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         function __construct( $params = array() ) {
  40                 $this->mParams = $params;
  41         }
  42
  43         /**
  44          * Fetch data from given URL
  45          *
  46          * @param $url String: The URL of the text to get
  47          * @param $params Array: associative array of parameters for the ExternalStore object.
  48          * @return string|bool The text stored or false on error
  49          */
  50         static function fetchFromURL( $url, $params = array() ) {
  51                 global $wgExternalStores;
  52
  53                 if( !$wgExternalStores )
  54                         return false;
  55
  56                 $parts = explode( '://', $url, 2 );
  57
  58                 if ( count( $parts ) != 2 ) {
  59                         return false;
  60                 }
  61
  62                 list( $proto, $path ) = $parts;
  63
  64                 if ( $path == '' ) { // Bad URL
  65                         return false;
  66                 }
  67
  68                 $store = self::getStoreObject( $proto, $params );
  69                 if ( $store === false )
  70                         return false;
  71                 return $store->fetchFromURL( $url );
  72         }
  73
  74         /**
  75          * Get an external store object of the given type, with the given parameters
  76          *
  77          * @param $proto String: type of external storage, should be a value in $wgExternalStores
  78          * @param $params Array: associative array of parameters for the ExternalStore object.
  79          * @return ExternalStore subclass or false on error
  80          */
  81         static function getStoreObject( $proto, $params = array() ) {
  82                 global $wgExternalStores;
  83                 if( !$wgExternalStores )
  84                         return false;
  85                 /* Protocol not enabled */
  86                 if( !in_array( $proto, $wgExternalStores ) )
  87                         return false;
  88
  89                 $class = 'ExternalStore' . ucfirst( $proto );
  90                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
  91                 if( !MWInit::classExists( $class ) ) {
  92                         return false;
  93                 }
  94
  95                 return new $class($params);
  96         }
  97
  98         /**
  99          * Store a data item to an external store, identified by a partial URL
 100          * The protocol part is used to identify the class, the rest is passed to the
 101          * class itself as a parameter.
 102          * @param $url
 103          * @param $data
 104          * @param $params array
 105          * @return string|bool The URL of the stored data item, or false on error
 106          */
 107         static function insert( $url, $data, $params = array() ) {
 108                 list( $proto, $params ) = explode( '://', $url, 2 );
 109                 $store = self::getStoreObject( $proto, $params );
 110                 if ( $store === false ) {
 111                         return false;
 112                 } else {
 113                         return $store->store( $params, $data );
 114                 }
 115         }
 116
 117         /**
 118          * Like insert() above, but does more of the work for us.
 119          * This function does not need a url param, it builds it by
 120          * itself. It also fails-over to the next possible clusters.
 121          *
 122          * @param $data String
 123          * @param $storageParams Array: associative array of parameters for the ExternalStore object.
 124          * @return string The URL of the stored data item, or false on error
 125          */
 126         public static function insertToDefault( $data, $storageParams = array() ) {
 127                 global $wgDefaultExternalStore;
 128                 $tryStores = (array)$wgDefaultExternalStore;
 129                 $error = false;
 130                 while ( count( $tryStores ) > 0 ) {
 131                         $index = mt_rand(0, count( $tryStores ) - 1);
 132                         $storeUrl = $tryStores[$index];
 133                         wfDebug( __METHOD__.": trying $storeUrl\n" );
 134                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
 135                         $store = self::getStoreObject( $proto, $storageParams );
 136                         if ( $store === false ) {
 137                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
 138                         }
 139                         try {
 140                                 $url = $store->store( $params, $data ); // Try to save the object
 141                         } catch ( DBConnectionError $error ) {
 142                                 $url = false;
 143                         } catch( DBQueryError $error ) {
 144                                 $url = false;
 145                         }
 146                         if ( $url ) {
 147                                 return $url; // Done!
 148                         } else {
 149                                 unset( $tryStores[$index] ); // Don't try this one again!
 150                                 $tryStores = array_values( $tryStores ); // Must have consecutive keys
 151                                 wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 152                         }
 153                 }
 154                 // All stores failed
 155                 if ( $error ) {
 156                         // Rethrow the last connection error
 157                         throw $error;
 158                 } else {
 159                         throw new MWException( "Unable to store text to external storage" );
 160                 }
 161         }
 162
 163         /**
 164          * @param $data
 165          * @param $wiki
 166          *
 167          * @return string
 168          */
 169         public static function insertToForeignDefault( $data, $wiki ) {
 170                 return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
 171         }
 172 }