On Fri, 29 Jul 2011 09:11:38 +0200, Willy Tarreau wrote:
Hi Julien,
On Thu, Jul 28, 2011 at 07:16:32PM -0400, Julien Vehent wrote:
Hey guys,
We've been happy users of haproxy in front of our tomcat farm for
some
time now, except for one thing: when we want to put a backend in
maintenance mode, via hatop, we have to deal with users coming back
a
few hours later with a SERVERID cookie and being routed to that
backend.
If it's in maintenance mode, it should not receive any traffic. I
suspect
you just changed its weight to zero, which means it's not elected for
LB
but will still serve persistent requests. Please double-check,
because if
you're certain that you're getting that, then you've spotted a bug.
Hey Willy,
You're right, I do set the weight at zero first, and then after a
couple of hours, put the server in maintenance mode.
What I'm trying to reduce is the time between setting a server's weight
to zero, and seeing no connections on it.
With maxlife 1h, I get a decent compromise. After one hour from setting
the server to zero, I would probably only disconnect 0.001% of obsessive
users, so it's "fine".
I initially configured haproxy to balance based on a SERVERID
cookie,
essentially because I didn't know if the JSESSIONID would provide
the
appropriate persistence, but now I'm thinking that it might be a
good
idea to remove the SERVERID cookie and do all the work on the
JSESSIONID. The goal would be to reduce the time between putting a
server in maintenance and not seeing any traffic on it at all (ie.
all
sessions are expired).
So my question is: what are the pros and cons of using a SERVERID
cookie vs a JSESSIONID ?
Cookie insertion is more reliable and more determinist since there
are
no tables to learn and maintain. Also, with recent versions, we now
have
features such as "force-persist" and "ignore-persist" which make it a
lot
easier to perform maintenance on live service without the user
noticing
and with the ability for the admin to check what he's going to put
online
before doing so. All these are good reasons to use a SERVERID cookie
instead of learning a JSESSIONID cookie.
I fail to see how ignore-persist can help me in this case... As I
understand it, ignore-persist will force haproxy to ignore the
persistence cookie and load balance the request to any available
backend. In my case, it would mean redirect the user with an active
session to another backend, effectively disconnecting it. Am I correct ?
Maybe I'm not seeing the use case properly here.
Thanks,
Julien
