feat(spanner): client built in metrics

spanner/client.go

@@ -350,6 +350,12 @@ type ClientConfig struct {
 	//
 	// Default: false
 	EnableEndToEndTracing bool
+
+	// DisableNativeMetrics indicates whether native metrics should be disabled or not.
+	// If true, native metrics will not be emitted.
+	//
+	// Default: false
+	DisableNativeMetrics bool
 }
 
 type openTelemetryConfig struct {
@@ -493,13 +499,8 @@ func newClientWithConfig(ctx context.Context, database string, config ClientConf
 		// Do not emit native metrics when emulator is being used
 		metricsProvider = noop.NewMeterProvider()
 	}
-
-	// SPANNER_ENABLE_BUILTIN_METRICS environment variable is used to enable
-	// native metrics for the Spanner client, which overrides the default.
-	//
-	// This is an EXPERIMENTAL feature and may be changed or removed in the future.
-	if os.Getenv("SPANNER_ENABLE_BUILTIN_METRICS") != "true" {
-		// Do not emit native metrics when SPANNER_ENABLE_BUILTIN_METRICS is not set to true
+	if config.DisableNativeMetrics {
+		// Do not emit native metrics when DisableNativeMetrics is set
 		metricsProvider = noop.NewMeterProvider()
 	}
 

spanner/metrics_test.go

@@ -19,7 +19,6 @@ package spanner
 import (
 	"context"
 	"fmt"
-	"os"
 	"sort"
 	"testing"
 
@@ -39,8 +38,6 @@ import (
 )
 
 func TestNewBuiltinMetricsTracerFactory(t *testing.T) {
-	os.Setenv("SPANNER_ENABLE_BUILTIN_METRICS", "true")
-	defer os.Unsetenv("SPANNER_ENABLE_BUILTIN_METRICS")
 	ctx := context.Background()
 	clientUID := "test-uid"
 	createSessionRPC := "Spanner.BatchCreateSessions"