Defines a data structure for configuring this library.

Config options

• dequeue_interval - The interval used by the producer to timout polls to the queue process. Defaults to 5000.
• client_id_prefix - The value is used to prefix the randomly generated client ids by the MQTT client. Defaults to "obmp". Keep in mind that some brokers limit the size of client_id size to 23 bytes!
• server_opts - See the "Server options" section for details.
• telemetry_prefix - Sets the prefix for any telemery events. Defaults to :off_broadway_mqtt.

Server options

All options given with the server_opts option are passed to Tortoise when starting the connection process. The following options can be given:

• host - The host the MQTT client uses by default. Defaults to "localhost".
• port - The port the MQTT client uses by default. Defaults to 1883.
• transport - The protocol the MQTT client uses by default. Defaults to :tcp.
• See Tortoise.Connection.start_link/1 for further options.

Dependency injection

Besides the other config options it is also possible to replace some modules used by providing an alternative implementation:

• queue_supervisor - The supervisor that supervises the queue processes started by the producer. Defaults to OffBroadway.MQTT.QueueSupervisor.
• queue_registry - The registry that is used to register the queue processes started by the producer. Defaults to OffBroadway.MQTT.QueueRegistry.
• acknowledger - The Broadway.Acknowledger implementation used when building the message strucs.
• client - The MQTT client module.
• handler- The handler module used by the default client.
• queue - The queue used in the handler and producer to enqueue / dequeue messages.

Compiletime configuration

The following options must be given at compile time:

• telemetry_enabled - Enables telemetry events if set to true. This option is disabled by default.

Configuration example

use Mix.Config

config :off_broadway_mqtt,
  client_id_prefix: "sensor_data_processor",
  server_opts: [
    host: "vernemq",
    port: 8883,
    transport: :ssl
  ],
  handler: MyApp.BetterHandler

Building configurations

iex> OffBroadway.MQTT.Config.new()
%OffBroadway.MQTT.Config{
  acknowledger: OffBroadway.MQTT.Acknowledger,
  client: OffBroadway.MQTT.Client,
  client_id_prefix: "obmp",
  dequeue_interval: 5000,
  handler: OffBroadway.MQTT.Handler,
  producer: OffBroadway.MQTT.Producer,
  queue: OffBroadway.MQTT.Queue,
  queue_registry: OffBroadway.MQTT.QueueRegistry,
  queue_supervisor: OffBroadway.MQTT.QueueSupervisor,
  server: {:tcp, [host: 'localhost', port: 1883]},
  telemetry_prefix: :off_broadway_mqtt
}

iex> OffBroadway.MQTT.Config.new(
...>   telemetry_prefix: :test,
...>     server_opts: [host: "vernemq", port: 8883, transport: :ssl]
...>   )
%OffBroadway.MQTT.Config{
  acknowledger: OffBroadway.MQTT.Acknowledger,
  client: OffBroadway.MQTT.Client,
  client_id_prefix: "obmp",
  dequeue_interval: 5000,
  handler: OffBroadway.MQTT.Handler,
  producer: OffBroadway.MQTT.Producer,
  queue: OffBroadway.MQTT.Queue,
  queue_registry: OffBroadway.MQTT.QueueRegistry,
  queue_supervisor: OffBroadway.MQTT.QueueSupervisor,
  server: {:ssl, [host: 'vernemq', port: 8883]},
  telemetry_prefix: :test
}

Keep in mind that any option with nil or the empty string will be removed from the server options to prevent issues when configuring the application from environment variables.