Disco

Simple, opinionated yet flexible library to build CQRS/ES driven systems.

## Status (2018-12-08)

Disco has been extracted from work done to build apps following the CQRS/ES pattern. Several ideas come from other excellent examples such as commanded. However, the goal was to build something simpler and more flexible, because it's not always possible to follow 100% CQRS/ES pattern neither anywhere in your apps. Disco tries to solve this gap.

Production ready?

Not yet. Well, this approach and code has been used to build several apps in production without problems, however before being really usable, it needs some polishing.

Installation

The package is available in Hex, follow these steps to install:

1. Add disco to your list of dependencies in mix.exs:

def deps do
  # Get from hex
  [{:disco, "~> 0.1.0"}]
  # Or use the latest from master
  [{:disco, github: "andreapavoni/disco"}]
end

1. Ensure disco is started before your application:

def application do
  [applications: [:disco]]
end

Usage

Quick and dirty console example, to show how it's supposed to work.

$ iex -S mix
# start Orchestrator process with the available aggregates
iex> Disco.Orchestrator.start_link [MyApp.Wallet]
{:ok, #PID<0.327.0>}

# get available commands
iex> Disco.Orchestrator.commands()
[:create_wallet]

# execute a command (sync)
iex> Disco.Orchestrator.dispatch(:create_wallet, %{user_id: UUID.uuid4(), balance: 100.0})
{:ok, %MyApp.Wallet.Aggregate{
  balance: 100.0,
  id: "4fd98a9e-8d6f-4e35-a8fc-aca5544596cb",
  user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"
}}

# execute a command (async -> returns {:ok, aggregate_id})
iex> Disco.Orchestrator.dispatch(:create_wallet, %{user_id: UUID.uuid4(), balance: 100.0}, async: true)
{:ok, "ce998b0d-8d6f-4e35-a8fc-aca5544596cb"}

# execute invalid command
iex> Disco.Orchestrator.dispatch(:create_wallet, %{balance: 100.0})
{:error, %{user_id: ["must be a valid UUID string"]}}

# get available queries
iex> Disco.Orchestrator.queries()
[:list_wallets]

# list user wallets
iex> Disco.Orchestrator.query(:list_wallets, %{user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"})
[%{
  balance: 100.0,
  id: "4fd98a9e-8d6f-4e35-a8fc-aca5544596cb",
  user_id: "13bbece9-9bf3-4158-92b4-7e8a62d62361"
}]

# execute invalid query
iex> Disco.Orchestrator.query(:list_wallets, %{})
{:error, %{user_id: ["must be a valid UUID string"]}}

Documentation

The documentation is available at https://hexdocs.pm/disco.

TODO / SHORT TERM ROADMAP

• [x] improve overall documentation
• [ ] consolidate Event to be a struct and/or protocol
• [ ] consolidate API (mostly based on feedback, if any)
• [ ] adopt an adapter-based approach for event store database
• [ ] add example app

Contributing

Everyone is welcome to contribute to PlugEtsCache and help tackling existing issues!

Use the issue tracker for bug reports or feature requests.

Please, do your best to follow the Elixir's Code of Conduct.

License

This source code is released under MIT License. Check LICENSE file for more information.