Added removal methods.

Closes #5.

Author: codahale

metrics.go

@@ -77,6 +77,19 @@ func (c Counter) SetBatchFunc(key interface{}, init func(), f func() uint64) {
 	}
 }
 
+// Remove removes the given counter.
+func (c Counter) Remove() {
+	cm.Lock()
+	defer cm.Unlock()
+
+	gm.Lock()
+	defer gm.Unlock()
+
+	delete(counters, string(c))
+	delete(counterFuncs, string(c))
+	delete(inits, string(c))
+}
+
 // A Gauge is an instantaneous measurement of a value.
 //
 // Use a gauge to track metrics which increase and decrease (e.g., amount of
@@ -115,6 +128,15 @@ func (g Gauge) SetBatchFunc(key interface{}, init func(), f func() int64) {
 	}
 }
 
+// Remove removes the given counter.
+func (g Gauge) Remove() {
+	gm.Lock()
+	defer gm.Unlock()
+
+	delete(gauges, string(g))
+	delete(inits, string(g))
+}
+
 // Reset removes all existing counters and gauges.
 func Reset() {
 	cm.Lock()
@@ -179,6 +201,7 @@ func NewHistogram(name string, minValue, maxValue int64, sigfigs int) *Histogram
 	}
 
 	hist := &Histogram{
+		name: name,
 		hist: hdrhistogram.NewWindowed(5, minValue, maxValue, sigfigs),
 		name: name,
 	}
@@ -194,10 +217,27 @@ func NewHistogram(name string, minValue, maxValue int64, sigfigs int) *Histogram
 	return hist
 }
 
+// Remove removes the given histogram.
+func (h *Histogram) Remove() {
+
+	hm.Lock()
+	defer hm.Unlock()
+
+	Gauge(h.name + ".P50").Remove()
+	Gauge(h.name + ".P75").Remove()
+	Gauge(h.name + ".P90").Remove()
+	Gauge(h.name + ".P95").Remove()
+	Gauge(h.name + ".P99").Remove()
+	Gauge(h.name + ".P999").Remove()
+
+	delete(histograms, h.name)
+}
+
 type hname string // unexported to prevent collisions
 
 // A Histogram measures the distribution of a stream of values.
 type Histogram struct {
+	name string
 	hist *hdrhistogram.WindowedHistogram
 	m    *hdrhistogram.Histogram
 	rw   sync.RWMutex

metrics_test.go

@@ -66,6 +66,18 @@ func TestCounterBatchFunc(t *testing.T) {
 	}
 }
 
+func TestCounterRemove(t *testing.T) {
+	metrics.Reset()
+
+	metrics.Counter("whee").Add()
+	metrics.Counter("whee").Remove()
+
+	counters, _ := metrics.Snapshot()
+	if v, ok := counters["whee"]; ok {
+		t.Errorf("Counter was %v, but expected nothing", v)
+	}
+}
+
 func TestGaugeValue(t *testing.T) {
 	metrics.Reset()
 
@@ -90,6 +102,18 @@ func TestGaugeFunc(t *testing.T) {
 	}
 }
 
+func TestGaugeRemove(t *testing.T) {
+	metrics.Reset()
+
+	metrics.Gauge("whee").Set(1)
+	metrics.Gauge("whee").Remove()
+
+	_, gauges := metrics.Snapshot()
+	if v, ok := gauges["whee"]; ok {
+		t.Errorf("Gauge was %v, but expected nothing", v)
+	}
+}
+
 func TestHistogram(t *testing.T) {
 	metrics.Reset()
 
@@ -127,6 +151,18 @@ func TestHistogram(t *testing.T) {
 	}
 }
 
+func TestHistogramRemove(t *testing.T) {
+	metrics.Reset()
+
+	h := metrics.NewHistogram("heyo", 1, 1000, 3)
+	h.Remove()
+
+	_, gauges := metrics.Snapshot()
+	if v, ok := gauges["heyo.P50"]; ok {
+		t.Errorf("Gauge was %v, but expected nothing", v)
+	}
+}
+
 func BenchmarkCounterAdd(b *testing.B) {
 	metrics.Reset()