refactor: switch metrics to Service pattern

cmd/serve.go

@@ -10,6 +10,7 @@ import (
 	"github.com/0xERR0R/blocky/config"
 	"github.com/0xERR0R/blocky/evt"
 	"github.com/0xERR0R/blocky/log"
+	"github.com/0xERR0R/blocky/metrics"
 	"github.com/0xERR0R/blocky/server"
 	"github.com/0xERR0R/blocky/util"
 
@@ -47,6 +48,10 @@ func startServer(_ *cobra.Command, _ []string) error {
 	ctx, cancelFn := context.WithCancel(context.Background())
 	defer cancelFn()
 
+	if cfg.Prometheus.Enable {
+		metrics.StartCollection()
+	}
+
 	srv, err := server.NewServer(ctx, cfg)
 	if err != nil {
 		return fmt.Errorf("can't start server: %w", err)

config/config.go

@@ -271,7 +271,8 @@ type Config struct {
 // The `yaml` struct tags are just for manual testing,
 // and require replacing `yaml:"-"` in Config to work.
 type Services struct {
-	DoH DoHService `yaml:"dns-over-https"`
+	DoH     DoHService     `yaml:"dns-over-https"`
+	Metrics MetricsService `yaml:"metrics"`
 }
 
 type Ports struct {
@@ -618,11 +619,14 @@ func (cfg *Config) validate(logger *logrus.Entry) {
 // This should be replaced with a migration once everything from Ports is supported in Services.
 // Done this way for now to avoid creating temporary generic services and updating all Ports related code at once.
 func (cfg *Config) CopyPortsToServices() {
+	httpAddrs := httpAddrs{
+		HTTPAddrs:  HTTPAddrs{HTTP: cfg.Ports.HTTP},
+		HTTPSAddrs: HTTPSAddrs{HTTPS: cfg.Ports.HTTPS},
+	}
+
 	cfg.Services = Services{
-		DoH: DoHService{Addrs: DoHAddrs{
-			HTTPAddrs:  HTTPAddrs{HTTP: cfg.Ports.HTTP},
-			HTTPSAddrs: HTTPSAddrs{HTTPS: cfg.Ports.HTTPS},
-		}},
+		DoH:     DoHService{Addrs: httpAddrs},
+		Metrics: MetricsService{Addrs: httpAddrs},
 	}
 }
 

config/doh_service.go

@@ -1,10 +1,16 @@
 package config
 
-type DoHService struct {
-	Addrs DoHAddrs `yaml:"addrs"`
+type (
+	DoHService     httpService
+	MetricsService httpService
+)
+
+// httpService can be used by any service that uses HTTP(S).
+type httpService struct {
+	Addrs httpAddrs `yaml:"addrs"`
 }
 
-type DoHAddrs struct {
+type httpAddrs struct {
 	HTTPAddrs  `yaml:",inline"`
 	HTTPSAddrs `yaml:",inline"`
 }

metrics/metrics.go

@@ -1,12 +1,8 @@
 package metrics
 
 import (
-	"github.com/0xERR0R/blocky/config"
-
-	"github.com/go-chi/chi/v5"
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/prometheus/client_golang/prometheus/collectors"
-	"github.com/prometheus/client_golang/prometheus/promhttp"
 )
 
 //nolint:gochecknoglobals
@@ -17,12 +13,9 @@ func RegisterMetric(c prometheus.Collector) {
 	_ = reg.Register(c)
 }
 
-// Start starts prometheus endpoint
-func Start(router *chi.Mux, cfg config.Metrics) {
-	if cfg.Enable {
-		_ = reg.Register(collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}))
-		_ = reg.Register(collectors.NewGoCollector())
-		router.Handle(cfg.Path, promhttp.InstrumentMetricHandler(reg,
-			promhttp.HandlerFor(reg, promhttp.HandlerOpts{})))
-	}
+func StartCollection() {
+	_ = reg.Register(collectors.NewProcessCollector(collectors.ProcessCollectorOpts{}))
+	_ = reg.Register(collectors.NewGoCollector())
+
+	registerEventListeners()
 }

metrics/metrics_event_publisher.go

@@ -11,8 +11,8 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 )
 
