Settings View Source KantanCluster

かんたんクラスター

Form a simple Erlang cluster easily in Elixir.

• A wrapper of Node and Phoenix.PubSub with simple API
• Reconnection forever in case nodes get disconnected

getting-started

Getting started

Add kantan_cluster to your list of dependencies in mix.exs:

def deps do
  [
    {:kantan_cluster, "~> 0.3"}
  ]
end

Start a node and connect it to other nodes based on specified options.

Start node1 in an IEx shell, then attempt to connect it to node2 that is not started yet.

iex> KantanCluster.start(name: :"node1@127.0.0.1", cookie: :hello, connect_to: :"node2@127.0.0.1")
:ok

iex(node1@127.0.0.1)2>
16:50:10.851 [warning] could not connect node1@127.0.0.1 to node2@127.0.0.1

Start node2 in another IEx shell, then the two nodes get connected.

See what happens in node1, when node2 is stopped and gets started again,

iex> KantanCluster.start(name: :"node2@127.0.0.1", cookie: :hello)
:ok

iex(node2@127.0.0.1)2> Node.list
[:"node1@127.0.0.1"]

iex(node2@127.0.0.1)3> Node.stop
:ok

iex> KantanCluster.start(name: :"node2@127.0.0.1", cookie: :hello)
:ok

Alternatively, options can be loaded from your config/config.exs.

config :kantan_cluster,
  name: :"node1@127.0.0.1",
  cookie: :hello,
  connect_to: [:"node2@127.0.0.1"]

kantan_cluster starts a server that monitors the connection per node name under a DynamicSupervisor.

kantan_cluster monitors all the connected nodes and attempts to reconnect them automatically in case they get disconnected.

You can connect to or disconnect from a node on demand.

KantanCluster.connect(:"nerves@nerves-mn01.local")

KantanCluster.disconnect(:"nerves@nerves-mn01.local")

For cleanup, just call KantanCluster.stop/0, which will stop the node and all the connections.

publish-subscribe

Publish-subscribe

The publish-subscribe allows us to make a published message available from anywhere in a cluster. Under the hood, kantan_cluster uses phoenix_pubsub for all the heavy-lifting.

# Somebody may publish temperature data on the topic "hello_nerves:measurements".
message = {:hello_nerves_measurements, %{temperature_c: 30.1}, node()}
KantanCluster.broadcast("hello_nerves:measurements", message)

# Anybody within the same cluster can subscribe to the topic and receive messages on the topic.
KantanCluster.subscribe("hello_nerves:measurements")

# In the subscribing process, you may receive the message using GenServer's handle_info callback.
defmodule HelloNervesSubscriber do
  use GenServer

  # ...

  @impl GenServer
  def handle_info({:hello_nerves_measurement, measurement, _node}, state) do
    {:noreply, %{state | last_measurement: measurement}}
  end

acknowledgements

Acknowledgements

• This project is inspired by nerves_pack（vintage_net含む）を使ってNerves起動時にNode.connect()するようにした by nishiuchikazuma.
• Forming an Erlang cluster of Pi Zeros by underjord is a great hands-on tutorial for connecting multiple Nerves devices.
• Some code is adopted from livebook.