matthew-hilty / cake-slayer

🍰🔪 Architecture of Haskell backend applications

cake-slayer

cake-slayer (do not confuse with cakes-layer) is a modern and batteries-included framework for creating backend in Haskell for web-applications. It allows you to scaffold working and extensible project in minutes.

Overview

The main goal of cake-slayer is to provide a backbone for your Haskell backend. Unlike many other Haskell libraries, cake-slayer doesn't try to be as abstract as possible. It includes best-practices and makes some architecture decisions for you. On the one hand, your application should satisfy the requirements for using this framework. On the other hand, it takes care of a lot of stuff for you, so you don't need to worry about everyday problems.

A typical backend does the following:

• Communicates with the frontend (web, mobile) via some wire format (JSON, Protocol Buffers, etc.)
• Talks to the database
• Authenticates and authorizes users
• Has some background jobs

cake-slayer works exceptionally well if your application uses:

1. PostgreSQL as database.
2. Elm on the frontend.

The following Haskell packages have been chosen to provide the necessary functional:

• postgresql-simple, postgresql-simple-named, postgresql-simple-migration
  • For connecting and talking to the PostgreSQL database
• servant, servant-swagger, swagger2
  • A family of libraries for defining and documenting Rest API using type-level eDSL
• elm-street
  • The bridge between Elm and Haskell — generating Elm data types, JSON encoders and decoders from Haskell types automatically
• jwt
  • User authentication via JWT
• bcrypt
  • Secure password hashing
• ekg, prometheus-client
  • Application performance monitoring.

  NOTE: Using prometheus-client is optional

Besides cake-slayer encourages (but doesn't force) to use the following libraries:

• relude
  • Alternative standard library
• co-log
  • Composable contravariant comonadic logging library

How to use?

The cake-slayer framework contains implementations of most common and useful functions. But at the same time, it provides enough flexibility to specify application-specific parts. To integrate cake-slayer smoothly into your project, you should perform the following steps:

1. Define a type of errors your application can throw. See CakeSlayer.Error module for details.
2. Define a monad for your application by specializing the App monad from the CakeSlayer.Monad module.
3. Derive or implement all necessary instances for your application monad. cake-slayer provides MonadJwt and MonadTimed effects with sensible default implementations for your convenience.

And you're good to go!