如何用Http4s HttpRoutes合成特效？

Question

我有一个http4s HttpRoutes和一个任务在我的效果类型(ZIO，如果重要的话)。其效果是副作用，并且不返回值。我想将两者组合在一起，创建一个新的HttpRoutes，它将在HttpRoutes中的任何匹配路由之前运行效果。

import zio.Task

val httpRoutes: HttpRoutes[Task] = ...
val effect: Task[Unit] = ...

val combined: HttpRoutes[Task] = ???

如何将HttpRoutes和特效结合在一起？

Answer 1

根据https://http4s.org/v0.21/middleware的朴素实现

对我很管用

@accessible
trait HttpServer {
  def bindHttp: UIO[Server[Task]]
}

object HttpServer {
  def make(
    httpRoutes: HttpRoutes[Task],
    cpuPool: ExecutionContext@Id("zio.cpu"),
  ) = {
    for {
      implicit0(rts: Runtime[Any]) <- ZIO.runtime[Any].toManaged_
      combined = Kleisli { (req: Request[Task]) =>
        val effect: Task[Unit] = Task.effectTotal(println("123"))
        OptionT.liftF(effect).flatMap { _ =>
          httpRoutes(req)
        }
      }
      srv <- BlazeServerBuilder[Task](cpuPool)
        .withHttpApp(combined.orNotFound)
        .bindHttp(host = "0.0.0.0")
        .resource
        .toManaged
    } yield new HttpServer {
      val bindHttp = IO.succeed(srv)
    }
  }
}