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From Christopher Schultz <ch...@christopherschultz.net>
Subject Re: mod jk - multiple applications, different server clusers, sticky sessions
Date Thu, 03 Sep 2009 21:31:13 GMT
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Rainer,

On 9/3/2009 4:36 AM, Rainer Jung wrote:
> No.
> 
> The stickyness doesn't magically track your clients. If the client sends
> a session information, and the session information contains a route tag
> (a suffix .nodeX, where nodeX is set by the jvmRoute attribute in
> server.xml), then mod_jk looks for a balancer member named nodeX.
> 
> When/How does the client send session information? Either as a cookie
> named JSESSIONID, or via URL encoding ...;jsessionid=....nodeX
> 
> By default, application A with context name /myappA uses cookies and
> only sends cookies if the request goes to something in /myappA. So a
> request for application B with context /myappB doesn't include the
> cookie for A and the load balancer is free to distribute the request to
> any node.

One caveat: if you have a ROOT context along with other non-ROOT
contexts, things can get tricky because you'll get cookies like:

name=JSESSIONID, path=/, expires=..., value=...
name=JSESSIONID, path=/foo, expires=..., value=...
name=JSESSIONID, path=/bar, expires=..., value=...

Whenever a client browses to webapps found on / and /foo, the requests
to /foo will get TWO cookies, and confusion may occur (I'm not sure what
mod_jk will do in this situation... Rainer?).

My advice is to avoid "nesting" webapp URL spaces. I accidentally did
this for years until I discovered the problem when adding
sessionid-passthrough to another webapp (where the session id couldn't
be validated before being passed-through) and everything went crazy.
When I separated the URL spaces, everything was fine.

Hope that helps,
- -chris
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