d9ba7cd005
This reduces the odds of having files without corresponding wiki pages, given that the later is done in a deferred update. Also made some documentation cleanups. Bug: T187942 Change-Id: Iff516669f535713d37e0011e2d7ed285c667f1c5
254 lines
8 KiB
PHP
254 lines
8 KiB
PHP
<?php
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/**
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* @defgroup ExternalStorage ExternalStorage
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*/
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use MediaWiki\MediaWikiServices;
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/**
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* Interface for data storage in external repositories.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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* http://www.gnu.org/copyleft/gpl.html
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*
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* @file
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*/
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/**
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* Constructor class for key/value blob data kept in external repositories.
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*
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* Objects in external stores are defined by a special URL. The URL is of
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* the form "<store protocol>://<location>/<object name>". The protocol is used
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* to determine what ExternalStoreMedium class is used. The location identifies
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* particular storage instances or database clusters for store class to use.
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*
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* When an object is inserted into a store, the calling code uses a partial URL of
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* the form "<store protocol>://<location>" and receives the full object URL on success.
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* This is useful since object names can be sequential IDs, UUIDs, or hashes.
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* Callers are not responsible for unique name generation.
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*
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* External repositories might be populated by maintenance/async
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* scripts, thus partial moving of data may be possible, as well
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* as the possibility to have any storage format (i.e. for archives).
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*
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* @ingroup ExternalStorage
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*/
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class ExternalStore {
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/**
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* Get an external store object of the given type, with the given parameters
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*
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* @param string $proto Type of external storage, should be a value in $wgExternalStores
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* @param array $params Associative array of ExternalStoreMedium parameters
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* @return ExternalStoreMedium|bool The store class or false on error
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*/
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public static function getStoreObject( $proto, array $params = [] ) {
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return MediaWikiServices::getInstance()
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->getExternalStoreFactory()
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->getStoreObject( $proto, $params );
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}
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/**
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* Fetch data from given URL
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*
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* @param string $url The URL of the text to get
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* @param array $params Associative array of ExternalStoreMedium parameters
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* @return string|bool The text stored or false on error
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* @throws MWException
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*/
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public static function fetchFromURL( $url, array $params = [] ) {
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$parts = explode( '://', $url, 2 );
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if ( count( $parts ) != 2 ) {
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return false; // invalid URL
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}
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list( $proto, $path ) = $parts;
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if ( $path == '' ) { // bad URL
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return false;
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}
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$store = self::getStoreObject( $proto, $params );
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if ( $store === false ) {
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return false;
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}
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return $store->fetchFromURL( $url );
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}
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/**
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* Fetch data from multiple URLs with a minimum of round trips
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*
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* @param array $urls The URLs of the text to get
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* @return array Map from url to its data. Data is either string when found
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* or false on failure.
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* @throws MWException
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*/
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public static function batchFetchFromURLs( array $urls ) {
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$batches = [];
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foreach ( $urls as $url ) {
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$scheme = parse_url( $url, PHP_URL_SCHEME );
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if ( $scheme ) {
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$batches[$scheme][] = $url;
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}
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}
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$retval = [];
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foreach ( $batches as $proto => $batchedUrls ) {
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$store = self::getStoreObject( $proto );
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if ( $store === false ) {
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continue;
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}
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$retval += $store->batchFetchFromURLs( $batchedUrls );
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}
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// invalid, not found, db dead, etc.
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$missing = array_diff( $urls, array_keys( $retval ) );
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if ( $missing ) {
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foreach ( $missing as $url ) {
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$retval[$url] = false;
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}
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}
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return $retval;
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}
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/**
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* Store a data item to an external store, identified by a partial URL
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* The protocol part is used to identify the class, the rest is passed to the
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* class itself as a parameter.
