Synapse is a CQRS and event sourcing framework for Ruby 1.9.3 and later.

Synapse is partially an idiomatic port of AxonFramework and Lokad.CQRS

Warning: Synapse is still under development; public API can change at any time.

Resources

Have questions? Come to #synapse-cqrs on irc.freenode.net. I'm usually around.

• CQRS Guide
• CQRS is too complicated
• AxonFramework reference guide

Quickstart

You know the drill, add it to your Gemfile:

gem 'synapse-core'
gem 'synapse-mongo'

# Or if you're feeling edgy
gem 'synapse-core', :github => 'ianunruh/synapse', :branch => :master
gem 'synapse-mongo', :github => 'ianunruh/synapse-mongo', :branch => :master

You can define your commands and events using plain old Ruby objects.

class CreateInventoryItem
  attr_reader :id, :description

  def initialize(id, description)
    @id = id
    @description = description
  end
end

Define the aggregate -- In this case, an event-sourced aggregate.

class InventoryItem
  include Synapse::EventSourcing::AggregateRoot

  def initialize(id, description)
    apply InventoryItemCreated.new id, description
  end

  def check_in(quantity)
    apply StockCheckedIn.new id, quantity
  end

  map_event InventoryItemCreated do |event|
    @id = event.id
  end

  map_event StockCheckedIn do |event|
    @stock = @stock + event.quantity
  end
end

Define the command handler

class InventoryItemCommandHandler
  include Synapse::Command::MappingCommandHandler

  attr_accessor :repository

  map_command CreateInventoryItem do |command|
    item = InventoryItem.new command.id, command.description
    @repository.add item
  end

  map_command CheckInStock do |command|
    item = @repository.load command.id
    item.check_in command.quantity
  end
end

Wire everything up

Synapse.build_with_defaults do
  mongo_event_store do
    use_client Mongo::MongoClient.new
  end

  es_repository :item_repository do
    use_aggregate_type InventoryItem
  end

  # Register your command handler so it can be subscribed to the command bus and get its own
  # dependencies injected upon creation
  factory :item_command_handler, :tag => :command_handler do
    handler = InventoryItemCommandHandler.new
    handler.repository = resolve :item_repository

    handler
  end
end

aaaaaand you're done!

class InventoryItemController < ApplicationController
  depends_on :gateway

  def create
    # ...

    command = CreateInventoryItem.new sku, description
    gateway.send command
  end
end

Features

• Event sourced aggregates
  • DSL for specifying event handlers and aggregate members
  • Event store backed by MongoDB
  • Aggregate snapshot support
  • Conflict resolution with optimistic locking
• Non-event sourced aggregates
  • Supports persistence using ActiveRecord, MongoMapper, DataMapper, Mongoid, etc.
• DSL for easy mapping of event and command handlers
• Command validation (using ActiveModel)
• Simple object serialization
  • Ox, Oj and Marshal
  • Attribute-based serialization to JSON/XML
  • Deprecated events can be loaded and upcast into new formats
• Process manager framework (also known as Saga management)

Compatibility

Synapse is tested and developed on several different runtimes, including:

• MRI 1.9.3
• MRI 2.0.0
• JRuby 1.7.3
• Rubinius 2.0.0-rc1 (rbx-head)

Coming soon

• Event store using Sequel
• Distributed command and event buses (partitioning)
• Aggregates as command handlers
• Event replay and projection framework
• Event scheduling