[LON-CAPA-admin] access server questions
Stuart Raeburn
raeburn at msu.edu
Sun Oct 19 13:33:18 EDT 2008
Bob,
I don't believe this is a caching issue. LON-CAPA servers should
reload their hosts tables every 24 hours, so your access server
(loncapa2.chem.binghamton.edu) should have been able to contact
servers at NAU and UIUC.
An "Unable to find" message is displayed when:
(a) LON-CAPA tries to read a non-existent file from a directory within
/home/httpd/html/res (where files retrieved from the networked content
repository are stored),
or
(b) The file name of the file to be read is not defined.
If the required file has not previously been copied to your access
server from the LON-CAPA content repository, before trying to read the
file, LON-CAPA will request it from the author's homeserver. Although
the repcopy() routine used to do this returns a variety of responses
(ok, unavailable, bad_request, not_found, forbidden) depending on the
outcome, you need to look in /home/httpd/perl/logs/lonnet.log, for the
log messages recorded when an error occurred, because the response
from repcopy is not currently displayed to you.
Start a session on loncapa2.chem.binghamton.edu, select a Course
Coordinator, Domain Coordinator or Author role and browse the LON-CAPA
content repository for /res/nau/jkn/CHM152L/ExpG/cell potential
calculation.problem and
/res/uiuc/cyerkes/Chem204/Homework_5/balance2.problem
As you have shell access to loncapa2.binghamton.chem.edu,login via
ssh, then su root. Use:
tail -50 /home/httpd/perl/logs/lonnet.log
to see what the outcome of the attempt to subscribe to and copy these
resources was.
Also look in /home/httpd/html/res/nau/jkn and
/home/httpd/html/res/uiuc/cyerkes/ on loncapa2.chem.binghamton.edu to
see whether you have any directories there, and if so what the
permissions are on those directories. If the directories are there,
and readable by user www, use:
ls -al /home/httpd/html/res/nau/jkn/CHM152L/ExpG
ls -al /home/httpd/html/res/uiuc/cyerkes/Chem204/Homework_5/
to see if you have any files for cell\ potential\ calculation.problem and
balance2.problem respectively. Look at the file size, and the
permissions (are they readable by www?).
Stuart Raeburn
MSU LON-CAPA group
Quoting Bob Gonzales <rgonzal at binghamton.edu>:
> Alright, my access server can see almost all of remote resources now.
> The ones I still get the 'Unable to Find' message are:
>
> /res/nau/jkn/CHM152L/ExpG/cell potential calculation.problem
> /res/uiuc/cyerkes/Chem204/Homework_5/balance2.problem
>
> I can browse to the folder containing them via 'Edit Course->Import'
> and I can see them listed but if I click on them I get a window
> with the 'Unable to Find' message.
>
> So, is there some kind of caching mechanism going on here? I couldn't
> even browse to the domain yesterday, today I can browse to the specific
> file but I can't view it. I can browse to the file and open it from
> my library server. I was just curious how this works.
>
> Bob Gonzales
> Binghamton University
> Chemistry Dept
>
> -----Original Message-----
> From: lon-capa-admin-admin at mail.lon-capa.org
> [mailto:lon-capa-admin-admin at mail.lon-capa.org] On Behalf Of Stuart Raeburn
> Sent: Wednesday, October 15, 2008 12:08 PM
> To: lon-capa-admin at mail.lon-capa.org
> Subject: RE: [LON-CAPA-admin] access server questions
>
> Bob,
>
> I have identified the reason why you cannot see remote resources from
> your access server.
>
> Currently binghamtona2 is no longer included in the dns_hosts.tab file
> installed on one of the LON-CAPA DNS servers, because an update to
> LON-CAPA 2.7.1 (released 9/25) on that particular server on 10/6
> overwrote the more recent file (which included binghamtona2)
> previously installed on the server on 10/2. As a consequence other
> servers in the cluster will not permit connections if their hosts
> information (cached for 24 hours) was retrieved from this particular
> LON-CAPA DNS server.
>
> I have contacted the system administrator for the particular DNS
> server and requested an update to the dns_hosts.tab file. Assuming
> the DNS server is updated today, binghamtona2 should be able to see
> resources again after 5 am tomorrow, once cached hosts tables on
> remote servers have been refreshed.
