Thanks guys, I think this explains it nicely but I'll play around with waypoints some more to ensure I fully understand it. Having read your description I think that it's a nomenclature issue.
To me prefixing "waypoints" and "phases" with "processing" i.e. processing phases and processing waypoints makes them clearer in my mind. Cheers Noel On Thu, Nov 19, 2015, 08:00 aconway <acon...@redhat.com> wrote: > On Sun, 2015-11-15 at 10:51 +0000, Noel OConnor wrote: > > Hi, > > I've struggling with understanding the context of phases in waypoints > > and > > how you would use them. > > Are phases an AMQP or dispatch routes concept ? > > Dispatch only, more below... > > > I've taken a look at the code and found the following > > > > >>* A waypoint sends/receives messages to/from an external entity > > such as a > > >>* broker as part of a multi-phase address. > > > > Is a multi-phase address something line a/b/c/d ? > > > > >>* An address can have multiple phases. Each phase acts like a > > separate > > address, > > >>* but sharing the same address string. > > > > >>* Phases are not visible to normal senders/receivers, they are set > > by > > >>* waypoints. Messages from normal senders go to the phase=0 > > address. > > Normal > > >>* subscribers subscribe to the highest phase defined for the > > address. > > > > >>* A waypoint takes messages for its in-phase and sends them to the > > external > > >>* entity. Messages received from the external entity are given the > > waypoint's > > >>* out-phase. Waypoints can be "chained" with the out-phase of one > > equal > > to the > > >>* in-phase for the next. Thus waypoints provide a way to route > > messages > > via > > >>* multiple external entities between a sender and a subscriber > > using the > > same > > >>* address. > > > > An example of the above would be great ? > > Are waypoints a kind of orchestration scheme i.e. routing from one > > broker > > to another ? > > Yes, exactly! Waypoints are a powerful feature but lots of people find > them confusing so we may change the way they are expressed in future to > be more easily understood. > > Phases are internal to dispatch, they represent different "stages" in > the lifecycle of a message associated with just *one* externally > -visible AMQP address. > > Simple example: exposing an AMQP queue as a dispatch address "Q". You > want messages to the address to go onto the queue, and subscribers to > the address to subscribe to the queue. You don't want messages sent to > the dispatch address to be sent directly to the subscribers, bypassing > the queue. So you have a waypoint with 2 phases. Messages arriving from > outside of dispatch are Q-0, so they get sent to the queue by the > waypoint. The waypoint defines a second phase Q-1, for messages coming > *from* the queue. Subscribers subscribe to Q-1. The external processes > only know about "Q", the phases are internal to the dispatch network. > > More complex example is a "distributed queue", there's code in > tests/system_tests_broker.py. Senders and subscribers to a single > external address get load-balanced over a set of broker queues > automatically. > > All the examples so far end up needing only 2 phases, so it's possible > that allowing N phases is overkill and we can simplify the presentation > a bit. > > Cheers, > Alan. > > > --------------------------------------------------------------------- > To unsubscribe, e-mail: users-unsubscr...@qpid.apache.org > For additional commands, e-mail: users-h...@qpid.apache.org > >
