[Koha-devel] Plack and memcached (was: Sessions terminated at random under Plack)

[Jonathan Druart]

> [1] This might deserve a warning entry in about page IMHO.

Done, see bug 17274.

2016-09-07 19:07 GMT+01:00 Tomas Cohen Arazi <tomascohen at gmail.com>:
> Ok, yesterday I took some time to fill (and provide patches for):
> - Bug 17261 - Add memcached configuration info to about.pl
> - Bug 17262 - Plack on packages is not having memcached set properly
>
> Bug 17261 highlighted something we suspected: the Plack processes don't get
> the right configuration variables through ENV for setting the memcached
> backend (on packages setup). It was pretty obvious. That's why it is falling
> back to CGI::Session even when you set sessionStorage=memcached, and results
> in weird permission issues trying to write the session files somewhere we
> don't have control of.
>
> Bug 17262 does what is needed to get the Plack processes have the right
> MEMCACHED_SERVERS and MEMCACHED_NAMESPACE variables set. It does so by
> patching the koha-plack and koha-functions.sh scripts in an obvious way.
>
> The problem is that Plack explodes with 17262 alone. It looks like circular
> dependencies issues. But...
>
> This morning I passed QA on:
> - Bug 17189 - Add the ability to define several memcached namespaces
> - Bug 11921 - memcached configuration should be moved back to koha-conf.xml
>
> They both change the way memcached configuration is handled and better
> reorganize the code around it (basically moving the configuration back to
> koha-conf.xml, and removing memcached handling from C4::Context, solving the
> circ dep issue).
>
> As Chris mentioned on 17262, moving the memcached configuration back to
> koha-conf.xml is the right thing to do.
>
> That's why 17189 and 11921 should be pushed to master ASAP, and I belive
> they should be backported down to 3.22 if the rmaints agree and with proper
> testing. People supporting 3.22 and 16.05 deployments should get involved on
> testing in the stable branches to make sure no regression is introduced (is
> it really possible if it is not working at all?).
>
> The only problem is that current setups won't have the koha-conf.xml entries
> (memcached_servers and memcached_namespace)[1]. But this is handled nicely
> by the current logic, that allows ENV to overload koha-conf.xml values. So
> it will work, YAY! (already tested it)
>
> So, IMHO, they could be backported to the stable branches, along with 17262,
> which will make it effective use of memcached. It shouldn't be pushed to
> master as it would be a step backwards and is not needed.
>
> My two cents.
>
> Regards
>
> [1] This might deserve a warning entry in about page IMHO.
>
> El mar., 30 ago. 2016 a las 15:40, Tomas Cohen Arazi
> (<tomascohen at gmail.com>) escribió:
>
> Magnus, there's been a lot of movement on the caching layer, and some of
> that work has been backported to the stable releases. Also, the
> RestrictSessionByIP setting was getting in the middle
> (https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=17050).
>
>
> There's also a problem with memcached initialization in C4::Context that
> makes sessionStorage=memcache fail to persist sessions.
>
>
> My suggestion would be to set sessionStorage to 'mysql' and disable the
> RestricSessionByIP syspref.
>
>
> Regards
>
>
>
>
>
> El mar., 30 ago. 2016 a las 8:24, Magnus Enger (<magnus at enger.priv.no>)
> escribió:
>
> Dear Community,
>
> I am seeing a strange problem, and I'm not sure where to start digging.
>
> I have a (big) server with 30 odd Koha instances. One of these
> instances has been running under Plack for quite some time now,
> without any problems.
>
> Two new instances have a problem where librarians get kicked out of
> the intranet more or less frequently, with a message like "Your
> session has expired, please log in again".
>
> We had this problem on 3.22.x.
> After upgrading to 16.05.02 it went away.
> After upgrading to 16.05.03 last night it came back again.
>
> It is not consistent. Earlier today it looked like you could log in,
> click on a link, get thrown out, login again and then things would
> work. Later users got kicked out every single time they clicked on a
> link in the intranet.
>
> All sites are running off the official Debian packages, on the same server.
> Memcached is installed, enabled and used for storing sessions.
> Switching SessionStorage to the DB does not stop the problem.
> Stopping and disabling Plack for these two instances makes the problem go
> away.
>
> I have not found anything interesting in Plack or Apache logs.
>
> Anyone got a hunch what might be causing this? Or where to start digging?
>
> Best regards,
> Magnus
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>
> --
>
> Tomás Cohen Arazi
> Theke Solutions (https://theke.io)
> ✆ +54 9351 3513384
> GPG: B2F3C15F
> --
> Tomás Cohen Arazi
> Theke Solutions (https://theke.io)
> ✆ +54 9351 3513384
> GPG: B2F3C15F
>
> _______________________________________________
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