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From Ted Ross <tr...@redhat.com>
Subject Re: Dispatch Router prefetch
Date Mon, 11 Mar 2019 18:53:55 GMT
On Mon, Mar 11, 2019 at 11:26 AM Gordon Sim <gsim@redhat.com> wrote:

> On 11/03/2019 2:32 pm, Ted Ross wrote:
> > We've avoided adding any kind of TTL support in Dispatch Router up to
> > this point.
> Dropping an expired message is less work than delivering it, even
> delivering pre-settled, I suspect.
> The ttl is defined in the header of the message, before annotations, so
> in the case of message routing at least we will always have read past
> that point. Parsing out the ttl will have some cost, but is suspect not
> a huge one.
> I wouldn't advocate setting up timers to trigger the processing of
> expired messages, but wherever it makes sense it could be part of the
> processing of deliveries, as a way of saving effort as much as anything.

Agreed.  We would need to store with the delivery an arrival timestamp of
sufficient granularity to satisfy the requirements.  If the granularity is
large (one second), this will have very little impact on the performance of
the router.

> I probably wouldn't bother too much initially with adjusting the ttl
> either, as generally messages flowing into the router network will
> pretty quickly reach the egress router (which is where at present they
> are 'delayed' until there is credit).
> Anyway, not advocating that this is needed, just commenting that I don't
> think it needs to have a negative effect on efficiency (indeed it could
> even be seen as an optimisation).
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