Notice: this library is no longer being developed. We have found it to be difficult to use something like Fourtrack in a situation where one needs the logged events to be serialized in a deterministic sequence. Most likely you can achieve what Fourtrack was trying to do using the transaction log / replication log of your database.

A gem for massive, parallel recording of streaming event logs for later replay. You know when you need one.

To record all of your SQL:

recorder = Fourtrack::Recorder.new(output_path: Rails.root.join('log/sql.jsonlines.gz'), flush_after: 1024)
ActiveSupport::Notifications.subscribe('sql.active_record') do |_, started, finished, id, payload|
  recorder << JSON.dump(payload)
end

and to replay later:

File.open(Rails.root.join('log/sql.jsonlines.gz')) do |f|
  player = Fourtrack::Player.new(f)
  player.each_line do |line|
    puts JSON.load(line)
  end
end

Add this line to your application's Gemfile:

gem 'fourtrack'

And then execute:

$ bundle

Or install it yourself as:

$ gem install fourtrack

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 tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/WeTransfer/fourtrack.

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