SwiftFileBackend.php

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<?php
class SwiftFileBackend extends FileBackendStore {
    protected $http;

    protected $authTTL;

    protected $swiftAuthUrl;

    protected $swiftUser;

    protected $swiftKey;

    protected $swiftTempUrlKey;

    protected $rgwS3AccessKey;

    protected $rgwS3SecretKey;

    protected $srvCache;

    protected $containerStatCache;

    protected $authCreds;

    protected $authSessionTimestamp = 0;

    protected $authErrorTimestamp = null;

    protected $isRGW = false;

    public function __construct( array $config ) {
        parent::__construct( $config );
        // Required settings
        $this->swiftAuthUrl = $config['swiftAuthUrl'];
        $this->swiftUser = $config['swiftUser'];
        $this->swiftKey = $config['swiftKey'];
        // Optional settings
        $this->authTTL = isset( $config['swiftAuthTTL'] )
            ? $config['swiftAuthTTL']
            : 15 * 60; // some sane number
        $this->swiftTempUrlKey = isset( $config['swiftTempUrlKey'] )
            ? $config['swiftTempUrlKey']
            : '';
        $this->shardViaHashLevels = isset( $config['shardViaHashLevels'] )
            ? $config['shardViaHashLevels']
            : '';
        $this->rgwS3AccessKey = isset( $config['rgwS3AccessKey'] )
            ? $config['rgwS3AccessKey']
            : '';
        $this->rgwS3SecretKey = isset( $config['rgwS3SecretKey'] )
            ? $config['rgwS3SecretKey']
            : '';
        // HTTP helper client
        $this->http = new MultiHttpClient( [] );
        // Cache container information to mask latency
        if ( isset( $config['wanCache'] ) && $config['wanCache'] instanceof WANObjectCache ) {
            $this->memCache = $config['wanCache'];
        }
        // Process cache for container info
        $this->containerStatCache = new ProcessCacheLRU( 300 );
        // Cache auth token information to avoid RTTs
        if ( !empty( $config['cacheAuthInfo'] ) && isset( $config['srvCache'] ) ) {
            $this->srvCache = $config['srvCache'];
        } else {
            $this->srvCache = new EmptyBagOStuff();
        }
    }

    public function getFeatures() {
        return ( FileBackend::ATTR_UNICODE_PATHS |
            FileBackend::ATTR_HEADERS | FileBackend::ATTR_METADATA );
    }

    protected function resolveContainerPath( $container, $relStoragePath ) {
        if ( !mb_check_encoding( $relStoragePath, 'UTF-8' ) ) {
            return null; // not UTF-8, makes it hard to use CF and the swift HTTP API
        } elseif ( strlen( urlencode( $relStoragePath ) ) > 1024 ) {
            return null; // too long for Swift
        }

        return $relStoragePath;
    }

    public function isPathUsableInternal( $storagePath ) {
        list( $container, $rel ) = $this->resolveStoragePathReal( $storagePath );
        if ( $rel === null ) {
            return false; // invalid
        }

        return is_array( $this->getContainerStat( $container ) );
    }

    protected function sanitizeHdrs( array $params ) {
        return isset( $params['headers'] )
            ? $this->getCustomHeaders( $params['headers'] )
            : [];

    }

    protected function getCustomHeaders( array $rawHeaders ) {
        $headers = [];

        // Normalize casing, and strip out illegal headers
        foreach ( $rawHeaders as $name => $value ) {
            $name = strtolower( $name );
            if ( preg_match( '/^content-(type|length)$/', $name ) ) {
                continue; // blacklisted
            } elseif ( preg_match( '/^(x-)?content-/', $name ) ) {
                $headers[$name] = $value; // allowed
            } elseif ( preg_match( '/^content-(disposition)/', $name ) ) {
                $headers[$name] = $value; // allowed
            }
        }
        // By default, Swift has annoyingly low maximum header value limits
        if ( isset( $headers['content-disposition'] ) ) {
            $disposition = '';
            // @note: assume FileBackend::makeContentDisposition() already used
            foreach ( explode( ';', $headers['content-disposition'] ) as $part ) {
                $part = trim( $part );
                $new = ( $disposition === '' ) ? $part : "{$disposition};{$part}";
                if ( strlen( $new ) <= 255 ) {
                    $disposition = $new;
                } else {
                    break; // too long; sigh
                }
            }
            $headers['content-disposition'] = $disposition;
        }

        return $headers;
    }

    protected function getMetadataHeaders( array $rawHeaders ) {
        $headers = [];
        foreach ( $rawHeaders as $name => $value ) {
            $name = strtolower( $name );
            if ( strpos( $name, 'x-object-meta-' ) === 0 ) {
                $headers[$name] = $value;
            }
        }

        return $headers;
    }

    protected function getMetadata( array $rawHeaders ) {
        $metadata = [];
        foreach ( $this->getMetadataHeaders( $rawHeaders ) as $name => $value ) {
            $metadata[substr( $name, strlen( 'x-object-meta-' ) )] = $value;
        }

        return $metadata;
    }

    protected function doCreateInternal( array $params ) {
        $status = $this->newStatus();

        list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
        if ( $dstRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['dst'] );

            return $status;
        }

        $sha1Hash = Wikimedia\base_convert( sha1( $params['content'] ), 16, 36, 31 );
        $contentType = isset( $params['headers']['content-type'] )
            ? $params['headers']['content-type']
            : $this->getContentType( $params['dst'], $params['content'], null );

        $reqs = [ [
            'method' => 'PUT',
            'url' => [ $dstCont, $dstRel ],
            'headers' => [
                'content-length' => strlen( $params['content'] ),
                'etag' => md5( $params['content'] ),
                'content-type' => $contentType,
                'x-object-meta-sha1base36' => $sha1Hash
            ] + $this->sanitizeHdrs( $params ),
            'body' => $params['content']
        ] ];

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $rcode === 201 ) {
                // good
            } elseif ( $rcode === 412 ) {
                $status->fatal( 'backend-fail-contenttype', $params['dst'] );
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually write the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doStoreInternal( array $params ) {
        $status = $this->newStatus();

        list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
        if ( $dstRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['dst'] );

            return $status;
        }

        MediaWiki\suppressWarnings();
        $sha1Hash = sha1_file( $params['src'] );
        MediaWiki\restoreWarnings();
        if ( $sha1Hash === false ) { // source doesn't exist?
            $status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );

            return $status;
        }
        $sha1Hash = Wikimedia\base_convert( $sha1Hash, 16, 36, 31 );
        $contentType = isset( $params['headers']['content-type'] )
            ? $params['headers']['content-type']
            : $this->getContentType( $params['dst'], null, $params['src'] );

