Prometheus
Prometheus is an “open-source systems monitoring and alerting toolkit” (SoundCloud origin; the
second CNCF project after kubernetes, 2016). It’s the de-facto metrics backend of the CNCF stack
this spoke keeps meeting — the very tool the kubernetes-integration-tax piece names (Cilium metrics
invisible to it without a ServiceMonitor). Source: official Prometheus docs.
Model
- Multidimensional time series identified by “metric name and key/value pairs” (labels);
- pull-based “collection happens via a pull model over HTTP” (scrape), with a push gateway for ephemeral jobs;
- PromQL query language; Alertmanager for alerting; each server is standalone (no network storage dependency — reliability under failure).
Strengths vs. limits
Great for “purely numeric time series” in microservices; explicitly not for billing-grade data (“not be detailed and complete enough … for 100% accuracy”) — the same metrics-vs-exactness caveat worth recording for observability. Pairs with opentelemetry (which can produce/ship metrics into a Prometheus-compatible store).
Related
observability · kubernetes · kubernetes-integration-tax · opentelemetry · platform-ops · site-reliability-engineering