等待多F# Akka.net可观察事件的Akka.net F#有状态参与者

Question

我对F#和Akka.Net都很陌生，并试图用它们实现以下目标：

我想要创建一个参与者(尾巴)，它接收一个文件位置，然后使用FileSystemWatcher和一些可观察到的值侦听该位置的事件，并将它们作为消息转发给其他参与者进行处理。

我遇到的问题是，侦听事件的代码一次只接收一个事件，而忽略所有其他事件。例如，如果我将20个文件复制到正在监视的目录中，它似乎只发送其中一个文件的事件。

这是我的演员代码：

module Tail

open Akka
open Akka.FSharp
open Akka.Actor
open System
open Model
open ObserveFiles
open ConsoleWriteActor

let handleTailMessages tm =
    match tm with
        | StartTail (f,r) ->
            observeFile f consoleWriteActor |!> consoleWriteActor

    |> ignore

let spawnTail =
    fun (a : Actor<IMessage> )  -> 
    let rec l (count : int) = actor{

        let! m = a.Receive()
        handleTailMessages m
        return! l (count + 1)
    } 
    l(0) 

下面是监听事件的代码：

module ObserveFiles
open System
open System.IO
open System.Threading
open Model
open Utils
open Akka
open Akka.FSharp
open Akka.Actor



let rec observeFile (absolutePath : string) (a : IActorRef )  = async{

    let fsw = new FileSystemWatcher(
                        Path = Path.GetDirectoryName(absolutePath), 
                        Filter = "*.*",
                        EnableRaisingEvents = true, 
                        NotifyFilter = (NotifyFilters.FileName ||| NotifyFilters.LastWrite ||| NotifyFilters.LastAccess ||| NotifyFilters.CreationTime ||| NotifyFilters.DirectoryName)
                        )

    let prepareMessage  (args: EventArgs) =
        let text = 
            match box args with
            | :? FileSystemEventArgs as fsa ->
                match fsa.ChangeType with
                | WatcherChangeTypes.Changed -> "Changed " + fsa.Name
                | WatcherChangeTypes.Created ->  "Created " + fsa.Name
                | WatcherChangeTypes.Deleted -> "Deleted " + fsa.Name
                | WatcherChangeTypes.Renamed -> "Renamed " + fsa.Name
                | _ -> "Some other change " + fsa.ChangeType.ToString()
            | :? ErrorEventArgs as ea -> "Error: " + ea.GetException().Message
            | o -> "some other unexpected event occurd" + o.GetType().ToString()
        WriteMessage text 


    let sendMessage x = async{  async.Return(prepareMessage x) |!> a
                                return! observeFile absolutePath a }

    let! occurance  = 
        [
        fsw.Changed |> Observable.map(fun x -> sendMessage (x :> EventArgs));
        fsw.Created |> Observable.map(fun x -> sendMessage (x :> EventArgs));
        fsw.Deleted |> Observable.map(fun x -> sendMessage (x :> EventArgs));
        fsw.Renamed |> Observable.map(fun x -> sendMessage (x :> EventArgs));
        fsw.Error |> Observable.map(fun x -> sendMessage (x :> EventArgs));
        ] 
        |> List.reduce Observable.merge
        |> Async.AwaitObservable

    return! occurance
}

花了相当多的技巧才能做到这一点，任何关于我如何改变它的建议都是非常感谢的，这样它就能在演员运行时收集和处理所有的事件。

Answer 1

在设计这样的任务时，我们可以将其分成以下组件：

1. 创建负责接收所有消息的管理器-它的主要角色是响应传入的目录侦听请求。一旦请求传入，它就会创建一个子角色，负责在这个特定目录下侦听。
2. 子参与者负责管理特定路径的FileSystemWatcher。它应该订阅传入的事件，并将它们作为消息重定向到负责接收更改事件的参与者。当它关闭时，它也应该免费使用可支配资源。
3. 负责接收更改事件的参与者--在我们的示例中，通过在控制台上显示更改事件。

示例代码：

open Akka.FSharp
open System
open System.IO

let system = System.create "observer-system" <| Configuration.defaultConfig()

let observer filePath consoleWriter (mailbox: Actor<_>) =    
    let fsw = new FileSystemWatcher(
                        Path = filePath, 
                        Filter = "*.*",
                        EnableRaisingEvents = true, 
                        NotifyFilter = (NotifyFilters.FileName ||| NotifyFilters.LastWrite ||| NotifyFilters.LastAccess ||| NotifyFilters.CreationTime ||| NotifyFilters.DirectoryName)
                        )
    // subscribe to all incoming events - send them to consoleWriter
    let subscription = 
        [fsw.Changed |> Observable.map(fun x -> x.Name + " " + x.ChangeType.ToString());
         fsw.Created |> Observable.map(fun x -> x.Name + " " + x.ChangeType.ToString());
         fsw.Deleted |> Observable.map(fun x -> x.Name + " " + x.ChangeType.ToString());
         fsw.Renamed |> Observable.map(fun x -> x.Name + " " + x.ChangeType.ToString());]
             |> List.reduce Observable.merge
             |> Observable.subscribe(fun x -> consoleWriter <! x)

    // don't forget to free resources at the end
    mailbox.Defer <| fun () -> 
        subscription.Dispose()
        fsw.Dispose()

    let rec loop () = actor {
        let! msg = mailbox.Receive()
        return! loop()
    }
    loop ()

// create actor responsible for printing messages
let writer = spawn system "console-writer" <| actorOf (printfn "%A")

// create manager responsible for serving listeners for provided paths
let manager = spawn system "manager" <| actorOf2 (fun mailbox filePath ->
    spawn mailbox ("observer-" + Uri.EscapeDataString(filePath)) (observer filePath writer) |> ignore)

manager <! "testDir"