[Hawkular-dev] availability as a computed metric (was availability and metric endpoints)

[Heiko W.Rupp]

On 23 Mar 2015, at 15:47, John Sanda wrote:
> I think that there was some general consensus or at least convergence 
> towards the notion that availability is a function that reports 
> resource state change. It could be a function of metric data or

Yes.

> I think we need to expand on what was done in RHQ. I think that 
> availability functions should be explicit and stored in inventory so 
> that users can easily see how availability is determined and also 
> change how availability is computed should the need arise. The

As I said.

> monitoring agent, not the server, should compute availability. I am 
> using the term agent loosely here because it applies to agents that

Which may be ok for the simple case, but certainly neither in cases
where availability is a composite (application with resources 
distributed
over several agents).
In fact I have proposed in the past that agents can do some local 
computation
and only forward metrics in case of error/change.

> There needs to be more done in terms of correlation. When there is a 
> state change, we should be reporting an accompanying event, e.g., 
> server shutdown, server restarted, etc. If we compute availability 
> based on some metric, then maybe the event reported is something like, 
> http status code is X or the response time is Y.

Yes.

See also 
http://lists.jboss.org/pipermail/hawkular-dev/2015-March/000413.html