[Server-devel] Possible Jabber Problem on Server

[John Watlington]

On May 7, 2008, at 10:28 PM, Martin Langhoff wrote:

> On Thu, May 8, 2008 at 2:19 AM, Berkowitz Andrew (Project Connect)
>> Greetings from New York.
>
> "G'day mate" from New Zealand!
>
>>  Although the short hostname, schoolserver, has stayed the same,  
>> the domain
>> has changed from 00b000.nycboe.org to 00b001.nycboe.org and back to
>> 00b000.nycboe.org. When I changed the domain & address, I changed the
>
> Hmmmm. That's unsupported at the moment. Wad might have more
> experience changing the FQDN...

I've only recovered from that by nuking the ejabberd installation
(rpm -e ejabberd; rm -r /var/lib/ejabberd/; yum install ejabberd)

>> Jabber servers are
>> notoriously finicky and frequently return the nodedown message if  
>> a server's
>> hostname changes.
>
> Exactly, and we haven't yet done the legwork to make sure that this
> works end-to-end.

We've done enough to know that changing the host/domain name is a big  
problem
with the current presence server.

>> The normal resolution is to export the database, convert it and  
>> import it. I
>> tried this conversion using the Erlang conversion utility.
>>
>> I also reimported the original database. Some people report that just
>> exporting and importing, without conversion, fixes the problem.  
>> This process
>> also did not resolve the issue.

I found at least one recipe which claimed to fix this problem a while  
back, but didn't test it.

> Hm. What happens if you wipe out the mnesia database and start from  
> scratch.

Fixes the problem.

>>  Also, I have another concern. The jabber database is kept in text  
>> files.
>> This configuration is fine for small sites. But with many users,  
>> it is
>> better to keep the database in MySQL for better performance and  
>> better
>> reliability.
>
> If I can get mnesia to use PostgreSQL as a backend, I'll do it.

There are configuration file option for ejabberd to use postgreSQL, etc.
for the database.   Perhaps some volunteers can play with these ?

>> Another question: You've reported a bug where If an XO is reimaged  
>> and then
>> needs to re-register with the server, it cannot. In this case, is  
>> it okay to
>> export the database as text, manually delete the entry, and then  
>> import the
>> database.

> For a quick fix, you can delete the entries in the SQLite db in
> /home/idmgr . We'll have a UI for this later.

Wrong database.  If that bug is due to a database, it is the ejabberd
database.

But if you are referring to #6919, it is harder to replicate than  
Giannis indicated
at first.   I do this all the time, when testing builds/servers, and  
hadn't seen it.
It was easier to replicate for a while, when the presence server in  
the local area
was misconfigured.

> All these ad-hoc DBs need to be under some control, and the UI will
> probably be handled as an extension of Moodle's user mgmt facilities.

Darn right...

Cheers,
wad