Questions on mod_jk, session affinity, etc

[Jess Holle]

For cases where the session data is too large and/or volatile to 
replicate without a performance penalty and where session affinity is 
thus required, is there any hope/possibility/interest of trying to 
balance the number of active sessions per Tomcat instance (i.e. sending 
new requests to the instance with the fewest active sessions)?

Or is there any possibility of transfering a session from one Tomcat 
instance to another when one gets overloaded -- rather than continually 
replicating every change to the session across all instances?  [This 
would seem to require changes to Tomcat and mod_jk/mod_proxy_ajp, right?]

--
Jess Holle
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Re: Questions on mod_jk, session affinity, etc

[Sandy McArthur]

On Nov 9, 2004, at 10:00 PM, Jess Holle wrote:
is there any hope/possibility/interest of trying to balance the number 
of active sessions per Tomcat instance (i.e. sending new requests to 
the instance with the fewest active sessions)?
We (UF, I cannot claim to represent the tomcat devs) are happy with a 
simple round robin distribution for new requests. We have 8 tomcat 
clones for simple load balancing and given enough users it all evens 
out. We've gutted the existing balancing code in mod_jk because it was 
broken and put in our own more simple algorithm that doesn't do load 
factors. Hopefully the balancing code back ported from the mod_proxy 
efforts will do the trick and we can ditch our own stuff.

Anyway, trying to be too smart in sending new requests to clones with 
the fewest number of sessions would probably create this weird flow 
where new users gravitate to the same clone as a batch of users 
sessions expire.

Even if that isn't the case, it's in our interests to separate new 
sessions between clones. Typically for us the first request a user 
makes after login is the most cpu/time intensive because we need lookup 
extended info about the user and generally setup their session.

--
Sandy McArthur
He who dares not offend cannot be honest.
- Thomas Paine


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