Support for only selecting certain fields (without using operator) in queries about prometheus

[roidelapluie]

What should happen when there are duplicates?

[a-roberts]

What should happen when there are duplicates?

That is a good point (so when the metrics exporter is writing back pod and pod for one particular result) - thinking "out loud" we could combine this with, say, some other identifier (like if pod is a child of some other object).

If there is always a metric field name called name, we could do something like:

kube_pod_container_resource_limits{namespace="${namespace}",resource=~"cpu|memory"} by pod[metricName], unit, __name__.

That could be a confusing syntax though because it looks like pod has an attribute called metricName (as would pod.metricName.). I think this is one of those that requires a little more thought.

The alternative (less work, less awesome) would be to throw an error and then it would be up to the exporter and the caller to query the right things. And as it would be a new function, we wouldn't need to deal with breaking folks just yet as nobody could be using this syntax...some food for thought.