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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?(),

      do: Logger.error "There's no lighthouse in this cluster. We should restart!" # Node.stop

  end



  defp in_cluster?,

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

end