feat(metrics): prometheus compatible metrics endpoint - #176
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Replace the three static config-mirror gauges with a certificate collector that reports the validity window of the kubesolo PKI. container_mode, load_balancer_enabled and portainer_edge_enabled only echoed flags back to the scraper and never changed after startup, so they carried no operational signal. full_mode is removed for the same reason plus a harder one: develop dropped Embedded.FullMode when --full became a deprecated no-op, so the gauge no longer compiled. In their place, certificate_expiry_timestamp_seconds and certificate_valid cover ca, apiserver, controller-manager, kubelet, admin, webhook and the request-header pair, plus the d2k server/client certs when --d2k is set. Nothing upstream covers these: apiserver_client_certificate_expiration_seconds measures client certs presented to the apiserver rather than its own serving cert, and the kubelet_certificate_manager_* gauges only register when kubelet runs a rotating cert manager, which kubesolo does not. Certificates are parsed at scrape time rather than cached at startup. InvalidateIfIPChanged re-signs leaf certs on node IP change or expiry, so a cached value would report the pre-rotation expiry until restart. The cost is eight small file reads per scrape. Expiry is an absolute timestamp rather than seconds-remaining so the value does not decay between scrapes; compute the delta with `- time()`. An unreadable or corrupt cert reports certificate_valid 0 instead of dropping both series, so the failure is visible without absent() alerting. Note ca and request-header-ca behave differently from the six leaf certs: removeLeafCerts preserves both CA directories across regeneration, so a CA nearing expiry needs manual intervention while a leaf is self-healing. Alert thresholds should differ accordingly
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Pull request overview
This PR adds an optional Prometheus-compatible metrics endpoint to kubesolo, enabling operators to scrape a lightweight /metrics HTTP endpoint for control-plane component health, build info, certificate validity, and kine DB sizing.
Changes:
- Introduces a new
pkg/components/metricscomponent implementing an HTTP server, collectors, and periodic health probes. - Adds metrics configuration to
types.Embeddedplus defaults/constants for bind address, probe interval, and kine DB filename. - Wires new CLI flags and startup logic in
cmd/kubesolo/main.goto enable/launch the metrics service.
Reviewed changes
Copilot reviewed 12 out of 12 changed files in this pull request and generated 1 comment.
Show a summary per file
| File | Description |
|---|---|
| types/types.go | Adds Metrics config to the embedded runtime configuration and defines MetricsConfig. |
| types/const.go | Introduces defaults for metrics bind/probe interval and a shared kine DB filename constant. |
| pkg/components/metrics/service.go | Defines the metrics service structure and constructor. |
| pkg/components/metrics/server.go | Implements the /metrics + /healthz HTTP server lifecycle. |
| pkg/components/metrics/probe.go | Implements component health probing (HTTP/TCP/file) and CoreDNS readiness via the Kubernetes API. |
| pkg/components/metrics/metrics.go | Orchestrates registry creation, readiness watching, probing loop, and shutdown. |
| pkg/components/metrics/collectors.go | Registers Prometheus collectors/gauges including build info, uptime, kine DB size, and component gauges. |
| pkg/components/metrics/certs.go | Adds a scrape-time collector for certificate expiry/validity. |
| pkg/components/metrics/certs_test.go | Adds unit tests for certificate parsing/collector behavior. |
| internal/config/flags/flags.go | Adds --metrics-server and --metrics-bind-address flags (and env vars). |
| go.mod | Promotes github.com/prometheus/client_golang to a direct dependency. |
| cmd/kubesolo/main.go | Wires metrics config into Embedded and starts the metrics service during startup. |
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stevensbkang
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