F#语言对异步程序设计的支持

Async Programming in F# Zhao Jie - SNDA - June 2010

About Me • / / Jeffrey Zhao / • Programmer • Blogger - http://blog.zhaojie.me/ • Twitterer: @jeffz_cn • F#, Scala, JavaScript, Python, .NET, mono... • Java (as the language) hater

What’s F# • Languages by Don Syme, MS Research • Strongly Statically Typed Language • Functional Language with OO Ability • General Purpose Language

Async programming is complex ...

...and will only get more complex in the near future

Four Big Concurrency Challenges • Shared State • Code Locality • I/O Parallelism • Scaling Up

Shared State • Difﬁcult to maintain and test • Very difﬁcult to parallelize • Locking is fundamentally error prone ‣ Must guess where parallelism is needed ‣ All consumers need to participate

Demo: Immutability

Immutability in F# • Immutable Union • Immutable Tuple • Immutable Record • Immutable List • Immutable Set • Immutable Map • Immutable Objects • Immutable ...

Code Locality • Used to expressing algorithms linearly • Async requires logical division of algorithms • Very difﬁcult to ‣ Combine multiple asynchronous operations ‣ Deal with exceptions and cancellation

Asynchronous Workﬂow async { ... }

React async { let! res = <async work> ... } an HTTP Response an UI Event a Timer Callback a Query Response a Web Servcie Response a Disk I/O Completion an Agent Message

async { let! img = AsyncRead "http://..." printfn "loaded!" do! AsyncWrite img @"c:..." printfn "saved!" } = async.Delay(fun -‐> async.Bind(AsyncRead "http://...", (fun img -‐> printfn "loaded!" async.Bind(AsyncWrite img @"c:...", (fun () -‐> printfn "saved!" async.Return())))))

Demo: Code Locality

I/O Parallelism • Software is often I/O-bound ‣ Leveraging web services ‣ Working with data on disk • Network and disk speeds increasing slower • I/O resources are inherently parallel ‣ Huge opportunity for performance

Demo: I/O Parallelism

Scaling to Multi-Machine • To scale up, must to go beyond a single machine • Multi-machine resources becoming common ‣ Roll-you-own clusters with cheap hardware ‣ On-demand cloud compute with Azure • But ‣ Shared memory doesn’t scale

... the principle we go by is, don't expect to see a particular concurrency model put into C# because there're many different concurrency model ... it's more about ﬁnding things are common to to all kinds of concurrency ... - Anders Hejlsberg

Demo: Agents

Concurrency Challenges • Shared State - Immutability • Code Locality - async { ... } • I/O Parallelism - async { ... } • Scaling to Multi-Machine - Agents

F# • Modern, simple, powerful and productive • Ready for production use with VS 2010 • Simpliﬁed parallel and async programming for today and tomorrow • Support .NET 4.0 / 3.5 and mono • Open Source *

F# Resources http://fsharp.net Programming F# Expert F# 2.0 Real World FP

Thanks!

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F#语言对异步程序设计的支持

by jeffz on Jun 19, 2010

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F#语言对异步程序设计的支持 — Presentation Transcript