Publish to Event Grid failing with "A task was canceled"

Hi,

We have recently started to see issues publishing events to the event grid in that it appears to be incredibly unreliable.  We are hosting the event grid topic in North Europe.  Searching the web, it seems that we are not alone in these issues and they have only surfaced very recently.  See;

https://github.com/Azure/azure-functions-host/issues/3160

https://github.com/Azure/azure-sdk-for-net/issues/4575

Stack Trace;

{System.Threading.Tasks.TaskCanceledException: A task was canceled.

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at Microsoft.Rest.RetryDelegatingHandler.<>c__DisplayClass11_0.<<SendAsync>b__1>d.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at Microsoft.Rest.RetryDelegatingHandler.<SendAsync>d__11.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at System.Runtime.CompilerServices.ConfiguredTaskAwaitable`1.ConfiguredTaskAwaiter.GetResult()

   at System.Net.Http.HttpClient.<FinishSendAsyncBuffered>d__58.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at Microsoft.Azure.EventGrid.EventGridClient.<PublishEventsWithHttpMessagesAsync>d__38.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at Microsoft.Azure.EventGrid.EventGridClientExtensions.<PublishEventsAsync>d__0.MoveNext()

--- End of stack trace from previous location where exception was thrown ---

   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)

   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)

   at EventBus.AzureEventGrid.EventPublisher.Publish[TEvent](TEvent integrationEvent)} System.Exception {System.Threading.Tasks.TaskCanceledException}