GOV.UK Message queue consumer

Standardise the way GOV.UK consumes messages from RabbitMQ.

Nomenclature

• Message queue: a method of providing asynchronous interprocess communication

Technical documentation

This is a ruby gem that deals with the boiler plate code of connecting, subscribing, etc, to RabbitMQ.

The user of this gem is left the task of supplying their rabbitmq infrastructure configuration and an instance of a class that processes messages.

The message format received by the message processor is found in lib/govuk_message_queue_consumer/message.rb

Dependencies

• bunny: to interact with RabbitMQ
• activesupport: use with_indifferent_access for Bunny

Running the application

We recommend creating a rake task like the following example:

namespace :message_queue do
  desc "Run worker to consume messages from rabbitmq"
  task consumer: :environment do
    config = get_rabbitmq_configuration_hash
    # ^ eg YAML.load_file(Rails.root.join('config', 'rabbitmq.yml'))[Rails.env]
    GovukMessageQueueConsumer::Consumer.new(config, MyProcessor.new).run
  end
end

govuk_message_queue_consumer expects configuration and a processor to be supplied:

# example configuration. Could be stored in YAML if preferred
config = {
    host: 'localhost',
    port: 5672,
    user: rabbitmq_user,
    pass: rabbitmq_pass,
    recover_from_connection_close: true,
    exchange: my_exchange,
    queue: my_queue,
}

# example message processor
class MyProcessor
  def process(message)
    message.ack
  end
end

Testing your processor

This gem provides a test helper for your processor.

require 'test_helper'
require 'govuk_message_queue_consumer/test_helpers'

describe MyProcessor do
  it_behaves_like "a message queue processor"
end

This will verify that your processor class implements the correct methods. You should add your own tests to verify its behaviour.

Running the test suite

bundle exec rake spec

Licence

MIT License

Versioning policy

Semantic versioning