[LON-CAPA-admin] Timeout Error when Preparing to Print

Stuart Raeburn raeburn at msu.edu
Fri Mar 18 01:01:53 EDT 2011


Yes, I reproduce this error for a LON-CAPA user session hosted on  
loncapa.tcc.fl.edu.  It is not restricted to printout generation.  The  
same occurs as a Course Coordinator when attempting to display a  
student's view of a problem.  The issue is not specific to a  
particular resource or resource type.

In both the printout generation case, and the CC's display of  
student's view of a problem, LON-CAPA internally uses an LWP  
(libwww-perl) request for the resource.  In these contexts, LON-CAPA  
will try the internal SSI call 5 times to render a resource before  
giving up, and as the default timeout for the LWP UserAgent is 180s,  
it can be 15 minutes before the "unrecoverable network error occurred"  
message is displayed.

The SSI call will be a request for a connection to:  
$ENV{'SERVER_NAME'}, which the error message suggests is:


One thing to determine is how DNS resolves that hostname on the server  
itself, via:

host loncapa.tcc.fl.edu

Although you report:

> I have verified that DNS is ok.

it seems likely that the cause of this connection problem is related  
to how the server is resolving loncapa.tcc.fl.edu on the server itself.

One thing to try from the command line on the server itself would be  
to check whether port 80 is accessible internally:

telnet loncapa.tcc.fl.edu 80

As regards logging, a successful internal SSI call via LWP would  
result in something similar to the following - - [DD/MMM/YYYY:HH:MM:SS -0400] "POST  
/adm/tccfl/carrj/1205767552/smppg HTTP/1.1" 200 NNNNN "-"  
(where NNNNN is the file size)

in /etc/httpd/logs/access_log

If you do find this type of request logged, then that suggests that  
the response to the request is not being routed back to the caller.   
It seems more likely, however, that there will be no entries of this  
type logged because the requests are not being received, handled and  
then logged by Apache.

On my own machines:

host loncapa.tcc.fl.edu reports:
loncapa.tcc.fl.edu is an alias for loncapa.tcc.fl.edu

It seems odd to alias a hostname to itself.

LON-CAPA will log an unsuccessful SSI call for the  
/adm/tccfl/carrj/1205767552/smppg resource in  

with entries beginning:

"Failed ssi_with_retries on /adm/tccfl/carrj/1205767552/smppg"

but I doubt that will provide any more information than is reported to  
screen when attempted printout generation finally times out.

One thing to check might be to log-in to loncapa.tcc.fl.edu as a  
Domain Coordinator, and then, after selecting the Domain Coordinator  
role, enter the URL:


In the information displayed on that page I would expect  
ENV{'SERVER_NAME'} to be loncapa.tcc.fl.edu, but if it is not, then  
that would be significant.

Stuart Raeburn

Quoting BRETT DORR <DORRB at tcc.fl.edu>:

> I am new to Lon-Capa and it is something that was setup by a   
> predecessor of mine but we currently have an issue when preparing to  
>  print.
> Preparing Printout takes very long and then eventually comes back   
> with an error:
> ---
> An unrecoverable network error occurred:
> At least one of the resources you chose to print could not be   
> rendered due to an unrecoverable error when communicating with a   
> server:
> /adm/tccfl/carrj/1205767552/smppg
> 500 Can't connect to loncapa.tcc.fl.edu:80 (connect: timeout)
> I have verified that DNS is ok.  Any suggestions on where I should   
> look to troubleshoot this?
> Thanks,
> Brett Dorr
> Network Systems/Data Communications Analyst
> Tallahassee Community College
> 444 Appleyard Drive
> Tallahassee, Florida 32304
> dorrb at tcc.fl.edu<mailto:dorrb at tcc.fl.edu>

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