[Operators] Ejabberd upgrades and mnesia multinode setup

Mickaël Rémond mremond at process-one.net
Mon Aug 3 15:23:52 UTC 2015

Hello Holger,

Holger Baust said:

> Hi!
> I am planning to upgrade jabber.freenet.de soon.
> But this is a multinode setup with 2 nodes.
> Has anyone done this yet and can give me some advises?
> (only ejabberd specific please)
> Since these Nodes run as Virtual Machines on VMWare clusters,
> I have the advantage of using snapshot for roll-backs.

It should be quite a straightforward operation.

My advice are the following:

1. Backup Mnesia DB and relational backend.
2. Take a snapshot of your VM for rollbacks.
3. Assess if you can migrate one node at a time. If you can simulate 
cluster update on snapshot outside of the production context it would be 
good. Depending on which version you are and which version you are 
getting two, it may be possible to mix cluster nodes from two versions 
(if internal data structure between the two versions did not change)
4. Shutdown nodes (or only one if possible) and upgrade code, but keep 
data and restart the nodes in reverse order (otherwise, the service will 
wait for the latest online master to go up to really start).

Does it make sense ? Do you have more specific questions ?

Mickaël Rémond
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