[Hawkular-dev] metrics on the bus

[John Sanda]

I considered clustering before making the suggestion. MetricDataListener listens to a JMS topic for data points. When it receives data points, it passes those data points to AlertsEngine which in turn writes the data points into an ISPN, distributed cache. And then it looks like those data point get processed via a cache entry listener in AlertsEngineImpl. If I understand this data flow correctly, then I think it will work just as well if not better in a single WAR. Rather than getting notifications from a JMS topic, MetricDataListener can receive notifications from an Observable that pushes data point as they received in client requests. Metrics will also subscribe to that same Observable so that it can persist the data points. The fact that alerts is using a distributed cache works to our advantage here because it provides a mechanism for distributing data across nodes.

> On Aug 16, 2016, at 3:29 AM, Lucas Ponce <lponce at redhat.com> wrote:
> 
> This is a big point.
> 
> I can see pros and cons on it.
> 
> First thing it comes to me is that metrics has a stateless nature meanwhile alerts is stateful.
> 
> So a first coupling would work for a single node but when we want to scale our troubles can start as the design in clustered scenarios is completely different and a single .war won't help IMO.
> 
> I don't think our current design is bad, in the context of the HAWKULAR-1102 and working in a demand publishing draft we are addressing the business issues that triggered this discussion.
> 
> But I would like to hold this topic for a future architecture face to face meeting, to discuss it from all angles as we did on Madrid.
> 
> (Counting with a face to face meeting in a reasonable timeframe, of course).
> 
> Lucas
> 
> ----- Mensaje original -----
>> De: "John Sanda" <jsanda at redhat.com>
>> Para: "Discussions around Hawkular development" <hawkular-dev at lists.jboss.org>
>> Enviados: Lunes, 15 de Agosto 2016 16:45:28
>> Asunto: Re: [Hawkular-dev] metrics on the bus
>> 
>> We use JMS in large part because metrics and alerts are in separate WARs (I
>> realize JMS is used for other purposes, but I am speaking strictly about
>> this scenario). Why not deploy metrics and alerts in the same WAR and
>> altogether bypass JMS? As data points are ingested, we broadcast them using
>> an Rx subject to which both metrics and alerts subscribe. We could do this
>> is in away that still keeps metrics and alerts decoupled as they are today.
>> We would also have the added benefit of having a stand alone deployment for
>> metrics and alerts.
>> 
>> 
>> 
>> 
>> On Aug 10, 2016, at 9:37 AM, Jay Shaughnessy < jshaughn at redhat.com > wrote:
>> 
>> 
>> Yes, in fact I should have made it more clear that this whole discussion is
>> bounded by H Metrics and H Alerting in the H Services context, so limiting
>> this to HS/Bus integration code is what we'd want to do.
>> 
>> On 8/10/2016 4:06 AM, Heiko W.Rupp wrote:
>> 
>> 
>> 
>> Someone remind me please.
>> 
>> That bus-sender in/or hawkular-metrics is not an
>> internal detail of metrics, but rather sort of
>> 'external add-on'?
>> 
>> If so, the logic to filter (or create many subscriptions)
>> could go into it and would not touch the core metrics.
>> Metrics would (as it does today) forward all new data-
>> points into this sender and the sender can then decide
>> how to proceed.
>> 
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