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         /* Fetch data from given URL */
  17         static function fetchFromURL( $url ) {
  18                 global $wgExternalStores;
  19
  20                 if( !$wgExternalStores )
  21                         return false;
  22
  23                 @list( $proto, $path ) = explode( '://', $url, 2 );
  24                 /* Bad URL */
  25                 if( $path == '' )
  26                         return false;
  27
  28                 $store = self::getStoreObject( $proto );
  29                 if ( $store === false )
  30                         return false;
  31                 return $store->fetchFromURL( $url );
  32         }
  33
  34         /**
  35          * Get an external store object of the given type
  36          */
  37         static function getStoreObject( $proto ) {
  38                 global $wgExternalStores;
  39                 if( !$wgExternalStores )
  40                         return false;
  41                 /* Protocol not enabled */
  42                 if( !in_array( $proto, $wgExternalStores ) )
  43                         return false;
  44
  45                 $class = 'ExternalStore' . ucfirst( $proto );
  46                 /* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
  47                 if( !class_exists( $class ) ) {
  48                         return false;
  49                 }
  50
  51                 return new $class();
  52         }
  53
  54         /**
  55          * Store a data item to an external store, identified by a partial URL
  56          * The protocol part is used to identify the class, the rest is passed to the
  57          * class itself as a parameter.
  58          * Returns the URL of the stored data item, or false on error
  59          */
  60         static function insert( $url, $data ) {
  61                 list( $proto, $params ) = explode( '://', $url, 2 );
  62                 $store = self::getStoreObject( $proto );
  63                 if ( $store === false ) {
  64                         return false;
  65                 } else {
  66                         return $store->store( $params, $data );
  67                 }
  68         }
  69
  70         /**
  71          * Like insert() above, but does more of the work for us.
  72          * This function does not need a url param, it builds it by
  73          * itself. It also fails-over to the next possible clusters.
  74          *
  75          * @param string $data
  76          * Returns the URL of the stored data item, or false on error
  77          */
  78         public static function randomInsert( $data ) {
  79                 global $wgDefaultExternalStore;
  80                 $tryStorages = (array)$wgDefaultExternalStore;
  81                 // Do not wait and do second retry per master if we
  82                 // have other active cluster masters to try instead.
  83                 $retry = count($tryStorages) > 1 ? false : true;
  84                 while ( count($tryStorages) > 0 ) {
  85                         $index = mt_rand(0, count( $tryStorages ) - 1);
  86                         $storeUrl = $tryStorages[$index];
  87                         list( $proto, $params ) = explode( '://', $storeUrl, 2 );
  88                         $store = self::getStoreObject( $proto );
  89                         if ( $store === false ) {
  90                                 throw new MWException( "Invalid external storage protocol - $storeUrl" );
  91                                 return false;
  92                         } else {
  93                                 $url = $store->store( $params, $data, $retry ); // Try to save the object
  94                                 if ( $url ) {
  95                                         return $url; // Done!
  96                                 } else {
  97                                         unset( $tryStorages[$index] ); // Don't try this one again!
  98                                         sort( $tryStorages ); // Must have consecutive keys
  99                                         wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
 100                                 }
 101                         }
 102                 }
 103                 throw new MWException( "Unable to store text to external storage" );
 104                 return false; // All cluster masters dead :(
 105         }
 106 }