>
> Stuart Raeburn
> MSU LON-CAPA group
>
>
> Quoting Bob Gonzales <rgonzal at binghamton.edu>:
>
>> Update: The IT guy looked at the firewall and found that the
>> library server had been removed from the list. So, he added it
>> back and we seem to be good. I can log into the Binghamton domain
>> from msu.
>>
>> However, I still cannot see remote resources from my access server.
>>
>> I got a note from Gerd about an update the dns tables for another
>> access server I am going to be installing. Here's part of what he sent:
>>
>>>
>>> Index: loncom/production_dns_hosts.tab diff -u
>>> loncom/production_dns_hosts.tab:1.47 loncom/
>>> production_dns_hosts.tab:1.48
>>> --- loncom/production_dns_hosts.tab:1.47 Thu Sep 25 23:15:14 2008
>>> +++ loncom/production_dns_hosts.tab Wed Oct 15 09:04:29 2008
>>> @@ -94,6 +94,7 @@
>>> ufml1:ufm:library:lon-capa-base1.server.uni-frankfurt.de:https
>>> binghamtonl1:binghamton:library:loncapa.chem.binghamton.edu
>>> binghamtona2:binghamton:access:loncapa2.chem.binghamton.edu
>>> +binghamtona3:binghamton:access:loncapa3.chem.binghamton.edu
>>> itul1:itu:library:www.fizikodev.itu.edu.tr
>>> uprml1:uprm:library:loncapa.hep.uprm.edu
>>> casel1:case:library:capa1.chem.cwru.edu
>>
>> Should I be able to see the access server that is already supposed to be
>> in the cluster, binghamtona2, in my local dns_hosts.tab files? Currently,
>> it doesn't appear in either my binghamtonl1 library server's file or the
>> binghamtona2 access server's file.
>>
>> Sorry if this is a dumb question or observation.
>>
>> Thanks,
>> Bob Gonzales
>> Binghamton University
>> Chemistry Dept
>>
>> -----Original Message-----
>> From: lon-capa-admin-admin at mail.lon-capa.org
>> [mailto:lon-capa-admin-admin at mail.lon-capa.org] On Behalf Of Stuart
> Raeburn
>> Sent: Tuesday, October 14, 2008 11:29 PM
>> To: lon-capa-admin at mail.lon-capa.org
>> Subject: RE: [LON-CAPA-admin] access server questions
>>
>> Bob,
>>
>> Curiously, it looks as though inbound traffic to port 5663 is being
>> blocked on your library server. nmap reports:
>>
>> Interesting ports on loncapa.chem.binghamton.edu (128.226.130.107):
>> PORT STATE SERVICE
>> 5663/tcp filtered unknown
>>
>> whereas port 5663 seems to open for inbound traffic on your access server:
>>
>> Interesting ports on loncapa2.chem.binghamton.edu (128.226.130.9):
>> PORT STATE SERVICE
>> 5663/tcp open unknown
>>
>> This is not consistent with the report that remote resources are
>> accessible on the library server but not on the access server.
>>
>> You should try in turn on each server to see if connection is possible
>> to the other server via port 5663.
>>
>> On 128.226.130.107
>> telnet 128.226.130.9 5663
>>
>> On: 128.226.130.9
>> telnet 128.226.130.107 5663
>>
>> You can also use:
>>
>> iptables --list
>>
>> to see whether the Fedora firewall is open for port 5663:
>>
>> e.g.,
>> ACCEPT tcp -- anywhere anywhere tcp dpt:5663
>>
>> Blocking inbound and/or outbound traffic may be occurring elsewhere in
>> the network.
>>
>> I am currently unable to start a session with a user in the msu domain
>> on either server.
>>
>> Stuart Raeburn
>> MSU LON-CAPA group
>>
>>
>> Quoting Bob Gonzales <rgonzal at binghamton.edu>:
>>
>>> lon-capa-admin at mail.lon-capa.org
>>>
>>> I made the changes outlined below, renaming my access server to
>>> what was entered in the loncapa DNS tables, and I was able to
>>> see remote resources in one of my homework sets from my access
>>> server. I only checked that one.
>>>
>>> Today, I went to check some other homework sets and I cannot see
>>> any of those remote resources (I get a message "Unable to Find...).
>>> I can still see the resources in the original set that I checked
>>> last week.
>>>
>>> On my library server I can see all the remote resources in all of
>>> my sets and I can browse to them via "Edit Course->Import".
>>>
>>> What can I check to help track down the problem?
