News

The objetive of this app is to expose an API that retrieves info from The NyTime's Website.

Stack

Scala
Cats Effect (Http4s, Doobie, Redis4Cats, PureConfig)
Sangria
Quill
Postgres
Redis
Hexagonal Architecture

Architecture overview

The application follows the Hexagonal Architecture (Ports and Adapters pattern) approach, having our Domain at core of the application layering and ony being accessed by the Application. Also we have different ports and adapters that allows the communication with the outside components in both directions (from outside to inside and viceversa).

Just to mention, I added Redis for caching news in order to avoid going every time to the NyTimes web site. In case of not being news in cache, a fallback strategy was implemented in order to go and scrap the web site. The key expiration is also configurable.

Disclaimer: I know, maybe hexagonal architecture is an overkill for this problem. However, using this approach allows me to have flexibility when add new adapters without changing the domain and application layer (for example, when I added GraphQL). Also, it allows lot of flexility for refactoring. For example, at the beginning I start using Skunk for the database layer. At the end I refactored to use Quill instead and the transition was transparent for the inner layers.

Instructions

Run dockers:

docker-compose up

Run the app:

sbt run

It will startup the app on localhost:8080.

Also, you can visualize the data stored in the db checking out the Adminer, who is running on localhost:8083.

Endpoints

The endpoints exposed by the API are on this file

Testing

Just the application layer was tested via unit test. Maybe, some it tests could be made using Test Containers as an improvement of the test coverage.

Some words about Styling

I tried to use Hexagonal Architecture in an OOP way but because of habit. For example, the following snippet:

class CacheServiceImpl[F[_]: Logger](redisCommands: RedisCommands[F, String, String], config: CacheConfig) extends CacheService[F] {
    // logic
}

Is used instead of a more value oriented Scala FP approach like the following:

object CacheService {
    def apply[F[_]: Logger](redisCommands: RedisCommands[F, String, String], config: CacheConfig) =
        new CacheService[F] {
            ???
        }
}

But it is just a matter of style.

TODO

log4cats is not working since some sangria and quill stuff was added. It needs some fixes.
add error handling and http response codes in case of errors

Future Improvements

some refactors in NewsRepositoryImpl
removing warning related with versions of log4j versions
add more logs
add integration tests with test containers
add docker artifact generation
add kubernetes
migrate to Scala 3
add api endpoints versioning
improve logging tracking info (nowaways it shows sdev.Main, instead of current service classes)
add github actions
add scalasteward
fix scalaFix command

ivanlp10n2 / news