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List:       openais
Subject:    Re: [Openais] Question about hold and retransmit timeout
From:       Steven Dake <sdake () redhat ! com>
Date:       2010-01-29 1:24:44
Message-ID: 1264728284.2569.85.camel () localhost ! localdomain
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On Thu, 2010-01-28 at 11:33 -0700, hj lee wrote:
> Hi all,
> 
> I am using corosync-1.1.2 on CentOS 5.3. I set token 200ms and hold
> 50ms in corosync.conf. Then token_retransmit_timeout is auto
> calculated as 47ms. Suppose very idle ring with two-node where there
> is no new message to send. Think about the following scenario.
> 
> 1. The node A sends a token to next node will start the reetransmit
> timer(47ms).
> 2. The next node B receives a token and starts hold timer(50ms).
> 3. When hold timeout, node B will pass the token to node A.
> 
> The 50ms is larger than 47ms, so at node A the retransmit timer will
> expire before receiving a token, as a result node A will resend the
> token until it receives it. Assuming no token lost, then there will be
> at least one token retransmission every token pass. Is my assessment
> correct? Or I am wrong? If I am correct, then should I reduce the hold
> timeout?

Yes your logic makes sense.  Another option besides reducing the hold
timer is to increase the retransmit timer (or reduce the number of
retransmissions 

token_retransmits_before_loss_const
              This value identifies  how  many  token  retransmits
should  be
              attempted  before forming a new configuration.  If this
value is
              set, retransmit and hold will be automatically  calculated
from
              retransmits_before_loss and token.


It may be that token hold timer is not being constrained and calculated
properly in the default configurations.

Regards
-steve

> 
> Thanks
> hj
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