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List:       linux-virtual-server
Subject:    Re: IPVS-persistance, weight and bringing down a realserver.
From:       Graeme Fowler <graeme () graemef ! net>
Date:       2007-02-16 10:30:13
Message-ID: 45D587B5.50002 () graemef ! net
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HiOn 16/02/2007 10:06, Olle ֖stlund wrote:
<snip long detailed description>
> To me it seems very strange that the direcor try to keep using a
> realserver which weight is 0 / has stopped ansvering the directors
> polling-requests. 

Not really.

Setting the weight to 0 means that a given realserver ceases to accept 
new connections from new clients. Established connections from 
established clients will continue, and if they've idled out in TCP terms 
(ie gone to FIN/WAIT state) but are still within their session 
persistence, then they'll come back to the same realserver - this is why 
you might see an *increase* in active sessions, even when quiesced.

There's a "blunt stick" approach to quiescing realservers in persistent 
states, which is to:

echo 1 > /proc/sys/net/ipv4/vs/expire_quiescent_template

That means that when the realserver is quiesced - weight set to 0 - all 
persistence templates will be removed, and sessions will fail 
immediately to other servers.

In my experience I've had to combine "affinity" - persistence in LVS 
terms - with session management/awareness across realservers. That way 
I've been able to fail out a realserver with no interruption.

Not what you were asking for - the graceful method - but a way forward 
nonetheless.

G
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