This clustering strategy relies on Erlang's built-in distribution protocol by using a .hosts.erlang file (as used by the :net_adm module).

Please see the net_adm docs for more details.

In short, the following is the gist of how it works:

File .hosts.erlang consists of a number of host names written as Erlang terms. It is looked for in the current work directory, the user's home directory, and $OTP_ROOT (the root directory of Erlang/OTP), in that order.

This looks a bit like the following in practice:

'super.eua.ericsson.se'.
'renat.eua.ericsson.se'.
'grouse.eua.ericsson.se'.
'gauffin1.eua.ericsson.se'.

You can have libcluster automatically connect nodes on startup for you by configuring the strategy like below:

config :libcluster,
  topologies: [
    erlang_hosts_example: [
      strategy: Elixir.Cluster.Strategy.ErlangHosts,
      config: [timeout: 30_000]
    ]
  ]

An optional timeout can be specified in the config. This is the timeout that will be used in the GenServer to connect the nodes. This defaults to :infinity meaning that the connection process will only happen when the worker is started. Any integer timeout will result in the connection process being triggered. In the example above, it has been configured for 30 seconds.