includes/ExternalStore.php

   1 <?php
   2 /**
   3  * Data storage in external repositories.
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License along
  16  * with this program; if not, write to the Free Software Foundation, Inc.,
  17  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  18  * http://www.gnu.org/copyleft/gpl.html
  19  *
  20  * @file
  21  */
  22
  23 /**
  24  * @defgroup ExternalStorage ExternalStorage
  25  */
  26
  27 /**
  28  * Constructor class for data kept in external repositories
  29  *
  30  * External repositories might be populated by maintenance/async
  31  * scripts, thus partial moving of data may be possible, as well
  32  * as possibility to have any storage format (i.e. for archives)
  33  *
  34  * @ingroup ExternalStorage
  35  */
  36 class ExternalStore {
  37         var $mParams;
  38
  39         /**
  40          * @param $params array
  41          */
  42         function __construct( $params = array() ) {
  43                 $this->mParams = $params;
  44         }
  45
  46         /**
  47          * Fetch data from given URL
  48          *
  49          * @param $url String: The URL of the text to get
  50          * @param $params Array: associative array of parameters for the ExternalStore object.
  51          * @return string|bool The text stored or false on error
  52          */
  53         static function fetchFromURL( $url, $params = array() ) {
  54                 global $wgExternalStores;
  55
  56                 if( !$wgExternalStores ) {
  57                         return false;
  58                 }
  59
  60                 $parts = explode( '://', $url, 2 );
  61
  62                 if ( count( $parts ) != 2 ) {
  63                         return false;
  64                 }
  65
  66                 list( $proto, $path ) = $parts;
  67
  68                 if ( $path == '' ) { // Bad URL
  69                         return false;
  70                 }
  71
  72                 $store = self::getStoreObject( $proto, $params );
  73                 if ( $store === false ) {
  74                         return false;
  75                 }
  76
  77                 return $store->fetchFromURL( $url );
  78         }
  79
  80         /**
  81          * Get an external store object of the given type, with the given parameters
  82          *
  83          * @param $proto String: type of external storage, should be a value in $wgExternalStores
  84          * @param $params Array: associative array of parameters for the ExternalStore object.
  85          * @return ExternalStore|bool ExternalStore class or false on error
  86          */
  87         static function getStoreObject( $proto, $params = array() ) {
  88                 global $wgExternalStores;
  89                 if( !$wgExternalStores ) {
  90                         return false;
  91                 }
  92
  93                 /* Protocol not enabled */
  94                 if( !in_array( $proto, $wgExternalStores ) ) {
  95                         return false;
  96                 }
  97
  98                 $class = 'ExternalStore' . ucfirst( $proto );
  99                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
 100                 if( !MWInit::classExists( $class ) ) {
 101                         return false;
 102                 }
 103
 104                 return new $class($params);
 105         }
 106
 107         /**
 108          * Store a data item to an external store, identified by a partial URL
 109          * The protocol part is used to identify the class, the rest is passed to the
 110          * class itself as a parameter.
 111          * @param $url
 112          * @param $data
 113          * @param $params array
 114          * @return string|bool The URL of the stored data item, or false on error
 115          */
 116         static function insert( $url, $data, $params = array() ) {
 117                 list( $proto, $params ) = explode( '://', $url, 2 );
 118                 $store = self::getStoreObject( $proto, $params );
 119                 if ( $store === false ) {
 120                         return false;
 121                 } else {
 122                         return $store->store( $params, $data );
 123                 }
 124         }
 125
 126         /**
 127          * Like insert() above, but does more of the work for us.
 128          * This function does not need a url param, it builds it by
 129          * itself. It also fails-over to the next possible clusters.
 130          *
 131          * @param $data String
 132          * @param $storageParams Array: associative array of parameters for the ExternalStore object.
 133          * @throws DBConnectionError|DBQueryError|MWException
 134          * @return string The URL of the stored data item, or false on error
 135          */
 136         public static function insertToDefault( $data, $storageParams = array() ) {
 137                 global $wgDefaultExternalStore;
 138                 $tryStores = (array)$wgDefaultExternalStore;
 139                 $error = false;
 140                 while ( count( $tryStores ) > 0 ) {
 141                         $index = mt_rand(0, count( $tryStores ) - 1);
 142                         $storeUrl = $tryStores[$index];
 143                         wfDebug( __METHOD__.": trying $storeUrl\n" );
 144                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
 145                         $store = self::getStoreObject( $proto, $storageParams );
 146                         if ( $store === false ) {
 147                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
 148                         }
 149                         try {
 150                                 $url = $store->store( $params, $data ); // Try to save the object
 151                         } catch ( DBConnectionError $error ) {
 152                                 $url = false;
 153                         } catch( DBQueryError $error ) {
 154                                 $url = false;
 155                         }
 156                         if ( $url ) {
 157                                 return $url; // Done!
 158                         } else {
 159                                 unset( $tryStores[$index] ); // Don't try this one again!
 160                                 $tryStores = array_values( $tryStores ); // Must have consecutive keys
 161                                 wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 162                         }
 163                 }
 164                 // All stores failed
 165                 if ( $error ) {
 166                         // Rethrow the last connection error
 167                         throw $error;
 168                 } else {
 169                         throw new MWException( "Unable to store text to external storage" );
 170                 }
 171         }
 172
 173         /**
 174          * @param $data
 175          * @param $wiki
 176          *
 177          * @return string
 178          */
 179         public static function insertToForeignDefault( $data, $wiki ) {
 180                 return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
 181         }
 182 }