- Return meta-labels for the discovered targets via promutils.Labels
instead of map[string]string. This improves the speed of generating
meta-labels for discovered targets by up to 5x.
- Remove memory allocations in hot paths during ScrapeWork generation.
The ScrapeWork contains scrape settings for a single discovered target.
This improves the service discovery speed by up to 2x.
Previously multiple scrape jobs could create multiple watchers for the same apiURL. Now only a single watcher is used.
This should reduce load on Kubernetes API server when many scrape job configs use Kubernetes service discovery.
Main points:
* Revert changes outside lib/promscrape/discovery/kuberntes . These changes can be applied later in a separate commit
* Minimize changes in lib/promscrape/discovery/kubernetes compared to a93e644001
* Corner case fixes.
