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                 $parts = explode( '://', $url, 2 );
  36
  37                 if ( count( $parts ) != 2 ) {
  38                         return false;
  39                 }
  40
  41                 list( $proto, $path ) = $parts;
  42
  43                 if ( $path == '' ) { // Bad URL
  44                         return false;
  45                 }
  46
  47                 $store = self::getStoreObject( $proto, $params );
  48                 if ( $store === false )
  49                         return false;
  50                 return $store->fetchFromURL( $url );
  51         }
  52
  53         /**
  54          * Get an external store object of the given type, with the given parameters
  55          *
  56          * @param $proto String: type of external storage, should be a value in $wgExternalStores
  57          * @param $params Array: associative array of parameters for the ExternalStore object.
  58          * @return ExternalStore subclass or false on error
  59          */
  60         static function getStoreObject( $proto, $params = array() ) {
  61                 global $wgExternalStores;
  62                 if( !$wgExternalStores )
  63                         return false;
  64                 /* Protocol not enabled */
  65                 if( !in_array( $proto, $wgExternalStores ) )
  66                         return false;
  67
  68                 $class = 'ExternalStore' . ucfirst( $proto );
  69                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
  70                 if( !class_exists( $class ) ) {
  71                         return false;
  72                 }
  73
  74                 return new $class($params);
  75         }
  76
  77         /**
  78          * Store a data item to an external store, identified by a partial URL
  79          * The protocol part is used to identify the class, the rest is passed to the
  80          * class itself as a parameter.
  81          * @return The URL of the stored data item, or false on error
  82          */
  83         static function insert( $url, $data, $params = array() ) {
  84                 list( $proto, $params ) = explode( '://', $url, 2 );
  85                 $store = self::getStoreObject( $proto, $params );
  86                 if ( $store === false ) {
  87                         return false;
  88                 } else {
  89                         return $store->store( $params, $data );
  90                 }
  91         }
  92
  93         /**
  94          * Like insert() above, but does more of the work for us.
  95          * This function does not need a url param, it builds it by
  96          * itself. It also fails-over to the next possible clusters.
  97          *
  98          * @param $data String
  99          * @param $storageParams Array: associative array of parameters for the ExternalStore object.
 100          * @return The URL of the stored data item, or false on error
 101          */
 102         public static function insertToDefault( $data, $storageParams = array() ) {
 103                 global $wgDefaultExternalStore;
 104                 $tryStores = (array)$wgDefaultExternalStore;
 105                 $error = false;
 106                 while ( count( $tryStores ) > 0 ) {
 107                         $index = mt_rand(0, count( $tryStores ) - 1);
 108                         $storeUrl = $tryStores[$index];
 109                         wfDebug( __METHOD__.": trying $storeUrl\n" );
 110                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
 111                         $store = self::getStoreObject( $proto, $storageParams );
 112                         if ( $store === false ) {
 113                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
 114                         }
 115                         try {
 116                                 $url = $store->store( $params, $data ); // Try to save the object
 117                         } catch ( DBConnectionError $error ) {
 118                                 $url = false;
 119                         } catch( DBQueryError $error ) {
 120                                 $url = false;
 121                         }
 122                         if ( $url ) {
 123                                 return $url; // Done!
 124                         } else {
 125                                 unset( $tryStores[$index] ); // Don't try this one again!
 126                                 $tryStores = array_values( $tryStores ); // Must have consecutive keys
 127                                 wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 128                         }
 129                 }
 130                 // All stores failed
 131                 if ( $error ) {
 132                         // Rethrow the last connection error
 133                         throw $error;
 134                 } else {
 135                         throw new MWException( "Unable to store text to external storage" );
 136                 }
 137         }
 138
 139         /** Like insertToDefault, but inserts on another wiki */
 140         public static function insertToForeignDefault( $data, $wiki ) {
 141                 return self::insertToDefault( $data, array( 'wiki' => $wiki ) );
 142         }
 143 }