[lvs-users] ldirectord question

Simon Horman horms at verge.net.au
Fri Jun 20 02:06:36 BST 2014


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
> >
> > BankservAfrica is a BBBEE level 4 procurement contributor
> >
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> >
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