Feature: Option to add clusterName for VMAgent

[micw]

I'm running VMAgent on all of my clusters and send to a central monitoring. Currently I need to add the cluster name to every agent as extra label. It would be great if the agent could do this automatically (so that I do not need to specify the cluster name for each cluster manually).

[f41gh7]

There is special setting - vmAgentExternalLabelName, it adds given label name (prometheus by default), to each series scrapped by vmagent with name of VMAgent CR. It's possible to define it as:

kind: VMAgent
metadata:
   name: east-prod-dc
spec:
  vmAgentExternalLabelName: cluster

in this case, all metrics scrapped by agent get label - cluster: east-prod-dc.

It looks like, this setting must be also added to the ingested metrics to vmagent by push clients, but it's not implemented yet.