Do nothing (no-op)
 221          * @code
 222          *     array(
 223          *         'op'                  => 'null',
 224          *     )
 225          * @endcode
 226          *
 227          * Boolean flags for operations (operation-specific):
 228          *   - ignoreMissingSource : The operation will simply succeed and do
 229          *                           nothing if the source file does not exist.
 230          *   - overwrite           : Any destination file will be overwritten.
 231          *   - overwriteSame       : An error will not be given if a file already
 232          *                           exists at the destination that has the same
 233          *                           contents as the new contents to be written there.
 234          *
 235          * $opts is an associative of boolean flags, including:
 236          *   - force               : Operation precondition errors no longer trigger an abort.
 237          *                           Any remaining operations are still attempted. Unexpected
 238          *                           failures may still cause remaning operations to be aborted.
 239          *   - nonLocking          : No locks are acquired for the operations.
 240          *                           This can increase performance for non-critical writes.
 241          *                           This has no effect unless the 'force' flag is set.
 242          *   - allowStale          : Don't require the latest available data.
 243          *                           This can increase performance for non-critical writes.
 244          *                           This has no effect unless the 'force' flag is set.
 245          *   - nonJournaled        : Don't log this operation batch in the file journal.
 246          *                           This limits the ability of recovery scripts.
 247          *   - parallelize         : Try to do operations in parallel when possible.
 248          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20).
 249          *
 250          * @remarks Remarks on locking:
 251          * File system paths given to operations should refer to files that are
 252          * already locked or otherwise safe from modification from other processes.
 253          * Normally these files will be new temp files, which should be adequate.
 254          *
 255          * @par Return value:
 256          *
 257          * This returns a Status, which contains all warnings and fatals that occured
 258          * during the operation. The 'failCount', 'successCount', and 'success' members
 259          * will reflect each operation attempted.
 260          *
 261          * The status will be "OK" unless:
 262          *     a) unexpected operation errors occurred (network partitions, disk full...)
 263          *     b) significant operation errors occured and 'force' was not set
 264          *
 265          * @param $ops Array List of operations to execute in order
 266          * @param $opts Array Batch operation options
 267          * @return Status
 268          */
 269         final public function doOperations( array $ops, array $opts = array() ) {
 270                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 271                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 272                 }
 273                 if ( empty( $opts['force'] ) ) { // sanity
 274                         unset( $opts['nonLocking'] );
 275                         unset( $opts['allowStale'] );
 276                 }
 277                 $opts['concurrency'] = 1; // off
 278                 if ( $this->parallelize === 'implicit' ) {
 279                         if ( !isset( $opts['parallelize'] ) || $opts['parallelize'] ) {
 280                                 $opts['concurrency'] = $this->concurrency;
 281                         }
 282                 } elseif ( $this->parallelize === 'explicit' ) {
 283                         if ( !empty( $opts['parallelize'] ) ) {
 284                                 $opts['concurrency'] = $this->concurrency;
 285                         }
 286                 }
 287                 return $this->doOperationsInternal( $ops, $opts );
 288         }
 289
 290         /**
 291          * @see FileBackend::doOperations()
 292          */
 293         abstract protected function doOperationsInternal( array $ops, array $opts );
 294
 295         /**
 296          * Same as doOperations() except it takes a single operation.
 297          * If you are doing a batch of operations that should either
 298          * all succeed or all fail, then use that function instead.
 299          *
 300          * @see FileBackend::doOperations()
 301          *
 302          * @param $op Array Operation
 303          * @param $opts Array Operation options
 304          * @return Status
 305          */
 306         final public function doOperation( array $op, array $opts = array() ) {
 307                 return $this->doOperations( array( $op ), $opts );
 308         }
 309
 310         /**
 311          * Performs a single create operation.
 312          * This sets $params['op'] to 'create' and passes it to doOperation().
