metrics: add label type in metrics package

metrics/exp/exp.go

@@ -95,6 +95,20 @@ func (exp *exp) getFloat(name string) *expvar.Float {
 	return v
 }
 
+func (exp *exp) getMap(name string) *expvar.Map {
+	var v *expvar.Map
+	exp.expvarLock.Lock()
+	p := expvar.Get(name)
+	if p != nil {
+		v = p.(*expvar.Map)
+	} else {
+		v = new(expvar.Map)
+		expvar.Publish(name, v)
+	}
+	exp.expvarLock.Unlock()
+	return v
+}
+
 func (exp *exp) publishCounter(name string, metric metrics.Counter) {
 	v := exp.getInt(name)
 	v.Set(metric.Count())
@@ -162,6 +176,60 @@ func (exp *exp) publishResettingTimer(name string, metric metrics.ResettingTimer
 	exp.getInt(name + ".99-percentile").Set(ps[3])
 }
 
+func (exp *exp) publishLabel(name string, metric metrics.Label) {
+	labels := metric.Value()
+	for k, v := range labels {
+		exp.getMap(name).Set(k, exp.interfaceToExpVal(v))
+	}
+}
+
+func (exp *exp) interfaceToExpVal(v interface{}) expvar.Var {
+	switch i := v.(type) {
+	case string:
+		newV := new(expvar.String)
+		newV.Set(i)
+		return newV
+	case int64:
+		newV := new(expvar.Int)
+		newV.Set(i)
+		return newV
+	case int32:
+		newV := new(expvar.Int)
+		newV.Set(int64(i))
+		return newV
+	case int16:
+		newV := new(expvar.Int)
+		newV.Set(int64(i))
+		return newV
+	case int8:
+		newV := new(expvar.Int)
+		newV.Set(int64(i))
+		return newV
+	case int:
+		newV := new(expvar.Int)
+		newV.Set(int64(i))
+		return newV
+	case float32:
+		newV := new(expvar.Float)
+		newV.Set(float64(i))
+		return newV
+	case float64:
+		newV := new(expvar.Float)
+		newV.Set(i)
+		return newV
+	case map[string]interface{}:
+		newV := new(expvar.Map)
+		for k, v := range i {
+			newV.Set(k, exp.interfaceToExpVal(v))
+		}
+		return newV
+	default:
+		newV := new(expvar.String)
+		newV.Set(fmt.Sprint(v))
+		return newV
+	}
+}
+
 func (exp *exp) syncToExpvar() {
 	exp.registry.Each(func(name string, i interface{}) {
 		switch i := i.(type) {
@@ -179,6 +247,8 @@ func (exp *exp) syncToExpvar() {
 			exp.publishTimer(name, i)
 		case metrics.ResettingTimer:
 			exp.publishResettingTimer(name, i)
+		case metrics.Label:
+			exp.publishLabel(name, i)
 		default:
 			panic(fmt.Sprintf("unsupported type for '%s': %T", name, i))
 		}

metrics/label.go

@@ -0,0 +1,48 @@
+package metrics
+
+import "encoding/json"
+
+// Label hold an map[string]interface{} value that can be set arbitrarily.
+type Label interface {
+	Value() map[string]interface{}
+	String() string
+	Mark(map[string]interface{})
+}
+
+// NewRegisteredLabel constructs and registers a new StandardLabel.
+func NewRegisteredLabel(name string, r Registry) Label {
+	c := NewStandardLabel()
+	if nil == r {
+		r = DefaultRegistry
+	}
+	r.Register(name, c)
+	return c
+}
+
+// NewStandardLabel constructs a new StandardLabel.
+func NewStandardLabel() *StandardLabel {
+	return &StandardLabel{}
+}
+
+// StandardLabel is the standard implementation of a Label.
+type StandardLabel struct {
+	value   map[string]interface{}
+	jsonStr string
+}
+
+// Value returns label values.
+func (l *StandardLabel) Value() map[string]interface{} {
+	return l.value
+}
+
+// Mark records the label.
+func (l *StandardLabel) Mark(value map[string]interface{}) {
+	buf, _ := json.Marshal(value)
+	l.jsonStr = string(buf)
+	l.value = value
+}
+
+// String returns label by JSON format.
+func (l *StandardLabel) String() string {
+	return l.jsonStr
+}

metrics/prometheus/collector.go

@@ -31,6 +31,7 @@ var (
 	typeSummaryTpl         = "# TYPE %s summary\n"
 	keyValueTpl            = "%s %v\n\n"
 	keyQuantileTagValueTpl = "%s {quantile=\"%s\"} %v\n"
+	keyLabelValueTpl       = "%s%s %v\n\n"
 )
 
 // collector is a collection of byte buffers that aggregate Prometheus reports
@@ -98,6 +99,15 @@ func (c *collector) addResettingTimer(name string, m metrics.ResettingTimer) {
 	c.buff.WriteRune('\n')
 }
 
+func (c *collector) addLabel(name string, m metrics.Label) {
+	c.writeLabel(mutateKey(name), m.String())
+}
+
+func (c *collector) writeLabel(name string, value interface{}) {
+	c.buff.WriteString(fmt.Sprintf(typeGaugeTpl, name))
+	c.buff.WriteString(fmt.Sprintf(keyLabelValueTpl, name, value, 1))
+}
+
 func (c *collector) writeGaugeCounter(name string, value interface{}) {
 	name = mutateKey(name)
 	c.buff.WriteString(fmt.Sprintf(typeGaugeTpl, name))

metrics/prometheus/prometheus.go

@@ -57,6 +57,8 @@ func Handler(reg metrics.Registry) http.Handler {
 				c.addTimer(name, m.Snapshot())
 			case metrics.ResettingTimer:
 				c.addResettingTimer(name, m.Snapshot())
+			case metrics.Label:
+				c.addLabel(name, m)
 			default:
 				log.Warn("Unknown Prometheus metric type", "type", fmt.Sprintf("%T", i))
 			}

metrics/registry.go

@@ -196,7 +196,7 @@ func (r *StandardRegistry) register(name string, i interface{}) error {
 		return DuplicateMetric(name)
 	}
 	switch i.(type) {
-	case Counter, Gauge, GaugeFloat64, Healthcheck, Histogram, Meter, Timer, ResettingTimer:
+	case Counter, Gauge, GaugeFloat64, Healthcheck, Histogram, Meter, Timer, ResettingTimer, Label:
 		r.metrics[name] = i
 	}
 	return nil