rcmgr: register prometheus metrics with the libp2p registerer (#2370)

* rcmgr: register prometheus metrics with the libp2p registerer

* update dashboard readme

config/config.go

@@ -26,6 +26,7 @@ import (
 	blankhost "github.com/libp2p/go-libp2p/p2p/host/blank"
 	"github.com/libp2p/go-libp2p/p2p/host/eventbus"
 	"github.com/libp2p/go-libp2p/p2p/host/peerstore/pstoremem"
+	rcmgrObs "github.com/libp2p/go-libp2p/p2p/host/resource-manager/obs"
 	routed "github.com/libp2p/go-libp2p/p2p/host/routed"
 	"github.com/libp2p/go-libp2p/p2p/net/swarm"
 	tptu "github.com/libp2p/go-libp2p/p2p/net/upgrader"
@@ -299,6 +300,10 @@ func (cfg *Config) NewNode() (host.Host, error) {
 		return nil, err
 	}
 
+	if !cfg.DisableMetrics {
+		rcmgrObs.MustRegisterWith(cfg.PrometheusRegisterer)
+	}
+
 	h, err := bhost.NewHost(swrm, &bhost.HostOpts{
 		EventBus:             eventBus,
 		ConnManager:          cfg.ConnManager,

dashboards/resource-manager/README.md

@@ -5,8 +5,10 @@ import follow the Grafana docs [here](https://grafana.com/docs/grafana/latest/da
 
 ## Setup
 
-To make sure you're emitting the correct metrics you'll have to register the
-metrics with a Prometheus Registerer. For example:
+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 (
@@ -18,8 +20,6 @@ import (
 )
 
     func SetupResourceManager() (network.ResourceManager, error) {
-        rcmgrObs.MustRegisterWith(prometheus.DefaultRegisterer)
-
         str, err := rcmgrObs.NewStatsTraceReporter()
         if err != nil {
             return nil, err

p2p/host/resource-manager/obs/stats.go

@@ -142,7 +142,7 @@ var (
 )
 
 func MustRegisterWith(reg prometheus.Registerer) {
-	reg.MustRegister(
+	metricshelper.RegisterCollectors(reg,
 		conns,
 		peerConns,
 		previousPeerConns,