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From Ted Ross <tr...@redhat.com>
Subject Re: Dispatch Router prefetch
Date Mon, 11 Mar 2019 14:32:12 GMT
On Fri, Mar 8, 2019 at 9:19 AM Gordon Sim <gsim@redhat.com> wrote:

> On 08/03/2019 2:12 pm, Gordon Sim wrote:
> > On 08/03/2019 12:59 pm, HADI Ali wrote:
> >> Hello,
> >>
> >> We are actually using in our cluster multiple brokers and thus we need
> >> to define the same address on multiple brokers.
> >> For this, we cannot use linkroutes as suggested, but we still need to
> >> have the correct behavior of the TTL in our cluster.
> >>
> >> Is it an option to manage the TTL of the message at the level of the
> >> dispatch router since we have all of the information needed in the
> >> message headers?
> >
> > It doesn't do that at present, but it doesn't seem like an reasonable
> > enhancement to me.
>
> Sorry, meant to say it doesn't seem like an *un*reasonable enhancement!
>

I'd like to better understand the use case here.  We've avoided adding any
kind of TTL support in Dispatch Router up to this point.

I assume, based on the fact that prefetch-1 didn't solve your problem, that
you have consumers that are attached but don't issue credit for long
periods of time.  Is this accurate?

What is the pattern of your consumers?  Do they attach, then later issue
credit to process a message?  How many messages per second/minute/hour do
your consumers handle?  Do they issue one credit at a time?

What are the typical TTLs in your messages?  How granular does the
expiration need to be (i.e. how accurate of a timer would need to be used
to tag each incoming delivery)?  Would one-second granularity be
sufficient, or do you need milliseconds?

An alternate approach would be to not consider a consumer to be a routable
destination until it issues initial credit.  Would this address your
problem?


>
> >> In Internet Protocol, ipv4 for example, the routers manage the TTL and
> >> discard any expired messages.
> >>
> >> Or make it feasible to have the autolinks propagate the credit
> >> directly from consumers?
> >
> > This isn't really possible when you have autolinks for same address to
> > multiple brokers. If the consumer gives 10 credits, how do you propagate
> > that to two brokers?  5 each? What if they don't both have 5 messages?
> > 10 each? Then you are back to the situation where you have more credit
> > issued at source than the consumer has granted.
> >
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>
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