LocalCluster

This library is designed to assist in testing distributed states in Elixir which require a number of local nodes.

The aim is to provide a small set of functions which hide the complexity of spawning local nodes, as well as providing the ease of cleaning up the started nodes. The entire library is simple shimming around the Erlang APIs for dealing with distributed nodes, As some of it is non-obvious, and as I need this code for several projects, I span it out as a smaller project.

Installation

To install it for your project, you can pull it directly from Hex. Rather than use the version shown below, you can use the the latest version from Hex (shown at the top of this README).

def deps do
  [{:local_cluster, "~> 1.0", only: [:test]}]
end

Documentation and examples can be found on Hexdocs as they're updated automatically alongside each release. Note that you should only use the :test flag in your dependency if you're not using it for other environments.

Usage

As mentioned above, the API is deliberately tiny to make it easier to use this library when testing. Below is an example of using this library to spawn a set of child nodes for testing:

defmodule MyTest do
  use ExUnit.Case

  test "something with a required cluster" do
    :ok = LocalCluster.start()

    nodes = LocalCluster.start_nodes("my-cluster", 3)

    [node1, node2, node3] = nodes

    assert Node.ping(node1) == :pong
    assert Node.ping(node2) == :pong
    assert Node.ping(node3) == :pong

    :ok = LocalCluster.stop_nodes([node1])

    assert Node.ping(node1) == :pang
    assert Node.ping(node2) == :pong
    assert Node.ping(node3) == :pong

    :ok = LocalCluster.stop()

    assert Node.ping(node1) == :pang
    assert Node.ping(node2) == :pang
    assert Node.ping(node3) == :pang
  end
end

After calling start_nodes/2, you will receive a list of node names you can then use to communicate with via RPC or however you'd like. Although they're automatically cleaned up when the calling process dies, you can manually stop nodes as well to test disconnection.