 313          *
 314          * @see FileBackend::doOperation()
 315          *
 316          * @param $params Array Operation parameters
 317          * @param $opts Array Operation options
 318          * @return Status
 319          */
 320         final public function create( array $params, array $opts = array() ) {
 321                 return $this->doOperation( array( 'op' => 'create' ) + $params, $opts );
 322         }
 323
 324         /**
 325          * Performs a single store operation.
 326          * This sets $params['op'] to 'store' and passes it to doOperation().
 327          *
 328          * @see FileBackend::doOperation()
 329          *
 330          * @param $params Array Operation parameters
 331          * @param $opts Array Operation options
 332          * @return Status
 333          */
 334         final public function store( array $params, array $opts = array() ) {
 335                 return $this->doOperation( array( 'op' => 'store' ) + $params, $opts );
 336         }
 337
 338         /**
 339          * Performs a single copy operation.
 340          * This sets $params['op'] to 'copy' and passes it to doOperation().
 341          *
 342          * @see FileBackend::doOperation()
 343          *
 344          * @param $params Array Operation parameters
 345          * @param $opts Array Operation options
 346          * @return Status
 347          */
 348         final public function copy( array $params, array $opts = array() ) {
 349                 return $this->doOperation( array( 'op' => 'copy' ) + $params, $opts );
 350         }
 351
 352         /**
 353          * Performs a single move operation.
 354          * This sets $params['op'] to 'move' and passes it to doOperation().
 355          *
 356          * @see FileBackend::doOperation()
 357          *
 358          * @param $params Array Operation parameters
 359          * @param $opts Array Operation options
 360          * @return Status
 361          */
 362         final public function move( array $params, array $opts = array() ) {
 363                 return $this->doOperation( array( 'op' => 'move' ) + $params, $opts );
 364         }
 365
 366         /**
 367          * Performs a single delete operation.
 368          * This sets $params['op'] to 'delete' and passes it to doOperation().
 369          *
 370          * @see FileBackend::doOperation()
 371          *
 372          * @param $params Array Operation parameters
 373          * @param $opts Array Operation options
 374          * @return Status
 375          */
 376         final public function delete( array $params, array $opts = array() ) {
 377                 return $this->doOperation( array( 'op' => 'delete' ) + $params, $opts );
 378         }
 379
 380         /**
 381          * Perform a set of independent file operations on some files.
 382          *
 383          * This does no locking, nor journaling, and possibly no stat calls.
 384          * Any destination files that already exist will be overwritten.
 385          * This should *only* be used on non-original files, like cache files.
 386          *
 387          * Supported operations and their parameters:
 388          *  - create
 389          *  - store
 390          *  - copy
 391          *  - move
 392          *  - delete
 393          *  - null
 394          *
 395          * a) Create a new file in storage with the contents of a string
 396          * @code
 397          *     array(
 398          *         'op'                  => 'create',
 399          *         'dst'                 => <storage path>,
 400          *         'content'             => <string of new file contents>
 401          *     )
 402          * @endcode
 403          * b) Copy a file system file into storage
 404          * @code
 405          *     array(
 406          *         'op'                  => 'store',
 407          *         'src'                 => <file system path>,
 408          *         'dst'                 => <storage path>
 409          *     )
 410          * @endcode
 411          * c) Copy a file within storage
 412          * @code
 413          *     array(
 414          *         'op'                  => 'copy',
 415          *         'src'                 => <storage path>,
 416          *         'dst'                 => <storage path>
 417          *     )
 418          * @endcode
 419          * d) Move a file within storage
 420          * @code
 421          *     array(
 422          *         'op'                  => 'move',
 423          *         'src'                 => <storage path>,
 424          *         'dst'                 => <storage path>
 425          *     )
 426          * @endcode
 427          * e) Delete a file within storage
 428          * @code
 429          *     array(
 430          *         'op'                  => 'delete',
 431          *         'src'                 => <storage path>,
 432          *         'ignoreMissingSource' => <boolean>
 433          *     )
 434          * @endcode
 435          * f) Do nothing (no-op)
 436          * @code
 437          *     array(
 438          *         'op'                  => 'null',
 439          *     )
 440          * @endcode
 441          *
 442          * @par Boolean flags for operations (operation-specific):
 443          *   - ignoreMissingSource : The operation will simply succeed and do
 444          *                           nothing if the source file does not exist.
