subscribex v0.10.0-rc.0 Subscribex
Subscribex is a simple way to interface with RabbitMQ. It’s split into 2 main components:
Subscribex.Broker
— Brokers are wrappers around the RabbitMQ instance. Actions go through the broker to get to the connection.Subscribex.Subscriber
— Subscribers are long-lived connections to a RabbitMQ instance that will handle messages as they are read from the queue.
If you want to quickly see an example of how to use Subscribex, please check the sample application.
Brokers
Subscribex.Broker
is a wrapper around a RabbitMQ instance. We can define a
broker as follows:
defmodule Broker do
use Subscribex.Broker, otp_app: :my_app
end
Where the configuration for the Broker must be in your application
environment, usually defined in your config/config.exs
:
config :my_app, Broker,
rabbit_host:
username: "guest",
password: "guest",
host: "localhost",
port: 5672
If you prefer, you can use a URL to connect instead:
config :my_app, Broker,
rabbit_host: "amqp://guest:guest@localhost:5672"
Each broker defines a start_link/0
function that needs to be invoked before
using the broker. In general, this function is not called directly, but used
as part of your application supervision tree.
If your application was generated with a supervisor (by passing --sup
to
mix new
) you will have a lib/my_app/application.ex
file (or
lib/my_app.ex
for Elixir versions < 1.4.0
) containing the application
start callback that defines and starts your supervisor. You just need to edit
the start/2
function to start the repo as a supervisor on your application’s
supervisor:
def start(_type, _args) do
import Supervisor.Spec
children = [
supervisor(Broker, [])
]
opts = [strategy: :one_for_one, name: MyApp.Supervisor]
Supervisor.start_link(children, opts)
end
Subscribers
Subscribers allow developers to monitor a queue and handle messages from that queue as they are published. Let’s see an example:
defmodule SubscribexExample.Queue1Subscriber do
use Subscribex.Subscriber
def init do
config = %Config{
broker: SubscribexExample.Broker,
queue: "queue_1.key",
exchange: "my_exchange",
exchange_type: :topic,
binding_opts: [routing_key: "key"]
}
{:ok, config}
end
def handle_payload(payload, _channel, _delivery_tag, _redelivered) do
Logger.info(inspect(payload))
end
def handle_error(payload, channel, delivery_tag, error) do
Logger.error("Raised #{inspect(error)} handling #{inspect(payload)}")
reject(channel, delivery_tag, requeue: false)
end
end
As messages are read off the queue, they will be passed into the subscriber’s
handle_payload/4
function for handling. In the case of an error, the
handle_error/4
function will be called.
end