From raeburn at msu.edu  Mon Feb  5 15:55:34 2024
From: raeburn at msu.edu (Raeburn, Stuart)
Date: Mon, 5 Feb 2024 20:55:34 +0000
Subject: [LON-CAPA-admin] Can't see one of my student's problems
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Nathan,

I have tried various ways to break my Ubuntu 20 LON-CAPA testing VM so it will display: "Invalid argument" (from /usr/share/perl5/LWP/Protocol/http.pm line 50) but so far I always get more useful output than simply: "Invalid argument" when IO::Socket::INET socket creation fails (when attempting to generate the student's view of a problem etc.).

You might create an executable testlwp.pl perl script file on your server containing the following minimal test case:

#!/usr/bin/perl

use strict;
use LWP::UserAgent();

my $ua=new LWP::UserAgent;
$ua->local_address('127.0.0.1');
my $request=new HTTP::Request('GET',"https://loncapa.winona.edu/adm/about.html");
my $response=$ua->request($request);
print "Result ".$response->status_line."\n";

and run it to see what response status is reported.

I am assuming that display of a student's view of a problem used to work. The question would be what changes have been made on your server/network since it last worked, e.g., 

(a) package updates
(b) network changes
(c) firewall changes
(d) certificate changes

I see that the SSL certificate for loncapa.winona.edu from letsencrypt.org has a start date of 1/10/2024, so that is one recent change.

Stuart Raeburn
LON-CAPA Academic Consortium
________________________________________
From: LON-CAPA-admin <lon-capa-admin-bounces at mail.lon-capa.org> on behalf of Moore, Nathan T via LON-CAPA-admin <lon-capa-admin at mail.lon-capa.org>
Sent: Wednesday, January 31, 2024 10:06 PM
To: list about administration and system updating
Subject: Re: [LON-CAPA-admin] Can't see one of my student's problems

Appreciate the quick reply Stuart! I tried your suggestions below and using the switchserver url made the problem go away.  I assume this means there's an internal error in my server somewhere?  Any suggestions appreciated - my notes are posted below.

> Can't connect to loncapa.winona.edu:443 when using LWP is typically seen when the SSL/TLS certificate chain is incorrect, but whatsmychaincert.com suggests the chain is correct for your server.

CONCUR

>Is the Ubuntu package liblwp-protocol-https-perl installed?

YES
sudo apt install liblwp-protocol-https-perl
Reading package lists... Done
Building dependency tree
Reading state information... Done
liblwp-protocol-https-perl is already the newest version (6.07-2ubuntu2).
liblwp-protocol-https-perl set to manually installed.
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.

>Does /home/httpd/lonTabs/hosts.tab contain:
>winonal1:winona:library:loncapa.winona.edu:https:winona.edu

YES
cat /home/httpd/lonTabs/hosts.tab
^s10.lite.msu.edu
^dalton.chem.sfu.ca
^library1.lon-capa.uiuc.edu
winonal1:winona:library:loncapa.winona.edu:https:winona.edu

>If you can view submissions by other students for the same problem, it might be that this student's submission(s) contain(s) control characters or other non-printable characters, etc. which are causing problems when LON-CAPA makes an internal call to render for the web and answer targets.

> PROBLEM IS PRESENT FOR OTHER STUDENT PROBLEMS/WORK AS WELL

> Unless you have your domain configured to disallow hosting of user sessions for users in the winona domain on servers in other LON-CAPA domains, one thing to try to troubleshoot this would, when already logged into loncapa.winona.edu would  be to replace the URL in the browser's address bar with

> loncapa.winona.edu/adm/switchserver?otherserver=<hostID>

> replacing <hostID> with the LON-CAPA hostID of another LON-CAPA server., so you could transfer your LON-CAPA session to a different server to see if the same problem is seen there, when accessing a student's view of

>You could transfer to the MSU "demo server, which has a hostID of msudemol1 if you like, although that server is running 2.11.4, whereas you own server is still on 2.11.3.

WHEN I CHANGED TO THE DEMO SERVER AS ABOVE I WAS ABLE TO SEE STUDENT PROBLEMS VIA THE GRADING SCREEN - THIS WORKED!

>Is encryptedURL set for this problem?
I CAN'T REMEMBER WHERE TO LOOK FOR THIS SETTING.

>Is there a discussion board attached to this problem (with posts from students).
NO POSTS FROM STUDENTS ON THIS PROBLEM

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