 445          *
 446          * $opts is an associative of boolean flags, including:
 447          *   - bypassReadOnly      : Allow writes in read-only mode (since 1.20)
 448          *
 449          * @par Return value:
 450          * This returns a Status, which contains all warnings and fatals that occured
 451          * during the operation. The 'failCount', 'successCount', and 'success' members
 452          * will reflect each operation attempted for the given files. The status will be
 453          * considered "OK" as long as no fatal errors occured.
 454          *
 455          * @param $ops Array Set of operations to execute
 456          * @param $opts Array Batch operation options
 457          * @return Status
 458          * @since 1.20
 459          */
 460         final public function doQuickOperations( array $ops, array $opts = array() ) {
 461                 if ( empty( $opts['bypassReadOnly'] ) && $this->isReadOnly() ) {
 462                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 463                 }
 464                 foreach ( $ops as &$op ) {
 465                         $op['overwrite'] = true; // avoids RTTs in key/value stores
 466                 }
 467                 return $this->doQuickOperationsInternal( $ops );
 468         }
 469
 470         /**
 471          * @see FileBackend::doQuickOperations()
 472          * @since 1.20
 473          */
 474         abstract protected function doQuickOperationsInternal( array $ops );
 475
 476         /**
 477          * Same as doQuickOperations() except it takes a single operation.
 478          * If you are doing a batch of operations, then use that function instead.
 479          *
 480          * @see FileBackend::doQuickOperations()
 481          *
 482          * @param $op Array Operation
 483          * @return Status
 484          * @since 1.20
 485          */
 486         final public function doQuickOperation( array $op ) {
 487                 return $this->doQuickOperations( array( $op ) );
 488         }
 489
 490         /**
 491          * Performs a single quick create operation.
 492          * This sets $params['op'] to 'create' and passes it to doQuickOperation().
 493          *
 494          * @see FileBackend::doQuickOperation()
 495          *
 496          * @param $params Array Operation parameters
 497          * @return Status
 498          * @since 1.20
 499          */
 500         final public function quickCreate( array $params ) {
 501                 return $this->doQuickOperation( array( 'op' => 'create' ) + $params );
 502         }
 503
 504         /**
 505          * Performs a single quick store operation.
 506          * This sets $params['op'] to 'store' and passes it to doQuickOperation().
 507          *
 508          * @see FileBackend::doQuickOperation()
 509          *
 510          * @param $params Array Operation parameters
 511          * @return Status
 512          * @since 1.20
 513          */
 514         final public function quickStore( array $params ) {
 515                 return $this->doQuickOperation( array( 'op' => 'store' ) + $params );
 516         }
 517
 518         /**
 519          * Performs a single quick copy operation.
 520          * This sets $params['op'] to 'copy' and passes it to doQuickOperation().
 521          *
 522          * @see FileBackend::doQuickOperation()
 523          *
 524          * @param $params Array Operation parameters
 525          * @return Status
 526          * @since 1.20
 527          */
 528         final public function quickCopy( array $params ) {
 529                 return $this->doQuickOperation( array( 'op' => 'copy' ) + $params );
 530         }
 531
 532         /**
 533          * Performs a single quick move operation.
 534          * This sets $params['op'] to 'move' and passes it to doQuickOperation().
 535          *
 536          * @see FileBackend::doQuickOperation()
 537          *
 538          * @param $params Array Operation parameters
 539          * @return Status
 540          * @since 1.20
 541          */
 542         final public function quickMove( array $params ) {
 543                 return $this->doQuickOperation( array( 'op' => 'move' ) + $params );
 544         }
 545
 546         /**
 547          * Performs a single quick delete operation.
 548          * This sets $params['op'] to 'delete' and passes it to doQuickOperation().
