Finagle Coding Dojo

Transcript

1. Finagle Dojo
   Scala meet up / 4th October 2017
   David Denton / Andrea Birotti
   @daviddenton/finagle-dojo
   

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2. • 2013 Whitepaper from Marius Eriksen @ Twitter
   Server as a Function
   • Defined 2 major concepts:
   
   • Service represents System Boundaries
   
   • Filter used to apply I/O transformation and stateful effects
   • Protocol agnostic RPC system
   
   • In production @ Twitter
   
   • Fault tolerance baked in
   
   • Scala + Netty
   

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3. Concept: Future
   “Represents the result of an Asynchronous operation.”
   val result: String = Await.result(
   Future.value("content")
   .map(v => v + v)
   .flatMap(v => Future(v))
   .handle {
   case _: Exception => "failed"
   }
   )
   • 2 end states: Value and Exception
   
   • Manipulate with: map() / flatMap() / handle() / rescue()
   
   • Can get the result with Await - but never block!!
   

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4. Concept: Service
   “It turns an Request into an (eventual) Response”
   Service: Request => Future[Response]
   ie. it’s a function!
   val service = new Service[Request, Response] {
   override def apply(request: Request): Future[Response] =
   {
   val response = Response(Status.Ok)
   response.content = request.content
   Future(response)
   }
   }
   

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5. Concept: Filter
   “Provides pre and post processing on an HTTP operation”
   Filter[ReqIn, RespIn, ReqOut, RespOut] =
   [ReqIn, Service[ReqOut, RespOut]] => Future[RespIn]
   ie. it’s a function!
   val addType = new Filter[Request, Response, Request, Response] {
   override def apply(request: Request, service: Service[Request,
   Response]) = {
   service(request).map(resp => {
   resp.headerMap("Content-type") = "application/json"
   resp
   })
   }
   }
   Filters compose with other Filters/Services using andThen()
   

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6. Let’s get started!
   • clone: https://github.com/daviddenton/finagle-dojo.git
   • project is using (sbt 1.0.1) - adjust before import!
   • use the readmes at the root & in each step folder
   • finagle docs @ https://twitter.github.io/finagle/guide/
   

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7. more?
   • Join us for the October LSUG meet up on October 23rd where we’ll be
   presenting Fintrospect - a type safe routing layer built on top of Finagle,
   and how it changed our CD and testing practices.
   fintrospect.io
   @daviddenton/fintrospect
   web: www.fintrospect.io
   

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