Looking for good examples of Projects that have tests that cover distributed behaviour

Crowdhailer · July 15, 2018, 2:35pm

To write a test suite for my [virtual actor framework] will require starting, or simulating multiple nodes.
i.e. I am trying to write a test that asserts an actor can only be running on one node at a time.

Is it possible to have multiple nodes running a single test suite. are there any good examples of projects that do this?

LostKobrakai · July 15, 2018, 2:56pm

Firenest would probably be a prime example of doing that.

idi527 · July 15, 2018, 3:17pm

Maybe https://github.com/lasp-lang/partisan/tree/master/test or https://github.com/SpaceTime-IoT/erleans/tree/master/test.

Crowdhailer · July 15, 2018, 3:43pm

Thanks for this. I have tried to follow the setup as in firenest but can’t work out to start Elixir on the other node.
My test setup is as follows.

:net_kernel.start([:"suite@127.0.0.1"])
|> IO.inspect()

:erl_boot_server.start([])
{:ok, ipv4} = :inet.parse_ipv4_address('127.0.0.1')
:erl_boot_server.add_slave(ipv4)
:ok

{:ok, peer_1} =
  :slave.start_link('127.0.0.1', :peer_1, inet_loader_args())
  |> IO.inspect()

Node.list()
|> IO.inspect()

Node.spawn(peer_1, Node, :list, [])
|> IO.inspect()

However this results in the following error

16:41:06.338 [error] Error in process #PID<17485.44.0> on node :"peer_1@127.0.0.1" with exit value:
{:undef, [{Node, :list, [], []}]}

Gazler · July 16, 2018, 8:08am

I think this is the relevant part from Firenest:

github.com

phoenixframework/firenest/blob/a9ef9eb5bcf2e91dbbdbd3a341f654a49ae87609/test/shared/test.ex#L129


      apply(module, function, args)
      send(parent, self())
      Process.sleep(:infinity)
    end)


  receive do
    ^task -> :ok
  end
end


defp spawn_node(node_host) do
  with_deadline(30_000, fn ->
    {:ok, node} = :slave.start_link('127.0.0.1', node_name(node_host), inet_loader_args())
    add_code_paths(node)
    transfer_configuration(node)
    ensure_applications_started(node)
    {:ok, node}
  end)
end


defp with_deadline(timeout, fun) do

Crowdhailer · July 16, 2018, 9:12am

Thanks this is helpful. I wonder if there is any reusable pattern here to wrap up all the steps involved in transferring code_paths/config etc