capital-match / hevents

Event Sourcing library in Haskell

HEvents: An Event Sourcing Library for Haskell

The goal of this library is to make it easy to develop and deploy production grade (micro-)services based on event sourced model. Each such service should be easily constructed and include the following:

• A underlying business model expressed as a pure data structures to which can be sent Commands and applied Events,
• Atomic application of some commands to underlying model,
  • Possibly with wrapping it in remote request,
• Storage of generated events in append-only data source with choice of underlying storage medium:
  • In memory list of events,
  • Local file,
  • Remote server,
• Call to other services as a client,
• Error handling in a consistent way,
• Web interface to the service,
• Logging,
• Metrics and monitoring,
• Testing,
• Packaging,
• ...

The overarching principle is to expose each feature as a mini-DSL and compose them using extensible-effects approach.