includes/ExternalStore.php

   1 <?php
   2 /**
   3  * @defgroup ExternalStorage ExternalStorage
   4  */
   5
   6 /**
   7  * Constructor class for data kept in external repositories
   8  *
   9  * External repositories might be populated by maintenance/async
  10  * scripts, thus partial moving of data may be possible, as well
  11  * as possibility to have any storage format (i.e. for archives)
  12  *
  13  * @ingroup ExternalStorage
  14  */
  15 class ExternalStore {
  16         var $mParams;
  17
  18         function __construct( $params = array() ) {
  19                 $this->mParams = $params;
  20         }
  21
  22         /* Fetch data from given URL */
  23         static function fetchFromURL( $url, $params = array() ) {
  24                 global $wgExternalStores;
  25
  26                 if( !$wgExternalStores )
  27                         return false;
  28
  29                 @list( $proto, $path ) = explode( '://', $url, 2 );
  30                 /* Bad URL */
  31                 if( $path == '' )
  32                         return false;
  33
  34                 $store = self::getStoreObject( $proto, $params );
  35                 if ( $store === false )
  36                         return false;
  37                 return $store->fetchFromURL( $url );
  38         }
  39
  40         /**
  41          * Get an external store object of the given type, with the given parameters
  42          */
  43         static function getStoreObject( $proto, $params = array() ) {
  44                 global $wgExternalStores;
  45                 if( !$wgExternalStores )
  46                         return false;
  47                 /* Protocol not enabled */
  48                 if( !in_array( $proto, $wgExternalStores ) )
  49                         return false;
  50
  51                 $class = 'ExternalStore' . ucfirst( $proto );
  52                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
  53                 if( !class_exists( $class ) ) {
  54                         return false;
  55                 }
  56
  57                 return new $class($params);
  58         }
  59
  60         /**
  61          * Store a data item to an external store, identified by a partial URL
  62          * The protocol part is used to identify the class, the rest is passed to the
  63          * class itself as a parameter.
  64          * Returns the URL of the stored data item, or false on error
  65          */
  66         static function insert( $url, $data, $params = array() ) {
  67                 list( $proto, $params ) = explode( '://', $url, 2 );
  68                 $store = self::getStoreObject( $proto, $params );
  69                 if ( $store === false ) {
  70                         return false;
  71                 } else {
  72                         return $store->store( $params, $data );
  73                 }
  74         }
  75
  76         /**
  77          * Like insert() above, but does more of the work for us.
  78          * This function does not need a url param, it builds it by
  79          * itself. It also fails-over to the next possible clusters.
  80          *
  81          * @param string $data
  82          * @param array $params Associative array of parameters for the ExternalStore object.
  83          * Returns the URL of the stored data item, or false on error
  84          */
  85         public static function insertToDefault( $data, $storageParams = array() ) {
  86                 global $wgDefaultExternalStore;
  87                 $tryStores = (array)$wgDefaultExternalStore;
  88                 $error = false;
  89                 while ( count( $tryStores ) > 0 ) {
  90                         $index = mt_rand(0, count( $tryStores ) - 1);
  91                         $storeUrl = $tryStores[$index];
  92                         wfDebug( __METHOD__.": trying $storeUrl\n" );
  93                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
  94                         $store = self::getStoreObject( $proto, $storageParams );
  95                         if ( $store === false ) {
  96                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
  97                         }
  98                         try {
  99                                 $url = $store->store( $params, $data ); // Try to save the object
 100                         } catch ( DBConnectionError $error ) {
 101                                 $url = false;
 102                         } catch( DBQueryError $error ) {
 103                                 $url = false;
 104                         }
 105                         if ( $url ) {
 106                                 return $url; // Done!
 107                         } else {
 108                                 unset( $tryStores[$index] ); // Don't try this one again!
 109                                 $tryStores = array_values( $tryStores ); // Must have consecutive keys
 110                                 wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 111                         }
 112                 }
 113                 // All stores failed
 114                 if ( $error ) {
 115                         // Rethrow the last connection error
 116                         throw $error;
 117                 } else {
 118                         throw new MWException( "Unable to store text to external storage" );
 119                 }
 120         }
 121
 122         /** Like insertToDefault, but inserts on another wiki */
 123         public static function insertToForeignDefault( $data, $wiki ) {
 124                 return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
 125         }
 126 }