HighLoad++ 2013

1. Distributing Systems in Scala
with Finagle
Julio Capote

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

3. This talk
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Services
Scala
Finagle
Examples

4. Scaling

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

11. Solution?

14. Distributed System
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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?
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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?
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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)
}

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

90. 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]

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

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

96. SimpleFilter[Request, Response]

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

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

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

100. 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
}
}
}

102. 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
}
}
}

103. 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
}
}
}

104. 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
}
}
}

105. 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
}
}
}

106. 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)

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

110. 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"))
}
}

117. 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"))
}
}

118. 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?
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http://tinyurl.com/finagle-guide
http://tinyurl.com/server-as-a-function
http://finatra.info
@capotej