 549          *
 550          * @see FileBackend::doQuickOperation()
 551          *
 552          * @param $params Array Operation parameters
 553          * @return Status
 554          * @since 1.20
 555          */
 556         final public function quickDelete( array $params ) {
 557                 return $this->doQuickOperation( array( 'op' => 'delete' ) + $params );
 558         }
 559
 560         /**
 561          * Concatenate a list of storage files into a single file system file.
 562          * The target path should refer to a file that is already locked or
 563          * otherwise safe from modification from other processes. Normally,
 564          * the file will be a new temp file, which should be adequate.
 565          *
 566          * @param $params Array Operation parameters
 567          * $params include:
 568          *   - srcs : ordered source storage paths (e.g. chunk1, chunk2, ...)
 569          *   - dst  : file system path to 0-byte temp file
 570          * @return Status
 571          */
 572         abstract public function concatenate( array $params );
 573
 574         /**
 575          * Prepare a storage directory for usage.
 576          * This will create any required containers and parent directories.
 577          * Backends using key/value stores only need to create the container.
 578          *
 579          * The 'noAccess' and 'noListing' parameters works the same as in secure(),
 580          * except they are only applied *if* the directory/container had to be created.
 581          * These flags should always be set for directories that have private files.
 582          *
 583          * $params include:
 584          *   - dir            : storage directory
 585          *   - noAccess       : try to deny file access (since 1.20)
 586          *   - noListing      : try to deny file listing (since 1.20)
 587          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 588          *
 589          * @param $params Array
 590          * @return Status
 591          */
 592         final public function prepare( array $params ) {
 593                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 594                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 595                 }
 596                 return $this->doPrepare( $params );
 597         }
 598
 599         /**
 600          * @see FileBackend::prepare()
 601          */
 602         abstract protected function doPrepare( array $params );
 603
 604         /**
 605          * Take measures to block web access to a storage directory and
 606          * the container it belongs to. FS backends might add .htaccess
 607          * files whereas key/value store backends might revoke container
 608          * access to the storage user representing end-users in web requests.
 609          * This is not guaranteed to actually do anything.
 610          *
 611          * @param $params Array
 612          * $params include:
 613          *   - dir            : storage directory
 614          *   - noAccess       : try to deny file access
 615          *   - noListing      : try to deny file listing
 616          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 617          * @return Status
 618          */
 619         final public function secure( array $params ) {
 620                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 621                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 622                 }
 623                 return $this->doSecure( $params );
 624         }
 625
 626         /**
 627          * @see FileBackend::secure()
 628          */
 629         abstract protected function doSecure( array $params );
 630
 631         /**
 632          * Remove measures to block web access to a storage directory and
 633          * the container it belongs to. FS backends might remove .htaccess
 634          * files whereas key/value store backends might grant container
 635          * access to the storage user representing end-users in web requests.
 636          * This essentially can undo the result of secure() calls.
 637          *
 638          * $params include:
 639          *   - dir            : storage directory
 640          *   - access         : try to allow file access
 641          *   - listing        : try to allow file listing
 642          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 643          *
 644          * @param $params Array
 645          * @return Status
 646          * @since 1.20
 647          */
 648         final public function publish( array $params ) {
 649                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 650                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 651                 }
 652                 return $this->doPublish( $params );
 653         }
 654
 655         /**
 656          * @see FileBackend::publish()
 657          */
 658         abstract protected function doPublish( array $params );
 659
 660         /**
 661          * Delete a storage directory if it is empty.
 662          * Backends using key/value stores may do nothing unless the directory
 663          * is that of an empty container, in which case it should be deleted.
