refactored and added tests

.travis.yml

@@ -0,0 +1,20 @@
+language: go
+
+go:
+  - 1.12.x
+
+script:
+  # build test for supported platforms
+  - GOOS=linux go build
+  - GOOS=darwin go build
+  - GOOS=freebsd go build
+  - GOOS=windows go build
+  - GOARCH=386 go build
+
+  # run tests on a standard platform
+  - go test -v ./... -coverprofile=coverage.txt -covermode=atomic
+  - go test -v ./... -race
+
+after_success:
+  # Upload coverage results to codecov.io
+  - bash <(curl -s https://codecov.io/bash)

README.md

@@ -1,5 +1,7 @@
+[![Build Status](https://travis-ci.org/VictoriaMetrics/metrics.svg)](https://travis-ci.org/VictoriaMetrics/metrics)
 [![GoDoc](https://godoc.org/github.com/VictoriaMetrics/metrics?status.svg)](http://godoc.org/github.com/VictoriaMetrics/metrics)
 [![Go Report](https://goreportcard.com/badge/github.com/VictoriaMetrics/metrics)](https://goreportcard.com/report/github.com/VictoriaMetrics/metrics)
+[![codecov](https://codecov.io/gh/VictoriaMetrics/metrics/branch/master/graph/badge.svg)](https://codecov.io/gh/VictoriaMetrics/metrics)
 
 # metrics - lightweight package for exporting metrics in Prometheus format
 
@@ -76,3 +78,9 @@ Because the `github.com/prometheus/client_golang` is too complex and is hard to
 Because this documentation is ignored by Prometheus. The documentation is for users.
 Just add comments in the source code or in other suitable place explaining each metric
 exposed from your application.
+
+
+#### How to implement [CounterVec](https://godoc.org/github.com/prometheus/client_golang/prometheus#CounterVec) in `metrics`?
+
+Just use [GetOrCreateCounter](http://godoc.org/github.com/VictoriaMetrics/metrics#GetOrCreateCounter)
+instead of `CounterVec.With`.

counter.go

@@ -0,0 +1,105 @@
+package metrics
+
+import (
+	"fmt"
+	"io"
+	"sync/atomic"
+)
+
+// NewCounter registers and returns new counter with the given name.
+//
+// name must be valid Prometheus-compatible metric with possible lables.
+// For instance,
+//
+//     * foo
+//     * foo{bar="baz"}
+//     * foo{bar="baz",aaa="b"}
+//
+// The returned counter is safe to use from concurrent goroutines.
+func NewCounter(name string) *Counter {
+	c := &Counter{}
+	registerMetric(name, c)
+	return c
+}
+
+// Counter is a counter.
+//
+// It may be used as a gauge if Dec and Set are called.
+type Counter struct {
+	n uint64
+}
+
+// Inc increments c.
+func (c *Counter) Inc() {
+	atomic.AddUint64(&c.n, 1)
+}
+
+// Dec decrements c.
+func (c *Counter) Dec() {
+	atomic.AddUint64(&c.n, ^uint64(0))
+}
+
+// Add adds n to c.
+func (c *Counter) Add(n int) {
+	atomic.AddUint64(&c.n, uint64(n))
+}
+
+// Get returns the current value for c.
+func (c *Counter) Get() uint64 {
+	return atomic.LoadUint64(&c.n)
+}
+
+// Set sets c value to n.
+func (c *Counter) Set(n uint64) {
+	atomic.StoreUint64(&c.n, n)
+}
+
+// marshalTo marshals c with the given prefix to w.
+func (c *Counter) marshalTo(prefix string, w io.Writer) {
+	v := c.Get()
+	fmt.Fprintf(w, "%s %d\n", prefix, v)
+}
+
+// GetOrCreateCounter returns registered counter with the given name
+// or creates new counter if the registry doesn't contain counter with
+// the given name.
+//
+// name must be valid Prometheus-compatible metric with possible lables.
+// For instance,
+//
+//     * foo
+//     * foo{bar="baz"}
+//     * foo{bar="baz",aaa="b"}
+//
+// The returned counter is safe to use from concurrent goroutines.
+//
+// Performance tip: prefer NewCounter instead of GetOrCreateCounter.
+func GetOrCreateCounter(name string) *Counter {
+	metricsMapLock.Lock()
+	nm := metricsMap[name]
+	metricsMapLock.Unlock()
+	if nm == nil {
+		// Slow path - create and register missing counter.
+		if err := validateMetric(name); err != nil {
+			panic(fmt.Errorf("BUG: invalid metric name %q: %s", name, err))
+		}
+		nmNew := &namedMetric{
+			name:   name,
+			metric: &Counter{},
+		}
+		metricsMapLock.Lock()
+		nm = metricsMap[name]
+		if nm == nil {
+			nm = nmNew
+			metricsMap[name] = nm
+			metricsList = append(metricsList, nm)
+		}
+		metricsMapLock.Unlock()
+	}
+
+	c, ok := nm.metric.(*Counter)
+	if !ok {
+		panic(fmt.Errorf("BUG: metric %q isn't a Counter. It is %T", name, nm.metric))
+	}
+	return c
+}

