This document introduces Finagle, an open source library developed by Twitter for building reliable services. It discusses how Finagle uses futures and promises to handle asynchronous operations. It also describes how Finagle provides networking capabilities like address resolution and load balancing. Finagle allows defining services as functions that return futures, and combines multiple services through composition of futures. This provides benefits like reliability, performance and flexibility in service definition.

1. @
Introduction to Finagle

2. puneet@twitter.com
Core Services - Platform Engineering

3. In the beginning ...

7. A brave new world ...
Typesafe
Expressive
Performant
(thank you JVM)
...

8. Futures

9. Synchronous Futures
def piDigit ( n : Int ) : Int def piDigit ( n : Int ) : Future[Int]
println ( piDigit ( 100 ) ) piDigit ( 100 ) onSuccess println

10. Synchronous Futures

11. Synchronous Futures
def piDigit ( n : Int ) : Int def piDigit ( n : Int ) : Future[Int]
println ( piDigit ( 100 ) ) piDigit ( 100 ) onSuccess println
println ( piDigit ( 100 ) * 10 ) ) piDigit ( 100 ) map { _ * 10 } onSuccess println
println ( piDigit ( piDigit ( 100 ) ) ) piDigit ( 100 ) flatMap piDigit onSuccess println
println ( ( 0 to 100 ) map piDigit ) Future.collect {
( 0 to 100 ) map piDigit
} onSuccess println

13. the networking glue ...
Address resolution
TCP handshake
Serialization => Deserialization

14. : Request => Future [ Response ]

15. trait UserService {
def getByUserId( userId : Long ) : Future [ User ]
def getByScreenName( screenName: String ) : Future [ User ]
}
trait TweetService {
def findByUserId( userId : Long ) : Future [ Seq[ Tweet ] ]
}

16. trait UserTweetService {
val userService : UserService
val tweetService : TweetService
def findUserAndTweets(
userId : Long
) : Future [ ( User, Seq[Tweet] ) ] =
Future.join (
userService.findByUserId( userId ),
tweetService.findByUserId( userId )
)
}
}
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17. trait ScreenNameTweetService {
val userService : UserService
val tweetService : TweetService
def findByScreenName(
screenName: String
) : Future [ Seq[Tweet] ] = {
userService.findByScreenName( screenName ) flatMap {
user => tweetService.findByUserId( user.id )
}
}
}
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18. other benefits ...

19. val someService = Http.client(“inet!google.com:80”)
val anotherService =
Http.client(
“zk!myzkhost.mycompany.com:2181!/my/zk/path”
)
Address Resolution

20. Source Load Balancing
vs

21. Thanks!
twitter.github.io/finagle
@finagle
@pzdk