 664          *
 665          * @param $params Array
 666          * $params include:
 667          *   - dir            : storage directory
 668          *   - recursive      : recursively delete empty subdirectories first (since 1.20)
 669          *   - bypassReadOnly : allow writes in read-only mode (since 1.20)
 670          * @return Status
 671          */
 672         final public function clean( array $params ) {
 673                 if ( empty( $params['bypassReadOnly'] ) && $this->isReadOnly() ) {
 674                         return Status::newFatal( 'backend-fail-readonly', $this->name, $this->readOnly );
 675                 }
 676                 return $this->doClean( $params );
 677         }
 678
 679         /**
 680          * @see FileBackend::clean()
 681          */
 682         abstract protected function doClean( array $params );
 683
 684         /**
 685          * Check if a file exists at a storage path in the backend.
 686          * This returns false if only a directory exists at the path.
 687          *
 688          * @param $params Array
 689          * $params include:
 690          *   - src    : source storage path
 691          *   - latest : use the latest available data
 692          * @return bool|null Returns null on failure
 693          */
 694         abstract public function fileExists( array $params );
 695
 696         /**
 697          * Get the last-modified timestamp of the file at a storage path.
 698          *
 699          * @param $params Array
 700          * $params include:
 701          *   - src    : source storage path
 702          *   - latest : use the latest available data
 703          * @return string|bool TS_MW timestamp or false on failure
 704          */
 705         abstract public function getFileTimestamp( array $params );
 706
 707         /**
 708          * Get the contents of a file at a storage path in the backend.
 709          * This should be avoided for potentially large files.
 710          *
 711          * @param $params Array
 712          * $params include:
 713          *   - src    : source storage path
 714          *   - latest : use the latest available data
 715          * @return string|bool Returns false on failure
 716          */
 717         abstract public function getFileContents( array $params );
 718
 719         /**
 720          * Get the size (bytes) of a file at a storage path in the backend.
 721          *
 722          * @param $params Array
 723          * $params include:
 724          *   - src    : source storage path
 725          *   - latest : use the latest available data
 726          * @return integer|bool Returns false on failure
 727          */
 728         abstract public function getFileSize( array $params );
 729
 730         /**
 731          * Get quick information about a file at a storage path in the backend.
 732          * If the file does not exist, then this returns false.
 733          * Otherwise, the result is an associative array that includes:
 734          *   - mtime  : the last-modified timestamp (TS_MW)
 735          *   - size   : the file size (bytes)
 736          * Additional values may be included for internal use only.
 737          *
 738          * @param $params Array
 739          * $params include:
 740          *   - src    : source storage path
 741          *   - latest : use the latest available data
 742          * @return Array|bool|null Returns null on failure
 743          */
 744         abstract public function getFileStat( array $params );
 745
 746         /**
 747          * Get a SHA-1 hash of the file at a storage path in the backend.
 748          *
 749          * @param $params Array
 750          * $params include:
 751          *   - src    : source storage path
 752          *   - latest : use the latest available data
 753          * @return string|bool Hash string or false on failure
 754          */
 755         abstract public function getFileSha1Base36( array $params );
 756
 757         /**
 758          * Get the properties of the file at a storage path in the backend.
 759          * Returns FSFile::placeholderProps() on failure.
 760          *
 761          * @param $params Array
 762          * $params include:
 763          *   - src    : source storage path
 764          *   - latest : use the latest available data
 765          * @return Array
 766          */
 767         abstract public function getFileProps( array $params );
 768
 769         /**
 770          * Stream the file at a storage path in the backend.
 771          * If the file does not exists, a 404 error will be given.
 772          * Appropriate HTTP headers (Status, Content-Type, Content-Length)
 773          * must be sent if streaming began, while none should be sent otherwise.
 774          * Implementations should flush the output buffer before sending data.
 775          *
 776          * @param $params Array
 777          * $params include:
 778          *   - src     : source storage path
 779          *   - headers : additional HTTP headers to send on success
 780          *   - latest  : use the latest available data
 781          * @return Status
 782          */
 783         abstract public function streamFile( array $params );
 784
 785         /**
 786          * Returns a file system file, identical to the file at a storage path.
 787          * The file returned is either:
 788          * a) A local copy of the file at a storage path in the backend.
 789          *    The temporary copy will have the same extension as the source.
 790          * b) An original of the file at a storage path in the backend.
