ConnectionImpl holds weak_ptrs to SessionImpl instances. If all the
Session objects referring to a given SessionImpl are allowed to go out
of scope, ConnectionImpl treats the session as having been detached and
throws a NotAttachedException if there are any incoming frames for the
channel the session was attached to.
This is particularly problematic when the session is sent an
execution.exception by the broker. This results in an exception being
thrown to the application which may well as a result let the session go
out of scope.
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.
I've raised a jira: https://issues.apache.org/jira/browse/QPID-1785. I
also have a proposed 'fix' (see patch below). This just prevents the
NotAttachedException being thrown, logging a message instead.
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.
Consequently unless there are objections I'll go ahead and apply this patch.
Index: src/qpid/client/ConnectionImpl.cpp
===================================================================
--- src/qpid/client/ConnectionImpl.cpp (revision 761362)
+++ src/qpid/client/ConnectionImpl.cpp (working copy)
@@ -111,9 +111,11 @@
Mutex::ScopedLock l(lock);
s = sessions[frame.getChannel()].lock();
}
- if (!s)
- throw NotAttachedException(QPID_MSG("Invalid channel: " <<
frame.getChannel()));
- s->in(frame);
+ if (!s) {
+ QPID_LOG(info, "Dropping frame received on invalid channel: "
<< frame);
+ } else {
+ s->in(frame);
+ }
}
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