86 lines
2 KiB
Elixir
86 lines
2 KiB
Elixir
defmodule MBU.AppRunner do
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@moduledoc """
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AppRunner is a script for ensuring that external apps are terminated
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properly when executed from BEAM.
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If you start an application that does not listen to STDIN from BEAM
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and BEAM is terminated, the application's STDIN is closed but it may
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never close. AppRunner is meant to sit in between, monitoring the
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STDIN pipe and killing the application if STDIN closes. This ensures
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no zombie processes are left behind if the host BEAM dies.
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Output from the application will be sent back to the host BEAM. If the
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application dies for any reason, AppRunner is also closed.
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"""
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def wait_for_eof() do
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case IO.getn("", 1024) do
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:eof -> nil
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_ -> wait_for_eof()
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end
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end
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def exec(program, args) do
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Port.open(
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{:spawn_executable, program},
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[
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:exit_status,
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:stderr_to_stdout, # Redirect stderr to stdout to log properly
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args: args,
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line: 1024
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]
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)
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end
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def get_pid(port) do
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case Port.info(port) do
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nil ->
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nil
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info when is_list(info) ->
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case Keyword.get(info, :os_pid) do
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nil -> nil
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pid -> Integer.to_string(pid)
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end
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end
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end
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def kill(pid) do
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System.find_executable("kill") |> System.cmd([pid])
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end
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def wait_loop(port) do
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receive do
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{_, {:data, {:eol, msg}}} ->
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msg |> :unicode.characters_to_binary(:unicode) |> IO.puts()
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{_, {:data, {:noeol, msg}}} ->
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msg |> :unicode.characters_to_binary(:unicode) |> IO.write()
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{_, :eof_received} ->
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get_pid(port) |> kill()
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:erlang.halt(0)
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{_, :closed} ->
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:erlang.halt(0)
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{_, {:exit_status, status}} ->
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:erlang.halt(status)
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{:EXIT, _, _} ->
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:erlang.halt(1)
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end
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wait_loop(port)
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end
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end
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[program | args] = System.argv()
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port = MBU.AppRunner.exec(program, args)
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Task.async(fn ->
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MBU.AppRunner.wait_for_eof()
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:eof_received
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end)
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MBU.AppRunner.wait_loop(port)
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