globalize mongo metrics

multiple calls for options would duplicate/override

cmd/mongo.go

@@ -11,8 +11,8 @@ import (
 	"go.uber.org/zap"
 )
 
-func mongoMonitoredClientOptions(l *zap.Logger) *mongoOpt.ClientOptions {
-	promDbHeartbeat := promauto.NewHistogramVec(prom.HistogramOpts{
+var (
+	promDbHeartbeat = promauto.NewHistogramVec(prom.HistogramOpts{
 		Namespace: PrometheusPrefix,
 		Subsystem: "database",
 		Name:      "heartbeat_time",
@@ -20,7 +20,7 @@ func mongoMonitoredClientOptions(l *zap.Logger) *mongoOpt.ClientOptions {
 		Buckets:   []float64{1},
 	}, []string{"connection_id"})
 
-	promDbCmd := promauto.NewHistogramVec(prom.HistogramOpts{
+	promDbCmd = promauto.NewHistogramVec(prom.HistogramOpts{
 		Namespace: PrometheusPrefix,
 		Subsystem: "database",
 		Name:      "operation_latency", // "command_time",
@@ -28,13 +28,15 @@ func mongoMonitoredClientOptions(l *zap.Logger) *mongoOpt.ClientOptions {
 		Buckets:   []float64{0.1, 0.2, 0.5, 1, 5, 10, 50},
 	}, []string{"connection_id", "command_name"})
 
-	promDbCmdErr := promauto.NewCounterVec(prom.CounterOpts{
+	promDbCmdErr = promauto.NewCounterVec(prom.CounterOpts{
 		Namespace: PrometheusPrefix,
 		Subsystem: "database",
 		Name:      "errors",
 		Help:      "Failed commands (also reflected elsewhere)",
 	}, []string{"connection_id", "command_name"})
+)
 
+func mongoMonitoredClientOptions(l *zap.Logger) *mongoOpt.ClientOptions {
 	return mongoOpt.Client().
 		SetServerMonitor(&mongoEvent.ServerMonitor{
 			ServerHeartbeatSucceeded: func(ev *mongoEvent.ServerHeartbeatSucceededEvent) {