        $handle = fopen( $params['src'], 'rb' );
        if ( $handle === false ) { // source doesn't exist?
            $status->fatal( 'backend-fail-store', $params['src'], $params['dst'] );

            return $status;
        }

        $reqs = [ [
            'method' => 'PUT',
            'url' => [ $dstCont, $dstRel ],
            'headers' => [
                'content-length' => filesize( $params['src'] ),
                'etag' => md5_file( $params['src'] ),
                'content-type' => $contentType,
                'x-object-meta-sha1base36' => $sha1Hash
            ] + $this->sanitizeHdrs( $params ),
            'body' => $handle // resource
        ] ];

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $rcode === 201 ) {
                // good
            } elseif ( $rcode === 412 ) {
                $status->fatal( 'backend-fail-contenttype', $params['dst'] );
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually write the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doCopyInternal( array $params ) {
        $status = $this->newStatus();

        list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
        if ( $srcRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['src'] );

            return $status;
        }

        list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
        if ( $dstRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['dst'] );

            return $status;
        }

        $reqs = [ [
            'method' => 'PUT',
            'url' => [ $dstCont, $dstRel ],
            'headers' => [
                'x-copy-from' => '/' . rawurlencode( $srcCont ) .
                    '/' . str_replace( "%2F", "/", rawurlencode( $srcRel ) )
            ] + $this->sanitizeHdrs( $params ), // extra headers merged into object
        ] ];

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $rcode === 201 ) {
                // good
            } elseif ( $rcode === 404 ) {
                $status->fatal( 'backend-fail-copy', $params['src'], $params['dst'] );
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually write the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doMoveInternal( array $params ) {
        $status = $this->newStatus();

        list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
        if ( $srcRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['src'] );

            return $status;
        }

        list( $dstCont, $dstRel ) = $this->resolveStoragePathReal( $params['dst'] );
        if ( $dstRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['dst'] );

            return $status;
        }

        $reqs = [
            [
                'method' => 'PUT',
                'url' => [ $dstCont, $dstRel ],
                'headers' => [
                    'x-copy-from' => '/' . rawurlencode( $srcCont ) .
                        '/' . str_replace( "%2F", "/", rawurlencode( $srcRel ) )
                ] + $this->sanitizeHdrs( $params ) // extra headers merged into object
            ]
        ];
        if ( "{$srcCont}/{$srcRel}" !== "{$dstCont}/{$dstRel}" ) {
            $reqs[] = [
                'method' => 'DELETE',
                'url' => [ $srcCont, $srcRel ],
                'headers' => []
            ];
        }

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $request['method'] === 'PUT' && $rcode === 201 ) {
                // good
            } elseif ( $request['method'] === 'DELETE' && $rcode === 204 ) {
                // good
            } elseif ( $rcode === 404 ) {
                $status->fatal( 'backend-fail-move', $params['src'], $params['dst'] );
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually move the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doDeleteInternal( array $params ) {
        $status = $this->newStatus();

        list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
        if ( $srcRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['src'] );

            return $status;
        }

        $reqs = [ [
            'method' => 'DELETE',
            'url' => [ $srcCont, $srcRel ],
            'headers' => []
        ] ];

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $rcode === 204 ) {
                // good
            } elseif ( $rcode === 404 ) {
                if ( empty( $params['ignoreMissingSource'] ) ) {
                    $status->fatal( 'backend-fail-delete', $params['src'] );
                }
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually delete the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doDescribeInternal( array $params ) {
        $status = $this->newStatus();

        list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
        if ( $srcRel === null ) {
            $status->fatal( 'backend-fail-invalidpath', $params['src'] );

            return $status;
        }

        // Fetch the old object headers/metadata...this should be in stat cache by now
        $stat = $this->getFileStat( [ 'src' => $params['src'], 'latest' => 1 ] );
        if ( $stat && !isset( $stat['xattr'] ) ) { // older cache entry
            $stat = $this->doGetFileStat( [ 'src' => $params['src'], 'latest' => 1 ] );
        }
        if ( !$stat ) {
            $status->fatal( 'backend-fail-describe', $params['src'] );

            return $status;
        }

        // POST clears prior headers, so we need to merge the changes in to the old ones
        $metaHdrs = [];
        foreach ( $stat['xattr']['metadata'] as $name => $value ) {
            $metaHdrs["x-object-meta-$name"] = $value;
        }
        $customHdrs = $this->sanitizeHdrs( $params ) + $stat['xattr']['headers'];

        $reqs = [ [
            'method' => 'POST',
            'url' => [ $srcCont, $srcRel ],
            'headers' => $metaHdrs + $customHdrs
        ] ];

        $method = __METHOD__;
        $handler = function ( array $request, StatusValue $status ) use ( $method, $params ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $request['response'];
            if ( $rcode === 202 ) {
                // good
            } elseif ( $rcode === 404 ) {
                $status->fatal( 'backend-fail-describe', $params['src'] );
            } else {
                $this->onError( $status, $method, $params, $rerr, $rcode, $rdesc );
            }
        };

        $opHandle = new SwiftFileOpHandle( $this, $handler, $reqs );
        if ( !empty( $params['async'] ) ) { // deferred
            $status->value = $opHandle;
        } else { // actually change the object in Swift
            $status->merge( current( $this->doExecuteOpHandlesInternal( [ $opHandle ] ) ) );
        }

        return $status;
    }

    protected function doPrepareInternal( $fullCont, $dir, array $params ) {
        $status = $this->newStatus();

        // (a) Check if container already exists
        $stat = $this->getContainerStat( $fullCont );
        if ( is_array( $stat ) ) {
            return $status; // already there
        } elseif ( $stat === null ) {
            $status->fatal( 'backend-fail-internal', $this->name );
            $this->logger->error( __METHOD__ . ': cannot get container stat' );

            return $status;
        }

        // (b) Create container as needed with proper ACLs
        if ( $stat === false ) {
            $params['op'] = 'prepare';
            $status->merge( $this->createContainer( $fullCont, $params ) );
        }

        return $status;
    }

    protected function doSecureInternal( $fullCont, $dir, array $params ) {
        $status = $this->newStatus();
        if ( empty( $params['noAccess'] ) ) {
            return $status; // nothing to do
        }

