Re: [Webpush] When UA should send an acknowledgement?

[Martin Thomson <[e-mail]>]

On 8 June 2016 at 13:17, Benjamin Bangert <[e-mail]> wrote:
> For our implementation, we will actually never send more notifications
> until all sent ones are ack'd. This means if a message is malformed or
> causes a UA error in a UA that actually follows the DOM spec, it will
> never get a notification again (except the notification it won't ack).


This is fine, as long as you regard unacknowledged messages that you
thought were delivered as poisonous after a certain amount of time (or
retries, if you do that).  If you follow that advice, then progress
will eventually be made.

I expect that Costin will agree with you, but we've discussed this in
the past.  The problem here is that an acknowledgment from the user
agent doesn't constitute a useful signal.  You have moved the problem
to a second middle-man.  When the user agent acknowledges prior to
processing the message, how will the application know that it was
processed?  Can you guarantee that?  When the browser crashes, your
message is still lost.

The only way for this to be a good signal is to have the
acknowledgment be end-to-end.

(p.s., I don't know if your assertion is true or not.  I don't think
that it matters.  I should know that code, but it's an absolute rats
nest, despite Kit's recent efforts at cleanup.)