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Async.RunSynchronously with a timeout question
f#

Hi,

I have a question regarding the use of Async.RunSynchronously with a timeout.

Example 1 :

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let foo =
  async
    { do! System.Threading.Thread.AsyncSleep 1000
       printfn "ok"
    }
Async.RunSynchronously(foo, 10)

Example 2 :

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open System
open System.Net
open System.Net.Sockets

let bar (ip, port) =
  async
    { let c = new TcpClient()
      printfn "connecting to: %s:%d" ip port
      c.Connect(IPAddress.Parse(ip), port)
      c.Close()
    }

Async.RunSynchronously(bar("10.00.00.000", 64996), 10)

In the first example, the timeout exception is expectedly raised after 10msec. However, in example 2, the timeout exception is not raised.

What am I missing ?

Thanks

.

Putting a block of code inside async{} does not magically make it cancellable, there needs to be some Async primitive inside that enables some kind of cooperative cancellation. In this instance, you could do

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let AsyncConnect (c : TcpClient, ipAddr:IPAddress, port:int) = 
    Async.FromBeginEnd((fun (cb,o)->c.BeginConnect(ipAddr,port,cb,o)), c.EndConnect)
let bar (ip, port) =
  async
    { 
      let c = new TcpClient()
      printfn "connecting to: %s:%d" ip port
      //c.Connect(IPAddress.Parse(ip), port)
      do! AsyncConnect(c, IPAddress.Parse(ip), port)
      c.Close()
    }

which uses BeginConnect/EndConnect inside the Async, and thus becomes cancellable via the timeout.

By on 8/3/2009 4:35 PM ()

(as usual:) many thanks !!!

By on 8/3/2009 5:05 PM ()

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