On 12/01/17 16:07, Robbie Gemmell wrote:
On 12 January 2017 at 15:21, Lorenz Quack <[email protected]> wrote:
Hello,
Robbie, Rob, Alex, and I had a discussion on IRC yesterday about the Qpid
Broker for Java support for JMS 2.0 shared subscriptions.
This is a follow-up from that discussion.
We discussed that it would be helpful to have a document describing the
broker behaviour purely in AMQP 1.0 terms.
Alex and I went ahead and created such a document [1].
We noticed a problem with unsubscribe as it is described in QPIDJMS-220.
There it is specified that unsubscription can be done with an Attach with a
null Source and that the broker should refuse the Link if it cannot find the
Queue the Link is referring to. This seems to violate the AMQP spec which
allows null Source Attachs.
Please review/comment.
What its meaning is that the 'null source lookup' reciever attach
should be responded to with ab attach with a null source if there is
no subscription, i.e there is no existing source that the broker can
provide the details for to complete the details of the link attach for
that named link. See an example in Figure 2.33 and 2.36 of the spec
for refusing and recovering links, albeit for the reverse case of a
client sending link,
http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html#doc-idp315568.
I was referring to the part "Existing non-shared subscriber
behaviour (used for JMS 1.1)" of QPIDJMS-220 where it says:
"[...] this is utilised by Session#unsubscribe by attaching a
receiving link using the subscription name, with a null Source,
requiring the server to perform a lookup for an existing
subscription using this link name. If none is found then the
link is refused and the client throws an exception, [...]"
Are you saying that it is okay if the broker does not refuse the
link? That seems to contradict the above quote. From an AMQP
perspective I don't see a reason a Attach of a Receiving Link as
in this case with a null Source should fail so I would always
accept such Attachs.
Kind regards,
Lorenz and Alex
[1]
https://cwiki.apache.org/confluence/display/qpid/JMS+2.0+shared+subscription+support
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