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From Gordon Sim <g...@redhat.com>
Subject Re: Apache Qpid Dispatch Router 0.6.0 Release Candidate 1 now available
Date Tue, 10 May 2016 20:10:50 GMT
On 09/05/16 08:55, Jakub Scholz wrote:
> If I want to use link routing the direction "in" means the client is
> sending messages and the direction "out" means client is receiving
> messages. However when using the autoLinks, the "in" direction means the
> client is receiving and the "out" direction means the client is sending. I
> guess this might have some logic from other pespective, but for me it was a
> bit confusing.

This has confused me more than once also! The in/out always describes 
the direction of message flow from the perspective of the router.

However, link-routes and auto-links use a different link as the 
reference point when determining that direction.

For link-routes it is the direction of message flow over the link 
established by the client. i.e. link a below is 'in', link c is 'out'.

       a    ________   b    ________
    P ---> | router | ---> | broker |
           |        |      |        |
    C <--- |________| <--- |________|
        c               d

For an autolink, it is the direction of message flow over that router 
established link. So if the above diagram was a waypoint address with 
autolinks, the direction of link b is 'out' and for d it is 'in'. This 
does mean though that the ingress-phase uses the 'out' autolink and the 
egress-phase uses the 'in' autolink (which seems confusing when put in 
those terms).

So, while I see that the current scheme is consistent and logical, I 
would also agree it is a little confusing.

E.g. If you want an autolink to a waypoint for the ingress phase, but a 
link route to that waypoint for egress (e.g. for a durable 
subscription), then the direction of each would be 'out' where I at 
least intuitively expected them to be opposites (one 'out', one 'in' as 
they would be if they were both auto-links or both link-routes).

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