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easy ejabberd clustering guide (mnesia, mysql, & postgres)

easy ejabberd clustering guide (mnesia, mysql, & postgres)

Ejabberd is a great little XMPP server, however it’s documentation makes me want to rip my fucking face off.  I have just spent way to long getting things configured (this is partly due to mysql5 support and 3rd party modules, dual NIC machines, public dns records… clustering issues were just icing on the cake) and I’m going to (hopefully) make your life a little easier.  To get things working properly I pieced together multiple tutorials and official documentation… which seems absurd considering the popularity of the ejabberd.  So below are the nitty gritty details and a helper module I wrote… because inputing mnesia commands into a debug shell for multiple slave node is… retarded.

before we begin, I want to point out that if you’re using mysql or postgres for authentication, offline messaging, etc. it doesn’t really matter to ejabberd for clustering purposes, although it is important when joining the cluster (which the official documentation seems to forget).

first things first, let’s configure our master node

(we’re assuming at this point you’ve installed ejabberd from source without a prefix, have it properly configured, and can successfully connect and message using it)

1: shut down your “master node”

ejabberdctl stop

2: edit ejabberdctl.cfg (/etc/ejabberd/ejabberctl.cfg)

2.1: change node name:

ERLANG_NODE=ejabberd@'master.domain.com'

2.2: change ip we listen on: (get this from ifconfig)

note: look closely, that’s a tuple, don’t use .’s use ,’s

INET_DIST_INTERFACE={192,168,10,100}

3: clear your ejabberd mnesia tables after hostname change

note: hostname changes are a pain, it’s easier to just let ejabberd rebuild the mnesia db’s at startup.

rm /var/lib/ejabberd/*

4: add hostname to /etc/hosts using address and hostname from confg

192.168.10.100    master.domain.com

5: start master node, and make sure it’s running

ejabberdctl start

ejabberdctl status

now we’ll need to configure our slaves

(once again we’re assuming the server is properly installed and functional as a stand alone server)

1: if the server is running, stop it.

ejabberdctl stop

2: update ejabberctl.cfg (/etc/ejabberd/ejabberdctl.cfg

2.1: change node name:

ERLANG_NODE=ejabberd@'slave1.domain.com'

2.2: change ip we listen on: (get this from ifconfig)

note: look closely, that’s a tuple, don’t use .’s use ,’s

INET_DIST_INTERFACE={192,168,10,150}

3: clear your ejabberd mnesia tables after hostname change

note: hostname changes are a pain, it’s easier to just let ejabberd rebuild the mnesia db’s at startup.

rm /var/lib/ejabberd/*

4: copy .erlang.cookie from “master node” (/var/lib/ejabberd/.erlang.cookie)

note: this is the unique cookie from ejabberd@master.domain.com, not the one already residing on slave1

5: add hostnames to /etc/hosts using address and hostname from confg

192.168.10.100    master.domain.com
192.168.10.150    slave1.domain.com

6: create and compile easy_cluster module

6.1: go to server binaries folder

cd /lib/ejabberd/ebin/

6.2: create empty module file

touch easy_cluster.erl

6.3: put the following contents in easy_cluster.erl and save the file

https://github.com/chadillac/ejabberd-easy_cluster/blob/master/easy_cluster.erl

6.4: compile easy_cluster.erl

erlc easy_cluster.erl

6.5: confirm compilation succeeded

note: you should see easy_cluster.beam in the directory if compilation was successful

ls | grep easy_cluster.beam

7: start the slave node & confirm it’s running

ejabberdctl start

ejabberdctl status

8: drop into a debugging session on the live server

note: you’ll see a warning message, just hit enter to continue

ejabberdctl debug

note: if you successfully drop a debug console, your prompt will resemble this

Erlang (BEAM) emulator version 5.6.5 [source] [64-bit] [smp:4] [async-threads:0] [hipe] [kernel-poll:true]

Eshell V5.6.5  (abort with ^G)
(ejabberd@slave1.domain.com)1>

9: test to see if we can connect to the node

note: at the end of each line we put a . this tells erlang to process our command

easy_cluster:test_node('ejabberd@master.domain.com').

if “server is reachable” we can continue, if it’s not, make sure you did ALL of the steps above.

10: join the cluster

easy_cluster:join('ejabberd@master.domain.com').

11: suspend your debug session by hitting Ctrl+c Ctrl+c

12: you’re done, go drink a beer, you probably need it.

Published

17 November 2012

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