Efremenko Arhip
e584cfc481
Adds internal/metrics: a private registry with the Go runtime + process
collectors and HTTP RED instrumentation (scimesh_http_requests_total and
request_duration_seconds), labelled by method/status and a normalized route so
per-id paths collapse to {id} and never blow up label cardinality.
/metrics is unauthenticated (like /health) for a Prometheus scraper; the
middleware wraps the whole router so every request is measured once.
113 lines
3.2 KiB
Go
113 lines
3.2 KiB
Go
// Package metrics exposes Prometheus instrumentation for the coordinator: an
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// HTTP RED middleware (rate, errors, duration) plus the standard Go runtime and
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// process collectors, all on a private registry so nothing leaks in from global
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// state.
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package metrics
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import (
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"net/http"
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"regexp"
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"strconv"
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"strings"
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"time"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/collectors"
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"github.com/prometheus/client_golang/prometheus/promhttp"
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)
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type Metrics struct {
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reg *prometheus.Registry
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requests *prometheus.CounterVec
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duration *prometheus.HistogramVec
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}
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// New builds the registry and registers the runtime, process, and HTTP metrics.
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func New() *Metrics {
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reg := prometheus.NewRegistry()
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reg.MustRegister(
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collectors.NewGoCollector(),
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collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}),
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)
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requests := prometheus.NewCounterVec(prometheus.CounterOpts{
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Namespace: "scimesh",
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Subsystem: "http",
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Name: "requests_total",
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Help: "HTTP requests, labelled by method, normalized route, and status.",
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}, []string{"method", "route", "status"})
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duration := prometheus.NewHistogramVec(prometheus.HistogramOpts{
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Namespace: "scimesh",
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Subsystem: "http",
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Name: "request_duration_seconds",
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Help: "HTTP request duration in seconds.",
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Buckets: prometheus.DefBuckets,
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}, []string{"method", "route"})
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reg.MustRegister(requests, duration)
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return &Metrics{reg: reg, requests: requests, duration: duration}
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}
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// Handler serves the metrics in Prometheus text format.
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func (m *Metrics) Handler() http.Handler {
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return promhttp.HandlerFor(m.reg, promhttp.HandlerOpts{})
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}
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// Registry exposes the registry so callers can register extra collectors.
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func (m *Metrics) Registry() *prometheus.Registry { return m.reg }
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// Middleware records one request into the RED metrics. It normalizes the path
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// so per-id routes collapse to a single low-cardinality label.
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func (m *Metrics) Middleware(next http.Handler) http.Handler {
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return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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start := time.Now()
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rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
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next.ServeHTTP(rec, r)
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route := normalizeRoute(r.URL.Path)
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m.requests.WithLabelValues(r.Method, route, strconv.Itoa(rec.status)).Inc()
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m.duration.WithLabelValues(r.Method, route).Observe(time.Since(start).Seconds())
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})
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}
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type statusRecorder struct {
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http.ResponseWriter
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status int
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}
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func (s *statusRecorder) WriteHeader(code int) {
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s.status = code
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s.ResponseWriter.WriteHeader(code)
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}
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var uuidRe = regexp.MustCompile(`^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{4}-[0-9a-fA-F]{12}$`)
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// normalizeRoute collapses uuid and numeric path segments to {id}, keeping the
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// route label cardinality bounded (otherwise every job/task id would be its own
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// time series).
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func normalizeRoute(path string) string {
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if path == "" {
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return "/"
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}
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segs := strings.Split(path, "/")
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for i, s := range segs {
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if s == "" {
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continue
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}
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if uuidRe.MatchString(s) || isAllDigits(s) {
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segs[i] = "{id}"
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}
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}
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return strings.Join(segs, "/")
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}
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func isAllDigits(s string) bool {
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for _, r := range s {
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if r < '0' || r > '9' {
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return false
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}
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}
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return s != ""
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}
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