[Hawkular-dev] Availability

[John Sanda]

> On Mar 20, 2015, at 11:43 AM, Heiko W.Rupp <hrupp at redhat.com> wrote:
> 
>>> I am not convinced (yet) that availability should be recorded into
>>> Hawkular-Metrics,
>>> as the Metrics api is lacking the mapping functionality.
>>> I rather think we need "Hawkular-Availability" which offers some
>>> end-points + api
>>> and which then defers the storage to the Hawkular-Inventory metrics
>>> storage engine.
>> 
>> I suppose I am a bit biased since I work on metrics, but I do think 
>> availability should be stored in metrics. I think that the mapping
> 
> I did not write it should not be stored in metrics, but rather that it 
> should
> not be reported into metrics in the first place, but into a (logical)
> availability component.
> 
>> functionality belongs on the client/agent side just as it was in RHQ.
> 
> Well, this only partially works, as an application most probably 
> consists
> of resources that are distributed over several machines and thus feeds.
> In this case we need to take multiple values into account to compute
> the final value.
> Also in cases where e.g. we have an agent like in classic RHQ that 
> monitors
> an application and also a pinger in some other place, wich also pings 
> that application.
> Now suppose that the agent loses its connection to the server, but the 
> pinger reports
> the application as UP. In this case we may even want to override the 
> "unknown"
> information from the agent, as the pinger shows that the app is up.

Great point about multiple resources. I have to therefore slightly refine my previous statement. I think that the functionality belongs on the agent. As I said in the agent discussions, I think that there are use cases for different types of agents - embedded, c-located, and remote. For the example of monitoring availability for a resource (or resources) spanning several machines, I think it should be the job of a remote agent. Maybe that remote agent is running inside the hawkular server. I am not sure. They key though is that the approach is consistent in terms of who is applying that availability function.

> 
>> Those mapping functions should probably stored be stored in inventory 
>> so that users can see precisely how availability is determined for a 
>> particular type of resource and so that the user can also change how 
>> availability is calculated.
> 
> Absolutely.
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