F# on the Server-Side
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The document discusses server-side programming with F#, focusing on the need for reliability and scalability in handling concurrent requests and I/O operations. It introduces event-based programming, asynchronous workflows, and agent-based programming as effective approaches to managing these challenges, with syntax examples and use cases. The author emphasizes the advantages of F# asynchronous workflows and agents for creating efficient server-side applications.
F# on the Server-Side
- 1. F# on the Server-Side Tomáš Petříčekhttp://tomasp.net/blog | @tomaspetricek
- 2. About meWrote book about F#Introduce functional conceptsand F# to C# developersWorked with the F# teamContributed to VS 2010 integrationReactive programming researchFirst blog post about F# in May 2006
- 3. Server-side specificsReliability and scalability is essentialMany concurrent requestsMany I/O bound operationsExist to share state with clientsWe need different programming style!
- 4. Plan of the talk
- 5. Event-based styleProgramming using explicit callbacksSolves part of the problemInherently concurrent modelAvoids blocking of threadsGaining popularity (e.g. Node.js)HttpServer.Start("http://localhost:8080/", fun ctx -> WebClient.DownloadAsync(getProxyUrl(ctx), fun data -> ctx.ResponseStream.WriteAsync(data, fun res -> ctx.ResponseStream.Close())))
- 6. Limitations of event-based styleWhat we really wanted to write?What we really should write…let data = WebClient.DownloadAsync(getProxyUrl(ctx))ctx.ResponseStream.WriteAsync(data)ctx.ResponseStream.Close()try let data = WebClient.DownloadAsync(getProxyUrl(ctx))ctx.ResponseStream.WriteAsync(data)finallyctx.ResponseStream.Close()
- 7. Plan of the talk
- 8. F# asynchronous workflowsWrite usual sequential codeAsynchronous calls using let!and do!Supports all F# control-flow constructslet copyPageTourloutputStream = async { try let! html = WebClient.AsyncDownload(url)do! outputStream.AsyncWrite(html) finally ctx.ResponseStream.Close()}
- 9. F# asynchronous workflowsTranslated using some primitive operationsLooks similar to event-based programs…Many thanks to Haskell for Monads™!let copyPageTourloutputStream = async.TryFinally(async.Bind(WebClient.AsyncDownload(url), fun html -> async.Bind( outputStream.AsyncWrite(html),async.Zero() )),fun () ->ctx.ResponseStream.Close())
- 10. DemoHTTP proxy using asynchronous workflows
- 11. Plan of the talk
- 12. Agent-based programmingProgram consists of agents (processes)Lightweight and asynchronousAgents communicate via messagesThread-safe and queuedEnables parallelismDifferent agents vs. multiple instancesMany thanks to Erlang for Agents™!
- 13. Simple agent in F#Send Hello to the callerWaiting for message is asynchronousCan perform long-running I/O before replyingCalling agent asynchronouslyletecho = Agent.Start(fun agent -> async { while true dolet!name, rchan= agent.Receive()rchan.Reply("Hello "+ name) })let!str = echo.PostAndAsyncReply(funch-> "Tomas", ch)
- 14. DemoCaching web pages using agent
- 15. Summary and Q&AEvent-based is good starting pointF# workflow syntax really helpsAsynchronous workflows enable agentsUse agents for server-side state
Editor's Notes
- #13: Agents are lightweight and have some body running inside them