RMQ - RabbitMQ tools.

A set of handy tools for working with RabbitMQ in Elixir projects. Based on AMQP library.

It includes:

1. RMQ.Connection
2. RMQ.Consumer
3. RMQ.RPQ

Installation

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

def deps do
  [
    {:rmq, "~> 0.3.0"}
  ]
end

RMQ.Connection

A GenServer which provides a robust connection to the RabbitMQ server.

Usage

defmodule MyApp.RabbitConnection do
  use RMQ.Connection,
    otp_app: :my_app,
    uri: "amqp://localhost",
    name: to_string(__MODULE__)
end

Meant to be started under the application's supervision tree as follows:

defmodule MyApp.Application do
  use Application

  def start(_type, _args) do
    children = [
      MyApp.RabbitConnection
      # ...
    ]

    opts = [strategy: :one_for_one, name: MyApp.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

Options

• :uri - an AMQP URI. Defaults to "amqp://localhost";
• :reconnect_interval - a reconnect interval in milliseconds. It can be also a function that accepts the current connection attempt as a number and returns a new interval. Defaults to 5000;
• other options for AMQP.Connection.open/2.

RMQ.Consumer

RabbitMQ Consumer.

Usage

defmodule MyApp.Consumer do
  use RMQ.Consumer,
    queue: "my-app-consumer-queue",
    exchange: {"my-exchange", :direct, durable: true}

  @impl RMQ.Consumer
  def consume(chan, payload, meta) do
    # do something with the payload
    ack(chan, meta.delivery_tag)
  end
end

# or with dynamic configuration
defmodule MyApp.Consumer2 do
  use RMQ.Consumer

  @impl RMQ.Consumer
  def config do
    [
      queue: System.fetch_env!("QUEUE_NAME"),
      reconnect_interval: fn attempt -> attempt * 1000 end,
    ]
  end

  @impl RMQ.Consumer
  def consume(chan, payload, meta) do
    # do something with the payload
    ack(chan, meta.delivery_tag)
  end
end

Options

• :connection - the connection module which implements RMQ.Connection behaviour. Defaults to RMQ.Connection;
• :queue - the name of the queue to consume. Will be created if does not exist. Also can be a tuple {queue, options}. See the options for AMQP.Queue.declare/3;
• :exchange - the name of the exchange to which queue should be bound. Also can be a tuple {type, exchange, options}. See the options for AMQP.Exchange.declare/4. Defaults to "";
• :routing_key - queue binding key. Defaults to queue; Will be created if does not exist. Defaults to "";
• :dead_letter - defines if the consumer should setup deadletter exchange and queue. Defaults to true;
• :dead_letter_queue - the name of dead letter queue. Also can be a tuple {queue, options}. See the options for AMQP.Queue.declare/3. Defaults to "#{queue}_error".;
• :dead_letter_exchange - the name of the exchange to which dead_letter_queue should be bound. Also can be a tuple {type, exchange} or {type, exchange, options}. See the options for AMQP.Exchange.declare/4. Defaults to "#{exchange}.dead-letter";
• :dead_letter_routing_key - routing key for dead letter messages. Defaults to queue;
• :concurrency - defines if c:consume/3 callback should be called in a separate process. Defaults to true;
• :prefetch_count - sets the message prefetch count. Defaults to 10;
• :consumer_tag - consumer tag. Defaults to a current module name;
• :reconnect_interval - a reconnect interval in milliseconds. It can be also a function that accepts the current connection attempt as a number and returns a new interval. Defaults to 5000;

RMQ.RPC

RPC via RabbitMQ.

Usage

# Application 1:

defmodule MyApp.RemoteResource do
  use RMQ.RPC, publishing_options: [app_id: "MyApp"]

  def find_by_id(id) do
    call("remote-resource-finder", %{id: id})
  end
end

#  Application 2:

defmodule MyOtherApp.Consumer do
  use RMQ.Consumer, queue: "remote-resource-finder"

  @impl RMQ.Consumer
  def consume(chan, payload, meta) do
    response =
      payload
      |> Jason.decode!()
      |> Map.fetch!("id")
      |> MyOtherApp.Resource.get()
      |> Jason.encode!()

    reply(chan, meta, response)
    ack(chan, meta)
  end
end

Options

• :connection - the connection module which implements RMQ.Connection behaviour;
• :queue - the queue name to which the module will be subscribed for consuming responses. Also can be a tuple {queue, options}. See the options for AMQP.Queue.declare/3. Defaults to "" which means the broker will assign a name to a newly created queue by itself;
• :exchange - the exchange name to which :queue will be bound. Please make sure the exchange exist. Defaults to "" - the default exchange;
• :consumer_tag - a consumer tag for :queue. Defaults to the current module name;
• :publishing_options - any valid options for AMQP.Basic.publish/5 except reply_to, correlation_id - these will be set automatically and cannot be changed. Defaults to [];
• :reconnect_interval - a reconnect interval in milliseconds. It can be also a function that accepts the current connection attempt as a number and returns a new interval. Defaults to 5000;
• :filter_parameters - a list of parameters that may contain sensitive data and have to be filtered out when logging. Defaults to ["password"].