This repository contains the source files of two (very) simple wishlist micro-services. Its purpose is to show how easy it is to get started with building micro-services in Haskell (and using the Servant library).

The first service wishlist-simple is a wishlist service storing a single user's personal wishes. The second service wishlist-multitenant extends wishlist-simple to also store the wishlists of multiple users. More information on the two services can be found in the original slides for this talk.

First, clone this git repository and cd into its root folder. Next, to run the wishlist-simple service, execute the command cabal run wishlist-simple. Similarly, to run the wishlist-multitenant service, run cabal run wishlist-multitenant. The respective service will then start locally on port 8080, where you can query it according to its API.

• The wishlist-simple service provides the following (informal) API:

  GET  /wishes         -- retrieve all wishes stored so far on the service
  
  GET  /wishes/{shop}  -- retrieve all wishes at the given {shop}, which
                       -- must be one of "amazon", "zalando", or "otto".
  
  POST /wishes         -- add a new wish to the wishlist, which needs to
                       -- be send in the request body as a JSON object as
                       -- follows:
                       --
                       -- {"name": "my favorite wish!", "shop": "Amazon"}
                       --
                       -- where the wishes "shop" attribute must be either
                       -- one of "Amazon", "Zalando", or "Otto".
  

  For example, when the wishlist-simple service is running, we could retrieve the current wishlist of stored wishes using the following HTTP request:

  curl http://localhost:8080/wishes
  

  And to add a new wish, we would send the follwing HTTP request:

  curl \
    -H "Content-Type: application/json" \
    -d '{"name": "Game of Thrones 8", "shop": "Amazon"}' \
    http://localhost:8080/wishes
  

• The wishlist-multitenant service provides the same API as wishlist-simple, except that a client also needs to provide a Tenant Header in all its request indicating which user's wishlist should be retrieved

  For instance, to add a new wish to the wishlist of user hans, we would send the following HTTP request:

    curl \
    -H "Content-Type: applicatpion/json" \
    -H "Tenant: hans" \
    -d '{"name": "Game of Thrones 8", "shop": "Amazon"}' \
    http://localhost:8080/wishes
  

  And similarly, to retrieve hanss wishlist:

  curl -H "Tenant: hans" http://localhost:8080/wishes
  

The main source file for the wishlist-simple service is in src/WishlistSimple.hs, the main source file for wishlist-multitenant is in src/WishlistMT.hs. Most code is shared among the two micro-services in src/Wishlist/Common; code that is specific to each one of the services, is located in src/Wishlist/Simple and src/Wishlist/MultiTenant, respectively.