seeker.ex

defmodule Hive.Seeker do
	require IO
	require Logger

	@cluster "hive"
	@label "[Seeker]:"

	def discover() do
		Hive.Colony.start_link([name: :settings])

		if Node.alive? === true do
			ips = []
			Task.Supervisor.start_child(Hive.TaskSupervisor, fn -> boot(1, ips) end)
		else
			Logger.info "#{@label} Single-node discovery mode"
		end
	end

	defp boot(n, ips) do
		hostent = :inet.gethostbyname(:"#{@cluster}#{n}.local")

		if elem(hostent, 0) !== :error do
			{:ok, hostent} = hostent
			Logger.info "#{@label} #{n} nodes found"

			ips = 
				if Node.self !== :"hive@#{@cluster}#{n}.local" do
					ips ++ elem(hostent, 5)
				else
					ips
				end
			
			boot(n + 1, ips)
		else
			Hive.Colony.create(:settings, "device_ips")
    	{:ok, colony} = Hive.Colony.lookup(:settings, "device_ips")
    	Hive.Cell.put(colony, 1, ips)
			Logger.info "#{@label} end discovery after #{n - 1} nodes found"
		end
	end
end

This is a simple TCP Elixir based supervisor service to discover all devices on a subnet which have the correct EPMD based cookie. The Hive.Colony module is just a simple ETS based registry to store data in memory. If a device is rebooted it should be discovered again. I use this service to relay data via websockets to each device and so that it can also talk to real-time web and native applications. I hope you like that it is a short and sweet solution compared to something like EPMDless discovery or Nerves.