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*
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* @param string $url A partial external store URL ("<store type>://<location>")
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* @param string $data
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* @param array $params Associative array of ExternalStoreMedium parameters
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* @return string|bool The URL of the stored data item, or false on error
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* @throws MWException
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*/
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public static function insert( $url, $data, array $params = [] ) {
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$parts = explode( '://', $url, 2 );
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if ( count( $parts ) != 2 ) {
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return false; // invalid URL
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}
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list( $proto, $path ) = $parts;
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if ( $path == '' ) { // bad URL
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return false;
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}
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$store = self::getStoreObject( $proto, $params );
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if ( $store === false ) {
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return false;
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} else {
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return $store->store( $path, $data );
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}
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}
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/**
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* Like insert() above, but does more of the work for us.
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* This function does not need a url param, it builds it by
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* itself. It also fails-over to the next possible clusters
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* provided by $wgDefaultExternalStore.
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*
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* @param string $data
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* @param array $params Map of ExternalStoreMedium::__construct context parameters
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* @return string|bool The URL of the stored data item, or false on error
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* @throws MWException
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*/
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public static function insertToDefault( $data, array $params = [] ) {
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global $wgDefaultExternalStore;
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return self::insertWithFallback( (array)$wgDefaultExternalStore, $data, $params );
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}
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/**
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* Like insert() above, but does more of the work for us.
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* This function does not need a url param, it builds it by
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* itself. It also fails-over to the next possible clusters
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* as provided in the first parameter.
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*
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* @param array $tryStores Refer to $wgDefaultExternalStore
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* @param string $data
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* @param array $params Map of ExternalStoreMedium::__construct context parameters
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* @return string|bool The URL of the stored data item, or false on error
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* @throws MWException
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*/
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public static function insertWithFallback( array $tryStores, $data, array $params = [] ) {
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$error = false;
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while ( count( $tryStores ) > 0 ) {
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$index = mt_rand( 0, count( $tryStores ) - 1 );
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$storeUrl = $tryStores[$index];
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wfDebug( __METHOD__ . ": trying $storeUrl\n" );
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list( $proto, $path ) = explode( '://', $storeUrl, 2 );
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$store = self::getStoreObject( $proto, $params );
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if ( $store === false ) {
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throw new MWException( "Invalid external storage protocol - $storeUrl" );
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}
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try {
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if ( $store->isReadOnly( $path ) ) {
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$msg = 'read only';
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} else {
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$url = $store->store( $path, $data );
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if ( strlen( $url ) ) {
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return $url; // a store accepted the write; done!
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}
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$msg = 'operation failed';
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}
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} catch ( Exception $error ) {
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$msg = 'caught exception';
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}
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unset( $tryStores[$index] ); // Don't try this one again!
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$tryStores = array_values( $tryStores ); // Must have consecutive keys
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wfDebugLog( 'ExternalStorage',
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"Unable to store text to external storage $storeUrl ($msg)" );
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}
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// All stores failed
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if ( $error ) {
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throw $error; // rethrow the last error
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} else {
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throw new MWException( "Unable to store text to external storage" );
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}
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}
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/**
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* @return bool Whether all the default insertion stores are marked as read-only
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* @since 1.31
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*/
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public static function defaultStoresAreReadOnly() {
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global $wgDefaultExternalStore;
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$tryStores = (array)$wgDefaultExternalStore;
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if ( !$tryStores ) {
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return false; // no stores exists which can be "read only"
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}
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foreach ( $tryStores as $storeUrl ) {
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list( $proto, $path ) = explode( '://', $storeUrl, 2 );
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$store = self::getStoreObject( $proto, [] );
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if ( !$store->isReadOnly( $path ) ) {
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return false; // at least one store is not read-only
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}
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}
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return true; // all stores are read-only
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}
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/**
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* @param string $data
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* @param string $wiki
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* @return string|bool The URL of the stored data item, or false on error
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* @throws MWException
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*/
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public static function insertToForeignDefault( $data, $wiki ) {
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return self::insertToDefault( $data, [ 'wiki' => $wiki ] );
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}
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}
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