Re: [amqp-bindmap] JMS Destination handling

[Robbie Gemmell <rgemmell@redhat.com>]

Hi Jakub,

I favoured option 3 as a means for implementations that wish to avoid option 1 to do so, essentially thinking of improving the optional functionality some JMS clients already offered to do so by defining a further optional mechanism to convey any inherent default prefix of the server (retaining client side ability to control/override it). Following this discussion and others, I am now of the opinion we should treat this only as an implementation detail, like JMS Destination names themselves are considered, and AMQP 1.0 addresses also.

In terms of using other clients, they would continue to utilise whatever address strings they are already required to by the server they are connecting to, as the actual AMQP address of the nodes would still be the same from any client.

In the case of networks of different [server] components, I think you would need to ensure the resulting node addresses used the same format everywhere if you wanted that level of cross-server compatibility right now. Ultimately, I would be looking to the Addressing spec to really offer a way to solve that issue through defined global addresses for nodes. As Rob pointed out in previous calls/mails, any client doing that type of prefixing would want to avoid changing such addresses.

The idea of incorporating management types into addressing interesting. One possible issue could be that people don't necessarily implement management but could use the global addressing. Really a subject for those groups at the core TC I think (though it may come up as we consider use of management for any JMS functionality, e.g shared subscriptions).