        $stat = $this->getContainerStat( $fullCont );
        if ( is_array( $stat ) ) {
            // Make container private to end-users...
            $status->merge( $this->setContainerAccess(
                $fullCont,
                [ $this->swiftUser ], // read
                [ $this->swiftUser ] // write
            ) );
        } elseif ( $stat === false ) {
            $status->fatal( 'backend-fail-usable', $params['dir'] );
        } else {
            $status->fatal( 'backend-fail-internal', $this->name );
            $this->logger->error( __METHOD__ . ': cannot get container stat' );
        }

        return $status;
    }

    protected function doPublishInternal( $fullCont, $dir, array $params ) {
        $status = $this->newStatus();

        $stat = $this->getContainerStat( $fullCont );
        if ( is_array( $stat ) ) {
            // Make container public to end-users...
            $status->merge( $this->setContainerAccess(
                $fullCont,
                [ $this->swiftUser, '.r:*' ], // read
                [ $this->swiftUser ] // write
            ) );
        } elseif ( $stat === false ) {
            $status->fatal( 'backend-fail-usable', $params['dir'] );
        } else {
            $status->fatal( 'backend-fail-internal', $this->name );
            $this->logger->error( __METHOD__ . ': cannot get container stat' );
        }

        return $status;
    }

    protected function doCleanInternal( $fullCont, $dir, array $params ) {
        $status = $this->newStatus();

        // Only containers themselves can be removed, all else is virtual
        if ( $dir != '' ) {
            return $status; // nothing to do
        }

        // (a) Check the container
        $stat = $this->getContainerStat( $fullCont, true );
        if ( $stat === false ) {
            return $status; // ok, nothing to do
        } elseif ( !is_array( $stat ) ) {
            $status->fatal( 'backend-fail-internal', $this->name );
            $this->logger->error( __METHOD__ . ': cannot get container stat' );

            return $status;
        }

        // (b) Delete the container if empty
        if ( $stat['count'] == 0 ) {
            $params['op'] = 'clean';
            $status->merge( $this->deleteContainer( $fullCont, $params ) );
        }

        return $status;
    }

    protected function doGetFileStat( array $params ) {
        $params = [ 'srcs' => [ $params['src'] ], 'concurrency' => 1 ] + $params;
        unset( $params['src'] );
        $stats = $this->doGetFileStatMulti( $params );

        return reset( $stats );
    }

    protected function convertSwiftDate( $ts, $format = TS_MW ) {
        try {
            $timestamp = new MWTimestamp( $ts );

            return $timestamp->getTimestamp( $format );
        } catch ( Exception $e ) {
            throw new FileBackendError( $e->getMessage() );
        }
    }

    protected function addMissingMetadata( array $objHdrs, $path ) {
        if ( isset( $objHdrs['x-object-meta-sha1base36'] ) ) {
            return $objHdrs; // nothing to do
        }

        $ps = $this->scopedProfileSection( __METHOD__ . "-{$this->name}" );
        $this->logger->error( __METHOD__ . ": $path was not stored with SHA-1 metadata." );

        $objHdrs['x-object-meta-sha1base36'] = false;

        $auth = $this->getAuthentication();
        if ( !$auth ) {
            return $objHdrs; // failed
        }

        // Find prior custom HTTP headers
        $postHeaders = $this->getCustomHeaders( $objHdrs );
        // Find prior metadata headers
        $postHeaders += $this->getMetadataHeaders( $objHdrs );

        $status = $this->newStatus();
        $scopeLockS = $this->getScopedFileLocks( [ $path ], LockManager::LOCK_UW, $status );
        if ( $status->isOK() ) {
            $tmpFile = $this->getLocalCopy( [ 'src' => $path, 'latest' => 1 ] );
            if ( $tmpFile ) {
                $hash = $tmpFile->getSha1Base36();
                if ( $hash !== false ) {
                    $objHdrs['x-object-meta-sha1base36'] = $hash;
                    // Merge new SHA1 header into the old ones
                    $postHeaders['x-object-meta-sha1base36'] = $hash;
                    list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $path );
                    list( $rcode ) = $this->http->run( [
                        'method' => 'POST',
                        'url' => $this->storageUrl( $auth, $srcCont, $srcRel ),
                        'headers' => $this->authTokenHeaders( $auth ) + $postHeaders
                    ] );
                    if ( $rcode >= 200 && $rcode <= 299 ) {
                        $this->deleteFileCache( $path );

                        return $objHdrs; // success
                    }
                }
            }
        }

        $this->logger->error( __METHOD__ . ": unable to set SHA-1 metadata for $path" );

        return $objHdrs; // failed
    }

    protected function doGetFileContentsMulti( array $params ) {
        $contents = [];

        $auth = $this->getAuthentication();

        $ep = array_diff_key( $params, [ 'srcs' => 1 ] ); // for error logging
        // Blindly create tmp files and stream to them, catching any exception if the file does
        // not exist. Doing stats here is useless and will loop infinitely in addMissingMetadata().
        $reqs = []; // (path => op)

        foreach ( $params['srcs'] as $path ) { // each path in this concurrent batch
            list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $path );
            if ( $srcRel === null || !$auth ) {
                $contents[$path] = false;
                continue;
            }
            // Create a new temporary memory file...
            $handle = fopen( 'php://temp', 'wb' );
            if ( $handle ) {
                $reqs[$path] = [
                    'method'  => 'GET',
                    'url'     => $this->storageUrl( $auth, $srcCont, $srcRel ),
                    'headers' => $this->authTokenHeaders( $auth )
                        + $this->headersFromParams( $params ),
                    'stream'  => $handle,
                ];
            }
            $contents[$path] = false;
        }

        $opts = [ 'maxConnsPerHost' => $params['concurrency'] ];
        $reqs = $this->http->runMulti( $reqs, $opts );
        foreach ( $reqs as $path => $op ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $op['response'];
            if ( $rcode >= 200 && $rcode <= 299 ) {
                rewind( $op['stream'] ); // start from the beginning
                $contents[$path] = stream_get_contents( $op['stream'] );
            } elseif ( $rcode === 404 ) {
                $contents[$path] = false;
            } else {
                $this->onError( null, __METHOD__,
                    [ 'src' => $path ] + $ep, $rerr, $rcode, $rdesc );
            }
            fclose( $op['stream'] ); // close open handle
        }

        return $contents;
    }

    protected function doDirectoryExists( $fullCont, $dir, array $params ) {
        $prefix = ( $dir == '' ) ? null : "{$dir}/";
        $status = $this->objectListing( $fullCont, 'names', 1, null, $prefix );
        if ( $status->isOK() ) {
            return ( count( $status->value ) ) > 0;
        }

        return null; // error
    }

    public function getDirectoryListInternal( $fullCont, $dir, array $params ) {
        return new SwiftFileBackendDirList( $this, $fullCont, $dir, $params );
    }

    public function getFileListInternal( $fullCont, $dir, array $params ) {
        return new SwiftFileBackendFileList( $this, $fullCont, $dir, $params );
    }

    public function getDirListPageInternal( $fullCont, $dir, &$after, $limit, array $params ) {
        $dirs = [];
        if ( $after === INF ) {
            return $dirs; // nothing more
        }

