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From Roy McMorran <mcmor...@mdibl.org>
Subject Re: Session Replication in Cluster
Date Fri, 03 Apr 2009 12:32:38 GMT
Hi Jorge, thanks for the reply.

Actually no, these are the access logs from the Tomcat cluster members; 
you can view the corresponding AccessLogValve entries in the server.xml 
files referenced below.

I included those logs for illustration, but I have confirmed that those 
are the actual session IDs at the browser.  After the failover the new 
Tomcat cluster member sends a new Set-Cookie header with the new session ID.

You're right that the first portion of the session ID does seem to be 
replicated properly, but I thought it was the function of 
JvmRouteBinderValve to update the entire session ID in a failover, 
including the jvmRoute portion.

Best wishes,
Roy

Jorge Medina wrote:
> Are your logs Apache logs? Mod_jk logs?
>
> If it is Apache, the question would probably better answer in the Apache
> mailing list. 
> Anyway, What does your LogFormat string looks like? 
>
> I bet what you see in the logs is the concatenation of the session ID
> and the worker name. I doubt two servers would generate the same hex
> digits for the session. Therefore, your server must be working as
> expected, you are just interpreting the logs incorrectly.
>
> -----Original Message-----
> From: Roy McMorran [mailto:mcmorran@mdibl.org] 
> Sent: Thursday, April 02, 2009 10:59 AM
> To: Tomcat Users List
> Subject: Session Replication in Cluster
>
> Hello all,
>
>
> I've built a very simple 2-member Tomcat cluster for testing, but I am
> unable to get the session replication quite right.  The problem is when
> I fail one member of the cluster.  The behavior I was expecting is that
> the other cluster member would take over the session ids for the failed
> member.  However it is appending it's own jvmRoute value to the session
> id, and thus setting a new cookie.
>
>
> Details:
> I have 2 cluster members, "itchy" and "scratchy", running on the same
> physical server, and CATALINA_BASE is /var/tomcat/itchy and
> /var/tomcat/scratchy respectively.  Tomcat 6.0.18 binaries, etc. are at
> /usr/local/tomcat.  Using mod_jk 1.2.27 on Apache 2.2.11 (Apache is also
> on the same server).  I am using sticky sessions.
>
>
> Here are the access logs for the 2 members from a short "failover" 
> experiment (note I'm including the session ID in the 2nd field).  The
> session starts on scratchy.  From scratchy_access_log.2009-04-02.txt:
>
> 192.168.200.177 E5BF3FFA9AEE1E3AB0DD4A96BA5E4011.scratchy -
> [02/Apr/2009:10:19:55 -0400] "GET / HTTP/1.1" 200 14612
> 192.168.200.177 E5BF3FFA9AEE1E3AB0DD4A96BA5E4011.scratchy -
> [02/Apr/2009:10:20:14 -0400] "GET /about/ HTTP/1.1" 200 19507
>
>
> At 10:21:39 AM I do a kill -9 on the scratchy instance.  Now the traffic
> goes to the other cluster member as expected.  From
> itchy_access_log.2009-04-02.txt:
>
> 192.168.200.177 E5BF3FFA9AEE1E3AB0DD4A96BA5E4011.itchy -
> [02/Apr/2009:10:22:11 -0400] "GET /about/publications/ HTTP/1.1" 200
> 18263
> 192.168.200.177 E5BF3FFA9AEE1E3AB0DD4A96BA5E4011.itchy -
> [02/Apr/2009:10:22:32 -0400] "GET /about/changes/ HTTP/1.1" 200 12736
>
>
> Note however that the new member's jvmRoute value is now appended to the
> session id.  I thought is was supposed to stay exactly the same after
> failover.
>
>
> Additional details can be found as follows:
>
> server.xml for "itchy" - see:
> http://gillnet.mdibl.org/~mcmorran/itchy-server.xml.txt
>
> server.xml for "scratchy" - see:
> http://gillnet.mdibl.org/~mcmorran/scratchy-server.xml.txt
>
> context.xml (identical) - see:
> https://gillnet.mdibl.org/~mcmorran/context.xml.txt
>
> workers.properties:
> https://gillnet.mdibl.org/~mcmorran/workers.properties
>
> I've also included the catalina.out file for both, from startup and
> through the test at:
> https://gillnet.mdibl.org/~mcmorran/itchy-catalina.out
> https://gillnet.mdibl.org/~mcmorran/scratchy-catalina.out
>
>
> I'd appreciate any advice on where I went wrong.  Thanks and best
> wishes,
> Roy
>
>   


-- 
Roy McMorran
Systems Administrator
MDI Biological Laboratory
mcmorran@mdibl.org



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