On 13.03.2009 14:08, Toni Menendez Lopez wrote:
The behaviour is the one that I explained in the first mail, that when I
stop one of the servers, I ahve very huge delays to respond to the
requests of the session that were managed by this server.
OK.
After reading documentation I think that problem is related with
parameter : #worker.izonetv.sticky_session_force=1, which if is not
commented I am not able to launch any call.
Hmm, above you say you have huge delays, here you say you are not able
to launch any call.
Let me first explain stickyness:
A request that is forwarded by mod_jk to Tomcat can carry a session id.
Session ids can be part of a request by either setting a so-called
session cookie. This cookie has the name JSESSIONID. Or the session id
is added at the end of the URL in the form ";jsessionid=...".
Now how does stickyness work:
- you set the so called jvmRoute in server.xml of your Tomcats. Each
Tomcat gets a different jvmRoute. Say you have jvmRoute node1 and node2.
- Tomcat automatically adds the jvmRoute to the end of each session id,
whenever it creates a session. The jvmRoute is separated from the rest
of the id by a dot ".".
- When a mod_jk load balancer operates sticky and it has to forward a
request, that contains a session id, it looks for a dot in this id, and
if it find it, it takes everything after the dot in the id as the name
of the backend. The load balancer then looks for a member worker, whose
name is equal to this jvmRoute. In the above example that would've been
node1 or node2.
By default any load balancer in mod_jk tries to be sticky, but if it
either cant find the correct worker, or this worker is in error, it
chooses another worker. If you set sticky_session_force, then you tell
mod_jk that it should not try another worker in this case, and instead
return an error.
From your previously send mod_jk log file we can see, that your JBoss
sets a session cookie for the root path "/". That means, this cookie
will be sent fr every request to this host. Since it is a session
cookie, this is a good candidate for desaster, because when you now
switch the application, but it is served by the same host, the browser
sends the JBoss session cookie, although that application will not know
this session.
With sticky_session_force set to true (not the default), when JBoss
sends the redirect to the Tomcat webapp, the browser will send a request
for this Tomcat webapp, but will also send the session cookie from
JBoss, because JBoss set the cookie path to "/". Furthermore JBoss
included a node name in the session id and the load balancer that
handles to forwarding to Tomcat doesn't know about that node, so it
can't preserve strict stickyness.
Usually you don't want sticky_session_force.
Normally so I comment this parameter otherwise my service does not work,
See above.
and if I comment I think the mod_jk with requeso of a loose session try
to go to other worked and it does not sent any error and takes a very
long delay.
No it didn't in the error log you sent previously. It immediately
returned an error because the request was handeled with forced
stickyness, and the wofrker name given by the session id didn't exist.
So, for this reason I am trying to investigate the problem with this
parameter.
So, focusing in this parameter, the log that I sent to you is with the
parameter commented, and I found a strange thing. I explain to you :
My request is the following : http://159.23.98.22/cdp-fe/Trigger.do?
<http://159.23.98.22/cdp-fe/Trigger.do>.....
When I send this to apache mod_jk redirects this to my JBOSS application
( MCDP worker) and my JBOSS aplication redirect this link to
http://159.23.98.22/CDP311/......
But now mod_jk when receives this second request is trying to send this
request to MCDP worker again and not to IZONETV worker.
The log shows that mod_jk tries to send it via izonetv:
It says:
- Found a wildchar match '/CDP311/*=izonetv'
- Into handler jakarta-servlet worker=izonetv
- found a worker izonetv
- Service error=0 for worker=izonetv
But it fails, because sticky_session_force was activated
- service sticky_session=1 id='oK+zmQoPUFefT2vcqTSagg**.MCDP-mifeas02_data'
and it can't find the worker MCDP-mifeas02_data as part of izonetv:
- searching worker for session route MCDP-mifeas02_data
Any idea why ?
Sorry, about the updating of mod_jk but is a close platform and I am not
able to update the mod_jk.
That's very bad. Someone should be able to update it and I do recommend
that (although in this case it wpouldn't solve your problem).
Thanks again,
Toni.
Regards,
Rainer
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