Tom Drake wrote:
> 
> Mathias;
> 
> Thanks for your very informative reply. From your reply, it seems
> that mod_jk comes close to doing what I want, and should actually
> provide the fail-over I'm looking for, however not in the most
> optimal way.
> 
> What would be involved in adding (optionally configured) logic to
> mod_jk that would prefer another running instance over a downed
> instance, and then remember this as the 'jvmroute' for the given
> JSESSIONID?

Humm the design Gal Shachor did for mod_jk is pretty slick, there
is no need to maintain any session table in Apache memory as the
jvmroute
is part of the session id.

Therefore I do not see any way coherent with that design to re-route
a given session id (containing a jvmroute not to be used) to a new
Tomcat in a sticky way.

My best shot would be, the first time a request is received on a Tomcat
which did not issue it, to reissue Set-Cookie and Set-Cookie2 headers to
force a new session id to be used. Therefore the mapping would be
explicit in
the new session id. The new session id would have to be used also in URL
rewritings.

This solution would provide the re-mapping you requested and the new
Tomcat would
become the new session parent.

There are though several drawbacks to issueing a new session id.

First the marketing guys won't be happy :-) Their client tracking would
probably suffer from this change of session id, even if the end user
doesn't notice anything.

Second, depending if you use load balancing equipment before the Apache
servers, and what kind of stickyness you
use those equipments with, you could end up with non optimal routings of
requests, but that's only minor since
it will only apply to sessions that were on the downed worker initially.

> Can you provide any insights into mod_webapp?

Nope, I only dug into mod_jk for now.

Mathias.

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