[LON-CAPA-users] limited number of concurrent users during midterm

[Stuart Raeburn]

Hi,

> The load on the server seemed OK, but perhaps some configurable limit was
> hit?

In /etc/httpd/conf/loncapa.conf in CentOS/Scientific Linux/RHEL/Fedora  
you will find:

PerlSetVar     lonUserLoadLim

If you are running SuSE/SLES/Ubuntu look in /etc/apache2/loncapa.conf

The default is 0, which means no user load limit.

If you encountered a limit in the number of users who could be hosted  
on your server, that suggests a value of 200 had been set previously  
for lonUserLoadLim by an administrator.

> The server administrator has set the correct
> portal url, but after some cron jobs run it's set back.  Maybe it's this
> bug we're seeing:
> http://install.lon-capa.org/bugzilla/show_bug.cgi?id=6608?
>

Bug 6608 would explain why the "Log-in" again link was no longer  
pointing at whatever URL had been set previously by an administrator,  
but it does not explain why it was pointing at http://capa

If no portal url is found, then LON-CAPA will determine which is the  
least busy server amongst the servers in your domain, and point at  
that instead.

Something may be awry in the mapping of LON-CAPA lonhostID to hostname  
in your domain, because based on a "log-in again" link of http://capa  
it would seem that LON-CAPA's lonhostID for your server (lonmathstat1)  
maps to a hostname of "capa" instead of to something like:  
"capa.mathstat.dal.ca", (which would have caused the link to point at  
http://capa instead of http://capa.mathstat.dal.ca)

You might check the contents of:
/home/httpd/lonTabs/hosts.tab

Notes:

1. If you only have a single server in your domain, then the "Log-in  
again" link should point at that server.  If that server has a user  
load or server load which exceeds the limits set for either  
lonUserLoadLim or lonLoadLim in loncapa.conf, then the LON-CAPA log-in  
mechanism will switch the user's session (following authentication) to  
another server in the LON-CAPA cluster to which your server belongs.

However, the mathstatdal domain is not part of the LON-CAPA network,  
so this type of cross-institutuional load-balancing will not currently  
be available to you.

2. The behavior whereby the portal URL is not used (despite being set)  
can be fixed in 2.10.1 by following the instructions in comment #6 in  
bug 6608:
http://install.lon-capa.org/bugzilla/show_bug.cgi?id=6608#c6

3. Your question is probably better suited for the lon-capa-admin  
mailing list: http://mail.lon-capa.org/mailman/listinfo/lon-capa-admin
which is intended for questions about LON-CAPA server administration  
and/or installation.


Stuart Raeburn
LON-CAPA Academic Consortium


Quoting Joseph Mingrone <jrm at mathstat.dal.ca>:

> Our first CAPA-based midterm went well, but there was one hiccup.
>
> After all but one student in the class logged in to take the test, no
> one else could log in.  (Quite a lucky coincidence only one of just
> under 200 students was left out.)  When anyone tried, including course
> administrators, they were redirected to the dead URL http://capa/.  The
> load on the server seemed OK, but perhaps some configurable limit was
> hit?  We believe they saw this dead URL because of a small bug in our
> version of CAPA, 2.10.1-2011113023.  When a user logs out, then clicks
> the "Log in again" link, instead of being taken to the correct URL he is
> taken to http://capa.  The server administrator has set the correct
> portal url, but after some cron jobs run it's set back.  Maybe it's this
> bug we're seeing:
> http://install.lon-capa.org/bugzilla/show_bug.cgi?id=6608?
>
> The pressing question: Is there a way to prevent the concurrent login
> limitation for our next midterm?
>
> Thanks,
>
> Joseph
>
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