Follows agents' events into your app.

A listener hands each event to handle/2, with the cursor past it. Save the cursor with your work, and return it from cursor/1. The listener then carries on from there after a restart.

defmodule MyApp.Runs do
  use WardrikEvents.Listener

  @impl true
  def handle(event, listener) do
    MyApp.Repo.transaction(fn ->
      MyApp.Repo.insert_all("agent_events", [MyApp.Runs.row(event)], on_conflict: :nothing)
      MyApp.Cursors.put!("runs", listener.cursor)
    end)

    :ok
  end

  @impl true
  def cursor(_listener), do: MyApp.Cursors.get("runs")
end

children = [{MyApp.Runs, events: MyApp.Events, types: ["wardrik.run.completed"]}]

Options

• :events - required. The name of your WardrikEvents.
• :resources - patterns of the logs to follow. ["*"], every agent, unless set.
• :types - the event types to take. Every type unless set. A wardrik.events.dropped always comes through.
• :after - the cursor to start after, if you don't define cursor/1. What's written next unless set.

Your module's own options can sit beside these. They're in the listener's :options.

Delivery

Each event is handed over at least once.

1. Save the cursor in the same transaction as your work.
2. If handle/2 raises or returns anything but :ok, the listener restarts.
3. On restart it calls cursor/1 again, and reads after what it returns.

So drop a repeat by the event's id.