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

It helps you migrate to event-driven architecture with at least once delivery guarantees.

1. Install gem

bundle add outboxer bundle install

2. Generate schema migrations, publisher script 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 after 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 

8. Publish outboxer messages

# bin/outboxer_publisher Outboxer::Publisher.publish_message do |publisher, message| # TODO: publish message here end

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

To ensure you have end to end coverage:

bundle exec rspec spec/bin/outboxer_publisher

Monitor using the built-in web UI:

Rails

# config/routes.rb require 'outboxer/web' mount Outboxer::Web, at: '/outboxer'

Rack

# config.ru require 'outboxer/web' map '/outboxer' { run Outboxer::Web }

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