[Ocfs2-devel] [PATCH 0/3] ocfs2: o2net: fix packets lost issue when reconnect

[Joseph Qi]

On 2014/5/15 12:26, Junxiao Bi wrote:
> 
> Hi,
> 
> After the tcp connection is established between two ocfs2 nodes, an idle
> timer will be set to check its state periodically, if no messages are
> received during this time, idle timer will timeout, it will shutdown
> the connection and try to rebuild, so pending message in tcp queues will
> be lost. This may cause the whole ocfs2 cluster hung. 
> This is very possible to happen when network state goes bad. Do the
> reconnect is useless, it will fail if network state doesn't recover.
> Just waiting there for network recovering may be a good idea, it will
> not lost messages and some node will be fenced until cluster goes into
> split-brain state, for this case, Tcp user timeout is used to override
> the tcp retransmit timeout. It will timeout after 25 days, user should
> have notice this through the provided log and fix the network, if they
> don't, ocfs2 will fall back to original reconnect way.
> The following is the serial of patches to fix the bug. Please help review.
TCP RTT is auto-regressive, that means the following case may take
place:
Suppose current retransmission interval is ΔT (somewhat long), network
recovers but down again before the next retransmission windows
comes (< ΔT), so the network recovery won't be detected and ocfs2
cluster still hungs.
> 
> Thanks,
> Junxiao.
> 
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