feat: move metrics server to a dedicated package

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

cmd/anubis/main.go

@@ -17,7 +17,6 @@ import (
 	"net"
 	"net/http"
 	"net/http/httputil"
-	"net/http/pprof"
 	"net/url"
 	"os"
 	"os/signal"
@@ -32,12 +31,12 @@ import (
 	"github.com/TecharoHQ/anubis/internal"
 	libanubis "github.com/TecharoHQ/anubis/lib"
 	"github.com/TecharoHQ/anubis/lib/config"
+	"github.com/TecharoHQ/anubis/lib/metrics"
 	botPolicy "github.com/TecharoHQ/anubis/lib/policy"
 	"github.com/TecharoHQ/anubis/lib/thoth"
 	"github.com/TecharoHQ/anubis/web"
 	"github.com/facebookgo/flagenv"
 	_ "github.com/joho/godotenv/autoload"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 	healthv1 "google.golang.org/grpc/health/grpc_health_v1"
 )
 
@@ -229,11 +228,6 @@ func main() {
 
 	wg := new(sync.WaitGroup)
 
-	if *metricsBind != "" {
-		wg.Add(1)
-		go metricsServer(ctx, *lg.With("subsystem", "metrics"), wg.Done)
-	}
-
 	var rp http.Handler
 	// when using anubis via Systemd and environment variables, then it is not possible to set targe to an empty string but only to space
 	if strings.TrimSpace(*target) != "" {
@@ -273,6 +267,26 @@ func main() {
 	lg.Debug("swapped to new logger")
 	slog.SetDefault(lg)
 
+	if *metricsBind != "" || policy.Metrics != nil {
+		wg.Add(1)
+
+		ms := &metrics.Server{
+			Config: policy.Metrics,
+			Log:    lg,
+		}
+
+		if policy.Metrics == nil {
+			lg.Debug("migrating flags to metrics config", "bind", *metricsBind, "network", *metricsBindNetwork, "socket-mode", *socketMode)
+			ms.Config = &config.Metrics{
+				Bind:       *metricsBind,
+				Network:    *metricsBindNetwork,
+				SocketMode: *socketMode,
+			}
+		}
+
+		go ms.Run(ctx, wg.Done)
+	}
+
 	// Warn if persistent storage is used without a configured signing key
 	if policy.Store.IsPersistent() {
 		if *hs512Secret == "" && *ed25519PrivateKeyHex == "" && *ed25519PrivateKeyHexFile == "" {
@@ -448,56 +462,6 @@ func main() {
 	wg.Wait()
 }
 
-func metricsServer(ctx context.Context, lg slog.Logger, done func()) {
-	defer done()
-
-	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()}
-	listener, metricsUrl, err := internal.SetupListener(*metricsBindNetwork, *metricsBind, *socketMode)
-	if err != nil {
-		log.Fatalf("SetupListener(%q, %q, %q): %v", *bindNetwork, *bind, *socketMode, err)
-	}
-	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 {
-			log.Printf("cannot shut down: %v", err)
-		}
-	}()
-
-	if err := srv.Serve(listener); !errors.Is(err, http.ErrServerClosed) {
-		log.Fatal(err)
-	}
-}
-
 func extractEmbedFS(fsys embed.FS, root string, destDir string) error {
 	return fs.WalkDir(fsys, root, func(path string, d fs.DirEntry, err error) error {
 		if err != nil {

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,
 	}
 }