Two Scoops of Scala

April tech talk at FullContact

Transcript

1. Two scoops of Scala & Unfiltered April 2014 FullContact techTalk @skazhy
2. Scala? • object oriented and functional programming language • Type safe • Runs on JVM
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
4. Toolchain • SBT - Scala Build Tool • Best conventions from Maven world • Iterative development in SBT shell
5. My setup • IntelliJ + SBT console(s) inside tmux • IntelliJ 13 has SBT support baked in
6. Deployment • Works great with Jenkins & Asgard • Minimal configuration tweaks needed (wait for the next 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
8. Using opinionated RESTful frameworks for microservices?
10. Example time!
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()
12. An Intent is a partial function that pattern matches HTTP requests
13. A Plan is a binding between intent and the underlying interface
14. Pattern matching • Decomposing data structures to extract certain fields or validate them • Really powerful in Scala • “routing” mechanism in Unfiltered
16. Match on request methods • Use builtins: GET(_) POST(_) PATCH(_) • Or define your own: object SPACEJUMP extends Method("SPACEJUMP")
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")
18. Match on request headers BasicAuth(username, password) UserAgent("Cobook")
19. ...on URN Path("/foobar") Path(Seg("contactLists" :: "v2" :: listId :: Nil)) // Will extract /contactLists/v2/1234
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
22. function composition!
23. Responses are composable case _ => Unauthorized ~> ResponseString("No pasaran") ~> ResponseHeader("WWW-Authenticate", "Basic realm=foo")
24. • HTTP requests are stateless • HTTP responses are side effects
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) }
26. Unfiltered plays well with RxJava too
27. case req @ GET(Path("/reactive")) => observableOp.subscribe( result => req.respond(ResponseString(result)) _ => req.respond(InternalServerError) )
28. What about testing?
29. • Separate library for testing with Specs2 • Mocking with Mockito • Comes bundled with the giter8 template unfiltered-specs2
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 } } }
31. Consider using Unfiltered when you... • need an async & lightweight HTTP service • Have separate business logic • Want to leverage the λ-force
32. Questions?