Functional Web Development with Elixir, OTP and Phoenix/

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Long-running Processes

Long-running Processes

Learn how to deal with long-running processes.

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Define a new module

To see how linking processes and trapping exits behave, we need processes that hang around long enough for us to observe them. IEx is a long-running process that is readily available, but we’ll need to spawn others for it to interact with.

To do that, let’s define a new module at lib/islands_engine/demo_proc.ex. All we need is a single function that implements an infinite recursion. We call it the loop/0 function. In the middle, we use receive/1 to retrieve the next message from the mailbox:

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defmodule IslandsEngine.DemoProc do
  def loop() do
    receive do
      message -> IO.puts "I got a message: #{message}"
    end
    loop()
  end
end

We don’t need an after-block here. This code will run in a separate ...