2012/12/7 Christopher Schultz <ch...@christopherschultz.net>:
> On 12/7/12 4:16 AM, André Warnier wrote:
>> Williams, Nick wrote:
>>>> -----Original Message----- From: Christopher Schultz
>>> (...)
>>>
>>> Earlier somebody (I'm sorry, I already deleted the email)
>>> suggested Tomcat returning a 308 or 309 or similar to the load
>>> balancer to trigger a "re-balance" if the session is expired. I
>>> think this is the best idea I've heard yet, solves the problem
>>> elegantly and simply, and seems (relatively) easy to achieve
>>> (this coming from someone who has no knowledge of the code used
>>> by mod_jk/isapi_redirector).
>>>
>>
>> I must admit that this sounds more elegant (and efficient) than my
>> suggested interceptor module.
>>
>> Alternatively, if one wanted to avoid touching mod_jk for this,
>> maybe tomcat could return a 302 redirect to the starting page of
>> this application, if known ? (without jsessionid.jvmroute of
>> course).
>
> That's definitely an idea worth pursuing: an expired session id could
> return 302 *and* strip the jsessionid path parameter *and* send a
> Set-Cookie JSESSIONID; expiration=0 header (which deletes the cookie).
> The client would re-try and the balancer would re-balance.
>
> Konstantin, what do you think? Obviously, this shouldn't be the
> default operation of Tomcat, but perhaps a setting that could be
> enabled on the session manager?
>
If anybody want to experiment with such a feature,
it is easy to write your own Filter or Valve that implements this.
Something like
if (request.getSession(false) == null &&
request.getRequestedSessionId() != null) {
response.sendRedirect(...);
return;
}
Things to be cautious
1. Different web applications may have different session ids. When a
browser sends us the session id cookie, there is no indication to what
web application it belongs.
2. I would check the value of request.getMethod().
3. I would do nothing if jvmRoute in requested session id belongs to a
different server.
See also org.apache.catalina.ha.session.JvmRouteBinderValve,
http://tomcat.apache.org/tomcat-7.0-doc/config/cluster-valve.html
Best regards,
Konstantin Kolinko
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