[ejabberd] Clustering question...

Michael Weibel michael.weibel at gmail.com
Sat May 5 11:45:17 MSK 2012

Hu felix,

Good that you solved it. I struggled with clustering as well but now I
think i know how to do it correctly.
I followed the guide once as well. While it seems to work it doesn't
mention a few things:
-extra_db_nodes is only used when you initially set up the mnesia
replication. After doing this, this param doesn't need to be in the startup
script at all.
- replication of mnesia: it's important that the configuration for each
table is the same on node2 as on node1.

as soon as my company has setup the planned labs blog I'll publish a step
by step guide and i hope i can write an automated join cluster script and
opensource it.

Am 04.05.2012 22:50 schrieb "Felix GV" <felix at mate1inc.com>:

> Hi Michael,
> Thanks for your reply :)
> I am actually launching ejabberd as root, which is probably not a good
> idea, but that's the way the binary installer set it up (it did not create
> an ejabberd user, like apt-get does, but I wanted 2.1.10 and apt-get was
> giving me an older version...). I should definitely set this up more
> appropriately at some point, but I found out what's causing the issue and
> it's not related to this.
> I checked the cookie and they're identical on my two nodes. I was also
> seeing the two nodes in the web admin interface, so it SEEMED like the
> clustering was done properly, but there is something that was not correct.
> I followed this guide to configure the nodes:
> tdewolf.blogspot.ca/2009/07/clustering-ejabberd-nodes-using-mnesia.html
> But there is something that this guide does not mention, which seems
> pretty evident in retrospect, but since it was not explicitly mentioned, I
> didn't think of doing it.
> The guide instructed me to modify the ejabberdctl script on node #2 so
> that it has the following extra parameter:
> *-mnesia extra_db_nodes "['ejabberd at ejabberd1']"*
> After doing this, I saw node #2 coming up in the web admin interface, so I
> thought everything was ok, but it was not ok, because I also needed to add
> this parameter to node #1's startup script (while mentioning that the
> extra_db_node is node #2, and not itself, obviously).
> Doing this made the clustering actually happen for real. After this, the
> status command outputted correct values on both nodes, and I could bring
> down any one node, and the other would keep serving chat messages. (The
> connected clients would be disconnected and reconnect automatically to the
> remaining alive node, but that is all right.)
> Now, having different configurations embedded in the ejabberdctl script of
> each node is not really convenient, so I tried having a uniform script
> instead, where all nodes mention all nodes (including themselves) in the
> extra_db_nodes parameter, and that seems to work correctly, so I'm planning
> to leave it this way.
> I really wish there was a complete and accurate guide to clustering
> ejabberd, because the official ejabberd administration guide does not go in
> depth and is missing some important pieces of information. Making this
> clustering work required a lot of guess work.
> I think the guide I provided a link to above, along with the clarification
> I just mentioned, should be enough for someone else to get it up and
> running, but it'd be nice to have this in the official doc!
> The mnesia replication also requires a fair amount of guesswork, and while
> I think my choices are ok, I'm afraid I might only discover that something
> is problematic once we're already in production. A default, official, up to
> date, recommended clustered mnesia configuration would be nice to have as
> well.
> Anyway, thanks again for your help! I didn't know about the debug command
> and poking around with it indirectly lead me to figure out what was going
> on :) ...
> Hopefully, this post might save someone else some headaches :)
> Cheers ;) !
> --
> Felix
> On Thu, May 3, 2012 at 2:31 AM, Michael Weibel <michael.weibel at gmail.com>wrote:
>> Hi,
>> >  sudo ./ejabberdctl status I get:
>> > The node ejabberd at jabber2 is started with status: started
>> > ejabberd is not running in that node
>> > Check for error messages: /opt/ejabberd-2.1.10/logs/ejabberd.log
>> > or other files in that directory.
>> >
>> > Commands to start an ejabberd node:
>> >   start  Start an ejabberd node in server mode
>> >   debug  Attach an interactive Erlang shell to a running ejabberd node
>> >   live   Start an ejabberd node in live (interactive) mode
>> I assume you're running ejabberd as the user ejabberd. If you do a sudo
>> ejabberdctl status, it could be possible that it takes a different
>> .erlang.cookie than ejabberd. This way, ejabberdctl can't get the status.
>> Usually erlang cookies in $HOME/.erlang.cookie. But it may be that there
>> are also other places where the erlang cookie is stored.
>> If you do a ejabberdctl debug, you can open a shell attached to the
>> ejabberd process. There you can get the cookie value by using
>> "erlang:get_cookie().". (Btw to close the shell: 2x ctrl+c)
>> Maybe that helps you.
>> >
>> > Whereas on jabber1.dev, the same command gives me:
>> >
>> > The node ejabberd at jabber1 is started with status: started
>> > ejabberd 2.1.10 is running in that node
>> >
>> > Is there someone that can help me debug this problem...?
>> >
>> > I can provide other informations if the above is not sufficient...!
>> >
>> > Thanks a lot :) !!
>> >
>> > --
>> > Felix
>> >
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