quasar.server.PortChangingServer.scala Maven / Gradle / Ivy
/*
* Copyright 2014–2017 SlamData Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package quasar.server
import slamdata.Predef._
import quasar.console.stdout
import quasar.fp._
import quasar.server.Http4sUtils._
import scala.concurrent.duration._
import org.http4s
import org.http4s.HttpService
import scalaz._, Scalaz._
import scalaz.concurrent.Task
/**
* A server that can change ports on which it is serving clients when requested to do so.
* A known limitation is that this server will always fail to send a response to a request
* makes use of restart function.
*/
object PortChangingServer {
type ServiceStarter = (Int => Task[String \/ Unit]) => HttpService
/** Start this server
* @param initialPort The port on which to start the initial server
* @param produceService A function that given a function to restart a server
* on a new port, returns an `HttpService`
* @return A function to shutdown the active server
*/
def start(
initialPort: Int,
produceService: ServiceStarter
): Task[Task[Unit]] =
TaskRef[Option[(http4s.server.Server, Int)]](None).flatMap { serverRef =>
def shutdown(s: Option[(http4s.server.Server, Int)]): Task[Unit] =
s.fold(Task.now(())){ case (server, port) =>
server.shutdown >> stdout(s"Stopped server listening on port $port")
}
@SuppressWarnings(Array("org.wartremover.warts.Recursion"))
def startNew(port: Int): Task[String \/ Unit] = {
for {
oldServer <- serverRef.read
newServer <- startServer(ServerBlueprint(port, idleTimeout = Duration.Inf, produceService(startNew)))
succeeded <- serverRef.compareAndSet(oldServer, (newServer, port).some)
result <- if (succeeded)
for {
_ <- shutdown(oldServer)
_ <- stdout(s"Server started listening on port $port")
} yield ().right
else newServer.shutdown.as("Concurrent attempt to restart server. Try again later".left)
} yield result
}
startNew(initialPort).as(serverRef.read.flatMap(shutdown))
}
}