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

[Benjamin Bangert <[e-mail]>]

On Tue, Jun 7, 2016 at 7:34 PM, Martin Thomson <[e-mail]> wrote:
> On 7 June 2016 at 09:02, Idel Pivnitskiy <[e-mail]> wrote:
>> Just a question: When should UA send an acknowledgement? Immediately after
>> receiving a push message or after decryption/decoding/processing a push
>> message?
>
> This is defined in
> http://w3c.github.io/push-api/index.html#the-push-event  (Step 6.5.3
> is the acknowledgment.)
>
> What a user agent does with the message is outside this spec.

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).

As such, our UA necessarily cannot and will not follow the DOM spec as
written. Instead we follow the WebPush spec which appears to conflict
with the DOM spec.

Per the WebPush spec, 6.2:
"To ensure that a push message is properly delivered to the user agent
at least once, the user agent MUST acknowledge receipt of the message
by performing a HTTP DELETE on the push message resource. "

The DOM spec in 6.5.3 notes that if the message is improperly
encrypted, the process is halted, and the webpush acknowledgement does
*not take place*.

The relevant portion of the DOM process:
"If the push message could not be decrypted for any reason, discard
the message and terminate this process. "

This makes it sound as if the following steps (including webpush ack)
*must not be run*.

Some clarification around this would be great.

Cheers,
Ben