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Chris Williams wrote:
>
> Hi all,
> I'm in the midst of setting up a LVS DR and am having troubles getting
> my head around persistance. My configuration sports three LVS real
> servers running apache/tomcat4 java applications. Obviously I need
> persistance to ensure each client remains with its choosen server
> through the entire session, or horrible things go wrong.
<caveat>
This is not my area, other people (eg Ratz) work in this area all day.
</caveat>
I've sat on https sites for more that 30mins of inactivity. Also I've
had the modem line drop on me in the middle of filling in forms on
badly written websites (eg registering a domainname)
- when I come back, I have a new IP. I expect
anyone who wants to do internet business to handle these problems seamlessly.
Persistence only gets you so far here, since memory requirements
limit you to the number of connections maintained.
Ratz's idea (in the HOWTO) is to redesign you application. He can do that.
Not everyone can. He maintains state data on the servers with a database.
Alternately in php3 you could write the url that the client moved to
on the next click to would contain the state information (functions
the same as cookies). If you can't rewrite the application, then you'll
risk loosing some customers and I would say that LVS is not for you.
> Also setting persistance to 1 seems to affect the result for much more
> then 1 second, what exactly does this do?
don't know. You will have to wait for the TCP timeouts which are of the order
of 2mins in Linux (look at the connections with `netstat -an`)
> All of this is, of course, ignoring the DoS problems.
This is difficult for everybody. With persistence it's just worse.
Joe
--
Joseph Mack PhD, Senior Systems Engineer, Lockheed Martin
contractor to the National Environmental Supercomputer Center,
mailto:mack.joseph@xxxxxxx ph# 919-541-0007, RTP, NC, USA
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