instrumentation: remove opencensus metrics exporter.

Remove the old opencensus-based prometheus exporter. Rework
prometheus exporting using our update metrics registry and
a promhttp /metrics-handler.

Signed-off-by: Krisztian Litkey <[email protected]>

go.mod

@@ -3,7 +3,6 @@ module github.com/containers/nri-plugins
 go 1.22
 
 require (
-	contrib.go.opencensus.io/exporter/prometheus v0.4.2
 	github.com/containerd/nri v0.6.0
 	github.com/containerd/otelttrpc v0.0.0-20240305015340-ea5083fda723
 	github.com/containerd/ttrpc v1.2.3-0.20231030150553-baadfd8e7956
@@ -17,10 +16,8 @@ require (
 	github.com/pelletier/go-toml/v2 v2.1.0
 	github.com/prometheus/client_golang v1.17.0
 	github.com/prometheus/client_model v0.5.0
-	github.com/prometheus/common v0.44.0
 	github.com/sirupsen/logrus v1.9.3
 	github.com/stretchr/testify v1.8.4
-	go.opencensus.io v0.24.0
 	go.opentelemetry.io/otel v1.19.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc v1.19.0
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracehttp v1.19.0
@@ -44,8 +41,6 @@ require (
 	github.com/davecgh/go-spew v1.1.1 // indirect
 	github.com/emicklei/go-restful/v3 v3.9.0 // indirect
 	github.com/evanphx/json-patch v5.6.0+incompatible // indirect
-	github.com/go-kit/log v0.2.1 // indirect
-	github.com/go-logfmt/logfmt v0.6.0 // indirect
 	github.com/go-logr/logr v1.4.1 // indirect
 	github.com/go-logr/stdr v1.2.2 // indirect
 	github.com/go-openapi/jsonpointer v0.19.6 // indirect
@@ -54,7 +49,6 @@ require (
 	github.com/go-task/slim-sprig v0.0.0-20230315185526-52ccab3ef572 // indirect
 	github.com/godbus/dbus/v5 v5.0.4 // indirect
 	github.com/gogo/protobuf v1.3.2 // indirect
-	github.com/golang/groupcache v0.0.0-20210331224755-41bb18bfe9da // indirect
 	github.com/golang/protobuf v1.5.3 // indirect
 	github.com/google/gnostic-models v0.6.8 // indirect
 	github.com/google/go-cmp v0.6.0 // indirect
@@ -73,8 +67,8 @@ require (
 	github.com/opencontainers/runtime-spec v1.1.0 // indirect
 	github.com/pkg/errors v0.9.1 // indirect
 	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/prometheus/common v0.44.0 // indirect
 	github.com/prometheus/procfs v0.12.0 // indirect
-	github.com/prometheus/statsd_exporter v0.24.0 // indirect
 	github.com/spf13/pflag v1.0.5 // indirect
 	go.opentelemetry.io/otel/exporters/otlp/otlptrace v1.19.0 // indirect
 	go.opentelemetry.io/otel/metric v1.19.0 // indirect

pkg/instrumentation/instrumentation.go

@@ -18,8 +18,6 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/prometheus/client_golang/prometheus"
-
 	cfgapi "github.com/containers/nri-plugins/pkg/apis/config/v1alpha1/instrumentation"
 	"github.com/containers/nri-plugins/pkg/http"
 	"github.com/containers/nri-plugins/pkg/instrumentation/metrics"
@@ -52,11 +50,6 @@ var (
 	Attribute = tracing.Attribute
 )
 
