Re: [Webpush] Message expiration (TTL) and Negative Acknowledgements

[Martin Thomson <[e-mail]>]

On 16 October 2015 at 14:20, Benjamin Bangert <[e-mail]> wrote:
> For the NACK's, speaking of server constraints, how many receipts is a Push
> Service expected to buffer for an App-Server? If an App-Server sends 500k
> notifications in, and happens to not be connected to the receipt server at
> the time.... how many of those is the Push Service supposed to hold onto
> until the app-server starts pulling them?

The number is bounded by the number of messages the app server has
successfully requested delivery for.  If you have 500k outstanding
messages from the same app server, then you are hold that much message
state; having some proportion of that translate into ack/nack state
seems like it should be less state.

Of course, if you are shedding load, then I see no reason not to be
fairly aggressive about dumping nacks.  That's probably worth noting
in the operational considerations.

> If the stream of NACK's is several magnitudes higher than an App-Server can
> process them, at what point can a Push Service start dropping NACK's on the
> floor?

Inability to deliver an ACK or NACK can be treated exactly like
failure to deliver a message, I'd imagine.  You can't be expected to
hold these forever.