On 06/16/2013 10:46 AM, Fraser Adams wrote:
Hi Gordon,
I'm afraid that I've *still* not got around to messing with proton/AMQP
1.0 (sorry, I've been tied in knots with various other things) so I
won't be able to do the sort of review this really deserves.
Firstly though thanks for doing this, I think that being able to provide
this sort of configuration fixes a real limitation on queues
"automagically" created under the hood (does this work with
static/dynamic "exchange" routes too?).
This is AMQP 1.0 only. In 0-10 it is the client that actually create the
queue (and at that point the broker can't tell what the queue is to be
used for). In 1.0 the outgoing link is established from the exchange (or
topic with this modification in use) and the subscription queue is under
the full control of the broker which knows the context in which it is
to be used.
I notice that you've also done some work with respect to the headers
exchange x-binding stuff we discussed a little while back and similar
for xquery/xml exchange.
Yes, the client still doesn't accept the 'x-bindings' option, but there
is now a general purpose way of specifying 1.0 filters that covers the
simple cases (i.e. a single binding from subscription queue to the
exchange referenced as the node).
E.g.
my-xml-exchange;
{link:{filter:{name:foo,descriptor:"apache.org:xquery-filter:string",value:"declare
variable $colour external; $colour = 'red'"}}}
my-headers-exchange;
{link:{filter:{name:bar,descriptor:"apache.org:legacy-amqp-headers-binding:map",value:{x-match:all,colour:red,
shape:square}}}}
As mentioned before it would in some cases be possible to auto-translate
from x-bindings to filter syntax if there is sufficient benefit to
justify the effort.
I should also modify the 0-10 client so that it also recognises this
form of filter, meaning that one address could be used for either protocol.
All of that is fantastic, so thanks very much. I don't suppose that
you'd be able to post syntax examples for all of these to the user list
(don't know if you've been able to update things like the Programming in
Apache Qpid book?).
No, I haven't yet updated the book. I must do so.
My headers bindings tend to follow a pattern similar
to below:
"testqueue; {create: receiver, node: {x-declare: {arguments:
{'qpid.policy_type': ring, 'qpid.max_size': 500000000}}, x-bindings:
[{exchange: 'amq.match', queue: 'testqueue', key: 'data1', arguments:
{x-match: all, data-service: amqp-delivery, item-owner: fadams}}]}}"
That would now be handled in two steps. The first is a configuration
step whereby a 'topic' is created referencing amq.match and specifying
the desired 'policy' for subscription queues for that topic.
E.g. qpidt create topic amq.match.default exchange=amq.match
qpid.policy_type=ring qpid.max_size=500000000
Then you would create your receiver using an address that referenced the
topic created, and specifying the filter instead of the x-bindings. E.g.
amq.match.default; {link:{filter:{value:x-match:all,data-service:
amqp-delivery, item-owner:
fadams},name:data1,descriptor:"apache.org:legacy-amqp-headers-binding:map"}}}
All subscriptions from this new topic would use the default queue
configuration specified for the topic.
It was really this approach - define subscription queue config via
configuration rather than directly through the address used by receivers
- that I wanted your thoughts on (more than on the actual code). Would
this be an acceptable/useful solution? (Note, you can create different
topics referencing the same exchange if you want to specify different
policies for different types of use case).
TBH it took a bit of trial and error to figure out the headers binding
syntax at all (sometimes still seems a bit of a black art) so perhaps
the most constructive review comment that I can come up with is that
plenty of example address strings and other config. for various use
cases (including the new shared topic subscription if it needs any
special syntax) would be *really* useful.
Thanks again for this - and sorry again I can't yet do it justice.
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