And here is another link which might be interesting.
It is a message on the Tomcat list (where I re-posted your original request,
hem), from
Rainer Jung, who is one of the Apache/Tomcat mod_jk connector developers :
"
Yes, go for TC 7:
http://tomcat.apache.org/tomcat-7.0-doc/config/filter.html#Expires_Filter
Regards,
Rainer
"
Now that Tomcat page, apart from its own interest, also points to the Apache "mod_expires"
module (which I never heard about before) in your case may be exactly what you're looking for.
It seems to be such that it can add headers in a response proxied to Tomcat, without
overwriting such headers if they already exist.
Here is what I would do :
1) identify some "usual suspects" among the URLs proxied to Tomcat
They would have to match the following criteria :
- they happen on an overloaded Tomcat
- they happen often
- I am reasonably sure that the information delivered by that URL
is stable over a period of time
- I am reasonably sure that if it happened that the browser would,
once in a while, get stale information, it would not be dramatic
2) carefully configure the front-end Apache to, for these particular URLs,
add an Expires header specifying "now + N", where N is initially not too large.
This way, a browser would not get a result that is more than N outdated, but any duplicate
request within a period N would get the cached version.
3) look at the impact and loop or not, increasing or decreasing N
YMMV.