>>>
>>> Thanks,
>>> Bob Gonzales
>>> Binghamton University
>>> Chemistry Dept
>>>
>>> -----Original Message-----
>>> From: lon-capa-admin-admin at mail.lon-capa.org
>>> [mailto:lon-capa-admin-admin at mail.lon-capa.org] On Behalf Of Stuart
>> Raeburn
>>> Sent: Saturday, October 04, 2008 5:14 PM
>>> To: lon-capa-admin at mail.lon-capa.org
>>> Subject: Re: [LON-CAPA-admin] access server questions
>>>
>>> Bob,
>>>
>>> Although the LON-CAPA cluster tables have been updated on the LON-CAPA
>>> "DNS" servers run by the LON-CAPA Academic Consortium, connections
>>> between your new server and other servers in the LON-CAPA network and
>>> are failing because there is a mismatch between the lonHostID used by
>>> your new server, and the lonHostID included in the record added to the
>>> hosts table on 9/26. This is the current entry in the dns_hosts.tab
>>> file:
>>>
>>> binghamtona2:binghamton:access:loncapa2.chem.binghamton.edu
>>>
>>> The login page for your new server reports:
>>> Domain: binghamton
>>> Server: binghamtona1 (access)
>>>
>>> The simplest thing would be for you to modify the lonHostID in:
>>> /etc/httpd/conf/loncapa.conf
>>>
>>> and the last line in /home/httpd/lonTabs/hosts.tab
>>> on loncapa2.chem.binghamton.edu
>>>
>>> so the new server is known as binghamtona2 everywhere.
>>>
>>> If you also added an entry for the access server to
>>> /home/httpd/lonTabs/hosts.tab on your library server
>>> (loncapa.chem.binghamton.edu)
>>> so the two servers could communicate with each other before the
>>> central dns_hosts tables had been updated you should modify that too.
>>> If you hadn't added a line to hosts.tab on your library server you can
>>> ignore this last part.
>>>
>>> You'll need to use:
>>>
>>> /etc/init.d/loncontrol restart
>>> /etc/init.d/httpd restart
>>>
>>> on your access server after you've made the change.
>>>
>>> The alternative to this would be to leave the entries on your own
>>> server(s) unchanged, and have the entry in the central DNS cluster
>>> tables changed to:
>>> binghamtona1:binghamton:access:loncapa2.chem.binghamton.edu. However,
>>> this will likely involve a greater delay because your server would
>>> only be able to connect to the network once the updated dns_hosts.tab
>>> file had been propagated to the LON-CAPA "DNS" servers at MSU, UIUC
>>> and SFU.
>>>
>>> I checked ports 80, 8080 and 5663 for inbound TCP/IP traffic to your
>>> new acces server. All looks good.
>>>
>>> loncapa2.chem.binghamton.edu (128.226.130.9):
>>> PORT STATE SERVICE
>>> 5663/tcp open unknown
>>> 8080/tcp open http-proxy
>>> 80/tcp open http
>>>
>>> Stuart Raeburn
>>> MSU LON-CAPA group
>>>
>>>
>>> Quoting Bob Gonzales <rgonzal at binghamton.edu>:
>>>
>>>> I've got a new access server in the domain. I've
>>>> been told it is in the cluster tables but it will
>>>> take a while to propagate around. It's been a week
>>>> now. How long does this usually take?
>>>>
>>>> When I log directly into the access server as a
>>>> course coordinator and go to edit contents
>>>> and go to import, I can see all of the domains but
>>>> clicking on a domain doesn't show me any resources,
>>>> it just turns the little arrow to point down without
>>>> showing anything from that domain.
>>>>
>>>> Likewise, if I log directly into the access server as
>>>> a student I can't see any of the resourses that are not
>>>> in my domain. For a composite page, wherever there is a
>>>> non-local resource I have the title of the resource displayed
>>>> and the words "Not available" displayed above it.
>>>>
>>>> My computer center has opened the 5663 and 80 for the
>>>> IP of the access server, 128.226.130.9, but if someone
>>>> would like to confirm that the ports are open for me that
>>>> might be helpful.
>>>>
>>>> Any other help would be appreciated, even if you just
>>>> tell me to be patient.
>>>>
>>>> Bob Gonzales
>>>> Binghamton University
>>>> Chemistry Dept
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> LON-CAPA-admin mailing list
>>>> LON-CAPA-admin at mail.lon-capa.org
>>>> http://mail.lon-capa.org/mailman/listinfo/lon-capa-admin
>>>>
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