Tomcat, Session objects and caching (most) URIs

[Torstein Krause Johansen]

Hi all,

I'm using Varnish 1.1.2 together with Tomcat 5.5.x as backend and I've 
got some questions regarding caching and the Java Session object.

When receiving a request, Tomcat always sets a Cookie for storing the 
Java Session object (JSESSIONID). Because of this, no pages returned 
from Tomcat are cached in Varnish with the default configuration.

I do understand the rationale behind this, but since Tomcat _always_ 
sets the cookie in order to supply the Session object (a part of the 
J2EE spec I believe), I have to find a way to cache (most of) these 
requests.

One workaround is to remove the Set-Cookie header in the Tomcat reply 
before Varnish treats it:

   vcl_fetch() {
     ...
     if (obj.http.Set-Cookie) {
       remove obj.http.Set-Cookie;
     }
     ...
   }

Now, as long as noone in any Java application running in the servlet 
container uses the Java Session object, this works fine. However, what's 
the prefered way of doing this, /if/ we want to use the  Session object 
for /some/ URIs?

Is it possible to add an additional test to the vcl_fetch block above to 
not remofve the header, if the URI is either starting with e.g. "/login" 
or "/register" ?

Another workaround I can think of would be to insert all requests with 
Cookies in their headers.

What is the preferred way of solving this problem?

Cheers,

-Torstein
-- 
Torstein Krause Johansen
Senior consultant
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