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         /**
  23          * Fetch data from given URL
  24          *
  25          * @param $url String: The URL of the text to get
  26          * @param $params Array: associative array of parameters for the ExternalStore object.
  27          * @return The text stored or false on error
  28          */
  29         static function fetchFromURL( $url, $params = array() ) {
  30                 global $wgExternalStores;
  31
  32                 if( !$wgExternalStores )
  33                         return false;
  34
  35                 @list( $proto, $path ) = explode( '://', $url, 2 );
  36                 /* Bad URL */
  37                 if( $path == '' )
  38                         return false;
  39
  40                 $store = self::getStoreObject( $proto, $params );
  41                 if ( $store === false )
  42                         return false;
  43                 return $store->fetchFromURL( $url );
  44         }
  45
  46         /**
  47          * Get an external store object of the given type, with the given parameters
  48          *
  49          * @param $proto String: type of external storage, should be a value in $wgExternalStores
  50          * @param $params Array: associative array of parameters for the ExternalStore object.
  51          * @return ExternalStore subclass or false on error
  52          */
  53         static function getStoreObject( $proto, $params = array() ) {
  54                 global $wgExternalStores;
  55                 if( !$wgExternalStores )
  56                         return false;
  57                 /* Protocol not enabled */
  58                 if( !in_array( $proto, $wgExternalStores ) )
  59                         return false;
  60
  61                 $class = 'ExternalStore' . ucfirst( $proto );
  62                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
  63                 if( !class_exists( $class ) ) {
  64                         return false;
  65                 }
  66
  67                 return new $class($params);
  68         }
  69
  70         /**
  71          * Store a data item to an external store, identified by a partial URL
  72          * The protocol part is used to identify the class, the rest is passed to the
  73          * class itself as a parameter.
  74          * @return The URL of the stored data item, or false on error
  75          */
  76         static function insert( $url, $data, $params = array() ) {
  77                 list( $proto, $params ) = explode( '://', $url, 2 );
  78                 $store = self::getStoreObject( $proto, $params );
  79                 if ( $store === false ) {
  80                         return false;
  81                 } else {
  82                         return $store->store( $params, $data );
  83                 }
  84         }
  85
  86         /**
  87          * Like insert() above, but does more of the work for us.
  88          * This function does not need a url param, it builds it by
  89          * itself. It also fails-over to the next possible clusters.
  90          *
  91          * @param $data String
  92          * @param $storageParams Array: associative array of parameters for the ExternalStore object.
  93          * @return The URL of the stored data item, or false on error
  94          */
  95         public static function insertToDefault( $data, $storageParams = array() ) {
  96                 global $wgDefaultExternalStore;
  97                 $tryStores = (array)$wgDefaultExternalStore;
  98                 $error = false;
  99                 while ( count( $tryStores ) > 0 ) {
 100                         $index = mt_rand(0, count( $tryStores ) - 1);
 101                         $storeUrl = $tryStores[$index];
 102                         wfDebug( __METHOD__.": trying $storeUrl\n" );
 103                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
 104                         $store = self::getStoreObject( $proto, $storageParams );
 105                         if ( $store === false ) {
 106                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
 107                         }
 108                         try {
 109                                 $url = $store->store( $params, $data ); // Try to save the object
 110                         } catch ( DBConnectionError $error ) {
 111                                 $url = false;
 112                         } catch( DBQueryError $error ) {
 113                                 $url = false;
 114                         }
 115                         if ( $url ) {
 116                                 return $url; // Done!
 117                         } else {
 118                                 unset( $tryStores[$index] ); // Don't try this one again!
 119                                 $tryStores = array_values( $tryStores ); // Must have consecutive keys
 120                                 wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 121                         }
 122                 }
 123                 // All stores failed
 124                 if ( $error ) {
 125                         // Rethrow the last connection error
 126                         throw $error;
 127                 } else {
 128                         throw new MWException( "Unable to store text to external storage" );
 129                 }
 130         }
 131
 132         /** Like insertToDefault, but inserts on another wiki */
 133         public static function insertToForeignDefault( $data, $wiki ) {
 134                 return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
 135         }
 136 }