        $ps = $this->scopedProfileSection( __METHOD__ . "-{$this->name}" );

        $prefix = ( $dir == '' ) ? null : "{$dir}/";
        // Non-recursive: only list dirs right under $dir
        if ( !empty( $params['topOnly'] ) ) {
            $status = $this->objectListing( $fullCont, 'names', $limit, $after, $prefix, '/' );
            if ( !$status->isOK() ) {
                throw new FileBackendError( "Iterator page I/O error." );
            }
            $objects = $status->value;
            foreach ( $objects as $object ) { // files and directories
                if ( substr( $object, -1 ) === '/' ) {
                    $dirs[] = $object; // directories end in '/'
                }
            }
        } else {
            // Recursive: list all dirs under $dir and its subdirs
            $getParentDir = function ( $path ) {
                return ( strpos( $path, '/' ) !== false ) ? dirname( $path ) : false;
            };

            // Get directory from last item of prior page
            $lastDir = $getParentDir( $after ); // must be first page
            $status = $this->objectListing( $fullCont, 'names', $limit, $after, $prefix );

            if ( !$status->isOK() ) {
                throw new FileBackendError( "Iterator page I/O error." );
            }

            $objects = $status->value;

            foreach ( $objects as $object ) { // files
                $objectDir = $getParentDir( $object ); // directory of object

                if ( $objectDir !== false && $objectDir !== $dir ) {
                    // Swift stores paths in UTF-8, using binary sorting.
                    // See function "create_container_table" in common/db.py.
                    // If a directory is not "greater" than the last one,
                    // then it was already listed by the calling iterator.
                    if ( strcmp( $objectDir, $lastDir ) > 0 ) {
                        $pDir = $objectDir;
                        do { // add dir and all its parent dirs
                            $dirs[] = "{$pDir}/";
                            $pDir = $getParentDir( $pDir );
                        } while ( $pDir !== false // sanity
                            && strcmp( $pDir, $lastDir ) > 0 // not done already
                            && strlen( $pDir ) > strlen( $dir ) // within $dir
                        );
                    }
                    $lastDir = $objectDir;
                }
            }
        }
        // Page on the unfiltered directory listing (what is returned may be filtered)
        if ( count( $objects ) < $limit ) {
            $after = INF; // avoid a second RTT
        } else {
            $after = end( $objects ); // update last item
        }

        return $dirs;
    }

    public function getFileListPageInternal( $fullCont, $dir, &$after, $limit, array $params ) {
        $files = []; // list of (path, stat array or null) entries
        if ( $after === INF ) {
            return $files; // nothing more
        }

        $ps = $this->scopedProfileSection( __METHOD__ . "-{$this->name}" );

        $prefix = ( $dir == '' ) ? null : "{$dir}/";
        // $objects will contain a list of unfiltered names or CF_Object items
        // Non-recursive: only list files right under $dir
        if ( !empty( $params['topOnly'] ) ) {
            if ( !empty( $params['adviseStat'] ) ) {
                $status = $this->objectListing( $fullCont, 'info', $limit, $after, $prefix, '/' );
            } else {
                $status = $this->objectListing( $fullCont, 'names', $limit, $after, $prefix, '/' );
            }
        } else {
            // Recursive: list all files under $dir and its subdirs
            if ( !empty( $params['adviseStat'] ) ) {
                $status = $this->objectListing( $fullCont, 'info', $limit, $after, $prefix );
            } else {
                $status = $this->objectListing( $fullCont, 'names', $limit, $after, $prefix );
            }
        }

        // Reformat this list into a list of (name, stat array or null) entries
        if ( !$status->isOK() ) {
            throw new FileBackendError( "Iterator page I/O error." );
        }

        $objects = $status->value;
        $files = $this->buildFileObjectListing( $params, $dir, $objects );

        // Page on the unfiltered object listing (what is returned may be filtered)
        if ( count( $objects ) < $limit ) {
            $after = INF; // avoid a second RTT
        } else {
            $after = end( $objects ); // update last item
            $after = is_object( $after ) ? $after->name : $after;
        }

        return $files;
    }

    private function buildFileObjectListing( array $params, $dir, array $objects ) {
        $names = [];
        foreach ( $objects as $object ) {
            if ( is_object( $object ) ) {
                if ( isset( $object->subdir ) || !isset( $object->name ) ) {
                    continue; // virtual directory entry; ignore
                }
                $stat = [
                    // Convert various random Swift dates to TS_MW
                    'mtime'  => $this->convertSwiftDate( $object->last_modified, TS_MW ),
                    'size'   => (int)$object->bytes,
                    'sha1'   => null,
                    // Note: manifiest ETags are not an MD5 of the file
                    'md5'    => ctype_xdigit( $object->hash ) ? $object->hash : null,
                    'latest' => false // eventually consistent
                ];
                $names[] = [ $object->name, $stat ];
            } elseif ( substr( $object, -1 ) !== '/' ) {
                // Omit directories, which end in '/' in listings
                $names[] = [ $object, null ];
            }
        }

        return $names;
    }

    public function loadListingStatInternal( $path, array $val ) {
        $this->cheapCache->set( $path, 'stat', $val );
    }

    protected function doGetFileXAttributes( array $params ) {
        $stat = $this->getFileStat( $params );
        if ( $stat ) {
            if ( !isset( $stat['xattr'] ) ) {
                // Stat entries filled by file listings don't include metadata/headers
                $this->clearCache( [ $params['src'] ] );
                $stat = $this->getFileStat( $params );
            }

            return $stat['xattr'];
        } else {
            return false;
        }
    }

    protected function doGetFileSha1base36( array $params ) {
        $stat = $this->getFileStat( $params );
        if ( $stat ) {
            if ( !isset( $stat['sha1'] ) ) {
                // Stat entries filled by file listings don't include SHA1
                $this->clearCache( [ $params['src'] ] );
                $stat = $this->getFileStat( $params );
            }

            return $stat['sha1'];
        } else {
            return false;
        }
    }

    protected function doStreamFile( array $params ) {
        $status = $this->newStatus();