 791          * Temporary files may be purged when the file object falls out of scope.
 792          *
 793          * Write operations should *never* be done on this file as some backends
 794          * may do internal tracking or may be instances of FileBackendMultiWrite.
 795          * In that later case, there are copies of the file that must stay in sync.
 796          * Additionally, further calls to this function may return the same file.
 797          *
 798          * @param $params Array
 799          * $params include:
 800          *   - src    : source storage path
 801          *   - latest : use the latest available data
 802          * @return FSFile|null Returns null on failure
 803          */
 804         abstract public function getLocalReference( array $params );
 805
 806         /**
 807          * Get a local copy on disk of the file at a storage path in the backend.
 808          * The temporary copy will have the same file extension as the source.
 809          * Temporary files may be purged when the file object falls out of scope.
 810          *
 811          * @param $params Array
 812          * $params include:
 813          *   - src    : source storage path
 814          *   - latest : use the latest available data
 815          * @return TempFSFile|null Returns null on failure
 816          */
 817         abstract public function getLocalCopy( array $params );
 818
 819         /**
 820          * Check if a directory exists at a given storage path.
 821          * Backends using key/value stores will check if the path is a
 822          * virtual directory, meaning there are files under the given directory.
 823          *
 824          * Storage backends with eventual consistency might return stale data.
 825          *
 826          * @param $params array
 827          * $params include:
 828          *   - dir : storage directory
 829          * @return bool|null Returns null on failure
 830          * @since 1.20
 831          */
 832         abstract public function directoryExists( array $params );
 833
 834         /**
 835          * Get an iterator to list *all* directories under a storage directory.
 836          * If the directory is of the form "mwstore://backend/container",
 837          * then all directories in the container should be listed.
 838          * If the directory is of form "mwstore://backend/container/dir",
 839          * then all directories directly under that directory should be listed.
 840          * Results should be storage directories relative to the given directory.
 841          *
 842          * Storage backends with eventual consistency might return stale data.
 843          *
 844          * @param $params array
 845          * $params include:
 846          *   - dir     : storage directory
 847          *   - topOnly : only return direct child dirs of the directory
 848          * @return Traversable|Array|null Returns null on failure
 849          * @since 1.20
 850          */
 851         abstract public function getDirectoryList( array $params );
 852
 853         /**
 854          * Same as FileBackend::getDirectoryList() except only lists
 855          * directories that are immediately under the given directory.
 856          *
 857          * Storage backends with eventual consistency might return stale data.
 858          *
 859          * @param $params array
 860          * $params include:
 861          *   - dir : storage directory
 862          * @return Traversable|Array|null Returns null on failure
 863          * @since 1.20
 864          */
 865         final public function getTopDirectoryList( array $params ) {
 866                 return $this->getDirectoryList( array( 'topOnly' => true ) + $params );
 867         }
 868
 869         /**
 870          * Get an iterator to list *all* stored files under a storage directory.
 871          * If the directory is of the form "mwstore://backend/container",
 872          * then all files in the container should be listed.
 873          * If the directory is of form "mwstore://backend/container/dir",
 874          * then all files under that directory should be listed.
 875          * Results should be storage paths relative to the given directory.
 876          *
 877          * Storage backends with eventual consistency might return stale data.
 878          *
 879          * @param $params array
 880          * $params include:
 881          *   - dir     : storage directory
 882          *   - topOnly : only return direct child files of the directory (since 1.20)
 883          * @return Traversable|Array|null Returns null on failure
 884          */
 885         abstract public function getFileList( array $params );
 886
 887         /**
 888          * Same as FileBackend::getFileList() except only lists
 889          * files that are immediately under the given directory.
 890          *
 891          * Storage backends with eventual consistency might return stale data.
 892          *
 893          * @param $params array
 894          * $params include:
 895          *   - dir : storage directory
 896          * @return Traversable|Array|null Returns null on failure
 897          * @since 1.20
 898          */
 899         final public function getTopFileList( array $params ) {
 900                 return $this->getFileList( array( 'topOnly' => true ) + $params );
 901         }
 902
 903         /**
 904          * Invalidate any in-process file existence and property cache.
