The ApmAsyncFactory interop hangs if a path in async method returns synchronously. #281
Description
Hi,
I observed a strange behavior in ApmAsyncFactory. If the task contains a path that returns synchronously, then the execution hangs. It's easy to reproduce, so I'll just provide an example. I'll use asmx web service to demonstrate the issue.
public class DemoService : System.Web.Services.WebService
{
[WebMethod]
public IAsyncResult BeginRun(int option, AsyncCallback callback, object state)
{
return ApmAsyncFactory.ToBegin<string>(GetResponseAsync(option), callback, state);
}
[WebMethod]
public string EndRun(IAsyncResult result)
{
return ApmAsyncFactory.ToEnd<string>(result);
}
private async Task<string> GetResponseAsync(int option)
{
if (option == 1)
{
await Task.Delay(1000);
return "Works";
}
else if (option == 2)
{
// I tried awaiting a completed task too, just to test it out
await Task.CompletedTask;
return "Hangs";
}
else
{
return "Hangs";
}
}
}To be sure that this is not a generic problem, I tried the solution provided in this article, and it works without issues.
public class DemoService : System.Web.Services.WebService
{
[WebMethod]
public IAsyncResult BeginRun(int option, AsyncCallback callback, object state)
{
return GetResponseAsync(option).AsApm(callback, state);
}
[WebMethod]
public string EndRun(IAsyncResult result)
{
return ((Task<string>)result).Result;
}
private async Task<string> GetResponseAsync(int option)
{
if (option == 1)
{
await Task.Delay(1000);
return "Works";
}
else if (option == 2)
{
await Task.CompletedTask;
return "Works";
}
else
{
return "Works";
}
}
}Metadata
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