jean-frederic clere wrote:
Should general support for a query URL be provided in
mod_proxy_balancer? Or should this be left to mod_cluster?
Can you explain more? I don't get the question.
What I mean is
1. Should mod_proxy_balancer be extended to provide a balancer
algorithm in which one specifies a backend URL that will provide a
single numeric health metric, throttle the number of such requests
via a time-to-live associated with this information, and balance
on this basis or
2. Should mod_cluster handle this issue?
3. Or both?
* For instance, mod_cluster might leverage special nuances in
AJP, JBoss, and Tomcat, whereas mod_proxy_balancer might
provide more generic support for helath checks on any back
end server that can expose a health metric URL.
From your response below, it sounds like you're saying it's #2, which
is /largely /fine and good -- but this raises questions:
1. How general is the health check metric in mod_cluster?
* I only care about Tomcat backends myself, but control over
the metric would be good.
2. Does this require special JBoss nuggets in Tomcat?
* I'd hope not, i.e. that this is a simple matter of a
pre-designated URL or a very simple standalone socket protocol.
3. When will mod_cluster support health metric based balancing of Tomcat?
4. How "disruptive" to an existing configuration using
mod_proxy_balancer/mod_proxy_ajp is mod_cluster?
* How much needs to be changed?
5. How portable is the mod_cluster code?
* Does it build on Windows? HPUX? AIX?
I say this is largely fine and good as I'd like to see just the
health-metric based balancing algorithm in Apache 2.2.x itself.
Does mod_cluster provide yet another approach top to bottom (separate
than mod_jk and mod_proxy/mod_proxy_ajp)?
Mod_cluster is just a balancer for mod_proxy but due to the dynamic
creation of balancers and workers it can't get in the httpd-trunk code
right now.
It would seem nice to me if mod_jk and/or mod_proxy_balancer could
do health checks, but you have to draw the line somewhere on growing
any given module and if mod_jk and mod_proxy_balancer are not going
in that direction at some point mod_cluster may be in my future.
--
Jess Holle
