defmodule Cluster.Strategy.Epmd do
@moduledoc """
This clustering strategy relies on Erlang's built-in distribution protocol.
You can have libcluster automatically connect nodes on startup for you by configuring
the strategy like below:
config :libcluster,
topologies: [
epmd_example: [
strategy: #{__MODULE__},
config: [
timeout: 30_000,
hosts: [:"a@127.0.0.1", :"b@127.0.0.1"]]]]
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.
"""
use GenServer
use Cluster.Strategy
alias Cluster.Strategy.State
@impl true
def start_link([%State{config: config} = state]) do
case Keyword.get(config, :hosts, []) do
[] ->
:ignore
nodes when is_list(nodes) ->
GenServer.start_link(__MODULE__, [state])
end
end
@impl true
def init([state]) do
connect_hosts(state)
{:ok, state, configured_timeout(state)}
end
@impl true
def handle_info(:timeout, state) do
handle_info(:connect, state)
end
def handle_info(:connect, state) do
connect_hosts(state)
{:noreply, state, configured_timeout(state)}
end
@spec configured_timeout(State.t()) :: integer() | :infinity
defp configured_timeout(%State{config: config}) do
Keyword.get(config, :timeout, :infinity)
end
@spec connect_hosts(State.t()) :: State.t()
defp connect_hosts(%State{config: config} = state) do
nodes = Keyword.get(config, :hosts, [])
Cluster.Strategy.connect_nodes(state.topology, state.connect, state.list_nodes, nodes)
state
end
end