Provides grpc configuration DSL and GrpcServer algebras

[juanpedromoreno]

Server Demo has been also adapted to the newly introduced changes, where the RPC core provides helpers in order to bootstrap the server in the runtime monad, according to the server configuration.

This is a preliminary version towards to fulfill #10. We still need to find the way to aggregate all the services which would run in such a server.

For now, the user has to provide an implicit list with all the services the server will register:

https://github.com/frees-io/freestyle-rpc/compare/feature/server-definitions#diff-09bc282791d5598d8a70f248fbb125b0R33

Thanks @peterneyens for your suggestions related to the GrpcConfigInterpreter :)

Server bootstrap:

import cats.implicits._
import runtime.implicits._
import freestyle.rpc.server._
import freestyle.rpc.server.implicits._

import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
import scala.concurrent.Await

object GreetingServerApp {

  def main(args: Array[String]): Unit =
    Await.result(server[GrpcServer.Op].bootstrapFuture, Duration.Inf)
}

(bootstrapFuture would be equivalent to bootstrap[Future])

Runtime dependencies:

import freestyle._
import freestyle.implicits._
import freestyle.rpc.demo.greeting._
import freestyle.rpc.server._
import freestyle.rpc.server.implicits._
import freestyle.rpc.server.handlers._

import scala.concurrent.{ExecutionContext, Future}

object implicits {

  implicit val config = Config(portNode1)

  implicit val grpcConfigs: List[GrpcConfig] = List(
    AddService(GreeterGrpc.bindService(new GreetingService, ExecutionContext.global))
  )

  implicit val grpcServerKleisli =
    new GrpcServerHandler[Future] andThen new GrpcConfigInterpreter[Future]

}

[codecov-io]

Codecov Report

Merging #13 into master will not change coverage.
The diff coverage is 0%.

@@         Coverage Diff          @@
##           master   #13   +/-   ##
====================================
  Coverage       0%    0%           
====================================
  Files           6     9    +3     
  Lines         103   122   +19     
  Branches        2     2           
====================================
- Misses        103   122   +19

Impacted Files	Coverage Δ
...ng/src/main/scala/greeting/GreetingClientApp.scala	0% <0%> (ø)	⬆️
rpc/src/main/scala/server/package.scala	0% <0%> (ø)
rpc/src/main/scala/server/implicits.scala	0% <0%> (ø)
...ng/src/main/scala/greeting/runtime/implicits.scala	0% <0%> (ø)
...main/scala/server/handlers/GrpcServerHandler.scala	0% <0%> (ø)
...ng/src/main/scala/greeting/GreetingServerApp.scala	0% <0%> (ø)	⬆️
demo/http/src/main/scala/user/package.scala	0% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update eac2453...47930f9. Read the comment docs.

[peterneyens]

Left a few comments, but looks good in general (for someone with no grpc experience 😃).

[peterneyens]

It looks like there is a Capture[Future] instance in the Capture companion object.

[peterneyens]

Maybe we can create a small helper method for this Kleisli(s => C.capture(s.foo)) pattern?

Something like

private def captureWithServer[A](f: Server => A] : GrpcServerOps[F, A] = Kleisli(s => C.capture(f(s))`

def getPort: GrpcServerOps[F, Int] = captureWithServer(_.getPort)

[peterneyens]

I haven't look too closely at the grpc api, but GetDirectExecutor seems a bit strange for something which will never return something?

[peterneyens]

We should probably add extends Product with Serializable, otherwise the type of something like List(GetDirectExecutor) would be inferred as List[GrpcConfig with Product with Serializable].

[raulraja]

Awesome stuff!