A behaviour used to implement custom AMQP channel pools.

By default, BroadwayRabbitMQ handles its own pool of AMQP connections and channels. However, there might be use cases where you want to use your own existing pool or custom pooling logic. In those cases, you can implement a custom channel pool using this behaviour.

To use a custom pool, pass {:custom_pool, module, args} as the value of the :connection option in BroadwayRabbitMQ.Producer. module needs to implement this behaviour, and args is passed down to checkout_channel/1 and checkin_channel/2.

Examples

Imagine we pass this option when starting the producer:

connection: {:custom_pool, MyPool, _amqp_connection = :big_pool}

Then, we could define the custom pool as:

defmodule MyPool do
  @behaviour BroadwayRabbitMQ.ChannelPool

  @impl true
  def checkout_channel(name) do
    conn = %AMQP.Connection{pid: Process.whereis(name)}

    case AMQP.Channel.open(conn) do
      {:ok, channel} -> {:ok, channel}
      {:error, reason} -> {:error, %RuntimeError{message: inspect(reason)}}
    end
  end

  @impl true
  def checkin_channel(_name, channel) do
    case AMQP.Channel.close(channel) do
      :ok -> :ok
      {:error, reason} -> {:error, %RuntimeError{message: inspect(reason)}}
    end
  end
end