Andrew Kennedy wrote:
Hi.
I have been looking at the 0-10 session close semantics, and been
meaning to ask this for a while...
There is no explicit close message in 0-10, rather the session timeout
is supposed to be set to 0 seconds and then a session detach message
is sent. I have implemented this, since it requires simply creating a
handler for sessionRequestTimeout messages that actually sets expiry
to 0, as discussed on QPID-2586 and in this message on the dev list:
http://apache-qpid-developers.2158895.n2.nabble.com/Java-0-10-Session-closure-expiry-timeout-td4865744.html#a4865744
Also, see comments in the code (in o.a.q.t.Session.java):
// XXX: when the broker and client support full session
// recovery we should use expiry as the requested timeout
// XXX: we manually set the expiry to zero here to
// simulate full session recovery in brokers that don't
// support it, we should remove this line when there is
// broker support for full session resume:
expiry = 0;
which is exactly what I have done, I use the expiry field (therefore
on session create the timeout is set to 1 on both sides now) and (in
o.a.q.t.SessionDelegate.java) we have:
// XXX: we ignore this right now, we should uncomment this
// when full session resume is supported:
where I have uncommented the line following, which just calls
ssn.setExpiry(t.getTimeout()) and done the same in the new handler
for sessionRequestTimeout.
I believe that this is a fairly simple and non-contentious change. One
thing that I noticed from other dev list messages is that this could
affect the failover mechanism used by the C++ clients. I ran the cpp
test suite with my changes and noticed no difference, but then I
couldn't see what tests would actually be affected. Can anyone shged
more light on the problems I might expect or be missing?
Sorry for not commenting on this sooner, but until being prompted by a
few conversations, I only had a very vague recollection of this area.
I think this change is going to be problematic for the C++ broker (and
possibly for the Java broker too).
The reason the 0-10 session only ever advertises zero as the timeout is
because it does not do frame level replay. It does a semantic resume. If
it advertises a non-zero timeout then it will end up doing a semantic
resume against a session that is expecting frame level replay, and that
won't be happy.
--Rafael
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