-// RegisterGatherer registers a prometheus metrics gatherer.
-func RegisterGatherer(g prometheus.Gatherer) {
-	metrics.RegisterGatherer(g)
-}
-
 // HTTPServer returns our HTTP server.
 func HTTPServer() *http.Server {
 	return srv
@@ -122,9 +115,11 @@ func start() error {
 
 	if err := metrics.Start(
 		srv.GetMux(),
+		metrics.WithNamespace("nri"),
 		metrics.WithExporterDisabled(!cfg.PrometheusExport),
-		metrics.WithServiceName(ServiceName),
-		metrics.WithPeriod(cfg.ReportPeriod.Duration),
+		metrics.WithReportPeriod(cfg.ReportPeriod.Duration),
+		// TODO(klihub): make this configurable via apis/config/.../instrumentation.Config
+		metrics.WithMetrics([]string{"misc/buildinfo"}, []string{"policy"}),
 	); err != nil {
 		return fmt.Errorf("failed to start metrics: %v", err)
 	}

pkg/instrumentation/metrics/metrics.go

@@ -15,14 +15,135 @@
 package metrics
 
 import (
-	oc "github.com/containers/nri-plugins/pkg/instrumentation/metrics/opencensus"
+	"fmt"
+	"slices"
+	"time"
+
+	"github.com/prometheus/client_golang/prometheus/promhttp"
+
+	"github.com/containers/nri-plugins/pkg/http"
+	logger "github.com/containers/nri-plugins/pkg/log"
+	"github.com/containers/nri-plugins/pkg/metrics"
+)
+
+type (
+	Option func() error
 )
 
 var (
-	RegisterGatherer     = oc.RegisterGatherer
-	WithExporterDisabled = oc.WithExporterDisabled
-	WithPeriod           = oc.WithPeriod
-	WithServiceName      = oc.WithServiceName
-	Start                = oc.Start
-	Stop                 = oc.Stop
+	disabled     bool
+	namespace    string
+	enabled      []string
+	polled       []string
+	reportPeriod time.Duration
+	mux          *http.ServeMux
+	gatherer     *metrics.Gatherer
+	log          = logger.Get("metrics")
 )
+
+func WithExporterDisabled(v bool) Option {
+	return func() error {
+		disabled = v
+		return nil
+	}
+}
+
+func WithNamespace(v string) Option {
+	return func() error {
+		namespace = v
+		return nil
+	}
+}
+
+func WithReportPeriod(v time.Duration) Option {
+	return func() error {
+		reportPeriod = v
+		return nil
+	}
+}
+
+func WithMetrics(enable []string, poll []string) Option {
+	return func() error {
+		enabled = slices.Clone(enable)
+		polled = slices.Clone(poll)
+		return nil
+	}
+}
+
+func Start(m *http.ServeMux, options ...Option) error {
+	Stop()
+
+	for _, opt := range options {
+		if err := opt(); err != nil {
+			return err
+		}
+	}
+
+	if m == nil {
+		log.Info("no mux provided, metrics exporter disabled")
+		return nil
+	}
+
+	if disabled {
+		log.Info("metrics exporter disabled")
+		return nil
+	}
+
+	log.Info("starting metrics exporter...")
+
+	g, err := metrics.NewGatherer(
+		metrics.WithNamespace("nri"),
+		metrics.WithPollInterval(reportPeriod),
+		metrics.WithMetrics(enabled, polled),
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create metrics gatherer: %v", err)
+	}
+
+	gatherer = g
+
+	handlerOpts := promhttp.HandlerOpts{
+		ErrorLog:      log,
+		ErrorHandling: promhttp.ContinueOnError,
+	}
+	m.Handle("/metrics", promhttp.HandlerFor(g, handlerOpts))
+
+	mux = m
+
+	return nil
+}
+
+func Stop() {
+	if mux == nil {
+		return
+	}
+
+	mux.Unregister("/metrics")
+	mux = nil
+	gatherer.Stop()
+	gatherer = nil
+}
+
+func Block() *MetricsBlock {
+	return newMetricsBlock(gatherer)
+}
+
+type MetricsBlock struct {
+	g *metrics.Gatherer
+}
+
+func newMetricsBlock(g *metrics.Gatherer) *MetricsBlock {
+	if g == nil {
+		return nil
+	}
+	g.Block()
+	return &MetricsBlock{g: g}
+}
+
+func (b *MetricsBlock) Done() {
+	if b == nil || b.g == nil {
+		return
+	}
+	b.g.Unblock()
+	b.g = nil
+}