refactor(cli): break down observability.startMetrics()

cli/observability_flags.go

@@ -79,72 +79,98 @@
 }
 
 func (c *observabilityFlags) startMetrics(ctx context.Context) error {
-	if c.metricsListenAddr != "" {
-		m := mux.NewRouter()
-		initPrometheus(m)
-
-		if c.enablePProf {
-			m.HandleFunc("/debug/pprof/", pprof.Index)
-			m.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
-			m.HandleFunc("/debug/pprof/profile", pprof.Profile)
-			m.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
-			m.HandleFunc("/debug/pprof/trace", pprof.Trace)
-			m.HandleFunc("/debug/pprof/{cmd}", pprof.Index) // special handling for Gorilla mux, see https://stackoverflow.com/questions/30560859/cant-use-go-tool-pprof-with-an-existing-server/71032595#71032595
-		}
+	c.maybeStartListener(ctx)
+
+	if err := c.maybeStartMetricsPusher(ctx); err != nil {
+		return err
+	}
+
+	return c.maybeStartTraceExporter()
+}
+
+// Starts observability listener when a listener address is specified.
+func (c *observabilityFlags) maybeStartListener(ctx context.Context) {
+	if c.metricsListenAddr == "" {
+		return
+	}
 
-		log(ctx).Infof("starting prometheus metrics on %v", c.metricsListenAddr)
+	m := mux.NewRouter()
+	initPrometheus(m)
 
-		go http.ListenAndServe(c.metricsListenAddr, m) //nolint:errcheck,gosec
+	if c.enablePProf {
+		m.HandleFunc("/debug/pprof/", pprof.Index)
+		m.HandleFunc("/debug/pprof/cmdline", pprof.Cmdline)
+		m.HandleFunc("/debug/pprof/profile", pprof.Profile)
+		m.HandleFunc("/debug/pprof/symbol", pprof.Symbol)
+		m.HandleFunc("/debug/pprof/trace", pprof.Trace)
+		m.HandleFunc("/debug/pprof/{cmd}", pprof.Index) // special handling for Gorilla mux, see https://stackoverflow.com/questions/30560859/cant-use-go-tool-pprof-with-an-existing-server/71032595#71032595
 	}
 
-	if c.metricsPushAddr != "" {
-		c.stopPusher = make(chan struct{})
-		c.pusherWG.Add(1)
+	log(ctx).Infof("starting prometheus metrics on %v", c.metricsListenAddr)
 
-		pusher := push.New(c.metricsPushAddr, c.metricsJob)
+	go http.ListenAndServe(c.metricsListenAddr, m) //nolint:errcheck,gosec
+}
 
-		pusher.Gatherer(prometheus.DefaultGatherer)
+func (c *observabilityFlags) maybeStartMetricsPusher(ctx context.Context) error {
+	if c.metricsPushAddr == "" {
+		return nil
+	}
 
-		for _, g := range c.metricsGroupings {
-			const nParts = 2
+	c.stopPusher = make(chan struct{})
+	c.pusherWG.Add(1)
 
-			parts := strings.SplitN(g, ":", nParts)
-			if len(parts) != nParts {
-				return errors.Errorf("grouping must be name:value")
-			}
+	pusher := push.New(c.metricsPushAddr, c.metricsJob)
 
-			name := parts[0]
-			val := parts[1]
+	pusher.Gatherer(prometheus.DefaultGatherer)
 
-			pusher.Grouping(name, val)
-		}
+	for _, g := range c.metricsGroupings {
+		const nParts = 2
 
-		if c.metricsPushUsername != "" {
-			pusher.BasicAuth(c.metricsPushUsername, c.metricsPushPassword)
+		parts := strings.SplitN(g, ":", nParts)
+		if len(parts) != nParts {
+			return errors.Errorf("grouping must be name:value")
 		}
 
-		if c.metricsPushFormat != "" {
-			pusher.Format(metricsPushFormats[c.metricsPushFormat])
-		}
+		name := parts[0]
+		val := parts[1]
 
-		log(ctx).Infof("starting prometheus pusher on %v every %v", c.metricsPushAddr, c.metricsPushInterval)
-		c.pushOnce(ctx, "initial", pusher)
+		pusher.Grouping(name, val)
+	}
 
-		go c.pushPeriodically(ctx, pusher)
+	if c.metricsPushUsername != "" {
+		pusher.BasicAuth(c.metricsPushUsername, c.metricsPushPassword)
 	}
 
-	se, err := c.getSpanExporter()
-	if err != nil {
-		return err
+	if c.metricsPushFormat != "" {
+		pusher.Format(metricsPushFormats[c.metricsPushFormat])
+	}
+
+	log(ctx).Infof("starting prometheus pusher on %v every %v", c.metricsPushAddr, c.metricsPushInterval)
+	c.pushOnce(ctx, "initial", pusher)
+
+	go c.pushPeriodically(ctx, pusher)
+
+	return nil
+}
+
+func (c *observabilityFlags) maybeStartTraceExporter() error {
+	if !c.enableJaeger {
+		return nil
 	}
 
-	r := resource.NewWithAttributes(
-		semconv.SchemaURL,
-		semconv.ServiceNameKey.String("kopia"),
-		semconv.ServiceVersionKey.String(repo.BuildVersion),
-	)
+	// Create the Jaeger exporter
+	se, err := jaeger.New(jaeger.WithCollectorEndpoint())
+	if err != nil {
+		return errors.Wrap(err, "unable to create Jaeger exporter")
+	}
 
 	if se != nil {
+		r := resource.NewWithAttributes(
+			semconv.SchemaURL,
+			semconv.ServiceNameKey.String("kopia"),
+			semconv.ServiceVersionKey.String(repo.BuildVersion),
+		)
+
 		tp := trace.NewTracerProvider(
 			trace.WithBatcher(se),
 			trace.WithResource(r),
@@ -158,20 +184,6 @@
 	return nil
 }
 
-func (c *observabilityFlags) getSpanExporter() (trace.SpanExporter, error) {
-	if c.enableJaeger {
-		// Create the Jaeger exporter
-		exp, err := jaeger.New(jaeger.WithCollectorEndpoint())
-		if err != nil {
-			return nil, errors.Wrap(err, "unable to create Jaeger exporter")
-		}
-
-		return exp, nil
-	}
-
-	return nil, nil
-}
-
 func (c *observabilityFlags) stopMetrics(ctx context.Context) {
 	if c.stopPusher != nil {
 		close(c.stopPusher)