0.0
The project is in a healthy, maintained state
A transactional outbox implementation for Ruby/ActiveRecord
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 Dependencies

Development

Runtime

>= 6.0.0
>= 0.23.1.1
>= 3.8.0, < 4.0.0
 Project Readme

StagedEvent

StagedEvent is a Ruby implementation of the transactional outbox architectural pattern.

This gem is relevant for any process that wants to publish events to a set of subscribers. It automatically saves outgoing events as records in a database table, from which a separate background process reads, publishes, and (once publishing is confirmed) deletes them. StagedEvent also provides a listener to subscribe to and receive these events from other processes.

Staging events this way allows them to be persisted within the same database transaction as associated domain-specific records, guaranteeing at-least-once delivery and thus eventual consistency with the receiving system(s).

For now, StagedEvent makes the following assumptions:

  • Events are defined as protobufs (and you have generated Ruby classes for them)
  • Google Pub/Sub is the underyling messaging infrastructure
  • You're using ActiveRecord (with a Postgres database >= version 9.5, due to the usage of the SQL SKIP LOCKED clause).

Installation

Add this line to your application's Gemfile:

gem "staged_event"

Then, in your application directory:

$ bundle install
$ rails generate staged_event:install

This will create an initializer at config/initializers/staged_event.rb, which you should modify with settings specific to your application.

The installer will also generate a migration to create the database table for staged events waiting to be published. Remember to run it using:

rails db:migrate

Publishing Events

In order for events to actually be published, StagedEvent provides a rake task that should be kept running alongside your application server(s):

rake staged_event:publisher

Receiving Events

In order to receive events from publishers, StagedEvent provides a rake task that should be kept running alongside your application server(s):

rake staged_event:subscriber

In order to process incoming events, you define a callback in the staged_event initializer file.

Regenerating Ruby from protobufs

StagedEvent uses a one-off protobuf definition to serialize and deserialize events that are defined as protobufs. In case it becomes necessary to recreate the auto-generated ruby, the command for that (from the repository root) is:

protoc --ruby_out=./ "./lib/staged_event/event_envelope.proto"