Yggdrasil is an immense mythical tree that connects the nine worlds in Norse cosmology.

Yggdrasil is an agnostic publisher/subscriber:

• Multi-node pubsub.
• Simple API (subscribe/1, unsubscribe/1, publish/2).
• GenServer wrapper for handling subscriber events easily.
• Several fault tolerant adapters (RabbitMQ, Redis, PostgreSQL, GraphQL, Ethereum).

small-example

Small Example

The following example uses the Elixir distribution to send the messages:

iex(1)> Yggdrasil.subscribe(name: "my_channel")
iex(2)> flush()
{:Y_CONNECTED, %Yggdrasil.Channel{...}}

and to publish a for the subscribers:

iex(3)> Yggdrasil.publish([name: "my_channel"], "message")
iex(4)> flush()
{:Y_EVENT, %Yggdrasil.Channel{...}, "message"}

When the subscriber wants to stop receiving messages, then it can unsubscribe from the channel:

iex(5)> Yggdrasil.unsubscribe(name: "my_channel")
iex(6)> flush()
{:Y_DISCONNECTED, %Yggdrasil.Channel{...}}

Though a GenServer can be used to receive these messages, this module also implements a behaviour for handling events e.g:

defmodule Subscriber do
  use Yggdrasil

  def start_link do
    channel = [name: "my_channel"]
    Yggdrasil.start_link(__MODULE__, [channel])
  end

  def handle_event(_channel, message, _state) do
    IO.inspect message
    {:ok, nil}
  end
end

The previous Yggdrasil subscriber would subscribe to [name: "my_channel"] and print every message it receives from it.