..
..                             Vortex Link
..
..    This software and documentation are Copyright 2010 to 2018 ADLINK
..    Technology Limited, its affiliated companies and licensors. All rights
..    reserved.
..
..    Licensed under the ADLINK Software License Agreement Rev 2.7 2nd October
..    2014 (the "License"); you may not use this file except in compliance with
..    the License.
..    You may obtain a copy of the License at:
..                        docs/LICENSE.html
..
..    See the License for the specific language governing permissions and
..    limitations under the License.
..

.. _`Selective Routing`:

#################
Selective Routing
#################

The selective routing functionality allows to define which kind of data (which topics
and which partitions) should be routed or not by Vortex Link. This is defined with 
the help of a black list and/or a white list. Each list is defined in a different file
containing a *partition.topic* combination on each line. *partition.topic* combinations 
may contain wild-card ‘*’ characters.

Example :

.. code-block:: bash

   partitionA.topicA
   *.topicB
   partitionB.*
   A*.C

Each Vortex Link service can be configured to point to a black list file and/or a white 
list file with the help of :ref:`config_link_blacklist_file` and :ref:`config_link_whitelist_file` 
configuration properties. 

When a white list is defined, *partition.topic* combinations not present in the white 
list will not be routed by Vortex Link. When a black list is defined, *partition.topic* 
combinations present in the black list will not be routed by Vortex Link. When both 
white list and black list are defined, black list has precedence over white list: 
*partition.topic* combinations present in both lists will not be routed by Vortex Link.

Different black lists and white lists can be defined in each different Vortex Link service 
of the system. This means that some *partition.topic* combinations may be routed from/to some
sub systems/applications but not from/to some other sub systems/applications in the system. 

|caution|
  **WARNING** Partitions containing a wild-card ‘*’ character are never blocked. So user entities 
  configured with partitions containing a wild-card ‘*’ character will always be able to send receive 
  data on those partitions whatever is defined in the black and white lists.

.. |caution| image:: ./images/icon-caution.png
            :height: 6mm


*************************************************************
Specific case of Vortex Link as an intermediate routing point
*************************************************************

Note that Vortex Link only applies Selective Routing to the subsystem or devices it routes directly
(i.e. only to DDS applications it discovered directly via UDP multicast or TCP).
If Vortex Link is used as an intermediate routing point between 2 (or more) services, it
wont apply Selective Routing to the data it routes between those services.

For instance, with an Indirect-LAN-to-LAN deployment as such:  

.. figure:: ./images/SelectiveRouting.png
   :alt: Selective Routing
   :width: 40em
   :align: center
      
   **Selective Routing**

Vortex Link applies the blacklisting of "topicA" only to DDS applications it directly discovered.
But it still routes data on "topicA" between the two Vortex Link services deployed in subsystems.