[solution] ejabberd join_cluster no_ping error

1. If you didn't open required ports,
    please check https://stackoverflow.com/questions/36862874/erlang-ejabberd-join-cluster-error-no-ping
    FIREWALL_WINDOW=4200-4210  in ejabberdctl.cfg setting is mandatory.

2. You already opened all required ports, but you are getting no_ping error,
    set hosts config. /etc/hosts -> add your ejabbered node hostname. (in my case, node1, node2)

ex)
...
node1    10.0.100.1
node2    10.0.100.2

How to set ejabberd cluster. step by setp

1. ejabberd.yml -> use same file config
2. ejabberdctl.cfg ->
  use same all but
  ERLANG_NODE=ejabberd@each-node-hostname
  FIREWALL_WINDOW=4200-4210

3. add node1, node2 on /etc/hosts
4. node1) ejabberdctl start
5. node2) ejabberdctl start
6. node2) ejabberdctl --no-timeout join_cluster 'ejabberd@node1'