[lvs-users] Connection Synchronisation for HA

Markhasin, Dan dan.markhasin at intel.com
Wed Dec 10 12:14:53 GMT 2014

Yes, ipvsadm can synchronize the connections table between active and passive servers.

In /etc/ipvsadm.rules, add the following on the active server:

--start-daemon master --syncid 11
--start-daemon backup --syncid 10

And the same, with reverse weights, on the passive server:

--start-daemon master --syncid 10
--start-daemon backup --syncid 11

This will allow bi-directional synchronization between active and passive LVS servers.

HOWEVER - there is a caveat here; the connection synchronization occurs only when a connection is made or updated. So in a scenario where one of the servers is rebooted for whatever reason, you will not be able to do automatic failback since the connections table will be out of sync, and there is no way (that I am aware of) of forcing a sync. You will need to wait for the connections table to synchronize (the time it takes should be equal to the timeout settings of ipvsadm) before you can perform a failback.


-----Original Message-----
From: M.Rajender [mailto:rajender at visolve.com] 
Sent: Tuesday, December 9, 2014 2:34 PM
To: LinuxVirtualServer.org users mailing list.
Subject: Re: [lvs-users] Connection Synchronisation for HA

Thanks for the information.

What you mean to say is that, we can synchronise the connections between 
*virtual/firewall* servers only and not between *application* servers. 
i.e, servers which acts as intermediate between two machines (client & 
internet) and which just forwards the request from one to another server.

Please correct me if i am wrong.

On 12/09/2014 03:31 AM, Jonathan Petersson wrote:
> I presume you're looking for something like this:
> http://backreference.org/2013/04/03/firewall-ha-with-conntrackd-and-keepalived/
> Although they're using keepalived in this example but you still want to get
> conntrackd going
> On Mon, Dec 8, 2014 at 11:09 AM, M.Rajender <rajender at visolve.com> wrote:
>> Hello All,
>> I have two Linux servers configured for High availability using
>> Heartbeat and everything is working fine.
>> But few of our applications use RPC calls for communication, which is a
>> state-ful connection. So when the fail-over happens we need to
>> re-connect the application since the connection gets terminated.
>> While checking the internet, I found that *ipvsadm* does Connection
>> Synchronisation between the servers.
>> This feature is wonderful; When a stand-by server becomes the active, it
>> will have all the information about the currently active connections and
>> will be able to continue to process the requests.
>> My goal is not achieving Linux Virtual Server and want to achieve HA for
>> state-full connection.
>> Please let me know whether the above will be possible using the LVS and
>> if possible, then can you provide me some tutorial (or) configuration
>> steps to achieve the same.
>> Thanks in advance.
>> --
>> Regards,
>> Rajender.M
>> _______________________________________________
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