📤 Outboxer

Outboxer is an implementation of the transactional outbox pattern for event driven Ruby on Rails applications.

Quickstart

1. Install gem

bundle add outboxer
bundle install

2. Generate schema migrations and tests

bundle exec rails g outboxer:install

3. Migrate database

bundle exec rails db:migrate

4. Generate event schema and model

bundle exec rails generate model Event type:string created_at:datetime --skip-timestamps
bundle exec rails db:migrate

5. Queue outboxer message when event created

# app/models/event.rb

class Event < ApplicationRecord
  after_create do |event|
    Outboxer::Message.queue(messageable: event)
  end
end

6. Derive event type

# app/models/accountify/invoice_raised_event.rb

module Accountify
  class InvoiceRaisedEvent < Event; end
end

7. Create derived event type

bundle exec rails c

ActiveRecord::Base.logger = Logger.new(STDOUT)

Accountify::InvoiceRaisedEvent.create!(created_at: Time.current)

8. Observe transactional consistency

TRANSACTION                (0.2ms)  BEGIN
Event Create               (0.4ms)  INSERT INTO "events" ...
Outboxer::Message Create   (0.3ms)  INSERT INTO "outboxer_messages" ...
TRANSACTION                (0.2ms)  COMMIT

9. Publish event

# bin/outboxer_publisher

Outboxer::Publisher.publish_message do |publisher, message|
  # TODO: publish event here
end

To integrate with Active Cable, Sidekiq, Bunny, Kafka, AWS SQS and others, see the publisher integration guide.

Testing

To ensure you have end to end coverage:

bundle exec rspec spec/bin/outboxer_publisher

Monitoring

Monitor multithreaded publishers using Outboxer's built-in web UI:

Publishers

Messages

Rails

# config/routes.rb

require 'outboxer/web'

mount Outboxer::Web, at: '/outboxer'

Rack

# config.ru

require 'outboxer/web'

map '/outboxer' { run Outboxer::Web }

Contributing

• Star us on GitHub
• Report issues
• Chat on Discord

All contributions are welcome!

License

Open-sourced under LGPL v3.0.