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Posted to users@tomcat.apache.org by Thomas Glanzmann <th...@glanzmann.de> on 2008/01/20 20:24:22 UTC
mod_jk taking a single tomcat-worker offline for software
maintenance
Hello,
I have mod_jk version 1:1.2.18-3etch1 (which comes with Debian Etch) as
loadbalancer in front of four tomcats version 5.5.20-2etch2 that do not
duplicate sessions because of their size (100Mbyte per session; 120 -
500 users). My workers.property looks the following:
worker.list=router, jkstatus
worker.router.type=lb
worker.router.balance_workers=tomcat-01, tomcat-02, tomcat-03, tomcat-04
worker.tomcat-01.type=ajp13
worker.tomcat-01.host=tomcat-01
worker.tomcat-01.port=8009
worker.tomcat-01.lbfactor=1
worker.tomcat-02.type=ajp13
worker.tomcat-02.host=tomcat-02
worker.tomcat-02.port=8009
worker.tomcat-02.lbfactor=1
worker.tomcat-03.type=ajp13
worker.tomcat-03.host=tomcat-03
worker.tomcat-03.port=8009
worker.tomcat-03.lbfactor=1
worker.tomcat-04.type=ajp13
worker.tomcat-04.host=tomcat-04
worker.tomcat-04.port=8009
worker.tomcat-04.lbfactor=2
worker.jkstatus.type=status
I have to schedule once a week a software update, so I have to take a
tomcat server offline to upgrade the software. The problem is that I
don't want to kick any users. So I switch in jk_status the mode to
disabled. This works for most of the users. After their session times
out, they're gone. But I have a few sticky users, who leave their
browser open (and come back after 4 hours or a day) or bookmark a site
that contains a session id. Mod jk sees the session id and directs it to
the disabled tomcat. On the tomcat itself the session id is invalid, it
generates a new one and I have the user back on my disabled tomcat.
Duplicating the session to another tomcat is currently not possible
because a single session has around 100 Mbyte and even in off-hours like
right now, there are 100 active sessions.
How do other people handle this problem? Is there a way to make mod_jk
to check if the session is still active on the tomcat (maybe with a
newer version) and only puts a session to a disabled tomcat if indeed
the session is still active on that tomcat?
Thomas
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Re: mod_jk taking a single tomcat-worker offline for
softwaremaintenance
Posted by Thomas Glanzmann <th...@glanzmann.de>.
Rainer,
> No, the design of mod_jk is stateless w.r.t. sessions. There are only the
> obvious solutions, i.e. assuming that after some time of disabling (time
> depending on typical session use cases like 10 minutes or an hour) you stop
> the worker and thereby redirect users that still try to use the node to
> another node. They'll get an error of course and would need to relogin.
> Usually with some time of disable status you can reduce the number of
> sessions, that will need to relogin and thus be disturbed by your
> maintenance to about 5% (your mileage may vary).
> If you want to improve user experience more, you could include a
> maintenance information in your app, like "Please logout and relogin during
> the next hour because we have a maintenance scheduled starting at ...".
thank you a lot for the fast follow-up and the clarification of the
stateless architecture of mod_jk in case of session ids. I will continue
to do the obvious as you described it.
Thomas
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Re: mod_jk taking a single tomcat-worker offline for softwaremaintenance
Posted by Rainer Jung <ra...@kippdata.de>.
Hi Thomas,
Thomas Glanzmann schrieb:
> Hello,
> I have mod_jk version 1:1.2.18-3etch1 (which comes with Debian Etch) as
> loadbalancer in front of four tomcats version 5.5.20-2etch2 that do not
> duplicate sessions because of their size (100Mbyte per session; 120 -
> 500 users). My workers.property looks the following:
>
> worker.list=router, jkstatus
>
> worker.router.type=lb
> worker.router.balance_workers=tomcat-01, tomcat-02, tomcat-03, tomcat-04
>
> worker.tomcat-01.type=ajp13
> worker.tomcat-01.host=tomcat-01
> worker.tomcat-01.port=8009
> worker.tomcat-01.lbfactor=1
>
> worker.tomcat-02.type=ajp13
> worker.tomcat-02.host=tomcat-02
> worker.tomcat-02.port=8009
> worker.tomcat-02.lbfactor=1
>
> worker.tomcat-03.type=ajp13
> worker.tomcat-03.host=tomcat-03
> worker.tomcat-03.port=8009
> worker.tomcat-03.lbfactor=1
>
> worker.tomcat-04.type=ajp13
> worker.tomcat-04.host=tomcat-04
> worker.tomcat-04.port=8009
> worker.tomcat-04.lbfactor=2
>
> worker.jkstatus.type=status
>
> I have to schedule once a week a software update, so I have to take a
> tomcat server offline to upgrade the software. The problem is that I
> don't want to kick any users. So I switch in jk_status the mode to
> disabled. This works for most of the users. After their session times
> out, they're gone. But I have a few sticky users, who leave their
> browser open (and come back after 4 hours or a day) or bookmark a site
> that contains a session id. Mod jk sees the session id and directs it to
> the disabled tomcat. On the tomcat itself the session id is invalid, it
> generates a new one and I have the user back on my disabled tomcat.
> Duplicating the session to another tomcat is currently not possible
> because a single session has around 100 Mbyte and even in off-hours like
> right now, there are 100 active sessions.
>
> How do other people handle this problem? Is there a way to make mod_jk
> to check if the session is still active on the tomcat (maybe with a
> newer version) and only puts a session to a disabled tomcat if indeed
> the session is still active on that tomcat?
>
> Thomas
No, the design of mod_jk is stateless w.r.t. sessions. There are only
the obvious solutions, i.e. assuming that after some time of disabling
(time depending on typical session use cases like 10 minutes or an hour)
you stop the worker and thereby redirect users that still try to use the
node to another node. They'll get an error of course and would need to
relogin.
Usually with some time of disable status you can reduce the number of
sessions, that will need to relogin and thus be disturbed by your
maintenance to about 5% (your mileage may vary).
If you want to improve user experience more, you could include a
maintenance information in your app, like "Please logout and relogin
during the next hour because we have a maintenance scheduled starting at
...".
Regards,
Rainer
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