EventBus

Simple event bus implementation using ETS as an event store.

Installation

The package can be installed by adding event_bus to your list of dependencies in mix.exs:

def deps do
  [{:event_bus, "~> 0.4.0"}]
end

Usage

Register events in config.exs In your config.exs you can register events

config :event_bus, events: [:message_received, :another_event_occured]

Register events on demand

EventBus.register_event(:my_test_event_occured)

Subscribe to the ‘event bus’ with a listener and list of given topics, EventManager will match with Regex

# to catch every event topic
EventBus.subscribe({MyEventListener, [".*"]})
> :ok

# to catch specific topics
EventBus.subscribe({MyEventListener, ["purchase_", "booking_confirmed$", "flight_passed$"]})
> :ok

Unsubscribe from the ‘event bus’

EventBus.unsubscribe(MyEventListener)
> :ok

List subscribers

EventBus.subscribers()
> [{MyEventListener, [".*"]}]

List subscribers of a specific event

EventBus.subscribers(:hello_received)
> [MyEventListener]

Notify all subscribers with any type of data

EventBus.notify({:hello_received, %{message: "Hello"}})
EventBus.notify({:bye_received, [user_id: 1, goal: "exit"]})

Fetch event data

EventBus.fetch_event_data({:bye_received, event_key})

Mark as completed on Event Watcher

EventBus.mark_as_completed({MyEventListener, :bye_received, event_key})

Mark as skipped on Event Watcher

EventBus.mark_as_skipped({MyEventListener, :bye_received, event_key})

Sample Listener Implementation

defmodule MyEventListener do
  ...

  def process({topic, key} = event_shadow) do
    GenServer.cast(__MODULE__, event_shadow)
    :ok
  end

  ...


  def handle_cast({:bye_received, event_key}, state) do
    event_data = EventBus.fetch_event_data({:bye_received, event_key})
    # do sth with event_data

    # update the watcher!
    EventBus.mark_as_completed({__MODULE__, :bye_received, event_key})
    ...
    {:noreply, state}
  end
  def handle_cast({:hello_received, event_key}, state) do
    event_data = EventBus.fetch_event_data({:hello_received, event_key})
    # do sth with event_data

    # update the watcher!
    EventBus.mark_as_completed({__MODULE__, :hello_received, event_key})
    ...
    {:noreply, state}
  end
  def handle_cast({topic, key}, state) do
    EventBus.mark_as_skipped({__MODULE__, topic, key})
    {:noreply, state}
  end

  ...
end

Documentation

Module docs can be found at https://hexdocs.pm/event_bus. Implementation detail can be found at: https://medium.com/@mustafaturan/event-bus-implementation-s-d2854a9fafd5

Contributing

Issues, Bugs, Documentation, Enhancements

1. Fork the project

2. Make your improvements and write your tests(make sure you covered all the cases).

3. Make a pull request.

License

MIT