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

Mon Oct 5 09:16:34 EDT 2015

Stuart, that's a great explanation.  Thank you.  I've been able to confirm
that we see these when a use tries to access a resource after their session
has ended.
Mike B

On Fri, Oct 2, 2015 at 2:51 PM, Stuart Raeburn <raeburn at msu.edu> wrote:

> Mike,
>
> Please help us understand and solve these errors.
>>
>
> An "Invalid symb" error message will be logged in the Apache error log
> file if the user's course session files have expired on the server
> currently hosting the user session.
>
> If you look in /home/httpd/perl/tmp you will find files named:
>
> <username>_<domain>_<coursenum>.db
> <username>_<domain>_<coursenum>_parms.db
> <username>_<domain>_<coursenum>.state
> <username>_<domain>_<coursenum>_symb.db
>
> where <username> is the username of the user (e.g., mikeb), <domain> is
> the course domain (i.e., purdue), and <coursenum> is the coursenumber
> (e.g., 74323912a211e547fpurduel1
>
> The script: /home/httpd/perl/loncron which is run as user www at 5.10 am
> (see entry in /etc/cron.d/loncapa) will, amongst other things, clean-up
> files in /home/httpd/perl/tmp with last modification times that are more
> than 24 hours ago (as determined by the value of lonExpire, in seconds,
> found in /etc/httpd/conf/loncapa.conf).
>
> If the <username>_<domain>_<coursenum>.db file is missing, and a student
> has left a browser tab/window open which is logged into LON-CAPA, certain
> actions (e.g., reloading a LON-CAPA page, make a submission to a displayed
> homework problem) will result in a 406 return code "HTTP_NOT_ACCEPTABLE",
> and a logged "Invalid symb" message.  An "Access denied" screen will be
> displayed in the student's browser.  Subsequent actions will typically
> result in display of the roles screen with the message: "As your session
> file for the course or community has expired, you will need to re-select
> it.".
>
> Anyway, you might look in the Apache access logs to see who the user was
> in each of these cases found in the Apache error logs, e.g., by matching
> the IP address, and then take a look at log-in history and access history,
> to determine if the "Invalid symb" was logged in the case of a request made
> after the last 5:10 am run of /home/httpd/perl/loncron had cleaned up stale
> session files for a user with more than 24 hours of inactivity.
>
> The user's activity.log file can also be useful -- you'll find that on the
> LON-CAPA library server in the user's directory:
>
> /home/httpd/lonUsers/purdue/<1>/<2>/<3>/<username>/
>
> where <1> is the first character, <2> second character, <3> third
> character in the user's username.
>
> The following perl one-liner run in that directory displays the
> dates/times in a more readable format:
>
> cat activity.log | perl -p -e '($date,$host,$command)=split /:/,
> $_;$_=localtime($date);$_.=":".$host.":".$command;'
>
>
> Stuart Raeburn
> LON-CAPA Academic Consortium
>
> Quoting Mike Budzik <mikeb at purdue.edu>:
>
> Stuart,
>> I'm not sure you addressed the Invalid symb issue in Richard's email and
>> we
>> are still seeing Invalid symb errors in our error logs.  At first we
>> thought it wasn't affecting users because problem reports from users
>> stopped, but the messages in the log didn't.  I no longer believe that
>> this
>> isn't impacting users.
>>
>> [Thu Oct 01 20:19:17 2015] [error] access to
>> /res/purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem failed for IP-ADDRESS, reason:
>> Invalid
>> symb for /res/purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem:
>>
>> uploaded/purdue/7p186918837ca553dpurduel1/default_1432132025.sequence___17___purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem
>>
>> [Thu Oct 01 21:05:30 2015] [error] access to
>> /res/purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem failed for IP-ADDRESS, reason:
>> Invalid
>> symb for /res/purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem:
>>
>> uploaded/purdue/7p186918837ca553dpurduel1/default_1432132025.sequence___17___purdue/purdue_math/math16010/Differentiation/Implicit
>> Differentiation/Problem/11_d.problem
>>
>> [Fri Oct 02 02:46:43 2015] [error] access to
>> /public/purdue/7p186918837ca553dpurduel1/syllabus failed for IP-ADDRESS,
>> reason: Invalid symb for
>> /public/purdue/7p186918837ca553dpurduel1/syllabus:
>>
>> uploaded/purdue/7p186918837ca553dpurduel1/default.sequence___1___public/purdue/7p186918837ca553dpurduel1/syllabus
>>
>> It looks like in the case of the last one, the user received a 406 error:
>> from the access log:
>> IP-ADDRESS - USERNAME [02/Oct/2015:02:46:42 -0400] "GET
>> /public/purdue/7p186918837ca553dpurduel1/syllabus HTTP/1.1" 406 386 "-"
>> "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_9_5) AppleWebKit/537.78.2
>> (KHTML, like Gecko) Version/7.0.6 Safari/537.78.2"
>>
>>
>> Please help us understand and solve these errors.
>> Thank you,
>> Mike Budzik
>>
>>
>> On Sun, Sep 20, 2015 at 6:41 PM, Stuart Raeburn <raeburn at msu.edu> wrote:
>>
>> 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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>>>
>>
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