[Hawkular-dev] HWKMETRICS-83 Create glue code component to integrate with hawkular-bus

[Thomas Segismont]

Hi everyone,

I sent a pull request to the Metrics repo to implement $subject.
https://github.com/hawkular/hawkular-metrics/pull/393

I won't paste here the whole PR description, but the following might be 
of interest.

There is a new "hawkular-metrics-component" WAR module. It is meant to 
replace "hawkular-metrics-api-jaxrs" module in Hawkular deployments.

This new WAR is a "super"-module: it uses Maven WAR plugin overlay 
mechanism to add extra classes to the standalone metrics web application.

The extra classes allow to subscribe to the 
MetricsService#insertedDataEvents observable and publish messages on the 
bus.

In order to make the migration easy, I have shamelessly copied Alerts' 
AvailDataMessage and MetricDataMessage classes. Theses messages are 
posted on to the "HawkularAvailData" and "HawkularMetricData" topics, 
respectively.

After this PR is merged we only need to change the agent code to remove 
the "double-push" part. And change Hawkular POM to switch to the new 
Metrics component. That's it.

I would like to discuss the JSON payload format later. It might need to 
be changed, but let's flip this coin first.

Thanks,
Thomas