includes/externalstore/ExternalStore.php

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