Robbie

----- Original Message -----
> From: "Jakub Scholz" <Jakub.Scholz@deutsche-boerse.com>
> To: "Robbie Gemmell" <rgemmell@redhat.com>
> Cc: amqp-bindmap@lists.oasis-open.org, amqp-bindmap@lists.oasis-open.org
> Sent: Thursday, 18 December, 2014 10:39:43 AM
> Subject: Re: [amqp-bindmap] JMS Destination handling
> 
> Hi Robbie,
> 
> Clearly, you seem to be in favor of the option 3. But it is not clear to me
> what impact will the prefixes have in other clients. From my brief
> experience with ActiveMQ/A-MQ, I didn't really liked the way it introduced
> the queue/topic concept into clients written in other languages (e.g. the
> addresses with different prefixes for queues versus topics which have to be
> used in the qpid.messaging C++ API). I'm sure that it can help in the JMS
> clients, but it isn't nice to other clients which are not based on the
> queue/topic concept and it basically breaks the cross-implementation
> compatibility there.
> 
> It is also not clear how this concept would work with a larger network of
> AMQP components. E.g. when JMS client connects to AMQP server X which tells
> him to use prefix "queue://" and "topic://" when connecting, but the
> message with your reply-to address would be forwarded from server X
> somewhere to server Y where the software works with prefixes "queue::" and
> "topic::"?
> 
> -----
> 
> To me it seems that there are several working streams - JMS, addressing and
> management - which very closely relate to each other but are being designed
> separately.
> - Addressing tries to define addresses which allow routing across global
> networks and thus are also compatible across implementations
> - JMS is trying to create addresses which would define the node type / node
> behavior
> - Management already talks about types ... e.g. org.amqp.queue
> 
> Shouldn't we use the Management stream to define the basic type
> hierarchy ... e.g. org.amqp.topic and org.amqp.queue (+ some other specific
> or generic nodes) ... afterwards incorporate these into the addressing ...
> and at the end use the address with org.amqp.queue or org.amqp.topic in the
> JMS? The fact that we define the type hierarchy doesn't necessarily mean
> everyone has to implement everything. But it would be clear that if you
> implement topic it should inherit from the org.amqp.topic type and be able
> to handle org.amqp.topic somewhere in the address.
> 
> Thanks & Regards
> Jakub
> 
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> 
> From:	Robbie Gemmell <rgemmell@redhat.com>
> To:	amqp-bindmap@lists.oasis-open.org,
> Date:	17/12/2014 13:31
> Subject:	[amqp-bindmap] JMS Destination handling
> Sent by:	<amqp-bindmap@lists.oasis-open.org>
> 
> 
> 
> Hi everyone,
> 
> I would like to have a discussion around JMS destination handling in the
> JMS Mapping for AMQP 1.0, in particular around how to handle JMS
> Destination names via the AMQP "address" field of a link
> (producer/consumer) source/target and the "to", and "reply-to" field of
> messages.
> 
> Apologies for the length of the mail, there is a fair bit to outline. I
> moved some information for full context to the end to help a tiny bit. I
> didn't use JIRA for this as mentioned on the call yesterday, as I noticed a
> problem with my account.
> 
> JMS defines multiple Destination types that each have their own inherent
> name space, so it is possible for example to have a Queue and a Topic with
> the same name (e.g "foo"). AMQP defines an "address" field on the
> source/target of links (producers/consumers), and a "to" and "reply-to"
> field are available on messages, to indicate the destination node (e.g
> queue/topic) address. These are typically string values, and they form a
> single space since as there is no additional node type information only the
> address name itself.
> 
> This is is mostly an issue for non-temporary Queues and Topics since
> TemporaryQueue and TemporaryTopic destinations will be given generated
> addresses by the 'broker' peer through use of dynamic nodes, and so can
> naturally be prevented from having the same addresses as each other, and be
> made unlikely or unable to clash with non-temporary nodes.
> 
> To handle this mapping between JMS and AMQP it would seem we must either:
> 1. Not support JMS Queues and Topics with the same name existing at all, OR
> 2. Allow multiple nodes to have the same address string but use type
> metadata (via capabilities + annotations, see additional context) to
> discriminate between them, OR
> 3. Utilise address string naming conventions (e.g prefixes) for them to
> separate the types into subspaces.
> 
> The first option is an issue for implementations that already do, and wish
> to continue to, allow Queues and Topics with the same name via other
> protocols while also supporting AMQP, and would be a limitation in terms of
> full JMS support. The second option would break reply-to usage for any
> clients or intermediaries that don't understand the message annotations
> and/or source+target capabilities carrying type metadata (see additional
> context). The third option either requires clients to always utilise the
> full address strings in session.createQueue("<queue-prefix>foo") etc calls,
> or providing a means to configure the prefixes within the client so that
> they are added/removed behind the scenes and the application just uses
> session.createQueue("foo"), but the resulting AMQP address string would be
> "<queue-prefix>foo". The main issue with requiring clients always use the
> full address as the session.createQueue(..) value would be for bridging
> between different systems using different conventions, though the values
> for those methods are noted as being provider-specific.
> 
> Both the old Qpid AMQP 1.0 JMS client, and the new JMS client we are
> creating that implements the JMS Mapping for AMQP being worked on,
> currently do some form of the third option, providing a way to configure a
> 'queue prefix' and 'topic prefix' that are used to prefix the application
> provided strings in session.createQueue(..) etc for outgoing addresses used
> for links and messages and be stripped from incoming addresses on messages
> to give the names used for the JMSDestination and JMSReplyTo objects.
> Temporary destinations are named by the 'broker' peer and their addresses
> are used as provided.
> 
> The main issue with this approach is that such configuration makes it more
> difficult to use the client against a number of different brokers, which is
> a goal, since this configuration is likely to differ between them meaning
> even the simplest HelloWorld type example may be unable to work against
> them without additional configuration.
> 
> An idea to handle this was to have the brokers use connection properties to
> inform the client of the prefixes (if any) they require it to use, allowing
> different brokers to supply their own specific value (if any) to meet their
> requirements, and allowing clients/simple applications to work against many
> of them without further configuration change.
> 
> An alternative suggestion was to have the JMS Mapping define a set of
> standard name prefixes the client would use by default, such that the issue
> of Topics and Queues with the same name is addressed by the mapping, while
> also allowing brokers to specify their own values via connection properties
> so that their specific needs can still be met if different (e.g they have
> existing naming conventions they wish/need to retain).
> 
> There was also a suggestion that something beyond a simple prefix may be
> needed, I will let the person behind those thoughts expand further to stop
> this getting any longer for now.
> 
> Thoughts?
> 
> Robbie
> 
> 
> 
> Additional Context:
> 
> We also need to transmit the destination type information during link (e.g
> producer/consumer) attachment and on sent messages to ensure we can support
> the required JMS behaviours (e.g. to indicate we are attaching to a
> particular type of node, say a queue, and for carrying JMSDestination and
> JMSReplyTo type on messages to indicate/discover where a message was sent).
> 
> For handling these points we are defining the following behaviour:
> 
> # During link attachment for producers/consumers:
> - Node name carried in source/target "address" field string.
> - JMS Destination type represented by capabilities on the source/target
> (e.g "queue", "topic", "temporary-queue", "temporary-topic").
> - Clients can optionally assert on the attach response that the required
> capabilities exist in the source/target to ensure they have attached to a
> node that meets their requirements.
> - 'Broker' peers can use the capabilities to determine the type of node to
> create if it is a dynamic node being requested (or if they support
> auto-creation of non-temporary nodes).
> 
> # When sending messages:
> - Node names carried in "to" and "reply-to" fields as appropriate.
> - JMS Destination type carried in "x-opt-jms-dest" and "x-opt-jms-reply-to"
> message annotations as a byte.
> 
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