Trabox

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Transactional-Outbox for Rails.

Features

• Publishing event data in transactional-outbox pattern
• Polling multiple databases and outbox tables
• Can use your own publisher/subscriber
• Custom Metrics with dogstatsd
• Ensure message ordering

Supported publisher

• Google Cloud Pub/Sub

Installation

Add this line to your application's Gemfile:

gem 'trabox'

And then execute:

bundle install
bin/rails g trabox:configure

This will generate config file config/initializers/trabox.rb.

Optional:

bundle binstubs trabox

Usage

Generate outbox tables

# generate model
bin/rails g trabox:model <NAME>

# Help
bin/rails g trabox:model --help
Usage:
  rails generate trabox:model NAME [field[:type][:index] field[:type][:index]] [options]
...

additional option: --polymorphic=<NAME> This option is inserted references column in generated outbox model. This use to associate event record with outbox record when the application is designed immutable data model.

example:bin/rails g trabox:model event --polymorphic=event

class CreateEvents < ActiveRecord::Migration[6.1]
  def change
    create_table :events do |t|
      t.references :event, polymorphic: true, null: false # additional column
      t.binary :event_data
      t.string :message_id
      t.datetime :published_at

      t.timestamps
    end
  end
end

Registering event data

Insert events to publish into the generated outbox table as part of the local transaction.

# Your rails application
ActiveRecord::Base.transaction do
  user = User.create! name: 'hoge'

  Event.create! event_data: <serialized_user_event>
end

Running relayer

bin/trabox relay

# Help
bin/trabox relay -h
Usage: trabox relay [OPTIONS]

Overwrite configuration

    -l, --limit NUM
    -i, --interval SEC
    -L, --[no-]lock
        --log-level LEVEL

Running subscriber

bin/trabox subscribe

# Help
bin/trabox subscribe -h
Usage: trabox subscribe [OPTIONS]

Overwrite configuration

        --log-level LEVEL

Metrics

The default namespace of metrics is trabox.
The namespace can be changed with TRABOX_METRIC_NAMESPACE environment variable.

name	description
unpublished_event_count	Number of events that will be published
published_event_count	Number of published events
find_events_error_count	Number of errors that find events to publish
publish_event_error_count	Number of publication errors
update_event_record_error_count	Number of record update errors

Health check

command	metric name
relay	relay.service.check
subscribe	subscribe.service.check

Sequence diagram

Contributing

Bug reports and pull requests are welcome.

Development

Install gems

bundle install

Start mysql / pubsub emulator

docker-compose up

setup db

cd spec/rails_app
bin/rails db:setup

create topic / subscribe

rake trabox:pubsub_setup

Test

bin/rspec

License

The gem is available as open source under the terms of the MIT License.