On 22.07.2010 16:19, Darren Kukulka wrote:
Hi Tomcatters,
Just a quick question regarding Apache Web Server load balancing down to
Tomcat cluster.
We have a number of 2-node Tomcat 6.0.20 clusters, all configured as
peer to peer pairs, on the same subnet with no real network oddities
mesh getting in the way to speak of.
Apache Mod_jk is used to balance connections from users down to the
Tomcat clusters, using the availability ('B') load balancing method,
with sticky sessions on.
There are situations where we need to restart either of the nodes to
affect a change...or use Probe to bring a single application down/up for
the same purpose on a single node.
When we do this sometimes, users report that their sessions are
lost...and they cannot re-establish a new connection, unless they
refresh their browsers (no proxy configuration getting involved here),
even if the node/app is back up.
Another, more difficult scenario, is when one of the Tomcat cluster
nodes begins to groan and become unresponsive, say when OldGen or
PermGen becomes full...in this case the mod_jk connector does not
identify the node as having failed and will continue to attempt to pass
requests to it, rather than pass them to the more responsive node.
Are there any configuration settings to be mindful of with these
scenarios?
Concerning the mod_jk configuration, grabbing a source tarball for
mod_jk 1.2.30 and looking at the contained example configuration is a
good start. Details can then be found at
http://tomcat.apache.org/connectors-doc/
especially in the "Reference Guide".
Versions before 1.2.30 do not contain a good example config, so grab the
latest.
Regards,
Rainer
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