        $flags = !empty( $params['headless'] ) ? StreamFile::STREAM_HEADLESS : 0;

        list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
        if ( $srcRel === null ) {
            StreamFile::send404Message( $params['src'], $flags );
            $status->fatal( 'backend-fail-invalidpath', $params['src'] );

            return $status;
        }

        $auth = $this->getAuthentication();
        if ( !$auth || !is_array( $this->getContainerStat( $srcCont ) ) ) {
            StreamFile::send404Message( $params['src'], $flags );
            $status->fatal( 'backend-fail-stream', $params['src'] );

            return $status;
        }

        // If "headers" is set, we only want to send them if the file is there.
        // Do not bother checking if the file exists if headers are not set though.
        if ( $params['headers'] && !$this->fileExists( $params ) ) {
            StreamFile::send404Message( $params['src'], $flags );
            $status->fatal( 'backend-fail-stream', $params['src'] );

            return $status;
        }

        // Send the requested additional headers
        foreach ( $params['headers'] as $header ) {
            header( $header ); // aways send
        }

        if ( empty( $params['allowOB'] ) ) {
            // Cancel output buffering and gzipping if set
            call_user_func( $this->obResetFunc );
        }

        $handle = fopen( 'php://output', 'wb' );
        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
            'method' => 'GET',
            'url' => $this->storageUrl( $auth, $srcCont, $srcRel ),
            'headers' => $this->authTokenHeaders( $auth )
                + $this->headersFromParams( $params ) + $params['options'],
            'stream' => $handle,
            'flags'  => [ 'relayResponseHeaders' => empty( $params['headless'] ) ]
        ] );

        if ( $rcode >= 200 && $rcode <= 299 ) {
            // good
        } elseif ( $rcode === 404 ) {
            $status->fatal( 'backend-fail-stream', $params['src'] );
            // Per bug 41113, nasty things can happen if bad cache entries get
            // stuck in cache. It's also possible that this error can come up
            // with simple race conditions. Clear out the stat cache to be safe.
            $this->clearCache( [ $params['src'] ] );
            $this->deleteFileCache( $params['src'] );
        } else {
            $this->onError( $status, __METHOD__, $params, $rerr, $rcode, $rdesc );
        }

        return $status;
    }

    protected function doGetLocalCopyMulti( array $params ) {
        $tmpFiles = [];

        $auth = $this->getAuthentication();

        $ep = array_diff_key( $params, [ 'srcs' => 1 ] ); // for error logging
        // Blindly create tmp files and stream to them, catching any exception if the file does
        // not exist. Doing a stat here is useless causes infinite loops in addMissingMetadata().
        $reqs = []; // (path => op)

        foreach ( $params['srcs'] as $path ) { // each path in this concurrent batch
            list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $path );
            if ( $srcRel === null || !$auth ) {
                $tmpFiles[$path] = null;
                continue;
            }
            // Get source file extension
            $ext = FileBackend::extensionFromPath( $path );
            // Create a new temporary file...
            $tmpFile = TempFSFile::factory( 'localcopy_', $ext, $this->tmpDirectory );
            if ( $tmpFile ) {
                $handle = fopen( $tmpFile->getPath(), 'wb' );
                if ( $handle ) {
                    $reqs[$path] = [
                        'method'  => 'GET',
                        'url'     => $this->storageUrl( $auth, $srcCont, $srcRel ),
                        'headers' => $this->authTokenHeaders( $auth )
                            + $this->headersFromParams( $params ),
                        'stream'  => $handle,
                    ];
                } else {
                    $tmpFile = null;
                }
            }
            $tmpFiles[$path] = $tmpFile;
        }

        $isLatest = ( $this->isRGW || !empty( $params['latest'] ) );
        $opts = [ 'maxConnsPerHost' => $params['concurrency'] ];
        $reqs = $this->http->runMulti( $reqs, $opts );
        foreach ( $reqs as $path => $op ) {
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $op['response'];
            fclose( $op['stream'] ); // close open handle
            if ( $rcode >= 200 && $rcode <= 299 ) {
                $size = $tmpFiles[$path] ? $tmpFiles[$path]->getSize() : 0;
                // Double check that the disk is not full/broken
                if ( $size != $rhdrs['content-length'] ) {
                    $tmpFiles[$path] = null;
                    $rerr = "Got {$size}/{$rhdrs['content-length']} bytes";
                    $this->onError( null, __METHOD__,
                        [ 'src' => $path ] + $ep, $rerr, $rcode, $rdesc );
                }
                // Set the file stat process cache in passing
                $stat = $this->getStatFromHeaders( $rhdrs );
                $stat['latest'] = $isLatest;
                $this->cheapCache->set( $path, 'stat', $stat );
            } elseif ( $rcode === 404 ) {
                $tmpFiles[$path] = false;
            } else {
                $tmpFiles[$path] = null;
                $this->onError( null, __METHOD__,
                    [ 'src' => $path ] + $ep, $rerr, $rcode, $rdesc );
            }
        }

        return $tmpFiles;
    }

    public function getFileHttpUrl( array $params ) {
        if ( $this->swiftTempUrlKey != '' ||
            ( $this->rgwS3AccessKey != '' && $this->rgwS3SecretKey != '' )
        ) {
            list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $params['src'] );
            if ( $srcRel === null ) {
                return null; // invalid path
            }

            $auth = $this->getAuthentication();
            if ( !$auth ) {
                return null;
            }

