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From Shaun Senecal <ssenecal.w...@gmail.com>
Subject Re: Apache Server failover and session replication
Date Thu, 03 Sep 2009 00:56:49 GMT
We had a similar problem with Tomcat 6 using clustering.  It turns out that
the SSO information is only propagated while all instances are running.  If
Instance-A fails, several users then log in to Instance-B, then Instance-A
comes back up, all of the SSO information for the users that logged in
during the downtime is not included in Instance-A so those users are forced
to re-login once the load balancer sends them to that instance.

I wrote a fix for it, which might be useful for you.  However, it hasnt been
fully tested and is designed to only share the SSO information at startup,
not all Session information.  If Tomcat doenst handle this case, then the
fix I wrote should be easily extended to handle that.  Basically, when an
instance comes up it broadcasts a request for all known SSO information to
the cluster.  It then takes the first response it gets and continues
processing as normal.

Let me know if you dont find a proper solution to the problem and I will try
to dig up that fix.  My intention was to post it back to the group, but I
got sidetracked once we (temporarily) stopped using clustering.


Shaun

On Thu, Sep 3, 2009 at 3:52 AM, Sumedh Sakdeo <sumedhsakdeo@gmail.com>wrote:

> Hi Rainer,
>
> I am using Tomcat session clustering and Apache Http Server for LB(using
> mod_jk module).  Also, using Tomcat 6. I have made appropriate changes to
> worker.properties and httpd.conf. Also I have made appropriate changes to
> server.xml on each tomcat.
>
> Thanks,
> Sumedh
>
> On Thu, Sep 3, 2009 at 12:15 AM, Rainer Jung <rainer.jung@kippdata.de
> >wrote:
>
> > On 02.09.2009 19:57, Sumedh Sakdeo wrote:
> > > Hello All,
> > >             I have a setup with two tomcat instances(A&B). I have
> > configured
> > > an apache web server 2.2 for load balancing and fail over. Setup looks
> > fine
> > > as per the configurations suggested. Let tomcat A be handling some
> > request
> > > at sometime. When tomcat instance(A) goes down, the session is
> replicated
> > to
> > > another tomcat instance(B) successfully. Now tomcat instance B is
> > handling
> > > those requests. Till this point everything goes fine, but when I bring
> up
> > > tomcat instance(A) and after that tomcat instance(B) goes down, the
> > session
> > > is no longer replicated. What might be the issue? In status page of
> > apache
> > > server I see even if node status is OK session is not replicated to
> fail
> > > over node for second time.
> >
> > How do you replicate? Are you using Tomcat session clustering? Tomcat
> > 5.5 or Tomcat 6?
> >
> > Regards,
> >
> > Rainer
> >
> > ---------------------------------------------------------------------
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> >
> >
>

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