Julio Capote, Twitter

1. Distributing Systems in Scala with Finagle Julio Capote

2. About me • • • Julio Capote API team at Twitter @capotej

3. This talk • • • • Services Scala Finagle Examples

4. Scaling

10. Monolithic System • • • Limited to a single language and runtime Can only support few developers Deploys get more dangerous

11. Solution?

14. Distributed System • • • Each service written in appropriate language Can only support many developers Granular deploys

15. But, this is complex...

19. Quick Scala Intro

20. What is Scala? • • • • JVM language Interoperable with Java Functional But Object Oriented too

21. Values

22. val foo: String = "bar"

23. val age: Int = 27

24. Type inference

25. val foo = "bar"

26. val foo: String = "bar"

27. Collections

28. List(61,31,34)

29. Seq(1,2,3)

30. Dictionaries / Hashes

31. Map("foo" -> "bar")

32. Functional

33. val addOne = { x: Int => x + 1 }

34. addOne.apply(2) => 3

35. addOne(2) => 3

36. val list = Seq(1,2,3,4)

37. list.map { x => addOne(x) }

38. list.map(addOne(_))

39. list.map(addOne)

40. list map(addOne)

41. list map addOne

42. list map addOne filter { item: Int => item % 2 == 0 }

43. Function Composition

44. val addOne = { x: Int => x + 1 } val addTwo = { x: Int => x + 2 } val addThree = addOne compose addTwo

45. val addOne = { x: Int => x + 1 } val addTwo = { x: Int => x + 2 } val addThree = addOne compose addTwo

46. addThree(2) => 5

47. Object oriented

48. class Dog extends Animal def bark = { println("woof") } }

49. Options

51. Map("foo" -> "bar").get("foo")

52. Some(bar)

53. Map("foo" -> "bar").get("zzz")

54. None

55. val a = Map("foo" -> "bar") val opt = a.get("zzz") val result = opt.getOrElse("default")

56. val a = Map("foo" -> "bar") val opt = a.get("zzz") val result = opt match { case Some(x) => x case None => "default" }

57. val a = Map("foo" -> "bar") val opt = a.get("zzz") opt foreach { result => println(result) }

58. Finagle

59. What is Finagle? • • • • Client/Server RPC Framework Asynchronous Functional Protocol Agnostic

60. Futures

65. def fetchUrl(url: String) = Future[Response]

66. val f: Future[Response] = fetchUrl("google.ru") f map { response => println(response.content) }

67. val f: Future[Response] = fetchUrl("google.ru") f onSuccess { response => println(response.content) } onFailure { case e => log.error(e) }

68. val f: Future[Response] = fetchUrl("google.ru") f onSuccess { response => println(response.content) } onFailure { case e => log.error(e) }

69. Services

70. “Your Server as a Function”

71. type Service[Req, Rep] = Req => Future[Rep]

72. Request => Future[Response]

74. Http Client

75. val client: Service[Request, Response] = Http.newService("www.google.ru:80")

76. Making a request

77. val req = Request("/") client(req) onSuccess { resp => println(resp.content) }

78. val req = Request("/") client.apply(req) onSuccess { resp => println(resp.content) }

79. val req = Request("/") val resp = client(req) resp onSuccess { resp => println(resp.content) } Await.ready(resp)

80. val req = Request("/") val resp = client(req) resp onSuccess { resp => println(resp.content) } Await.ready(resp)

81. Http Server

82. class MyServer extends Service[Request, Response] { def apply(request: Request) = { Future.value(new Response("hi")) } }

83. class MyServer extends Service[Request, Response] { def apply(request: Request) = { Future.value(new Response("hi")) } }

84. Request => Future[Response]

85. Starting the server

86. val service = new MyServer val server = Http.serve(":8080", service) Await.ready(server)

87. Http Proxy

88. object Proxy extends App { val client: Service[Request, Response] = Http.newService("www.google.ru:80") val server = Http.serve(":8080", client) Await.ready(server) }

91. Filters

93. Filter[InRequest, InResponse, OutRequest, OutResponse]

96. SimpleFilter[Request, Response]

97. def apply(request: Req, service: Service[Req, Rep]): Future[Rep]

101. class ScreamFilter[Req, Rep] extends SimpleFilter[Req, Rep] def apply(request: Req, service: Service[Req, Rep]) = { service(request) onSuccess { response => response.setContent(response.content + "!") response } } }

107. val service = new MyServer val server = Http.serve(":8080", service) Await.ready(server)

108. val service = new MyServer val myFilter = new MyFilter val newService = myFilter andThen service val server = Http.serve(":8080", newService) Await.ready(server)

111. Metrics

113. curl http://localhost:9990/admin/metrics.json

115. Add your own

116. class MyServer(stats: StatsReceiver) extends Service[Request, Response] { def apply(request: Request) = { stats.counter("my counter").incr() stats.time("fetch") { expensiveOperation() } Future.value(new Response("hi")) } }

119. Finatra

120. Finagle with Sinatra

121. class Example extends Controller { get("/") { request => render.plain("hi").toFuture } }

122. class Example extends Controller { get("/") { request => render.plain("hi").toFuture } }

123. class MyServer extends FinatraServer { val controller = new Example() register(controller) }

124. http://finatra.info

125. Questions? • • • • http://tinyurl.com/finagle-guide http://tinyurl.com/server-as-a-function http://finatra.info @capotej

Julio Capote, Twitter

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Julio Capote, Twitter