A ZIO + http4s + Circe + Quill + Tapir giter8 template

Prerequisites

1. Lanuch H2 database at your local machine For example: using H2 docker image

docker pull oscarfonts/h2
docker run -d -p 1521:1521 -p 81:81 -v /path/to/local/data_dir:/opt/h2-data --name=MyH2Instance oscarfonts/h2

2. Import SQL to H2 database

CREATE TABLE IF NOT EXISTS user
(
    id INT NOT NULL,
    name VARCHAR(255) NOT NULL,
    age INT NOT NULL,
    PRIMARY KEY(id)
);

How to install

brew update && brew install giter8
g8 pandaforme/ultron.g8

How to add a new API

1. Create a package in module for example: xyz

2. Create an interface in module.xyz

trait XYZ {

  val service: XYZ.Service
}

object XYZ {

  trait Service {

    def doXYZ(): ZIO[Any, Error, Unit]
  }
}

3. Create a package object in module.xyz

package object xyz {

  def doXYZ(id: Long): ZIO[XYZ, Error, Unit] =
    ZIO.accessM(_.service.doXYZ())
}

4. Create an instance for test/live in module.xyz

trait LiveXYZ extends XYZ {
    override val service: XYZ.Service = new XYZ.Service {
        def doXYZ(): ZIO[Any, Error, Unit] = ???
    }
}

5. Create your own route in route and pass your interface into enviroment type

class XyzRoute[R <: XYZ] extends Http4sDsl[TaskR[R, ?]] {
  private val xyzEndPoint = endpoint.get
    .in("xyz" / path[Long]("user id"))
    .errorOut(emptyOutput)
    .out(emptyOutput)    

  val getRoutes: HttpRoutes[TaskR[R, ?]] = ???
  val getEndPoints = List(xyzEndPoint)   
}

6. Write unit test

7. Add your interfaces to AppEnvironment, routes to httpApp and provide Live instances in Main.scala

object Main extends App {
  type AppEnvironment = Clock with Console with UserRepository with MyLogger with XYZ
  private val userRoute = new UserRoute[AppEnvironment]
  private val xyzRoute = new XyzRoute[AppEnvironment]
  private val yaml = userRoute.getEndPoints.toOpenAPI("User", "1.0").toYaml

  override def run(args: List[String]): ZIO[Main.Environment, Nothing, Int] = {
    val result = for {
      application <- ZIO.fromTry(Try(Application.getConfig))

      httpApp = Router(
          "/" -> userRoute.getRoutes,
          "/" -> xyzRoute.getRoutes, 
          "/docs" -> new SwaggerHttp4s(yaml).routes[TaskR[AppEnvironment, ?]]).orNotFound
      finalHttpApp = Logger.httpApp[ZIO[AppEnvironment, Throwable, ?]](true, true)(httpApp)

      server = ZIO.runtime[AppEnvironment].flatMap { implicit rts =>
        BlazeServerBuilder[ZIO[AppEnvironment, Throwable, ?]]
          .bindHttp(application.server.port, application.server.host.getHostAddress)
          .withHttpApp(finalHttpApp)
          .serve
          .compile[ZIO[AppEnvironment, Throwable, ?], ZIO[AppEnvironment, Throwable, ?], ExitCode]
          .drain
      }
      program <- server.provideSome[Environment] { base =>
        new Clock with Console with LiveUserRepository with LiveLogger with LiveXyz{
          val clock: Clock.Service[Any] = base.clock
          val console: Console.Service[Any] = base.console
          val config: Config = ConfigFactory.parseMap(
            Map(
              "dataSourceClassName" -> application.database.className.value,
              "dataSource.url" -> application.database.url.value,
              "dataSource.user" -> application.database.user.value,
              "dataSource.password" -> application.database.password.value
            ).asJava)
        }
      }
    } yield program

    result
      .foldM(failure = err => putStrLn(s"Execution failed with: $err") *> ZIO.succeed(1), success = _ => ZIO.succeed(0))
  }
}

API Endpoints

Swagger: http://localhost:5566/docs
User API: http://localhost:5566/user

Challenges

1. Try to implement LiveLogger
2. Because quill driver of H2 database is not Asynced, we need to push blocking IO to another thread pool. How to achieve it via ZIO?

Referneces

• ZIO with http4s and doobie
• mschuwalow/zio-todo-backend
• loicdescotte/pureWebappSample