MetalK8s monitoring stack can generate alerts from observed statistics and a set of rules. These alerts are then persisted for providing a historical view in MetalK8s UI, and can be routed to custom receivers if needed (see csc-alertmanager-customization for how to do this).
There are two categories of alerting rules deployed with MetalK8s: simple and composite.
Simple alerting rules define an expression only from "standard" Prometheus metrics, while composite rules rely on the special ALERTS metric to generate alerts from the state of other alerts.
Composite rules are used to build a hierarchy of alerts, encoding the relationship between low-level components and their simple alerting rules into higher level services.
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