Retrieving Events from a Notification Port

To retrieve event notifications, set up a program loop that calls GetClusterNotify. This function will return the type of event (dwFilterType), the event key or index (dwNotifyKey), and the name of the object affected (lpszName). Use this information to take appropriate action.

Note the potential for a race condition if multiple threads access the same notification port. For example, one thread could be calling CloseClusterNotifyPort to close the notification port while another thread, which has called GetClusterNotify, is waiting to retrieve information from the same port. Prevent this problem by having the thread that is calling GetClusterNotify check for a CLUSTER_CHANGE_HANDLE_CLOSE event.

The following code fragment detects when a resource is added to the cluster and takes action if the new resource is a Physical Disk.


// code fragment; all error handling omitted
while( 1 )
{
dwStatus = GetClusterNotify( hChange,
                             &dwNotifyKey,
                             &dwFilterType,
                             lpszObjName,
                             &cchObjNameSize,
                             500 );
if( dwStatus == ERROR_SUCCESS )
{
    switch( dwNotifyKey )
    {
    case ResourceEvents:
        if( dwFilterType == CLUSTER_CHANGE_RESOURCE_ADDED )
        {
            // Use the object name to get a resource handle and check the resource type.
            hResource = OpenClusterResource( hCluster, lpszObjName );
            dwResult = ClusterResourceControl( hResource,
                                               NULL,
                                               CLUSCTL_RESOURCE_GET_RESOURCE_TYPE,
                                               NULL,
                                               0,
                                               lpszResType,
                                               cbAllocated,
                                               cbReturned );
            if( lstrcmpi( lpszResType, L"Physical Disk" ) == 0 )
            {
                // perform some action
            }
        }
        break;

    case 2:
    default:
        break;

    } // end switch
} // end if
} // end while


 

 

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