            $ttl = isset( $params['ttl'] ) ? $params['ttl'] : 86400;
            $expires = time() + $ttl;

            if ( $this->swiftTempUrlKey != '' ) {
                $url = $this->storageUrl( $auth, $srcCont, $srcRel );
                // Swift wants the signature based on the unencoded object name
                $contPath = parse_url( $this->storageUrl( $auth, $srcCont ), PHP_URL_PATH );
                $signature = hash_hmac( 'sha1',
                    "GET\n{$expires}\n{$contPath}/{$srcRel}",
                    $this->swiftTempUrlKey
                );

                return "{$url}?temp_url_sig={$signature}&temp_url_expires={$expires}";
            } else { // give S3 API URL for rgw
                // Path for signature starts with the bucket
                $spath = '/' . rawurlencode( $srcCont ) . '/' .
                    str_replace( '%2F', '/', rawurlencode( $srcRel ) );
                // Calculate the hash
                $signature = base64_encode( hash_hmac(
                    'sha1',
                    "GET\n\n\n{$expires}\n{$spath}",
                    $this->rgwS3SecretKey,
                    true // raw
                ) );
                // See http://s3.amazonaws.com/doc/s3-developer-guide/RESTAuthentication.html.
                // Note: adding a newline for empty CanonicalizedAmzHeaders does not work.
                // Note: S3 API is the rgw default; remove the /swift/ URL bit.
                return str_replace( '/swift/v1', '', $this->storageUrl( $auth ) . $spath ) .
                    '?' .
                    http_build_query( [
                        'Signature' => $signature,
                        'Expires' => $expires,
                        'AWSAccessKeyId' => $this->rgwS3AccessKey
                    ] );
            }
        }

        return null;
    }

    protected function directoriesAreVirtual() {
        return true;
    }

    protected function headersFromParams( array $params ) {
        $hdrs = [];
        if ( !empty( $params['latest'] ) ) {
            $hdrs['x-newest'] = 'true';
        }

        return $hdrs;
    }

    protected function doExecuteOpHandlesInternal( array $fileOpHandles ) {
        $statuses = [];

        $auth = $this->getAuthentication();
        if ( !$auth ) {
            foreach ( $fileOpHandles as $index => $fileOpHandle ) {
                $statuses[$index] = $this->newStatus( 'backend-fail-connect', $this->name );
            }

            return $statuses;
        }

        // Split the HTTP requests into stages that can be done concurrently
        $httpReqsByStage = []; // map of (stage => index => HTTP request)
        foreach ( $fileOpHandles as $index => $fileOpHandle ) {
            $reqs = $fileOpHandle->httpOp;
            // Convert the 'url' parameter to an actual URL using $auth
            foreach ( $reqs as $stage => &$req ) {
                list( $container, $relPath ) = $req['url'];
                $req['url'] = $this->storageUrl( $auth, $container, $relPath );
                $req['headers'] = isset( $req['headers'] ) ? $req['headers'] : [];
                $req['headers'] = $this->authTokenHeaders( $auth ) + $req['headers'];
                $httpReqsByStage[$stage][$index] = $req;
            }
            $statuses[$index] = $this->newStatus();
        }

        // Run all requests for the first stage, then the next, and so on
        $reqCount = count( $httpReqsByStage );
        for ( $stage = 0; $stage < $reqCount; ++$stage ) {
            $httpReqs = $this->http->runMulti( $httpReqsByStage[$stage] );
            foreach ( $httpReqs as $index => $httpReq ) {
                // Run the callback for each request of this operation
                $callback = $fileOpHandles[$index]->callback;
                call_user_func_array( $callback, [ $httpReq, $statuses[$index] ] );
                // On failure, abort all remaining requests for this operation
                // (e.g. abort the DELETE request if the COPY request fails for a move)
                if ( !$statuses[$index]->isOK() ) {
                    $stages = count( $fileOpHandles[$index]->httpOp );
                    for ( $s = ( $stage + 1 ); $s < $stages; ++$s ) {
                        unset( $httpReqsByStage[$s][$index] );
                    }
                }
            }
        }

        return $statuses;
    }

    protected function setContainerAccess( $container, array $readGrps, array $writeGrps ) {
        $status = $this->newStatus();
        $auth = $this->getAuthentication();

        if ( !$auth ) {
            $status->fatal( 'backend-fail-connect', $this->name );

            return $status;
        }

        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
            'method' => 'POST',
            'url' => $this->storageUrl( $auth, $container ),
            'headers' => $this->authTokenHeaders( $auth ) + [
                'x-container-read' => implode( ',', $readGrps ),
                'x-container-write' => implode( ',', $writeGrps )
            ]
        ] );

        if ( $rcode != 204 && $rcode !== 202 ) {
            $status->fatal( 'backend-fail-internal', $this->name );
            $this->logger->error( __METHOD__ . ': unexpected rcode value (' . $rcode . ')' );
        }

        return $status;
    }

    protected function getContainerStat( $container, $bypassCache = false ) {
        $ps = $this->scopedProfileSection( __METHOD__ . "-{$this->name}" );

        if ( $bypassCache ) { // purge cache
            $this->containerStatCache->clear( $container );
        } elseif ( !$this->containerStatCache->has( $container, 'stat' ) ) {
            $this->primeContainerCache( [ $container ] ); // check persistent cache
        }
        if ( !$this->containerStatCache->has( $container, 'stat' ) ) {
            $auth = $this->getAuthentication();
            if ( !$auth ) {
                return null;
            }

            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
                'method' => 'HEAD',
                'url' => $this->storageUrl( $auth, $container ),
                'headers' => $this->authTokenHeaders( $auth )
            ] );

            if ( $rcode === 204 ) {
                $stat = [
                    'count' => $rhdrs['x-container-object-count'],
                    'bytes' => $rhdrs['x-container-bytes-used']
                ];
                if ( $bypassCache ) {
                    return $stat;
                } else {
                    $this->containerStatCache->set( $container, 'stat', $stat ); // cache it
                    $this->setContainerCache( $container, $stat ); // update persistent cache
                }
            } elseif ( $rcode === 404 ) {
                return false;
            } else {
                $this->onError( null, __METHOD__,
                    [ 'cont' => $container ], $rerr, $rcode, $rdesc );

                return null;
            }
        }

        return $this->containerStatCache->get( $container, 'stat' );
    }

    protected function createContainer( $container, array $params ) {
        $status = $this->newStatus();

        $auth = $this->getAuthentication();
        if ( !$auth ) {
            $status->fatal( 'backend-fail-connect', $this->name );

            return $status;
        }

        // @see SwiftFileBackend::setContainerAccess()
        if ( empty( $params['noAccess'] ) ) {
            $readGrps = [ '.r:*', $this->swiftUser ]; // public
        } else {
            $readGrps = [ $this->swiftUser ]; // private
        }
        $writeGrps = [ $this->swiftUser ]; // sanity

