Stream is causing iex to hang for some reason...

gistfile1.ex

defmodule LoggerHandler do
  use GenEvent

  # Callbacks

  def handle_event({:log, x}, messages) do
    {:ok, [x|messages]}
  end

  def handle_call(:messages, messages) do
    {:ok, Enum.reverse(messages), []}
  end
end

{:ok, pid} = GenEvent.start_link()

GenEvent.add_handler(pid, LoggerHandler, [])
GenEvent.notify(pid, {:log, 1})
GenEvent.notify(pid, {:log, 2})
GenEvent.notify(pid, {:log, 3})

# uncomment the following line and iex hangs indefinitely.
# pid |> GenEvent.stream |> Enum.take(1) # this hangs inside iex

pid |> GenEvent.stream(timeout: 500) |> Enum.take(1) # this times out after half a second

This works.

defmodule LoggerHandler do
  use GenEvent

  # Callbacks

  def handle_event({:log, x}, messages) do
    {:ok, [x|messages]}
  end

  def handle_call(:messages, messages) do
    {:ok, Enum.reverse(messages), []}
  end
end

{:ok, pid} = GenEvent.start_link()

Task.start_link fn -> IO.inspect pid |> GenEvent.stream(timeout: 500) |> Enum.take(3) end 

GenEvent.add_handler(pid, LoggerHandler, [])
GenEvent.notify(pid, {:log, 1})
GenEvent.notify(pid, {:log, 2})
GenEvent.notify(pid, {:log, 3})

# =>  [log: 1, log: 2, log: 3]  to stdout

Jose Valim has my thanks for his help in this solution.