Sporadic failure to dispatch push notifications is invisible to consuming app

[JimKerslake]

Very occasionally:

Failed requesting push message delivery to "https://wns2-ln2p.notify.windows.com/w/?token=BQYAAAAX******".

Exception
System.InvalidOperationException: The request message was already sent. Cannot send the same request message multiple times. at System.Net.Http.HttpClient.CheckRequestMessage(HttpRequestMessage request) at System.Net.Http.HttpClient.CheckRequestBeforeSend(HttpRequestMessage request) at Lib.Net.Http.WebPush.PushServiceClient.RequestPushMessageDeliveryAsync(PushSubscription subscription, PushMessage message, VapidAuthentication authentication, VapidAuthenticationScheme authenticationScheme, CancellationToken cancellationToken) at cloudscribe.PwaKit.Services.PushServicePushNotificationService.SendNotificationAsync(PushSubscription subscription, PushMessage message, CancellationToken cancellationToken)

But because this is happening from a background task / queue in this assembly, there is no way that this can report the failure back up to a consuming app so that it can re-schedule and try again. Failure is therefore invisible in consuming app (apart from the log line above).

Try updating:
Lib.Net.Http.WebPush
Lib.AspNetCore.WebPush

But also perhaps need some kind of injectable custom error handler somewhere in around
DequeueMessagesAsync >> SendNotificationAsync >> HandlePushMessageDeliveryExceptionAsync

Is this perhaps even something at the endpoint side of things?:
https://wns2-ln2p.notify.windows.com/w/
Test - does it happen with google endpoints too?
It's very sporadic - (not provoked it today at all yet.)