DNS Configuration

The following setting applies only to the DNS backend:

DNS Hostname

The FQDN to use when the backend type is dns for looking up the RabbitMQ nodes to cluster via a DNS A record round-robin.

Environment Variable	AUTOCLUSTER_HOST
Setting Key	autocluster_host
Data type	string
Default Value	consul

Example Configuration

The following configuration example enables the DNS based cluster discovery and sets the autocluster_host variable to your DNS Round-Robin A record:

[
  {rabbit, [
    {log_levels, [{autocluster, debug}, {connection, debug}]}
  ]},
  {autocluster, [
    {backend, dns},
    {autocluster_host, "YOUR_ROUND_ROBIN_A_RECORD"}
  ]}
].

Troubleshooting

If you are having issues getting your RabbitMQ cluster formed, please check that Erlang can resolve:

• The DNS Round-Robin A Record. Imagine having 3 nodes with IPS 10.0.0.2, 10.0.0.3 and 10.0.0.4

> inet_res:lookup("YOUR_ROUND_ROBIN_A_RECORD", in, a).
[{10,0,0,2},{10,0,0,3},{10,0,0,4}]

• All the nodes have reverse lookup entries in your DNS server. You should get something similar to this:

> inet_res:gethostbyaddr({10,0,0,2}).
{ok,{hostent,"YOUR_REVERSE_LOOKUP_ENTRY",[],
             inet,4,
             [{10,0,0,2}]}}

• Erlang will always receive lowercase DNS names so be careful if you use your /etc/hosts file to resolve the other nodes in the cluster and you use uppercase there as RabbitMQ will get confused and the cluster will not form