Storage - UploadObjectAsync - "Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead." (.NET Core 3.0)

Much like https://github.com/googleapis/google-api-dotnet-client/pull/1469, I’m getting:

Synchronous operations are disallowed. Call ReadAsync or set AllowSynchronousIO to true instead.

The stack trace I have is:

   at Google.Cloud.Storage.V1.StorageClientImpl.UploadHelper.CheckFinalProgress()
   at Google.Cloud.Storage.V1.StorageClientImpl.UploadHelper.ExecuteAsync(CancellationToken cancellationToken)

My guess is CheckFinalProgress is finding and rethrowing an exception from elsewhere in the (comprehensively intimidating) upload infrastructure.

I’m on 2.4.0-beta3. After (a lot!) of paging through releases, I couldn’t see anything in the changelogs. In the meantime, I see there’s a 2.5.0 now, so I’ll update, and set AllowSynchronousIO=true.

For others looking to make a one-off exception for a single request:

var syncIOFeature = HttpContext.Features.Get<IHttpBodyControlFeature>();
if (syncIOFeature != null)
{
    syncIOFeature.AllowSynchronousIO = true;
}

[jskeet]

Thanks for reporting this. I’ll have a look on Monday.

[kierenj]

I have now, yes, thank you - all working as expected 😃