On Friday 01 April 2016 15:02:05 Jon Maloy wrote:
> > I saw that the problem is in the lack of memory.
> > I also made a simple stress test (one side sends in a loop) and received
> > this problem immediately.
> > But User's Manual states that if there is no room for the receiving side
> > to accept message it prevents the sending side from sending, effectively
> > blocking the sender.
>
> That is true only for connection oriented messaging (SOC_STREAM,
> SOCK_SEQPACKET). Is that what you are running?
> If you are just doing a tight loop with 66k messages using TIPC_PORT_NAME
> you will not have any flow control, and the messages might be dropped in the
> receiving socket.
> But if you are really tight of memory they might also be dropped at the link
> layer, which is what you are seeing.
> I have never seen that happening before, but it is fully possible in TIPC
> versions before commit 40ba3cdf542a469aaa9 ("tipc: message reassembly using
> fragment chain") from Nov 6th 2013. (I don't remember which Linux version
> this corresponds to, but that should be easy to find out). Furthermore, this
> might even happen with connection oriented messaging, but is less likely.
>
> So, if you are running connectionless, I recommend you to go to a connection
oriented mode. If you already are connection oriented, you can try to find out
which version this fix was in, and re-adapt the code.
Thanks a lot, Jon, again.
After your answer I again looked through the both manuals and did not find
anything saying that connectionless messaging allows drops. Vice verse, the
programmer's manual explicitly states that "TIPC is designed to be a reliable
messaging mechanism, in which an application can send a message and assume
that the message will be delivered to the specified destination as long as
that destination is reachable."
Now, is it a bug, corrected in Nov 6th 2013? Or a feature?
i can't move to connection oriented methods, because I need to support one-
to-3 and 3-to-one.
Sorry.
--
Leon
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