Server

This section describes, ZIO HTTP Server and different configurations you can provide while creating the Server

Start a ZIO HTTP Server with default configurations

  override def run(args: List[String]): URIO[zio.ZEnv, ExitCode] =
    Server.start(8090, app.silent).exitCode

Start a ZIO HTTP Server with custom configurations.

1. Imports required by the customised server.

   import zio.http._
   import zio.http.service.ServerChannelFactory
   import zio.http.service.{EventLoopGroup, Server}
   import zio._
   import scala.util.Try
2. The Server can be built incrementally with a ++ each returning a new Server overriding any default configuration. (More properties are given in the Server Configurations section below.)

   private val server =
     Server.port(PORT) ++              // Setup port
       Server.maxRequestSize(8 * 1024) ++ // handle max request size of 8 KB (default 4 KB)
       Server.app(fooBar ++ app)       // Setup the Http app
3. And then use Server.make to get a "managed" instance use it to run a server forever

   override def run(args: List[String]): URIO[zio.ZEnv, ExitCode] = {
     server.make
       .use(start =>
         console.putStrLn(s"Server started on port ${start.port}")
         *> ZIO.never,
       ).provideCustomLayer(ServerChannelFactory.auto ++ EventLoopGroup.auto(2))
       .exitCode
   Tip : ServerChannelFactory.auto ++ EventLoopGroup.auto(num Threads) is supplied as an external dependency to choose netty transport type. One can leave it as auto to let the application handle it for you. Also in EventLoopGroup.auto(numThreads) you can choose number of threads based on number of available processors.

Binding Server to a socket address

One can bind server to Inet address in multiple ways, either by providing a port number or

• If no port is provided, the default port is 8080
• If specified port is 0, it will use a dynamically selected port.

A complete example

• Example below shows how the server can be started in forever mode to serve HTTP requests:

import zio.http._
import zio.http.service._
import zio.http.service.ServerChannelFactory
import zio._

import scala.util.Try

object HelloWorldAdvanced extends App {
  // Set a port
  private val PORT = 8090

  private val fooBar: HttpApp[Any, Nothing] = Http.collect[Request] {
    case Method.GET -> !! / "foo" => Response.text("bar")
    case Method.GET -> !! / "bar" => Response.text("foo")
  }

  private val app = Http.collectM[Request] {
    case Method.GET -> !! / "random" => random.nextString(10).map(Response.text)
    case Method.GET -> !! / "utc"    => clock.currentDateTime.map(s => Response.text(s.toString))
  }

  private val server =
    Server.port(PORT) ++              // Setup port
            Server.paranoidLeakDetection ++ // Paranoid leak detection (affects performance)
            Server.app(fooBar +++ app)      // Setup the Http app

  override def run(args: List[String]): URIO[zio.ZEnv, ExitCode] = {
    // Configure thread count using CLI
    val nThreads: Int = args.headOption.flatMap(x => Try(x.toInt).toOption).getOrElse(0)

    // Create a new server
    server.make
            .use(_ =>
              // Waiting for the server to start
              console.putStrLn(s"Server started on port $PORT")

                      // Ensures the server doesn't die after printing
                      *> ZIO.never,
            )
            .provideCustomLayer(ServerChannelFactory.auto ++ EventLoopGroup.auto(nThreads))
            .exitCode
  }
}

Server Configurations

Configuration	Purpose and usage
Server.app(httpApp)	Mount routes. Refer to complete example above
Server.maxRequestSize(8 * 1024)	handle max request size of 8 KB (default 4 KB)
Server.port(portNum) or Server.bind(portNum)	Bind server to the port, refer to examples above
Server.ssl(sslOptions)	Creates a new server with ssl options. HttpsHelloWorld
Server.acceptContinue	Sends a 100 CONTINUE
Server.disableFlowControl	Refer Netty FlowControlHandler
Server.disableLeakDetection	Disable any leak detection Refer netty's ResourceLeakDetector
Server.simpleLeakDetection	Simplistic leak detection comes with small over head. Refer netty's ResourceLeakDetector
Server.paranoidLeakDetection	Comes with highest possible overhead (for testing purposes only). Refer netty's ResourceLeakDetector
Server.consolidateFlush	Flushing content is done in batches. Can potentially improve performance.