Two Scoops of Scala

April tech talk at FullContact

Transcript

1. Two scoops of Scala &
   Unfiltered
   April 2014 FullContact techTalk
   @skazhy
   

   View Slide

2. Scala?
   ● object oriented and functional programming
   language
   ● Type safe
   ● Runs on JVM
   

   View Slide

3. Unfiltered?
   ● A toolkit for HTTP in Scala
   ● Really, really modular
   ● Works with Netty and Jetty
   ● Built for meetup.com realtime API
   ● Makes good use of Scala's idioms
   

   View Slide

4. Toolchain
   ● SBT - Scala Build Tool
   ● Best conventions from Maven world
   ● Iterative development in SBT shell
   

   View Slide

5. My setup
   ● IntelliJ + SBT console(s) inside tmux
   ● IntelliJ 13 has SBT support baked in
   

   View Slide

6. Deployment
   ● Works great with Jenkins & Asgard
   ● Minimal configuration tweaks needed (wait
   for the next slide)
   

   View Slide

7. ● A tool for fetching templates for Scala
   projects
   ● g8 skazhy/unfiltered-netty-rx
   ● All SBT plugins for deployment and IntelliJ
   are included
   Bootstrapping with giter8
   

   View Slide

8. Using opinionated
   RESTful frameworks for
   microservices?
   

   View Slide

9. View Slide

10. Example time!
    

    View Slide

11. object MyPlan extends cycle.Plan with
    cycle.ThreadPool with ServerErrorResponse {
    def intent = {
    case GET(Path("/")) => ResponseString("Hello!")
    case OPTIONS(_) => Created ~> Location("/foo")
    case _ => NotFound
    }
    }
    unfiltered.netty.Http(1337).handler(MyPlan).run()
    

    View Slide

12. An Intent is a partial function that pattern
    matches HTTP requests
    

    View Slide

13. A Plan is a binding between intent and the
    underlying interface
    

    View Slide

14. Pattern matching
    ● Decomposing data structures to extract
    certain fields or validate them
    ● Really powerful in Scala
    ● “routing” mechanism in Unfiltered
    

    View Slide

15. View Slide

16. Match on request methods
    ● Use builtins:
    GET(_)
    POST(_)
    PATCH(_)
    ● Or define your own:
    object SPACEJUMP extends Method("SPACEJUMP")
    

    View Slide

17. What happens under the hood?
    class Method(method: String) {
    def unapply[T](req: HttpRequest[T]) =
    if (req.method.equalsIgnoreCase(method)) Some(req)
    else None
    }
    object POST extends Method("POST")
    

    View Slide

18. Match on request headers
    BasicAuth(username, password)
    UserAgent("Cobook")
    

    View Slide

19. ...on URN
    Path("/foobar")
    Path(Seg("contactLists" :: "v2" :: listId :: Nil))
    // Will extract /contactLists/v2/1234
    

    View Slide

20. ...or query parameters
    object AccountIdParam extends
    Params.Extract("numericId", Params.first ~>
    Params.nonempty ~> Params.long)
    PATCH(Params(AccountIdParam(accountId)))
    // Will extract 1234 from PATCH /foo?numericId=1234
    

    View Slide

21. View Slide

22. function composition!
    

    View Slide

23. Responses are composable
    case _ =>
    Unauthorized ~>
    ResponseString("No pasaran") ~>
    ResponseHeader("WWW-Authenticate", "Basic realm=foo")
    

    View Slide

24. ● HTTP requests are stateless
    ● HTTP responses are side effects
    

    View Slide

25. Async made easy
    case req @ GET(Path("/async")) =>
    val futureOp = asyncOperation
    futureOp.onSuccess {
    case result =>
    req.respond(Ok ~> ResponseString(result))
    }
    futureOp.onFailure {
    case _ => req.respond(InternalServerError)
    }
    

    View Slide

26. Unfiltered plays well with
    RxJava too
    

    View Slide

27. case req @ GET(Path("/reactive")) =>
    observableOp.subscribe(
    result => req.respond(ResponseString(result))
    _ => req.respond(InternalServerError)
    )
    

    View Slide

28. What about testing?
    

    View Slide

29. ● Separate library for testing with Specs2
    ● Mocking with Mockito
    ● Comes bundled with the giter8 template
    unfiltered-specs2
    

    View Slide

30. object OperationPostSpec extends Specification {
    "PATCH /foo" should {
    lazy val r = Http(url((host \ "foo").PATCH))
    lazy val response = r()
    "return HTTP 200" in {
    response.getResponseStatus mustEqual 200
    }
    }
    }
    

    View Slide

31. Consider using Unfiltered when you...
    ● need an async & lightweight HTTP service
    ● Have separate business logic
    ● Want to leverage the λ-force
    

    View Slide

32. Questions?
    

    View Slide