kruise-state-metrics is a simple service that listens to the Kubernetes API server and generates metrics about the state of the objects. (See examples in the Metrics section below.) It is not focused on the health of the individual OpenKruise components, but rather on the health of the various objects inside, such as clonesets, advanced statefulsets and sidecarsets.
kruise-state-metrics is about generating metrics from OpenKruise API objects without modification. This ensures that features provided by kruise-state-metrics have the same grade of stability as the OpenKruise API objects themselves. In turn, this means that kruise-state-metrics in certain situations may not show the exact same values as kubectl, as kubectl applies certain heuristics to display comprehensible messages. kruise-state-metrics exposes raw data unmodified from the Kubernetes API, this way users have all the data they require and perform heuristics as they see fit.
The metrics are exported on the HTTP endpoint /metrics on the listening port
(default 8080). They are served as plaintext. They are designed to be consumed
either by Prometheus itself or by a scraper that is compatible with scraping a
Prometheus client endpoint. You can also open /metrics in a browser to see
the raw metrics. Note that the metrics exposed on the /metrics endpoint
reflect the current state of OpenKruise objects in the Kubernetes cluster.
When the objects are deleted they are no longer visible on the /metrics endpoint.