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Re: [lvs-users] Problem using LVS

To: Hugo Delchini <delchini@xxxxxxxx>
Subject: Re: [lvs-users] Problem using LVS
Cc: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
From: Julian Anastasov <uli@xxxxxxxxxxxxxxxxxxxxxx>
Date: Sun, 23 Jan 2000 16:35:00 +0200 (EET)
        Hi,

On Fri, 21 Jan 2000, Hugo Delchini wrote:

> Hi,
> 
> thanx for this greate tool called "LVS".
> 
> I have a question about a problem we experiment on our cluster.
> 
> We use ipvs-0.9.7 and Linux 2.2.11 on a cluster of six nodes, one
> director and
> 5 real servers.
> 
...
> When we use a benchmark program we wrote to generate a lot of http
> queries, everything works fine
> during our, great tool.
> 
> But now we want to delete a node from the service by issuing the command
> 
> on the
> director while our bench is running :
> ipvsadm -d -t 192.168.7.100:80 -R 192.168.7.5:80
> Here we want to delete the node 5.
> 
> Immediatelly, the service stops on all nodes, the director seem to hang,
> 
> only for the
> ipvs part of the system, everything else seem to work normally.
> This is nearly the same if we add a node. When we add it it is never
> used by the director.
> When we delete a node we see with ipvsadm -l that it is really deleted.
> When we add a node we see that it is really added.
> 

        Did you tried another "great" tool. I suspect your tool because
when the traffic to the deleted server is stopped the acknowledgments
through the director are not forwarded to the real server and you tool is
blocked. When this occurs you have to check with telnet to port 80 if the
service is still working. I think that it is still possible connections to
other real servers to succeed. If the telnet is blocked too I don't know
where is the problem. You can stop and start again your tool. If the
service is working after that, the problem is in your tool. If nothing
helps you have to enable LVS debugging:

        put "#define CONFIG_IP_VS_DEBUG" in
/usr/src/linux/include/linux/config.h and recompile the kernel. You can
check with "tcpdump -e ..." where is the problem: in the client, in the
director or in the real server.

        Do you use any other patches for the masquerading code?

        What about trying VS/DR mode instead of VS/TUN mode? Just change
the method in the Director. The setup is same for the Real servers.

        Everything in my setups is same as your setup. The difference is
that I don't use your tool. There are no other reports for such/any
problems already 2-3 months. I can tell you that LVS 0.9.7 is very stable.
The only thing I can do is to wait for your bug report if the problem is
not in your testing tool :)

Regards,

Julian Anastasov


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