[lvs-users] Session "persistence" issues

Elliott Barrere elliott at barrere.us
Tue Sep 23 01:00:56 BST 2014


Thanks Malcolm, that's great.  I am a little curious why that isn't the default, since it seems less common that someone would go to the trouble of managing the table through userspace, but what do I know? :)

On Sep 22, 2014, at 1:43 PM, Malcolm Turnbull <malcolm at loadbalancer.org> wrote:

> 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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>> 
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> 
> 
> 
> -- 
> Regards,
> 
> Malcolm Turnbull.
> 
> Loadbalancer.org Ltd.
> Phone: +44 (0)330 1604540
> http://www.loadbalancer.org/
> 
> _______________________________________________
> Please read the documentation before posting - it's available at:
> http://www.linuxvirtualserver.org/
> 
> LinuxVirtualServer.org mailing list - lvs-users at LinuxVirtualServer.org
> Send requests to lvs-users-request at LinuxVirtualServer.org
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