rcmgr: enable metrics by default (#2389) (#2409)

Co-authored-by: Sukun <sukunrt@gmail.com>

dashboards/resource-manager/README.md

@@ -5,28 +5,9 @@ import follow the Grafana docs [here](https://grafana.com/docs/grafana/latest/da
 
 ## Setup
 
-To make sure you're emitting the metrics you'll have to create the Resource
-Manager with a StatsTraceReporter. By default metrics will be sent to
-prometheus.DefaultRegisterer. To use a different Registerer use the libp2p
-option libp2p.PrometheusRegisterer. For example:
-
-``` go
-import (
-    // ...
-	rcmgr "github.com/libp2p/go-libp2p/p2p/host/resource-manager"
-
-	"github.com/prometheus/client_golang/prometheus"
-)
-
-    func SetupResourceManager() (network.ResourceManager, error) {
-        str, err := rcmgr.NewStatsTraceReporter()
-        if err != nil {
-            return nil, err
-        }
-
-        return rcmgr.NewResourceManager(limiter, rcmgr.WithTraceReporter(str))
-    }
-```
+Metrics are enabled by default. By default, metrics will be sent to
+`prometheus.DefaultRegisterer`. To use a different Registerer use the libp2p
+option `libp2p.PrometheusRegisterer`.
 
 ## Updating Dashboard json
 

p2p/host/resource-manager/README.md

@@ -47,15 +47,10 @@ limits := cfg.Build(scaledDefaultLimits)
 // The resource manager expects a limiter, se we create one from our limits.
 limiter := rcmgr.NewFixedLimiter(limits)
 
-// (Optional if you want metrics)
-rcmgr.MustRegisterWith(prometheus.DefaultRegisterer)
-str, err := rcmgr.NewStatsTraceReporter()
-if err != nil {
-  panic(err)
-}
-
+// Metrics are enabled by default. If you want to disable metrics, use the 
+// WithMetricsDisabled option
 // Initialize the resource manager
-rm, err := rcmgr.NewResourceManager(limiter, rcmgr.WithTraceReporter(str))
+rm, err := rcmgr.NewResourceManager(limiter, rcmgr.WithMetricsDisabled())
 if err != nil {
   panic(err)
 }

p2p/host/resource-manager/rcmgr.go

@@ -20,8 +20,9 @@ var log = logging.Logger("rcmgr")
 type resourceManager struct {
 	limits Limiter
 
-	trace   *trace
-	metrics *metrics
+	trace          *trace
+	metrics        *metrics
+	disableMetrics bool
 
 	allowlist *Allowlist
 
@@ -141,6 +142,28 @@ func NewResourceManager(limits Limiter, opts ...Option) (network.ResourceManager
 		}
 	}
 
+	if !r.disableMetrics {
+		var sr TraceReporter
+		sr, err := NewStatsTraceReporter()
+		if err != nil {
+			log.Errorf("failed to initialise StatsTraceReporter %s", err)
+		} else {
+			if r.trace == nil {
+				r.trace = &trace{}
+			}
+			found := false
+			for _, rep := range r.trace.reporters {
+				if rep == sr {
+					found = true
+					break
+				}
+			}
+			if !found {
+				r.trace.reporters = append(r.trace.reporters, sr)
+			}
+		}
+	}
+
 	if err := r.trace.Start(limits); err != nil {
 		return nil, err
 	}

p2p/host/resource-manager/stats.go

@@ -160,6 +160,13 @@ func MustRegisterWith(reg prometheus.Registerer) {
 	)
 }
 
+func WithMetricsDisabled() Option {
+	return func(r *resourceManager) error {
+		r.disableMetrics = true
+		return nil
+	}
+}
+
 // StatsTraceReporter reports stats on the resource manager using its traces.
 type StatsTraceReporter struct{}
 

p2p/test/resource-manager/rcmgr_test.go

@@ -317,14 +317,10 @@ func TestReadmeExample(t *testing.T) {
 	// The resource manager expects a limiter, se we create one from our limits.
 	limiter := rcmgr.NewFixedLimiter(limits)
 
-	// (Optional if you want metrics) Construct the OpenCensus metrics reporter.
-	str, err := rcmgr.NewStatsTraceReporter()
-	if err != nil {
-		panic(err)
-	}
-
+	// Metrics are enabled by default. If you want to disable metrics, use the
+	// WithMetricsDisabled option
 	// Initialize the resource manager
-	rm, err := rcmgr.NewResourceManager(limiter, rcmgr.WithTraceReporter(str))
+	rm, err := rcmgr.NewResourceManager(limiter, rcmgr.WithMetricsDisabled())
 	if err != nil {
 		panic(err)
 	}
@@ -334,6 +330,5 @@ func TestReadmeExample(t *testing.T) {
 	if err != nil {
 		panic(err)
 	}
-
 	host.Close()
 }