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]>

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 +115,9 @@ 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),
 	); err != nil {
 		return fmt.Errorf("failed to start metrics: %v", err)
 	}

pkg/instrumentation/metrics/metrics.go

@@ -15,14 +15,105 @@
 package metrics
 
 import (
-	oc "github.com/containers/nri-plugins/pkg/instrumentation/metrics/opencensus"
+	"fmt"
+	"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
+	enable       []string
+	poll         []string
+	reportPeriod time.Duration
+	mux          *http.ServeMux
+	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 {
+		enable = enable
+		poll = 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(enable, poll),
+	)
+	if err != nil {
+		return fmt.Errorf("failed to create metrics gatherer: %v", err)
+	}
+
+	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
+}

pkg/log/log.go

@@ -77,6 +77,9 @@ type Logger interface {
 	// Fatal formats and emits an error message and os.Exit()'s with status 1.
 	Fatal(format string, args ...interface{})
 
+	// Println to mimick minimal stdlin log.Logger interface.
+	Println(v ...any)
+
 	// DebugBlock formats and emits a multiline debug message.
 	DebugBlock(prefix string, format string, args ...interface{})
 	// InfoBlock formats and emits a multiline information message.
@@ -410,6 +413,10 @@ func (l logger) Panic(format string, args ...interface{}) {
 	panic(msg)
 }
 
+func (l logger) Println(a ...any) {
+	l.Info("%s", fmt.Sprintln(a...))
+}
+
 func (l logger) DebugBlock(prefix string, format string, args ...interface{}) {
 	if l.DebugEnabled() {
 		l.block(LevelDebug, prefix, format, args...)