-// RegisterEventListeners registers all metric handlers by the event bus
-func RegisterEventListeners() {
+// registerEventListeners registers all metric handlers on the event bus
+func registerEventListeners() {
 	registerBlockingEventListeners()
 	registerCachingEventListeners()
 	registerApplicationEventListeners()

metrics/service.go

@@ -0,0 +1,48 @@
+package metrics
+
+import (
+	"github.com/0xERR0R/blocky/config"
+	"github.com/0xERR0R/blocky/service"
+	"github.com/0xERR0R/blocky/util"
+	"github.com/go-chi/chi/v5"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+)
+
+// Service implements service.HTTPService.
+type Service struct {
+	service.HTTPInfo
+}
+
+func NewService(cfg config.MetricsService, metricsCfg config.Metrics) *Service {
+	endpoints := util.ConcatSlices(
+		service.EndpointsFromAddrs(service.HTTPProtocol, cfg.Addrs.HTTP),
+		service.EndpointsFromAddrs(service.HTTPSProtocol, cfg.Addrs.HTTPS),
+	)
+
+	if !metricsCfg.Enable || len(endpoints) == 0 {
+		// Avoid setting up collectors and listeners
+		return new(Service)
+	}
+
+	s := &Service{
+		HTTPInfo: service.HTTPInfo{
+			Info: service.Info{
+				Name:      "Metrics",
+				Endpoints: endpoints,
+			},
+
+			Mux: chi.NewMux(),
+		},
+	}
+
+	s.Mux.Handle(
+		metricsCfg.Path,
+		promhttp.InstrumentMetricHandler(reg, promhttp.HandlerFor(reg, promhttp.HandlerOpts{})),
+	)
+
+	return s
+}
+
+func (s *Service) Merge(other service.Service) (service.Merger, error) {
+	return service.MergeHTTP(s, other)
+}

server/server.go

@@ -118,8 +118,6 @@ func newTLSConfig(cfg *config.Config) (*tls.Config, error) {
 }
 
 // NewServer creates new server instance with passed config
-//
-//nolint:funlen
 func NewServer(ctx context.Context, cfg *config.Config) (server *Server, err error) {
 	cfg.CopyPortsToServices()
 
@@ -142,8 +140,6 @@ func NewServer(ctx context.Context, cfg *config.Config) (server *Server, err err
 		return nil, err
 	}
 
-	metrics.RegisterEventListeners()
-
 	bootstrap, err := resolver.NewBootstrap(ctx, cfg)
 	if err != nil {
 		return nil, err
@@ -194,6 +190,7 @@ func (s *Server) createServices() ([]service.Service, error) {
 	res := []service.Service{
 		newHTTPMiscService(s.cfg, openAPIImpl),
 		newDoHService(s.cfg.Services.DoH, s.handleReq),
+		metrics.NewService(s.cfg.Services.Metrics, s.cfg.Prometheus),
 	}
 
 	// Remove services the user has not enabled
@@ -244,6 +241,8 @@ func createListeners(ctx context.Context, cfg *config.Config, tlsCfg *tls.Config
 		newListeners(ctx, service.HTTPSProtocol, cfg.Ports.HTTPS, listenTLS, res),
 		newListeners(ctx, service.HTTPProtocol, cfg.Services.DoH.Addrs.HTTP, service.ListenTCP, res),
 		newListeners(ctx, service.HTTPSProtocol, cfg.Services.DoH.Addrs.HTTPS, listenTLS, res),
+		newListeners(ctx, service.HTTPProtocol, cfg.Services.Metrics.Addrs.HTTP, service.ListenTCP, res),
+		newListeners(ctx, service.HTTPSProtocol, cfg.Services.Metrics.Addrs.HTTPS, listenTLS, res),
 	)
 	if err != nil {
 		return nil, err

server/server_endpoints.go

@@ -7,7 +7,6 @@ import (
 	"net"
 	"net/http"
 
-	"github.com/0xERR0R/blocky/metrics"
 	"github.com/0xERR0R/blocky/resolver"
 
 	"github.com/0xERR0R/blocky/api"
@@ -74,8 +73,6 @@ func createHTTPRouter(cfg *config.Config, openAPIImpl api.StrictServerInterface)
 
 	configureRootHandler(cfg, router)
 
-	metrics.Start(router, cfg.Prometheus)
-
 	return router
 }