Hi Allati,

My answer is based on the new (3.4) development. In case you have missed the latest 
changes ( I suspect you didn't, since you seem to keep yourself always up to date :) 
), the gateway queues are now "joined" in a central, Service level queue.

What you are describing seems like an extension to the current central queue logic. 
Currently, the queue pushes on the first available (via routers) gateway. If this 
fails, it will requeue the message a couple of times, but it will probably not try 
all gateways. I guess you want to apply some logic in order to try other (or all) 
gateways as well before deciding that the message indeed fails.

It seems to me like a good idea, especially for those managing multiple gateways.

I don't understand one thing, though (I may be missing something):
Your idea of DPL is quite dynamic, i.e. can be a per-message setting, etc. I guess 
that you have already thought about a "static" alternative - something like "always 
try all gateways before deciding the fate of a message". Why did you rule out this 
alternative?

Actually, "central queue" was the reason why I thought described changes can be made
relatively painless. Previously with gateway queues it was way much harder. But even
with this central queue Service does not handle message "switching" from one gateway
to another (Router will return the same gateways set all the time and Balancer will
select one from them, maybe the same one from the set every time).

The dpl was one way to handle message routing a little differently and more
effectively. Now I see that I missed balancing part. Maybe it should be used when
there are several gateways with the same priority (round-robin balancing seems to be
the best choice for this task). However balancing should function outside of DPL and
be service-global. Should think about it a little more.

About static/dynamic DPL:
All gateways are assigned priority when created. However message can provide
different priority for specific gateway, so frankly it looks something like this:

public int getGatewayPriority( Message msg, Gateway gtw )
{
   if (msg.hasPriorityForGateway( gtw ))
      return msg.getPriorityForGateway( gtw );
   else
      return gtw.getPriority();
}

In the end, if message does not provide "override" list, it will be associated with
default DPL. And default DPL will contain all defined gateways. To remove gateways
from DPL for the specific message, "override" list with negative priorities can be
used (or message can provide something like "ignore" list).

Hope I answered the question you asked :)

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