feat: move metrics server to a dedicated package

Signed-off-by: Xe Iaso <me@xeiaso.net>

lib/config/config.go

@@ -2,7 +2,6 @@ package config
 
 import (
 	"errors"
-	"flag"
 	"fmt"
 	"io"
 	"io/fs"
@@ -390,16 +389,6 @@ func (c *fileConfig) Valid() error {
 	return nil
 }
 
-func flagLookup(name string) string {
-	fl := flag.CommandLine.Lookup(name)
-
-	if fl == nil {
-		return ""
-	}
-
-	return fl.Value.String()
-}
-
 func Load(fin io.Reader, fname string) (*Config, error) {
 	c := &fileConfig{
 		StatusCodes: StatusCodes{
@@ -414,11 +403,6 @@ func Load(fin io.Reader, fname string) (*Config, error) {
 			Backend: "memory",
 		},
 		Logging: (Logging{}).Default(),
-		Metrics: &Metrics{
-			Bind:       flagLookup("metrics-bind"),
-			Network:    flagLookup("metrics-bind-network"),
-			SocketMode: flagLookup("socket-mode"),
-		},
 	}
 
 	if err := yaml.NewYAMLToJSONDecoder(fin).Decode(&c); err != nil {

lib/metrics/metrics.go

@@ -0,0 +1,81 @@
+package metrics
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"net/http/pprof"
+	"time"
+
+	"github.com/TecharoHQ/anubis/internal"
+	"github.com/TecharoHQ/anubis/lib/config"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+	healthv1 "google.golang.org/grpc/health/grpc_health_v1"
+)
+
+type Server struct {
+	Config *config.Metrics
+	Log    *slog.Logger
+}
+
+func (s *Server) Run(ctx context.Context, done func()) error {
+	defer done()
+	lg := s.Log.With("subsystem", "metrics")
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("GET /debug/pprof/", pprof.Index)
+	mux.HandleFunc("GET /debug/pprof/cmdline", pprof.Cmdline)
+	mux.HandleFunc("GET /debug/pprof/profile", pprof.Profile)
+	mux.HandleFunc("GET /debug/pprof/symbol", pprof.Symbol)
+	mux.HandleFunc("GET /debug/pprof/trace", pprof.Trace)
+	mux.Handle("/metrics", promhttp.Handler())
+	mux.HandleFunc("/healthz", func(w http.ResponseWriter, r *http.Request) {
+		st, ok := internal.GetHealth("anubis")
+		if !ok {
+			slog.Error("health service anubis does not exist, file a bug")
+		}
+
+		switch st {
+		case healthv1.HealthCheckResponse_NOT_SERVING:
+			http.Error(w, "NOT OK", http.StatusInternalServerError)
+			return
+		case healthv1.HealthCheckResponse_SERVING:
+			fmt.Fprintln(w, "OK")
+			return
+		default:
+			http.Error(w, "UNKNOWN", http.StatusFailedDependency)
+			return
+		}
+	})
+
+	srv := http.Server{
+		Handler:  mux,
+		ErrorLog: internal.GetFilteredHTTPLogger(),
+	}
+
+	ln, metricsURL, err := internal.SetupListener(s.Config.Bind, s.Config.Network, s.Config.SocketMode)
+	if err != nil {
+		return fmt.Errorf("can't setup listener: %w", err)
+	}
+
+	defer ln.Close()
+
+	lg.Debug("listening for metrics", "url", metricsURL)
+
+	go func() {
+		<-ctx.Done()
+		c, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+		if err := srv.Shutdown(c); err != nil {
+			lg.Error("can't shut down metrics server", "err", err)
+		}
+	}()
+
+	if err := srv.Serve(ln); !errors.Is(err, http.ErrServerClosed) {
+		return fmt.Errorf("can't serve metrics server: %w", err)
+	}
+
+	return nil
+}

lib/policy/policy.go

@@ -46,6 +46,7 @@ type ParsedConfig struct {
 	DnsCache          *dns.DnsCache
 	Dns               *dns.Dns
 	Logger            *slog.Logger
+	Metrics           *config.Metrics
 }
 
 func newParsedConfig(orig *config.Config) *ParsedConfig {
@@ -53,6 +54,7 @@ func newParsedConfig(orig *config.Config) *ParsedConfig {
 		orig:        orig,
 		OpenGraph:   orig.OpenGraph,
 		StatusCodes: orig.StatusCodes,
+		Metrics:     orig.Metrics,
 	}
 }