        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
            'method' => 'PUT',
            'url' => $this->storageUrl( $auth, $container ),
            'headers' => $this->authTokenHeaders( $auth ) + [
                'x-container-read' => implode( ',', $readGrps ),
                'x-container-write' => implode( ',', $writeGrps )
            ]
        ] );

        if ( $rcode === 201 ) { // new
            // good
        } elseif ( $rcode === 202 ) { // already there
            // this shouldn't really happen, but is OK
        } else {
            $this->onError( $status, __METHOD__, $params, $rerr, $rcode, $rdesc );
        }

        return $status;
    }

    protected function deleteContainer( $container, array $params ) {
        $status = $this->newStatus();

        $auth = $this->getAuthentication();
        if ( !$auth ) {
            $status->fatal( 'backend-fail-connect', $this->name );

            return $status;
        }

        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
            'method' => 'DELETE',
            'url' => $this->storageUrl( $auth, $container ),
            'headers' => $this->authTokenHeaders( $auth )
        ] );

        if ( $rcode >= 200 && $rcode <= 299 ) { // deleted
            $this->containerStatCache->clear( $container ); // purge
        } elseif ( $rcode === 404 ) { // not there
            // this shouldn't really happen, but is OK
        } elseif ( $rcode === 409 ) { // not empty
            $this->onError( $status, __METHOD__, $params, $rerr, $rcode, $rdesc ); // race?
        } else {
            $this->onError( $status, __METHOD__, $params, $rerr, $rcode, $rdesc );
        }

        return $status;
    }

    private function objectListing(
        $fullCont, $type, $limit, $after = null, $prefix = null, $delim = null
    ) {
        $status = $this->newStatus();

        $auth = $this->getAuthentication();
        if ( !$auth ) {
            $status->fatal( 'backend-fail-connect', $this->name );

            return $status;
        }

        $query = [ 'limit' => $limit ];
        if ( $type === 'info' ) {
            $query['format'] = 'json';
        }
        if ( $after !== null ) {
            $query['marker'] = $after;
        }
        if ( $prefix !== null ) {
            $query['prefix'] = $prefix;
        }
        if ( $delim !== null ) {
            $query['delimiter'] = $delim;
        }

        list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
            'method' => 'GET',
            'url' => $this->storageUrl( $auth, $fullCont ),
            'query' => $query,
            'headers' => $this->authTokenHeaders( $auth )
        ] );

        $params = [ 'cont' => $fullCont, 'prefix' => $prefix, 'delim' => $delim ];
        if ( $rcode === 200 ) { // good
            if ( $type === 'info' ) {
                $status->value = FormatJson::decode( trim( $rbody ) );
            } else {
                $status->value = explode( "\n", trim( $rbody ) );
            }
        } elseif ( $rcode === 204 ) {
            $status->value = []; // empty container
        } elseif ( $rcode === 404 ) {
            $status->value = []; // no container
        } else {
            $this->onError( $status, __METHOD__, $params, $rerr, $rcode, $rdesc );
        }

        return $status;
    }

    protected function doPrimeContainerCache( array $containerInfo ) {
        foreach ( $containerInfo as $container => $info ) {
            $this->containerStatCache->set( $container, 'stat', $info );
        }
    }

    protected function doGetFileStatMulti( array $params ) {
        $stats = [];

        $auth = $this->getAuthentication();

        $reqs = [];
        foreach ( $params['srcs'] as $path ) {
            list( $srcCont, $srcRel ) = $this->resolveStoragePathReal( $path );
            if ( $srcRel === null ) {
                $stats[$path] = false;
                continue; // invalid storage path
            } elseif ( !$auth ) {
                $stats[$path] = null;
                continue;
            }

            // (a) Check the container
            $cstat = $this->getContainerStat( $srcCont );
            if ( $cstat === false ) {
                $stats[$path] = false;
                continue; // ok, nothing to do
            } elseif ( !is_array( $cstat ) ) {
                $stats[$path] = null;
                continue;
            }

            $reqs[$path] = [
                'method'  => 'HEAD',
                'url'     => $this->storageUrl( $auth, $srcCont, $srcRel ),
                'headers' => $this->authTokenHeaders( $auth ) + $this->headersFromParams( $params )
            ];
        }

        $opts = [ 'maxConnsPerHost' => $params['concurrency'] ];
        $reqs = $this->http->runMulti( $reqs, $opts );

        foreach ( $params['srcs'] as $path ) {
            if ( array_key_exists( $path, $stats ) ) {
                continue; // some sort of failure above
            }
            // (b) Check the file
            list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $reqs[$path]['response'];
            if ( $rcode === 200 || $rcode === 204 ) {
                // Update the object if it is missing some headers
                $rhdrs = $this->addMissingMetadata( $rhdrs, $path );
                // Load the stat array from the headers
                $stat = $this->getStatFromHeaders( $rhdrs );
                if ( $this->isRGW ) {
                    $stat['latest'] = true; // strong consistency
                }
            } elseif ( $rcode === 404 ) {
                $stat = false;
            } else {
                $stat = null;
                $this->onError( null, __METHOD__, $params, $rerr, $rcode, $rdesc );
            }
            $stats[$path] = $stat;
        }

        return $stats;
    }

    protected function getStatFromHeaders( array $rhdrs ) {
        // Fetch all of the custom metadata headers
        $metadata = $this->getMetadata( $rhdrs );
        // Fetch all of the custom raw HTTP headers
        $headers = $this->sanitizeHdrs( [ 'headers' => $rhdrs ] );

        return [
            // Convert various random Swift dates to TS_MW
            'mtime' => $this->convertSwiftDate( $rhdrs['last-modified'], TS_MW ),
            // Empty objects actually return no content-length header in Ceph
            'size'  => isset( $rhdrs['content-length'] ) ? (int)$rhdrs['content-length'] : 0,
            'sha1'  => isset( $metadata['sha1base36'] ) ? $metadata['sha1base36'] : null,
            // Note: manifiest ETags are not an MD5 of the file
            'md5'   => ctype_xdigit( $rhdrs['etag'] ) ? $rhdrs['etag'] : null,
            'xattr' => [ 'metadata' => $metadata, 'headers' => $headers ]
        ];
    }

