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<?php
/**
* @defgroup ExternalStorage ExternalStorage
*/
/**
* Constructor class for data kept in external repositories
*
* External repositories might be populated by maintenance/async
* scripts, thus partial moving of data may be possible, as well
* as possibility to have any storage format (i.e. for archives)
*
* @ingroup ExternalStorage
*/
class ExternalStore {
/* Fetch data from given URL */
static function fetchFromURL( $url ) {
global $wgExternalStores;
if( !$wgExternalStores )
return false;
@list( $proto, $path ) = explode( '://', $url, 2 );
/* Bad URL */
if( $path == '' )
return false;
$store = self::getStoreObject( $proto );
if ( $store === false )
return false;
return $store->fetchFromURL( $url );
}
/**
* Get an external store object of the given type
*/
static function getStoreObject( $proto ) {
global $wgExternalStores;
if( !$wgExternalStores )
return false;
/* Protocol not enabled */
if( !in_array( $proto, $wgExternalStores ) )
return false;
$class = 'ExternalStore' . ucfirst( $proto );
/* Any custom modules should be added to $wgAutoLoadClasses for on-demand loading */
if( !class_exists( $class ) ) {
return false;
}
return new $class();
}
/**
* Store a data item to an external store, identified by a partial URL
* The protocol part is used to identify the class, the rest is passed to the
* class itself as a parameter.
* Returns the URL of the stored data item, or false on error
*/
static function insert( $url, $data ) {
list( $proto, $params ) = explode( '://', $url, 2 );
$store = self::getStoreObject( $proto );
if ( $store === false ) {
return false;
} else {
return $store->store( $params, $data );
}
}
/**
* Like insert() above, but does more of the work for us.
* This function does not need a url param, it builds it by
* itself. It also fails-over to the next possible clusters.
*
* @param string $data
* Returns the URL of the stored data item, or false on error
*/
public static function insertToDefault( $data ) {
global $wgDefaultExternalStore;
$tryStores = (array)$wgDefaultExternalStore;
$error = false;
while ( count( $tryStores ) > 0 ) {
$index = mt_rand(0, count( $tryStores ) - 1);
$storeUrl = $tryStores[$index];
wfDebug( __METHOD__.": trying $storeUrl\n" );
list( $proto, $params ) = explode( '://', $storeUrl, 2 );
$store = self::getStoreObject( $proto );
if ( $store === false ) {
throw new MWException( "Invalid external storage protocol - $storeUrl" );
}
try {
$url = $store->store( $params, $data ); // Try to save the object
} catch ( DBConnectionError $error ) {
$url = false;
} catch( DBQueryError $error ) {
$url = false;
}
if ( $url ) {
return $url; // Done!
} else {
unset( $tryStores[$index] ); // Don't try this one again!
$tryStores = array_values( $tryStores ); // Must have consecutive keys
wfDebugLog( 'ExternalStorage', "Unable to store text to external storage $storeUrl" );
}
}
// All stores failed
if ( $error ) {
// Rethrow the last connection error
throw $error;
} else {
throw new MWException( "Unable to store text to external storage" );
}
}
}
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