chore(v2): add example of setting store metrics (#22819)

Author: tac0turtle

simapp/v2/app_di.go

@@ -167,11 +167,19 @@ func NewSimApp[T transaction.Tx](
 		return nil, fmt.Errorf("store builder did not return a db")
 	}
 
+	/****  Store Metrics ****/
+	/*
+		// In order to set store metrics uncomment the below
+		storeMetrics, err := metrics.NewMetrics([][]string{{"module", "store"}})
+		if err != nil {
+			return nil, err
+		}
+		app.store.SetMetrics(storeMetrics)
+	*/
 	/****  Module Options ****/
 
 	// RegisterUpgradeHandlers is used for registering any on-chain upgrades.
 	app.RegisterUpgradeHandlers()
-
 	if err = app.LoadLatest(); err != nil {
 		return nil, err
 	}

store/v2/metrics/metrics.go

@@ -45,3 +45,14 @@ func NewMetrics(labels [][]string) (Metrics, error) {
 func (m Metrics) MeasureSince(start time.Time, keys ...string) {
 	metrics.MeasureSinceWithLabels(keys, start.UTC(), m.Labels)
 }
+
+// NoOpMetrics is a no-op implementation of the StoreMetrics interface
+type NoOpMetrics struct{}
+
+// NewNoOpMetrics returns a new instance of the NoOpMetrics
+func NewNoOpMetrics() NoOpMetrics {
+	return NoOpMetrics{}
+}
+
+// MeasureSince is a no-op implementation of the StoreMetrics interface to avoid time.Now() calls
+func (m NoOpMetrics) MeasureSince(start time.Time, keys ...string) {}

store/v2/root/factory.go

@@ -12,6 +12,7 @@ import (
 	"cosmossdk.io/store/v2/commitment/mem"
 	"cosmossdk.io/store/v2/db"
 	"cosmossdk.io/store/v2/internal"
+	"cosmossdk.io/store/v2/metrics"
 	"cosmossdk.io/store/v2/pruning"
 )
 
@@ -127,5 +128,5 @@ func CreateRootStore(opts *FactoryOptions) (store.RootStore, error) {
 	}
 
 	pm := pruning.NewManager(sc, storeOpts.SCPruningOption)
-	return New(opts.SCRawDB, opts.Logger, sc, pm, nil, nil)
+	return New(opts.SCRawDB, opts.Logger, sc, pm, nil, metrics.NoOpMetrics{})
 }