feat(metric): added Dec() and Sub() in GaugeVec interface (#3666)

core/metric/gauge.go

@@ -16,8 +16,12 @@ type (
 		Set(v float64, labels ...string)
 		// Inc increments labels.
 		Inc(labels ...string)
+		// Dec decrements labels.
+		Dec(labels ...string)
 		// Add adds v to labels.
 		Add(v float64, labels ...string)
+		// Sub subtracts v to labels.
+		Sub(v float64, labels ...string)
 		close() bool
 	}
 
@@ -50,6 +54,14 @@ func NewGaugeVec(cfg *GaugeVecOpts) GaugeVec {
 	return gv
 }
 
+func (gv *promGaugeVec) Set(v float64, labels ...string) {
+	if !prometheus.Enabled() {
+		return
+	}
+
+	gv.gauge.WithLabelValues(labels...).Set(v)
+}
+
 func (gv *promGaugeVec) Inc(labels ...string) {
 	if !prometheus.Enabled() {
 		return
@@ -58,6 +70,13 @@ func (gv *promGaugeVec) Inc(labels ...string) {
 	gv.gauge.WithLabelValues(labels...).Inc()
 }
 
+func (gv *promGaugeVec) Dec(labels ...string) {
+	if !prometheus.Enabled() {
+		return
+	}
+	gv.gauge.WithLabelValues(labels...).Dec()
+}
+
 func (gv *promGaugeVec) Add(v float64, labels ...string) {
 	if !prometheus.Enabled() {
 		return
@@ -66,12 +85,11 @@ func (gv *promGaugeVec) Add(v float64, labels ...string) {
 	gv.gauge.WithLabelValues(labels...).Add(v)
 }
 
-func (gv *promGaugeVec) Set(v float64, labels ...string) {
+func (gv *promGaugeVec) Sub(v float64, labels ...string) {
 	if !prometheus.Enabled() {
 		return
 	}
-
-	gv.gauge.WithLabelValues(labels...).Set(v)
+	gv.gauge.WithLabelValues(labels...).Sub(v)
 }
 
 func (gv *promGaugeVec) close() bool {

core/metric/gauge_test.go

@@ -40,6 +40,23 @@ func TestGaugeInc(t *testing.T) {
 	assert.Equal(t, float64(2), r)
 }
 
+func TestGaugeDec(t *testing.T) {
+	startAgent()
+	gaugeVec := NewGaugeVec(&GaugeVecOpts{
+		Namespace: "rpc_client",
+		Subsystem: "requests",
+		Name:      "duration_ms",
+		Help:      "rpc server requests duration(ms).",
+		Labels:    []string{"path"},
+	})
+	defer gaugeVec.close()
+	gv, _ := gaugeVec.(*promGaugeVec)
+	gv.Dec("/users")
+	gv.Dec("/users")
+	r := testutil.ToFloat64(gv.gauge)
+	assert.Equal(t, float64(-2), r)
+}
+
 func TestGaugeAdd(t *testing.T) {
 	startAgent()
 	gaugeVec := NewGaugeVec(&GaugeVecOpts{
@@ -57,6 +74,23 @@ func TestGaugeAdd(t *testing.T) {
 	assert.Equal(t, float64(20), r)
 }
 
+func TestGaugeSub(t *testing.T) {
+	startAgent()
+	gaugeVec := NewGaugeVec(&GaugeVecOpts{
+		Namespace: "rpc_client",
+		Subsystem: "request",
+		Name:      "duration_ms",
+		Help:      "rpc server requests duration(ms).",
+		Labels:    []string{"path"},
+	})
+	defer gaugeVec.close()
+	gv, _ := gaugeVec.(*promGaugeVec)
+	gv.Sub(-100, "/classroom")
+	gv.Sub(30, "/classroom")
+	r := testutil.ToFloat64(gv.gauge)
+	assert.Equal(t, float64(70), r)
+}
+
 func TestGaugeSet(t *testing.T) {
 	startAgent()
 	gaugeVec := NewGaugeVec(&GaugeVecOpts{