[LON-CAPA-admin] Student logins on multiple servers affecting performance

[Stuart Raeburn]

Hi Ray,

> -rw-r--r-- 1 www www      41 Sep 13 15:47   
> username_sfu_1410648463_13247673_plot.data.17
> etc etc...

Those files are used by gnuplot (called by  
/home/httpd/cgi-bin/plot.gif) to generate a plot for a LON-CAPA  
problem that uses data instead of a curve for a specified function.

> I am tempted to delete all files beginning with this particular   
> username, in /home/httpd/perl/tmp/ on the nernst.chem.sfu.ca server.
>

Those files can be deleted before the daily clean-up of stale files  
(see below).
You'd likely want to leave any very recently generated date files in  
place, as they might be in active use.

> However that is only a guess. So I am leery of proceed to test out   
> that idea.  I also have a notion that there may some automatic   
> clearing out of such files in the /home/httpd/perl/tmp directories   
> on the servers each night.

Yes, the /home/httpd/perl/loncron process which runs at 5.10 am local  
time every night will remove files from /home/httpd/perl/tmp which  
have a "last modified" date that is 24 hours or more in the past.

(The value of 24 hours is the number of seconds defined for the  
lonExpire perlvar in /etc/httpd/conf/loncapa.conf).

You might check that the entry for /home/httpd/perl/loncron is NOT  
commented out in /etc/cron.d/loncapa, and if it is, uncomment it.  If  
the dates for any of the files are older than yesterday that would  
suggest that loncron has not been removing them as it should.

Stuart Raeburn
LON-CAPA Academic Consortium


Quoting Raymond Batchelor <batchelo at sfu.ca>:

> I have a student who is getting errors messages like:
>
> "LON-CAPA Access Control  .....  Sorry.  This action is currently   
> not authorized."
>
> He says:
>
> "This message occurs everytime i try to navigate to the next   
> homework question. If i want to go to another question , I have to   
> click back to the home page and select the lon capa for chemistry   
> once more , and then the assignment again. after that i can choose   
> the question after. Its not allowing me to press the green button."
>
> The URL he shows in the address bar (in a screenshot) looks like
> "nernst.chem.sfu.ca/res/sfu/batchelo/chem121/problems/lecture/set2/nernst.chem.sfu.ca/adm/navmaps"
>
> He also maintains that:
> "also , when i try to navigate my math 150 lon capa a "bad request"   
> appears. ( I have attached a screenshot.)"
>
>
> That screenshot appears to have the URL
> "nernst.chem.sfu.ca/enc/61/nernst.chem.sfu.ca/adm/flip"
>
> Interestingly, User Status displays for our different servers imply   
> that he does NOT, at this time, have any current session on
> nernst.chem.sfu.ca
>
> but rather that he has a session on
> newton.science.sfu.ca (Role: st./sfu/9R29554f6c6f253d3sfulc/D100   
> Course: 2014 Fall MATH 150 D100 (sfu_9R29554f6c6f253d3sfulc))
>
> and another session on
> lewis.chem.sfu.ca  (Role: cm Not in a course)
>
>
> When I look in /home/https/perl/tmp directories of each of our   
> servers, I find that on nernst.chem.sfu.ca, there are a great many   
> (apparently redundant) files of the type
>
> -rw-r--r-- 1 www www      41 Sep 13 15:47   
> username_sfu_1410648463_13247673_plot.data.17
> etc etc...
>
> On each of the other servers there are fewer such files and not   
> redundant ones.
>
> I am wondering what I should do about this situation.
>
> I am tempted to delete all files beginning with this particular   
> username, in /home/httpd/perl/tmp/ on the nernst.chem.sfu.ca server.
>
> However that is only a guess. So I am leery of proceed to test out   
> that idea.  I also have a notion that there may some automatic   
> clearing out of such files in the /home/httpd/perl/tmp directories   
> on the servers each night.
>
> At this point, I think I will just wait until sun-up before   
> attempting to address this issue further.
>
> Perhaps you could comment on how this might have occurred and how I   
> can remedy the situation and prevent it occurring again?
>
> Thanks!!!
>
> Ray