 905          * If $paths is given, then only the cache for those files will be cleared.
 906          *
 907          * @param $paths Array Storage paths (optional)
 908          * @return void
 909          */
 910         public function clearCache( array $paths = null ) {}
 911
 912         /**
 913          * Lock the files at the given storage paths in the backend.
 914          * This will either lock all the files or none (on failure).
 915          *
 916          * Callers should consider using getScopedFileLocks() instead.
 917          *
 918          * @param $paths Array Storage paths
 919          * @param $type integer LockManager::LOCK_* constant
 920          * @return Status
 921          */
 922         final public function lockFiles( array $paths, $type ) {
 923                 return $this->lockManager->lock( $paths, $type );
 924         }
 925
 926         /**
 927          * Unlock the files at the given storage paths in the backend.
 928          *
 929          * @param $paths Array Storage paths
 930          * @param $type integer LockManager::LOCK_* constant
 931          * @return Status
 932          */
 933         final public function unlockFiles( array $paths, $type ) {
 934                 return $this->lockManager->unlock( $paths, $type );
 935         }
 936
 937         /**
 938          * Lock the files at the given storage paths in the backend.
 939          * This will either lock all the files or none (on failure).
 940          * On failure, the status object will be updated with errors.
 941          *
 942          * Once the return value goes out scope, the locks will be released and
 943          * the status updated. Unlock fatals will not change the status "OK" value.
 944          *
 945          * @param $paths Array Storage paths
 946          * @param $type integer LockManager::LOCK_* constant
 947          * @param $status Status Status to update on lock/unlock
 948          * @return ScopedLock|null Returns null on failure
 949          */
 950         final public function getScopedFileLocks( array $paths, $type, Status $status ) {
 951                 return ScopedLock::factory( $this->lockManager, $paths, $type, $status );
 952         }
 953
 954         /**
 955          * Get an array of scoped locks needed for a batch of file operations.
 956          *
 957          * Normally, FileBackend::doOperations() handles locking, unless
 958          * the 'nonLocking' param is passed in. This function is useful if you
 959          * want the files to be locked for a broader scope than just when the
 960          * files are changing. For example, if you need to update DB metadata,
 961          * you may want to keep the files locked until finished.
 962          *
 963          * @see FileBackend::doOperations()
 964          *
 965          * @param $ops Array List of file operations to FileBackend::doOperations()
 966          * @param $status Status Status to update on lock/unlock
 967          * @return Array List of ScopedFileLocks or null values
 968          * @since 1.20
 969          */
 970         abstract public function getScopedLocksForOps( array $ops, Status $status );
 971
 972         /**
 973          * Get the root storage path of this backend.
 974          * All container paths are "subdirectories" of this path.
 975          *
 976          * @return string Storage path
 977          * @since 1.20
 978          */
 979         final public function getRootStoragePath() {
 980                 return "mwstore://{$this->name}";
 981         }
 982
 983         /**
 984          * Get the file journal object for this backend
 985          *
 986          * @return FileJournal
 987          */
 988         final public function getJournal() {
 989                 return $this->fileJournal;
 990         }
 991
 992         /**
 993          * Check if a given path is a "mwstore://" path.
 994          * This does not do any further validation or any existence checks.
 995          *
 996          * @param $path string
 997          * @return bool
 998          */
 999         final public static function isStoragePath( $path ) {
1000                 return ( strpos( $path, 'mwstore://' ) === 0 );
1001         }
1002
1003         /**
1004          * Split a storage path into a backend name, a container name,
1005          * and a relative file path. The relative path may be the empty string.
1006          * This does not do any path normalization or traversal checks.
