Quick Started

Server

To run Http4s app on Finagle Http server, simply just use Finagle.mkService to adapt Http4s HttpApp[F] to Fingale Service[Request, Response].

import org.http4s.finagle._
import com.twitter.finagle.Http

val http4sService: HttpApp[IO] = HttpRoutes.of[IO] {...}.orNotFound

val server = Http.server.serve(":8080", Finagle.mkService(http4sService))
Await.ready(server)

Client

To make a Finagle Client is the other way around, we need to adapt Finagle Service[Request, Response] to Http4s Client[IO]:

import org.http4s.finagle._
import com.twitter.finagle.Http

val host = "blog.oyanglul.us"
Finagle.mkClient[IO](Http.client.withTls(host).newService(s"$host:443")).use {
  client: Client[IO] =>
  ...
}

A fundamental different from usual Http client is that finagle Client[IO] is actually a RPC Http client, which means it cannot send arbitrary request to any host, the host endpoint is already set when created this client. This machinism is very useful to identify endpoint healthy, load balancer, circuit breaker. But a little bit weird when using:

val host = "blog.oyanglul.us"
Finagle.mkClient[IO](Http.client.withTls(host).newService(s"$host:443")).use {
  client: Client[IO] =>
  client.status(uri"https://twiter.com")
  client.status(uri"https://abc.com/blahblah")
}

• client.status(uri"https://twiter.com") will still send request to https://blog.oyanglul.us
• client.status(uri"https://abc.com/blahblah") will send request to https://blog.oyanglul.us/blahblah