[lvs-users] ldirectord question

Ilo Lorusso IloL at bankservafrica.com
Fri Jun 20 09:02:16 BST 2014


Thanks for the feedback,

Once we have scheduled new connections to the new real server and we have this existing connection  using quiescence ,

Why can't we move that existing connection to another real server ?

I know firewalls can move existing connections and TCP states between failover pairs 

-----Original Message-----
From: lvs-users-bounces at linuxvirtualserver.org [mailto:lvs-users-bounces at linuxvirtualserver.org] On Behalf Of Simon Horman
Sent: Friday, June 20, 2014 3:07 AM
To: Aaron West
Cc: LinuxVirtualServer.org users mailing list.
Subject: Re: [lvs-users] ldirectord question

Hi,

On Thu, Jun 19, 2014 at 06:20:02PM +0100, Aaron West wrote:
> Hi Ilo,
> 
> To my knowledge a real server failing a health check done by an agent 
> such as ldirectord/keepalived is pulled from the LVS table.
> 
> This will break any established connections to this server. A new 
> connection should then start on a remaining live server on the next 
> click/refresh for something like a web application or next connection 
> retry for something else.

It is possible, though not necessarily desirable, to avoid breaking existing connections by using quiescence. On the LVS side this is implemented by setting a server weight to zero, which allows existing connections to continue but prevents new connections from being "scheduled".

This is exposed in ldirectord as a quiescence setting by which it sets the weight of a real-server to zero rather than removing it in the case where its health check fails.

I am not familiar with keepalived but I suspect it has a similar feature.

> How this affects your app/users depends on your application design, 
> mostly HTTP sessions would be fine while things like RDP/SSH/HTTPS 
> would require you to reconnect/re-authenticate.
> 
> Regards
> 
> Aaron West
> 
> 
> On 19 June 2014 16:42, Ilo Lorusso <IloL at bankservafrica.com> wrote:
> 
> > Hi ,
> >
> >
> > I have a general question of how ldirectord works, I have setup my 
> > virtual service and real servers
> >
> > I have an active connection and traffic is flowing through to the 
> > real server perfectly as shown below
> >
> >
> > I want to know is it possible to move an established connection 
> > between the real servers without resetting or reestablishing the TCP connection ?
> >
> > [root at lbmaster ~]# ipvsadm -Ln
> > IP Virtual Server version 1.2.1 (size=32768) Prot LocalAddress:Port 
> > Scheduler Flags
> >   -> RemoteAddress:Port           Forward Weight ActiveConn InActConn
> > TCP  172.16.162.190:40054 wlc persistent 300
> >   -> 172.16.162.199:40054         Masq    100    1          0
> >   -> 172.16.162.200:40054         Masq    99     0          0
> >
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_______________________________________________
Please read the documentation before posting - it's available at:
http://www.linuxvirtualserver.org/

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http://www.bankservafrica.com/Contactus/EmailDisclaimer.aspx 

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