[LON-CAPA-admin] Students not seeing homework on access servers

[Lucas, Richard]

Stuart,

Thanks for the pointers. I checked and found memcached running with the same parameters as you outlined below. I ran memcached-tool and found stuff definitely in there. I also ran netstat and seen about ~35 connections per access node. The second link did make me think about limits on open files and processes for the www user, not an issue now but could be in the future.

Could upping the memory allocated to memcached help? As a side performance related question, have you done any tuning on parameters in httpd.conf?


Thanks,
Richard

-----Original Message-----
From: lon-capa-admin-bounces at mail.lon-capa.org [mailto:lon-capa-admin-bounces at mail.lon-capa.org] On Behalf Of Stuart Raeburn
Sent: Sunday, September 20, 2015 6:42 PM
To: lon-capa-admin at mail.lon-capa.org
Subject: Re: [LON-CAPA-admin] Students not seeing homework on access servers

Richard,

> Apache2::RequestIO::print: (103) Software caused connection abort at....
>
> And then there are different files they are getting that at
>
> at /home/httpd/lib/perl//Apache/lonerrorhandler.pm line 53 at 
> /home/httpd/lib/perl//Apache/lonnavmaps.pm line 1831 at 
> /home/httpd/lib/perl//Apache/lonnavmaps.pm line 1864 at 
> /home/httpd/lib/perl//Apache/lonnavdisplay.pm line 118 at 
> /home/httpd/lib/perl//Apache/lonhomework.pm line 1108 and others.

This usually means a student got tired of waiting for the page to load, and clicked away.  As a result the server's response could be longer be returned to the client, so the message "Software caused connection abort" is logged and Apache/mod_perl aborts at the current
$r->print() line, which is what you'll find at those lines in each of the reported perl modules.

The first of these -- the one involving lonerrorhandler.pm is potentially the most interesting, as it suggests an internal server error occurred first, so you might look in the Apache error_log to find out what the error was.

Of course, students clicking away, is a symptom.  The larger question is why are pages loading slowly on your access servers.  The first thing I would check is that the memcached daemon is running:

ps -ef |grep memcached |grep -v grep

(The output should be something like:
www  <process> 1  0 <date> <time> /usr/bin/memcached -m 400 -v

and is caching; see my post to the admin list from earlier this year for a script you can use to dump the contents of memcached:

http://mail.lon-capa.org/pipermail/lon-capa-admin/2015-February/003005.html

Also see:
http://mail.lon-capa.org/pipermail/lon-capa-admin/2015-February/003013.html


Stuart Raeburn
LON-CAPA Academic Consortium


Quoting "Lucas, Richard" <clucas at purdue.edu>:

> Ok apparently the student issue was a false alarm raised by the   
> instructor so no issues there. I am still wondering if there is   
> anything I can do about the errors though.
>
> Thanks,
> Richard
>
> From: lon-capa-admin-bounces at mail.lon-capa.org   
> [mailto:lon-capa-admin-bounces at mail.lon-capa.org] On Behalf Of   
> Lucas, Richard
> Sent: Sunday, September 20, 2015 4:04 PM
> To: lon-capa-admin at mail.lon-capa.org
> Subject: [LON-CAPA-admin] Students not seeing homework on access 
> servers
>
> We just added two access servers on Friday and today there are many   
> students reporting they are unable to see their homework. I am not   
> sure what to look at here, but I do see a bunch of errors in the   
> httpd error_log. Most of them start with this:
>
> Apache2::RequestIO::print: (103) Software caused connection abort at....
>
> And then there are different files they are getting that at
>
> at /home/httpd/lib/perl//Apache/lonerrorhandler.pm line 53 at 
> /home/httpd/lib/perl//Apache/lonnavmaps.pm line 1831 at 
> /home/httpd/lib/perl//Apache/lonnavmaps.pm line 1864 at 
> /home/httpd/lib/perl//Apache/lonnavdisplay.pm line 118 at 
> /home/httpd/lib/perl//Apache/lonhomework.pm line 1108 and others.
>
> I also see some other messages like this, but they are a lot fewer:
>
> [Sun Sep 20 15:21:09 2015] [error] access to   
> /res/purdue/purdue_math/math15800/Polynomial and Rational   
> Functions/Rational Functions/Rational   
> Functions_problems/asyp1_03_d.problem faile
> d for 10.192.57.242, reason: Invalid symb for   
> /res/purdue/purdue_math/math15800/Polynomial and Rational   
> Functions/Rational Functions/Rational   
> Functions_problems/asyp1_03_d.problem: upl
> oaded/purdue/4o12229eff3c955c9purduel1/default_1442167687.sequence___4___purdue/purdue_math/math15800/Polynomial and Rational Functions/Rational Functions/Rational   
> Functions_problems/a
> syp1_03_d.problem
> [Sun Sep 20 15:21:09 2015] [error] access to   
> /res/purdue/purdue_math/math15800/Polynomial and Rational   
> Functions/Rational Functions/Rational   
> Functions_problems/asyp1_03_d.problem faile
> d for 10.192.57.242, reason: Invalid Access for peng119 domain   
> purdue access bre
>
> Any ideas here?
>
>
> Thanks,
> Richard

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