feat: implement metrics for Image Factory

Fixes #14

This adds "standard" HTTP metrics for the frontend, and also three kinds
of custom metrics:

* schematic get/create
* system extension popularity score
* asset build metrics: cached/not cached, bytes, requests, in dimension
  of asset kind

Signed-off-by: Andrey Smirnov <andrey.smirnov@siderolabs.com>

Author: smira

cmd/image-factory/cmd/options.go

@@ -53,6 +53,11 @@ type Options struct { //nolint:govet
 	CacheRepository string
 	// Allow insecure connection to the cache repository.
 	InsecureCacheRepository bool
+
+	// Bind address for Prometheus metrics.
+	//
+	// Leave empty to disable.
+	MetricsListenAddr string
 }
 
 // DefaultOptions are the default options.
@@ -77,4 +82,6 @@ var DefaultOptions = Options{
 	TalosVersionRecheckInterval: 15 * time.Minute,
 
 	CacheRepository: "ghcr.io/siderolabs/image-factory/cache",
+
+	MetricsListenAddr: ":2122",
 }

cmd/image-factory/cmd/service.go

@@ -20,6 +20,8 @@ import (
 	"github.com/google/go-containerregistry/pkg/authn/github"
 	"github.com/google/go-containerregistry/pkg/name"
 	"github.com/google/go-containerregistry/pkg/v1/remote"
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promhttp"
 	"github.com/sigstore/cosign/v2/cmd/cosign/cli/fulcio"
 	"github.com/sigstore/cosign/v2/pkg/cosign"
 	"github.com/sigstore/sigstore/pkg/cryptoutils"
@@ -121,9 +123,44 @@ func RunFactory(ctx context.Context, logger *zap.Logger, opts Options) error {
 		return httpServer.Shutdown(shutdownCtx) //nolint:contextcheck
 	})
 
+	if opts.MetricsListenAddr != "" {
+		runMetricsServer(ctx, logger, eg, opts)
+	}
+
 	return eg.Wait()
 }
 
+func runMetricsServer(ctx context.Context, logger *zap.Logger, eg *errgroup.Group, opts Options) {
+	var metricsMux http.ServeMux
+
+	metricsMux.Handle("/metrics", promhttp.Handler())
+
+	metricsServer := &http.Server{
+		Addr:    opts.MetricsListenAddr,
+		Handler: &metricsMux,
+	}
+
+	eg.Go(func() error {
+		logger.Info("serving metrics", zap.String("listen_addr", opts.MetricsListenAddr))
+
+		err := metricsServer.ListenAndServe()
+		if errors.Is(err, http.ErrServerClosed) {
+			err = nil
+		}
+
+		return err
+	})
+
+	eg.Go(func() error {
+		<-ctx.Done()
+
+		shutdownCtx, shutdownCtxCancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer shutdownCtxCancel()
+
+		return metricsServer.Shutdown(shutdownCtx) //nolint:contextcheck
+	})
+}
+
 func buildArtifactsManager(ctx context.Context, logger *zap.Logger, opts Options) (*artifacts.Manager, error) {
 	rootCerts, err := fulcio.GetRoots()
 	if err != nil {
@@ -197,7 +234,14 @@ func buildAssetBuilder(logger *zap.Logger, artifactsManager *artifacts.Manager,
 		return nil, fmt.Errorf("failed to parse cache repository: %w", err)
 	}
 
-	return asset.NewBuilder(logger, artifactsManager, builderOptions)
+	builder, err := asset.NewBuilder(logger, artifactsManager, builderOptions)
+	if err != nil {
+		return nil, err
+	}
+
+	prometheus.MustRegister(builder)
+
+	return builder, nil
 }
 
 func buildSchematicFactory(logger *zap.Logger, opts Options) (*schematic.Factory, error) {
@@ -211,7 +255,11 @@ func buildSchematicFactory(logger *zap.Logger, opts Options) (*schematic.Factory
 		return nil, fmt.Errorf("failed to initialize storage: %w", err)
 	}
 
-	return schematic.NewFactory(logger, cache.NewCache(storage), schematic.Options{}), nil
+	factory := schematic.NewFactory(logger, cache.NewCache(storage), schematic.Options{})
+
+	prometheus.MustRegister(factory)
+
+	return factory, nil
 }
 
 // remoteOptions returns options for remote registry access.

cmd/image-factory/flags.go

@@ -50,6 +50,8 @@ func initFlags() cmd.Options {
 		"allow an insecure connection to the cache repository",
 	)
 
+	flag.StringVar(&opts.MetricsListenAddr, "metrics-listen-addr", cmd.DefaultOptions.MetricsListenAddr, "metrics listen address (set empty to disable)")
+
 	flag.Parse()
 
