James Mansion wrote:
Gordon Sim wrote:
However, following the execution.exception is the session.detach as
required by the AMQP 0-10 spec. If the session goes out of scope
before this is handled, then the whole connection ends up being
destroyed due to the NotAttachedException thrown.
To me that suggests that some representation of a Channel object *must*
live on until the client and server have both agreed that it has been
closed,
Yes, I agree. It is logically incorrect to treat a session that the
application has let go out of scope as detached without ensuring that
the server has been informed of the detachment[1].
otherwise something might cause the client to try to reuse the
channel while there are still messages in transit for it.
True. The current API doesn't yet support reusing channels on a given
connection, though[2].
It does mean that the client would not correctly handle an erroneous
attempt by the broker to send frames on a session that has genuinely
been detached. That isn't as serious in my view and seems like a
worthwhile trade for getting the issue describe in the jira resolved.
Surely the problem is also that the broker has (or will shortly) send
frames that the protocol requires - that's hardly erroneous?
After sending an execution.exception, the broker will only send the
detach frame. The current client implementation takes the detach as
implied by the exception and marks the session as detached on handling
the exception. Therefore the detach frame will not have actually have
any effect. Dropping it is in my view preferable to throwing an
exception, which will result in the whole connection being lost.
Correcting the design is even better of course. My proposed patch
doesn't attempt to do that, it is just a simple fix for an immediate and
real problem. However I've created a couple of Jiras for these other
issues if anyone wants to take them on.
[1] https://issues.apache.org/jira/browse/QPID-1789
[2] https://issues.apache.org/jira/browse/QPID-1788
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