    protected function getAuthentication() {
        if ( $this->authErrorTimestamp !== null ) {
            if ( ( time() - $this->authErrorTimestamp ) < 60 ) {
                return null; // failed last attempt; don't bother
            } else { // actually retry this time
                $this->authErrorTimestamp = null;
            }
        }
        // Session keys expire after a while, so we renew them periodically
        $reAuth = ( ( time() - $this->authSessionTimestamp ) > $this->authTTL );
        // Authenticate with proxy and get a session key...
        if ( !$this->authCreds || $reAuth ) {
            $this->authSessionTimestamp = 0;
            $cacheKey = $this->getCredsCacheKey( $this->swiftUser );
            $creds = $this->srvCache->get( $cacheKey ); // credentials
            // Try to use the credential cache
            if ( isset( $creds['auth_token'] ) && isset( $creds['storage_url'] ) ) {
                $this->authCreds = $creds;
                // Skew the timestamp for worst case to avoid using stale credentials
                $this->authSessionTimestamp = time() - ceil( $this->authTTL / 2 );
            } else { // cache miss
                list( $rcode, $rdesc, $rhdrs, $rbody, $rerr ) = $this->http->run( [
                    'method' => 'GET',
                    'url' => "{$this->swiftAuthUrl}/v1.0",
                    'headers' => [
                        'x-auth-user' => $this->swiftUser,
                        'x-auth-key' => $this->swiftKey
                    ]
                ] );

                if ( $rcode >= 200 && $rcode <= 299 ) { // OK
                    $this->authCreds = [
                        'auth_token' => $rhdrs['x-auth-token'],
                        'storage_url' => $rhdrs['x-storage-url']
                    ];
                    $this->srvCache->set( $cacheKey, $this->authCreds, ceil( $this->authTTL / 2 ) );
                    $this->authSessionTimestamp = time();
                } elseif ( $rcode === 401 ) {
                    $this->onError( null, __METHOD__, [], "Authentication failed.", $rcode );
                    $this->authErrorTimestamp = time();

                    return null;
                } else {
                    $this->onError( null, __METHOD__, [], "HTTP return code: $rcode", $rcode );
                    $this->authErrorTimestamp = time();

                    return null;
                }
            }
            // Ceph RGW does not use <account> in URLs (OpenStack Swift uses "/v1/<account>")
            if ( substr( $this->authCreds['storage_url'], -3 ) === '/v1' ) {
                $this->isRGW = true; // take advantage of strong consistency in Ceph
            }
        }

        return $this->authCreds;
    }

    protected function storageUrl( array $creds, $container = null, $object = null ) {
        $parts = [ $creds['storage_url'] ];
        if ( strlen( $container ) ) {
            $parts[] = rawurlencode( $container );
        }
        if ( strlen( $object ) ) {
            $parts[] = str_replace( "%2F", "/", rawurlencode( $object ) );
        }

        return implode( '/', $parts );
    }

    protected function authTokenHeaders( array $creds ) {
        return [ 'x-auth-token' => $creds['auth_token'] ];
    }

    private function getCredsCacheKey( $username ) {
        return 'swiftcredentials:' . md5( $username . ':' . $this->swiftAuthUrl );
    }

    public function onError( $status, $func, array $params, $err = '', $code = 0, $desc = '' ) {
        if ( $status instanceof StatusValue ) {
            $status->fatal( 'backend-fail-internal', $this->name );
        }
        if ( $code == 401 ) { // possibly a stale token
            $this->srvCache->delete( $this->getCredsCacheKey( $this->swiftUser ) );
        }
        $this->logger->error(
            "HTTP $code ($desc) in '{$func}' (given '" . FormatJson::encode( $params ) . "')" .
            ( $err ? ": $err" : "" )
        );
    }
}

class SwiftFileOpHandle extends FileBackendStoreOpHandle {
    public $httpOp;
    public $callback;

    public function __construct( SwiftFileBackend $backend, Closure $callback, array $httpOp ) {
        $this->backend = $backend;
        $this->callback = $callback;
        $this->httpOp = $httpOp;
    }
}

abstract class SwiftFileBackendList implements Iterator {
    protected $bufferIter = [];

    protected $bufferAfter = null;

    protected $pos = 0;

    protected $params = [];

    protected $backend;

    protected $container;

    protected $dir;

    protected $suffixStart;

    const PAGE_SIZE = 9000; // file listing buffer size

    public function __construct( SwiftFileBackend $backend, $fullCont, $dir, array $params ) {
        $this->backend = $backend;
        $this->container = $fullCont;
        $this->dir = $dir;
        if ( substr( $this->dir, -1 ) === '/' ) {
            $this->dir = substr( $this->dir, 0, -1 ); // remove trailing slash
        }
        if ( $this->dir == '' ) { // whole container
            $this->suffixStart = 0;
        } else { // dir within container
            $this->suffixStart = strlen( $this->dir ) + 1; // size of "path/to/dir/"
        }
        $this->params = $params;
    }

    public function key() {
        return $this->pos;
    }

    public function next() {
        // Advance to the next file in the page
        next( $this->bufferIter );
        ++$this->pos;
        // Check if there are no files left in this page and
        // advance to the next page if this page was not empty.
        if ( !$this->valid() && count( $this->bufferIter ) ) {
            $this->bufferIter = $this->pageFromList(
                $this->container, $this->dir, $this->bufferAfter, self::PAGE_SIZE, $this->params
            ); // updates $this->bufferAfter
        }
    }

    public function rewind() {
        $this->pos = 0;
        $this->bufferAfter = null;
        $this->bufferIter = $this->pageFromList(
            $this->container, $this->dir, $this->bufferAfter, self::PAGE_SIZE, $this->params
        ); // updates $this->bufferAfter
    }

    public function valid() {
        if ( $this->bufferIter === null ) {
            return false; // some failure?
        } else {
            return ( current( $this->bufferIter ) !== false ); // no paths can have this value
        }
    }

    abstract protected function pageFromList( $container, $dir, &$after, $limit, array $params );
}

class SwiftFileBackendDirList extends SwiftFileBackendList {
    public function current() {
        return substr( current( $this->bufferIter ), $this->suffixStart, -1 );
    }

    protected function pageFromList( $container, $dir, &$after, $limit, array $params ) {
        return $this->backend->getDirListPageInternal( $container, $dir, $after, $limit, $params );
    }
}

class SwiftFileBackendFileList extends SwiftFileBackendList {
    public function current() {
        list( $path, $stat ) = current( $this->bufferIter );
        $relPath = substr( $path, $this->suffixStart );
        if ( is_array( $stat ) ) {
            $storageDir = rtrim( $this->params['dir'], '/' );
            $this->backend->loadListingStatInternal( "$storageDir/$relPath", $stat );
        }

        return $relPath;
    }

    protected function pageFromList( $container, $dir, &$after, $limit, array $params ) {
        return $this->backend->getFileListPageInternal( $container, $dir, $after, $limit, $params );
    }
}