Transaction Outbox for Postgres

This gem provides a way to implement the transaction outbox pattern using triggers (stored procedures) in Postgres.

It utilizes the ruby Sequel ORM to interact with the database, but once it’s set up, it doesn’t require any ruby nor Sequel code for the outbox population to operate. It all runs on the PostgreSQL cluster, guaranteeing no matter how the database writes occur, the outbox events will always be generated.

Installation

Install the gem and add to the application’s Gemfile by executing:

bundle add sequel-pgt_outbox

If bundler is not being used to manage dependencies, install the gem by executing:

gem install sequel-pgt_outbox

Usage

Using the sequel cli

sequel -r sequel/pgt_outbox postgres://localhost/mydb
Your database is stored in DB...
irb(main):001> DB.create_table(:foo) { primary_key :id; String :s; Integer :i }
=> nil
irb(main):002> function = DB.pgt_setup_outbox(:foo)
=> "pgt_outbox_foo_outbox"
irb(main):003> DB[:foo].insert(s: 'foo', i: 1)
=> 1
irb(main):004> DB[:foo_outbox].first
=> nil
irb(main):005> DB.pgt_outbox_events(:foo, function)
=>
#<Rubyists::PgtOutbox::Trigger:0x00007f1ae2fbc2b0
 @db=#<Sequel::Postgres::Database database=spgt_test>,
 @events=[:insert, :update, :delete],
 @function="pgt_outbox_foo_outbox",
 @name="pgt_outbox_foo_outbox",
 @opts={when: nil},
 @table=:foo,
 @trigger_opts={after: true, each_row: true}>
irb(main):006> DB[:foo].insert(s: 'bar', i: 2)
=> 2
irb(main):007> DB[:foo_outbox].first
=>
{id: 1,
 attempts: 0,
 completed: nil,
 created: 2025-02-15 18:20:30.28394 +0000,
 updated: 2025-02-15 18:20:30.28394 +0000,
 attempted: nil,
 event_type: "foo_created",
 last_error: nil,
 data_before: nil,
 data_after: "{\"i\": 2, \"s\": \"bar\", \"id\": 2}",
 metadata: nil}

Development

After checking out the repo, run bin/setup to install dependencies. Then, run rake test to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and the created tag, and push the .gem file to [rubygems.org](https://rubygems.org).

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/rubyists/sequel-pgt_outbox. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the [code of conduct](https://github.com/rubyists/sequel-pgt_outbox/blob/main/CODE_OF_CONDUCT.md).

License

The gem is available as open source under the terms of the [MIT License](https://opensource.org/licenses/MIT).

Code of Conduct

Everyone interacting in the Sequel::PgtOutbox project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the [code of conduct](https://github.com/rubyists/sequel-pgt_outbox/blob/main/CODE_OF_CONDUCT.md).