Functional Programming: A PragPub Anthology

Monitoring Your Processes

Remember the example where our child process didn’t loop and we sent it two messages? The first was processed, but the child exited, and we never got a response to the second message.

We can handle this by linking our original process and the child process. If we do this, and one of the processes dies, the other will be sent a message. Let’s go back to that example, and change our spawn call with spawn_link.

elixir/spawn9.exs

cheery = fn ->
  receive do
    { from_pid, :en, msg } ->
        send from_pid, "Well, hello #{msg}"
    { from_pid, :fr, msg } ->
        send from_pid, "Bonjour #{msg}"
    { from_pid, :es, msg } ->
        send from_pid, "Hola #{msg}"
  end
end

Process.flag(:trap_exit ...