example.md

Example Usage

Create Your Poller

Somewhere in your app you would create the poller. In the example below we will create a poller when MyApp starts itself to help throttle API calls to a Weather API. This will help our app throttle itself for anything needing to use the Weather API.

defmodule MyApp do
  use Application

  def start(_type, _args) do
    # Start the poller
    {:ok, _pid} =
      Poller.create_poller("Weather API Poller", "weather", :timer.seconds(5))

    children = []

    Supervisor.start_link(children, strategy: :one_for_one, name:
    MyApp.Supervisor)
  end
end

This will create a poller that will send a call to any other processes registered to the poller. This is tracked in the Elixir Registry.

Subscribe to Your Poller

Now we will create a GenServer that can respond to the poller. The poller will send a call message to your process which is handled with a handle_info/2. Let's try that out:

defmodule MyApp.Weather do
  use GenServer

  @impl GenServer
  def init(state) do
    Poller.register("weather")
    {:ok, state}
  end

  @impl GenServer
  def handle_info(:call, state) do
    results = WeatherApi.use_throttled_endpoint(%{zip: "90210"})
    {:noreply, Map.put(state, :results, result)}
  end
end

Now our API is throttled to 1 API call per 5 seconds.

Multiple Processes on the same Poller

If we create and register another GenServer process that used the same weather API and registered it to the same "weather" poller, all API calls to that server would be throttled together. Poller rotates through registered processes in a round-robin fashion, so each process would be called once every 10 seconds.

Time	Event
0	Started Poller with 5 second interval
1	Registered GenServerOne
5	GenServerOne called
7	Registered GenServerTwo
10	GenServerOne called
15	GenServerTwo called
18	GenServerOne dies
20	GenServerTwo called
25	GenServerTwo called