[英]MailboxProcessor crashes during Finalize
该代码在Mono(5.4.1.7)上运行。
我正在使用F#的代理来处理Web应用程序中的许多数据处理,其中之一就是关机。 处理已发布的关机消息后,代理会清理某些内容并停止其消息循环。 这很好用,但如果我尝试从Finalize()
执行Shutdown,它会炸毁我的脸。 我设法重现了这一点:
open System
open System.Threading
type ConsoleMessage =
| Clear
| Println of string
// Reply back (with unit) so that calling code is able to wait for the agent to clean up (for code dependent on the
// agent's resources definitely being released and such)
| Shutdown of AsyncReplyChannel<unit>
type ConsoleAgent() =
let mutable disposed = false
let mutable stopped = false
let agent = MailboxProcessor.Start(fun agent ->
let rec messageLoop () = async {
let! message = agent.Receive ()
match message with
| Clear -> System.Console.Clear ()
| Println str -> printfn "%s" str
| Shutdown rc ->
// Cleanup goes here
printfn "Shutting Down"
stopped <- true
rc.Reply ()
System.Threading.Thread.Sleep 100
if not stopped then
return! messageLoop () }
messageLoop ())
member this.Post msg = agent.Post msg
member this.PostAndAsyncReply msg = agent.PostAndAsyncReply msg
member this.Dispose disposing =
printfn "Disposing (disposing = %b)" disposing
if not disposed then
Async.RunSynchronously (agent.PostAndAsyncReply Shutdown)
disposed <- true
override this.Finalize () =
this.Dispose false
interface IDisposable with
member this.Dispose () =
this.Dispose true
module Main =
[<EntryPoint>]
let main args =
let console = new ConsoleAgent()
console.Post (Println "Print 1")
console.Post (Println "Print 2")
Thread.Sleep 1000
0
当然,在实际的应用程序中,它们与控制台打印无关。
这是我得到的堆栈跟踪:
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Runtime.Remoting.Contexts.SynchronizationAttribute.EnterContext () [0x00000] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/corlib/System.Runtime.Remoting.Contexts/SynchronizationAttribute.cs:184
at System.Threading.WaitHandle.WaitOneNative (System.Runtime.InteropServices.SafeHandle waitableSafeHandle, System.UInt32 millisecondsTimeout, System.Boolean hasThreadAffinity, System.Boolean exitContext) [0x0002d] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/corlib/System.Threading/WaitHandle.cs:111
at System.Threading.WaitHandle.InternalWaitOne (System.Runtime.InteropServices.SafeHandle waitableSafeHandle, System.Int64 millisecondsTimeout, System.Boolean hasThreadAffinity, System.Boolean exitContext) [0x00014] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:250
at System.Threading.WaitHandle.WaitOne (System.Int64 timeout, System.Boolean exitContext) [0x00000] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:239
at System.Threading.WaitHandle.WaitOne (System.Int32 millisecondsTimeout, System.Boolean exitContext) [0x00019] in /Users/builder/data/lanes/4992/mono-mac-sdk/external/bockbuild/builds/mono-x64/mcs/class/referencesource/mscorlib/system/threading/waithandle.cs:206
at Microsoft.FSharp.Control.AsyncImpl+ResultCell`1[T].TryWaitForResultSynchronously (Microsoft.FSharp.Core.FSharpOption`1[T] timeout) [0x0002a] in <5a7d678a904cf4daa74503838a677d5a>:0
at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronouslyInCurrentThread[a] (System.Threading.CancellationToken token, Microsoft.FSharp.Control.FSharpAsync`1[T] computation) [0x0001c] in <5a7d678a904cf4daa74503838a677d5a>:0
at Microsoft.FSharp.Control.CancellationTokenOps.RunSynchronously[a] (System.Threading.CancellationToken token, Microsoft.FSharp.Control.FSharpAsync`1[T] computation, Microsoft.FSharp.Core.FSharpOption`1[T] timeout) [0x00013] in <5a7d678a904cf4daa74503838a677d5a>:0
at Microsoft.FSharp.Control.FSharpAsync.RunSynchronously[T] (Microsoft.FSharp.Control.FSharpAsync`1[T] computation, Microsoft.FSharp.Core.FSharpOption`1[T] timeout, Microsoft.FSharp.Core.FSharpOption`1[T] cancellationToken) [0x00070] in <5a7d678a904cf4daa74503838a677d5a>:0
at Program+ConsoleAgent.Dispose (System.Boolean disposing) [0x00027] in /Users/jwostenberg/Code/FSharp/Sandbox/Sandbox/Program.fs:38
at Program+ConsoleAgent.Finalize () [0x00000] in /Users/jwostenberg/Code/FSharp/Sandbox/Sandbox/Program.fs:42
而且,如果通过处置模式正确处置了对象,则不会发生这种情况(例如,将let console = new ConsoleAgent()
更改为use console = new ConsoleAgent()
)。 我不能在不弯腰的情况下用自己的代码真正做到这一点,因为我没有对这些代理的直接引用(一次运行着许多代理),但是我不应该让它们通过反正垃圾收集器?
这是我的错,F#的错还是Mono的错? 现在,我将Dispose()方法的相关部分包装在一个try / catch中,该日志仅记录异常,但这确实很脏。
在极少数情况下,您需要覆盖Finalize
,并且看起来不适合您的用例。 请参阅此处的 “实施者注意事项”部分以及整篇文章 。
默认情况下,
Object.Finalize
方法不执行任何操作,但是只有在必要时才应覆盖Finalize,并且仅释放非托管资源。
回复:您的评论:
如何确保在没有
Finalize
情况下关闭MailboxProcessor
消息循环?
您可以只使用IDisposable
模式,或者更明确地管理MailboxProcessor
的生存期,这可能需要重构项目。
我不能在不弯腰的情况下用自己的代码真正做到这一点,因为我没有对这些代理的直接引用(一次运行着许多代理),但是我不应该让它们通过反正垃圾收集器?
是的,假设他们不拥有非托管资源,您应该能够让他们“自然”处置。 看不到实际的用例很难说,但是听起来您想要对处理器的生命周期进行更多控制。 这可能是XY问题 。
出于某种原因,此处使用Dispose方法的参数“ dispose”。 它区分Dispose的托管应用程序和非托管应用程序。 简而言之,Dispose(true)表示此调用是显式的(使用语句或F#的use
)。 它基本上是“正常” .NET编程的延续。
Dispose(false)表示正在完成。 这意味着任何引用的.NET对象都可以处于活动状态,被处置或最终确定。 因此,您的代码仅需要关心非托管资源,而不要尝试调用或以任何其他方式使用托管对象。
重要的是,终结器不会自动调用Dispose()。 使示例正确需要进行两项更改:
码:
member this.Dispose disposing =
if disposing && not disposed then
Async.RunSynchronously (agent.PostAndAsyncReply Shutdown)
disposed <- true
module Main =
[<EntryPoint>]
let main args =
use console = new ConsoleAgent()
Thread.Sleep 1000
0
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