feat: add IM service health and metrics endpoints

server/monitoring_http.go

@@ -0,0 +1,151 @@
+package main
+
+import (
+	"bufio"
+	"context"
+	"encoding/json"
+	"io"
+	"net"
+	"net/http"
+	"regexp"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	immetrics "github.com/tinode/chat/server/metrics"
+	"github.com/tinode/chat/server/store"
+)
+
+var (
+	metricsHandler        = promhttp.HandlerFor(immetrics.Registry, promhttp.HandlerOpts{})
+	uuidLikeMetricSegment = regexp.MustCompile(`^[0-9a-fA-F]{8}-[0-9a-fA-F-]{13,}$`)
+)
+
+type healthzResponse struct {
+	Status string            `json:"status"`
+	Checks map[string]string `json:"checks"`
+}
+
+func serveHealthz(wrt http.ResponseWriter, req *http.Request) {
+	if req.Method != http.MethodGet && req.Method != http.MethodHead {
+		wrt.Header().Set("Allow", http.MethodGet+", "+http.MethodHead)
+		http.Error(wrt, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	wrt.Header().Set("Content-Type", "application/json; charset=utf-8")
+
+	checks := map[string]string{}
+	status := http.StatusOK
+	ctx, cancel := context.WithTimeout(req.Context(), 2*time.Second)
+	defer cancel()
+	if err := store.Store.HealthCheck(ctx); err != nil {
+		checks["mysql"] = err.Error()
+		status = http.StatusServiceUnavailable
+	} else {
+		checks["mysql"] = "ok"
+	}
+
+	body := healthzResponse{Status: "ok", Checks: checks}
+	if status != http.StatusOK {
+		body.Status = "error"
+	}
+	wrt.WriteHeader(status)
+	if req.Method != http.MethodHead {
+		_ = json.NewEncoder(wrt).Encode(body)
+	}
+}
+
+func serveMetrics(wrt http.ResponseWriter, req *http.Request) {
+	if req.Method != http.MethodGet && req.Method != http.MethodHead {
+		wrt.Header().Set("Allow", http.MethodGet+", "+http.MethodHead)
+		http.Error(wrt, "method not allowed", http.StatusMethodNotAllowed)
+		return
+	}
+	metricsHandler.ServeHTTP(wrt, req)
+}
+
+func monitorHTTP(next http.Handler) http.Handler {
+	return http.HandlerFunc(func(wrt http.ResponseWriter, req *http.Request) {
+		if req.URL.Path == "/metrics" {
+			next.ServeHTTP(wrt, req)
+			return
+		}
+		started := time.Now()
+		rec := &monitoringResponseWriter{ResponseWriter: wrt, status: http.StatusOK}
+		next.ServeHTTP(rec, req)
+		status := strconv.Itoa(rec.status)
+		path := normalizeMetricPath(req.URL.Path)
+		immetrics.HTTPRequestsTotal.WithLabelValues(req.Method, path, status).Inc()
+		immetrics.HTTPRequestDuration.WithLabelValues(req.Method, path, status).Observe(time.Since(started).Seconds())
+	})
+}
+
+type monitoringResponseWriter struct {
+	http.ResponseWriter
+	status int
+}
+
+func (w *monitoringResponseWriter) WriteHeader(status int) {
+	w.status = status
+	w.ResponseWriter.WriteHeader(status)
+}
+
+func (w *monitoringResponseWriter) Flush() {
+	if f, ok := w.ResponseWriter.(http.Flusher); ok {
+		f.Flush()
+	}
+}
+
+func (w *monitoringResponseWriter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	h, ok := w.ResponseWriter.(http.Hijacker)
+	if !ok {
+		return nil, nil, http.ErrNotSupported
+	}
+	return h.Hijack()
+}
+
+func (w *monitoringResponseWriter) Push(target string, opts *http.PushOptions) error {
+	p, ok := w.ResponseWriter.(http.Pusher)
+	if !ok {
+		return http.ErrNotSupported
+	}
+	return p.Push(target, opts)
+}
+
+func (w *monitoringResponseWriter) ReadFrom(r io.Reader) (int64, error) {
+	if rf, ok := w.ResponseWriter.(io.ReaderFrom); ok {
+		return rf.ReadFrom(r)
+	}
+	return io.Copy(w.ResponseWriter, r)
+}
+
+func normalizeMetricPath(path string) string {
+	path = strings.TrimSpace(path)
+	if path == "" {
+		return "/"
+	}
+	parts := strings.Split(path, "/")
+	for i, part := range parts {
+		if part == "" {
+			continue
+		}
+		if isMetricDynamicSegment(part) {
+			parts[i] = "{id}"
+		}
+	}
+	return strings.Join(parts, "/")
+}
+
+func isMetricDynamicSegment(segment string) bool {
+	if strings.HasPrefix(segment, "usr") || strings.HasPrefix(segment, "grp") || strings.HasPrefix(segment, "p2p") || strings.HasPrefix(segment, "chn") {
+		return true
+	}
+	if _, err := strconv.ParseInt(segment, 10, 64); err == nil {
+		return true
+	}
+	if uuidLikeMetricSegment.MatchString(segment) {
+		return true
+	}
+	return false
+}