[lvs-users] Session "persistence" issues

Malcolm Turnbull malcolm at loadbalancer.org
Mon Sep 22 21:43:22 BST 2014


Elliot,

Their are a couple of mechanisms to handle this, the behaviour that
you probably want is:

net.ipv4.vs.expire_nodest_conn=1

expire the entry in table immediately and inform client that
connection is closed.


Also if you are using ldirectord to manage your lvs table you would
probably use: quiescent=no
i.e. on real server failure remove the entry completely from the LVS table





On 22 September 2014 21:04, Elliott Barrere <elliott at barrere.us> wrote:
> Hi guys -
>
> I'm having an issue with a 2-node setup (similar setup to what's described here) where established sessions to a particular real server don't fail over when that real server fails.  That is, if a connection exists in the LVS connection state table and that real server goes down, the connections to that real server persist, rather than being cleared from the table as I would expect.
>
> My test in a little more detail:
>
> 1) Start my service on realserver1 ONLY and open a connection (thus forcing a connection to realserver1)
> 2) Stop the service on realserver1 and start it on realserver2, verifying "ipvsadm -Ln" shows realserver1 down and realserver2 up
> 3) Establish a "new" connection to the VIP, forcing the same source port & IP with nc
> 4) The connection fails, trying to connect to realserver1 (verified by tcpdump)
>
> It appears that this is because the state table still contains an entry for "SRCIP:SRCPORT VIP:DSTPORT realserver1:DSTPORT".  I am new to LVS, but I assume this is not the expected behavior, because it seems it would be a fairly typical scenario if both load balancers were, for example, behind a PAT firewall.
>
> Can anyone shed some light on this, and how I might possibly fix it?  I am new to LVS so any help is appreciated!
>
> Cheers -
>
> elliott barrere | 206.351.3520
>
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-- 
Regards,

Malcolm Turnbull.

Loadbalancer.org Ltd.
Phone: +44 (0)330 1604540
http://www.loadbalancer.org/



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