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extreme_system

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Building blocks for distributed systems

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extreme_system lib system node_monitor.ex
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lib/system/node_monitor.ex 

defmodule Extreme.System.NodeMonitor do

  require Logger



  def start_link do

    {:ok,

     spawn_link(fn ->

       :global_group.monitor_nodes(true)

       Process.register(self(), __MODULE__)

       monitor()

     end)}

  end



  def monitor do

    receive do

      {:nodeup, node} ->

        Logger.info("NodeMonitor: #{node} joined")



      {:nodedown, node} ->

        Logger.warn("NodeMonitor: #{node} left")

        check_cluster()

    end



    monitor()

  end



  defp check_cluster do

    unless in_cluster?(),

      # Node.stop

      do: Logger.error("There's no lighthouse in this cluster. We should restart!")

  end



  defp in_cluster?,

    do:

      Node.list()

      |> Enum.any?(fn node -> node |> to_string |> String.starts_with?("lighthouse") end)

end