 	return opts

go.mod

@@ -16,12 +16,14 @@ require (
 	github.com/h2non/filetype v1.1.3
 	github.com/julienschmidt/httprouter v1.3.0
 	github.com/opencontainers/go-digest v1.0.0
+	github.com/prometheus/client_golang v1.17.0
 	github.com/siderolabs/gen v0.4.7
 	github.com/siderolabs/go-pointer v1.0.0
 	github.com/siderolabs/talos v1.6.0-alpha.1.0.20231030094658-cbe6e7622d01
 	github.com/siderolabs/talos/pkg/machinery v1.6.0-alpha.1.0.20231030094658-cbe6e7622d01
 	github.com/sigstore/cosign/v2 v2.2.0
-	github.com/sigstore/sigstore v1.7.2
+	github.com/sigstore/sigstore v1.7.5
+	github.com/slok/go-http-metrics v0.11.0
 	github.com/stretchr/testify v1.8.4
 	github.com/u-root/u-root v0.11.0
 	github.com/ulikunitz/xz v0.5.11
@@ -105,7 +107,7 @@ require (
 	github.com/containerd/ttrpc v1.2.2 // indirect
 	github.com/containerd/typeurl/v2 v2.1.1 // indirect
 	github.com/containernetworking/cni v1.1.2 // indirect
-	github.com/coreos/go-oidc/v3 v3.6.0 // indirect
+	github.com/coreos/go-oidc/v3 v3.7.0 // indirect
 	github.com/coreos/go-semver v0.3.1 // indirect
 	github.com/coreos/go-systemd/v22 v22.5.0 // indirect
 	github.com/cosi-project/runtime v0.3.13 // indirect
@@ -145,7 +147,7 @@ require (
 	github.com/go-openapi/validate v0.22.1 // indirect
 	github.com/go-playground/locales v0.14.1 // indirect
 	github.com/go-playground/universal-translator v0.18.1 // indirect
-	github.com/go-playground/validator/v10 v10.15.1 // indirect
+	github.com/go-playground/validator/v10 v10.15.5 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
 	github.com/golang-jwt/jwt/v4 v4.5.0 // indirect
 	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
@@ -183,15 +185,15 @@ require (
 	github.com/josharian/native v1.1.0 // indirect
 	github.com/jsimonetti/rtnetlink v1.3.5 // indirect
 	github.com/json-iterator/go v1.1.12 // indirect
-	github.com/klauspost/compress v1.16.7 // indirect
+	github.com/klauspost/compress v1.17.1 // indirect
 	github.com/leodido/go-urn v1.2.4 // indirect
 	github.com/letsencrypt/boulder v0.0.0-20221109233200-85aa52084eaf // indirect
 	github.com/magiconair/properties v1.8.7 // indirect
 	github.com/mailru/easyjson v0.7.7 // indirect
 	github.com/martinlindhe/base36 v1.1.1 // indirect
 	github.com/mattn/go-colorable v0.1.13 // indirect
-	github.com/mattn/go-isatty v0.0.19 // indirect
-	github.com/matttproud/golang_protobuf_extensions v1.0.4 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/matttproud/golang_protobuf_extensions/v2 v2.0.0 // indirect
 	github.com/mdlayher/arp v0.0.0-20220512170110-6706a2966875 // indirect
 	github.com/mdlayher/ethernet v0.0.0-20220221185849-529eae5b6118 // indirect
 	github.com/mdlayher/ethtool v0.1.0 // indirect
@@ -221,16 +223,15 @@ require (
 	github.com/opentracing/opentracing-go v1.2.0 // indirect
 	github.com/packethost/packngo v0.30.0 // indirect
 	github.com/pelletier/go-toml v1.9.5 // indirect
-	github.com/pelletier/go-toml/v2 v2.0.8 // indirect
+	github.com/pelletier/go-toml/v2 v2.1.0 // indirect
 	github.com/pierrec/lz4/v4 v4.1.14 // indirect
 	github.com/pin/tftp v2.1.0+incompatible // indirect
 	github.com/pkg/browser v0.0.0-20210911075715-681adbf594b8 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
 	github.com/pmorjan/kmod v1.1.0 // indirect
-	github.com/prometheus/client_golang v1.17.0 // indirect
-	github.com/prometheus/client_model v0.4.1-0.20230718164431-9a2bf3000d16 // indirect
-	github.com/prometheus/common v0.44.0 // indirect
+	github.com/prometheus/client_model v0.5.0 // indirect
+	github.com/prometheus/common v0.45.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
 	github.com/rs/xid v1.5.0 // indirect
 	github.com/ryanuber/go-glob v1.0.0 // indirect
@@ -300,16 +301,16 @@ require (
 	go.uber.org/multierr v1.11.0 // indirect
 	go4.org/netipx v0.0.0-20230824141953-6213f710f925 // indirect
 	golang.org/x/crypto v0.14.0 // indirect
-	golang.org/x/exp v0.0.0-20230321023759-10a507213a29 // indirect
+	golang.org/x/exp v0.0.0-20230905200255-921286631fa9 // indirect
 	golang.org/x/mod v0.12.0 // indirect
-	golang.org/x/oauth2 v0.12.0 // indirect
+	golang.org/x/oauth2 v0.13.0 // indirect
 	golang.org/x/term v0.13.0 // indirect
 	golang.org/x/text v0.13.0 // indirect
 	golang.org/x/time v0.3.0 // indirect
-	golang.org/x/tools v0.12.0 // indirect
+	golang.org/x/tools v0.13.0 // indirect
 	golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b // indirect
 	golang.zx2c4.com/wireguard/wgctrl v0.0.0-20230429144221-925a1e7659e6 // indirect
-	google.golang.org/appengine v1.6.7 // indirect
+	google.golang.org/appengine v1.6.8 // indirect
 	google.golang.org/genproto v0.0.0-20231012201019-e917dd12ba7a // indirect
 	google.golang.org/genproto/googleapis/api v0.0.0-20231002182017-d307bd883b97 // indirect
 	google.golang.org/genproto/googleapis/rpc v0.0.0-20231016165738-49dd2c1f3d0b // indirect