[LON-CAPA-users] Unresponsive lon-capa

[Stuart Raeburn]

Hi,

Gerd mentioned the Apache server-status page:  
"http://(yourserver)/server-status/" and indicated he would send the  
password to access this page.

Starting with LON-CAPA 2.8.0 access to this page (and some other  
status pages) was switched from using htpasswd-based authentication  
and authorization, to using access control via LON-CAPA (and  
configured for a domain by the Domain Coordinator).

When logged into LON-CAPA, Domain Coordinators can view this page via:
Main Menu -> Status of domain servers -> Apache Server Status

A Domain Coordinator can also configure access to this page via:
Main Menu -> Set domain configuration -> Display [Access to server  
status pages (checked)]

One of the access modes supported is IP-based, which permits display  
of server-status from a specified machine without the need for log-in  
to LON-CAPA.  This can be useful for remote monitoring.

> Yes, http://(yourserver)/server-status/
>
> - that will show you what the server is busy doing and you can find   
> the problem that's the problem. I'll send you passwords in a minute.
>

There can be a difficulty here in that once Apache has reached its  
maximum clients limit, and all clients are busy, possibly serving  
looped processes, it is difficult to get a free Apache client to  
display the server-status page.

Stuart Raeburn
MSU LON-CAPA group


Quoting Gerd Kortemeyer <korte@lite.msu.edu>:

> Hi,
>
> On Feb 7, 2011, at 10:03 AM, D G Teed wrote:
>>
>> We've been seeing problems with our lon-capa, where it
>> becomes unresponsive, and yet the OS doesn't show
>> any problems with load, free RAM, etc.
>>
>> Restarting httpd and loncontrol seems to reset the situation.
>>
>> It happened with the previous release, and it is again happening
>> while running 2.9.1.  We are using Redhat Enterprise 4, recently updated,
>> but again the problems were seen before and after these updates.
>>
>> Sometimes this appears in the error log:
>>
>> [error] server reached MaxClients setting, consider raising the   
>> MaxClients setting
>
> That can happen if there is a problem that has an endless loop in   
> it: Apache child processes are busy trying to process the request,   
> and of course the users keep hitting "Reload"
>
>>
>> Are there typical things to check when running into an unresponsive service?
>
> Yes, http://(yourserver)/server-status/
>
> - that will show you what the server is busy doing and you can find   
> the problem that's the problem. I'll send you passwords in a minute.
>
> - Gerd.