On 28 February 2012 05:37, Rajith Attapattu <rajit...@gmail.com> wrote: > If the "queue" and "topic" qualifiers are used then I guess it makes > it really easy for us to work out the validation. > > What are we going to do with the "destination" qualifier ? > Ex destination.my-dest=<address-string> > > 1. We deprecate this and get qpid users to use one of "queue" or > "topic" as the administrator who writes the jndi file surely knows > what it's going to be. > > 2. We create the destination but not allow it to be used with any > methods that require the Queue or Topic interface.
^^ This - it should be created as a Destination that implements neither Queue nor Topic. > 3. Attempt to figure out if the address is a Topic or a Queue based on > the current behaviour (as described in my first email) and then > convert it a Queue or Topic if the Destination object is passed to any > methods that require a Queue/Topic interface. As per my previous comment on the JIRA, I think it's not actually possible to determine from an address string what is a "topic" and what is a "queue". I can define a "queue" which distributes the messages it hold to every consumer, and removes messages only when every current consumer has irrevocably passed that message... is this a "queue" or a "topic"? From a JMS perspective it behaves exactly as you would expect from a topic (especially in an AMQP 1-0 scenario where you can create durable subscribers with durable links). However from an AMQP 0-x perspective this looks like a "queue". (Indeed on my AMQP 1-0 branch I have implemented exactly this type of "queue" in the Java broker... in a class called "Topic" :-) ). Conversely I could define an exchange type which for any given message will route to *at most one* bound queue... this "work sharing exchange" has many of the properties of a "queue" in JMS semantics, but looks like how we currently implement "topics" in AMQP 0-x. Given the above I think it is fruitless and indeed even incorrect to attempt to determine whether a given address satisfies JMS "Queue" or JMS "Topic" semantics based on the address itself. -- Rob > Regards, > > Rajith > > On Mon, Feb 27, 2012 at 11:30 PM, Rajith Attapattu <rajit...@gmail.com> wrote: >> As per the discussion on QPID-792, I'm moving the discussion onto the >> dev list under. >> I have attempted to summarise the current behaviour and some of the >> comments expressed by Rob and Robbie. >> >> Currently the clients (C++, python and JMS) resolves an address (with >> the 0-10 protocol) as follows. >> >> 1. If the name resolves to a queue, we treat it as a Queue >> 2. If the name resolves to an exchange, we treat is a Topic >> 3. If it doesn't resolve to either, we treat it as a Queue. >> >> Rob made the following comments >> "I don't think that we should be trying to do this because I'm pretty >> sure that it is impossible to determine what is a Queue and what is a >> Topic. >> >> I think the closest we can come is to say that an address that says >> you have to create a new temporary auto-delete exclusive queue for >> every consumer should be treated as a topic... but the converse is not >> true. As far as I am concerned the distinction between Queue and Topic >> is something that only the "administrator" can determine, and the code >> cannot determine dynamically." >> >> Robbie also expressed the following, >> "I also think that the (Java) client shouldnt be making gueses as to >> whether something is a Queue or a Topic, as I'm sure was fairly >> evident from previous mailings on the subject last year. If that >> questionable behaviour is causing pain, then we should at least >> consider simply not doing it. Destination is itself only the parent >> interface of Queue and Topic, it doesnt actually offer any methods >> (even the toString, though for backwards compatibility reasons >> admitedly) and really only serves to allow creating Topic and Queue >> consumers etc without having to have a specific Session type. I >> realise forcing users to specify queue or topic in the address string >> wouldnt be consistent with the other clients, but I do think its worth >> noting that the Java client isn't entirely consistent with the other >> clients for obvious reasons and trying to make it more so isnt >> necessarily always going to be a helpful or useful thing." >> >> Rob, further states that we could utilize the queue and topic >> qualifiers that is currently present in our JNDI mechanism. >> "I don't think the queue/topic distinction even needs to go into the >> address - it should only needs to be defined some way in the JNDI >> source >> >> e.g. in a properties file then things that begin >> >> queue.<NAME>=<address string> >> >> would be queues, and >> >> topic.<NAME>=<address string> >> >> would be topics" >> >> Regards, >> >> Rajith > > --------------------------------------------------------------------- > Apache Qpid - AMQP Messaging Implementation > Project: http://qpid.apache.org > Use/Interact: mailto:dev-subscr...@qpid.apache.org > --------------------------------------------------------------------- Apache Qpid - AMQP Messaging Implementation Project: http://qpid.apache.org Use/Interact: mailto:dev-subscr...@qpid.apache.org