1007          *
1008          * @param $storagePath string
1009          * @return Array (backend, container, rel object) or (null, null, null)
1010          */
1011         final public static function splitStoragePath( $storagePath ) {
1012                 if ( self::isStoragePath( $storagePath ) ) {
1013                         // Remove the "mwstore://" prefix and split the path
1014                         $parts = explode( '/', substr( $storagePath, 10 ), 3 );
1015                         if ( count( $parts ) >= 2 && $parts[0] != '' && $parts[1] != '' ) {
1016                                 if ( count( $parts ) == 3 ) {
1017                                         return $parts; // e.g. "backend/container/path"
1018                                 } else {
1019                                         return array( $parts[0], $parts[1], '' ); // e.g. "backend/container"
1020                                 }
1021                         }
1022                 }
1023                 return array( null, null, null );
1024         }
1025
1026         /**
1027          * Normalize a storage path by cleaning up directory separators.
1028          * Returns null if the path is not of the format of a valid storage path.
1029          *
1030          * @param $storagePath string
1031          * @return string|null
1032          */
1033         final public static function normalizeStoragePath( $storagePath ) {
1034                 list( $backend, $container, $relPath ) = self::splitStoragePath( $storagePath );
1035                 if ( $relPath !== null ) { // must be for this backend
1036                         $relPath = self::normalizeContainerPath( $relPath );
1037                         if ( $relPath !== null ) {
1038                                 return ( $relPath != '' )
1039                                         ? "mwstore://{$backend}/{$container}/{$relPath}"
1040                                         : "mwstore://{$backend}/{$container}";
1041                         }
1042                 }
1043                 return null;
1044         }
1045
1046         /**
1047          * Get the parent storage directory of a storage path.
1048          * This returns a path like "mwstore://backend/container",
1049          * "mwstore://backend/container/...", or null if there is no parent.
1050          *
1051          * @param $storagePath string
1052          * @return string|null
1053          */
1054         final public static function parentStoragePath( $storagePath ) {
1055                 $storagePath = dirname( $storagePath );
1056                 list( $b, $cont, $rel ) = self::splitStoragePath( $storagePath );
1057                 return ( $rel === null ) ? null : $storagePath;
1058         }
1059
1060         /**
1061          * Get the final extension from a storage or FS path
1062          *
1063          * @param $path string
1064          * @return string
1065          */
1066         final public static function extensionFromPath( $path ) {
1067                 $i = strrpos( $path, '.' );
1068                 return strtolower( $i ? substr( $path, $i + 1 ) : '' );
1069         }
1070
1071         /**
1072          * Check if a relative path has no directory traversals
1073          *
1074          * @param $path string
1075          * @return bool
1076          * @since 1.20
1077          */
1078         final public static function isPathTraversalFree( $path ) {
1079                 return ( self::normalizeContainerPath( $path ) !== null );
1080         }
1081
1082         /**
1083          * Validate and normalize a relative storage path.
1084          * Null is returned if the path involves directory traversal.
1085          * Traversal is insecure for FS backends and broken for others.
1086          *
1087          * This uses the same traversal protection as Title::secureAndSplit().
1088          *
1089          * @param $path string Storage path relative to a container
1090          * @return string|null
1091          */
1092         final protected static function normalizeContainerPath( $path ) {
1093                 // Normalize directory separators
1094                 $path = strtr( $path, '\\', '/' );
1095                 // Collapse any consecutive directory separators
1096                 $path = preg_replace( '![/]{2,}!', '/', $path );
1097                 // Remove any leading directory separator
1098                 $path = ltrim( $path, '/' );
1099                 // Use the same traversal protection as Title::secureAndSplit()
1100                 if ( strpos( $path, '.' ) !== false ) {
1101                         if (
1102                                 $path === '.' ||
1103                                 $path === '..' ||
1104                                 strpos( $path, './' ) === 0 ||
1105                                 strpos( $path, '../' ) === 0 ||
1106                                 strpos( $path, '/./' ) !== false ||
1107                                 strpos( $path, '/../' ) !== false
1108                         ) {
1109                                 return null;
1110                         }
1111                 }
1112                 return $path;
1113         }
1114 }