[ejabberd] which mnesia tables to replicate in cluster?

Jesse Thompson jesse.thompson at doit.wisc.edu
Tue Oct 27 23:31:05 MSK 2009

We have a 2-node ejabberd cluster.  We begin with both running, then we 
shut down the master node, and the slave node continues to serve traffic 
just fine.  However, when we restart the slave node (or if it crashes 
for some reason) while the master is down it does not start back up.

I seem to remember this working with ejabberd 1.4 by only replicating 
the roster table (we don't use internal authentication, so we don't have 
a password table) however we seem to have misplaced our documentation. 
It looks like the table replication settings were reset when we upgraded 
to 2.x (2.0.5 current.)

As an experiment, we have set up the slave node so that *every* mnesia 
table is 'RAM and disc copy'.  The slave node now starts up.  However, I 
don't think that it would necessarily be wise to run with this 
configuration in production.

2 questions:

1. Which tables specifically need to be replicated in order for a slave 
node to start without the master being available?

2. Is there any way to define the table replication settings in the 
configuration instead of doing this manually?


   Jesse Thompson
   Division of Information Technology, University of Wisconsin-Madison
   Email/IM: jesse.thompson at doit.wisc.edu
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