counter_test.go

@@ -0,0 +1,76 @@
+package metrics
+
+import (
+	"fmt"
+	"testing"
+)
+
+func TestCounterSerial(t *testing.T) {
+	name := "CounterSerial"
+	c := NewCounter(name)
+	c.Inc()
+	if n := c.Get(); n != 1 {
+		t.Fatalf("unexpected counter value; got %d; want 1", n)
+	}
+	c.Set(123)
+	if n := c.Get(); n != 123 {
+		t.Fatalf("unexpected counter value; got %d; want 123", n)
+	}
+	c.Dec()
+	if n := c.Get(); n != 122 {
+		t.Fatalf("unexpected counter value; got %d; want 122", n)
+	}
+	c.Add(3)
+	if n := c.Get(); n != 125 {
+		t.Fatalf("unexpected counter value; got %d; want 125", n)
+	}
+
+	// Verify MarshalTo
+	testMarshalTo(t, c, "foobar", "foobar 125\n")
+}
+
+func TestCounterConcurrent(t *testing.T) {
+	name := "CounterConcurrent"
+	c := NewCounter(name)
+	err := testConcurrent(func() error {
+		nPrev := c.Get()
+		for i := 0; i < 10; i++ {
+			c.Inc()
+			if n := c.Get(); n <= nPrev {
+				return fmt.Errorf("counter value must be greater than %d; got %d", nPrev, n)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGetOrCreateCounterSerial(t *testing.T) {
+	name := "GetOrCreateCounterSerial"
+	if err := testGetOrCreateCounter(name); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestGetOrCreateCounterConcurrent(t *testing.T) {
+	name := "GetOrCreateCounterConcurrent"
+	err := testConcurrent(func() error {
+		return testGetOrCreateCounter(name)
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func testGetOrCreateCounter(name string) error {
+	c1 := GetOrCreateCounter(name)
+	for i := 0; i < 10; i++ {
+		c2 := GetOrCreateCounter(name)
+		if c1 != c2 {
+			return fmt.Errorf("unexpected counter returned; got %p; want %p", c2, c1)
+		}
+	}
+	return nil
+}

gauge.go

@@ -0,0 +1,47 @@
+package metrics
+
+import (
+	"fmt"
+	"io"
+)
+
+// NewGauge registers and returns gauge with the given name, which calls f
+// to obtain gauge value.
+//
+// name must be valid Prometheus-compatible metric with possible labels.
+// For instance,
+//
+//     * foo
+//     * foo{bar="baz"}
+//     * foo{bar="baz",aaa="b"}
+//
+// f must be safe for concurrent calls.
+//
+// The returned gauge is safe to use from concurrent goroutines.
+func NewGauge(name string, f func() float64) *Gauge {
+	g := &Gauge{
+		f: f,
+	}
+	registerMetric(name, g)
+	return g
+}
+
+// Gauge is a float64 gauge.
+type Gauge struct {
+	f func() float64
+}
+
+// Get returns the current value for g.
+func (g *Gauge) Get() float64 {
+	return g.f()
+}
+
+func (g *Gauge) marshalTo(prefix string, w io.Writer) {
+	v := g.f()
+	if float64(int64(v)) == v {
+		// Marshal integer values without scientific notations
+		fmt.Fprintf(w, "%s %d\n", prefix, int64(v))
+	} else {
+		fmt.Fprintf(w, "%s %g\n", prefix, v)
+	}
+}

gauge_test.go

@@ -0,0 +1,55 @@
+package metrics
+
+import (
+	"fmt"
+	"sync"
+	"testing"
+)
+
+func TestGaugeSerial(t *testing.T) {
+	name := "GaugeSerial"
+	n := 1.23
+	var nLock sync.Mutex
+	g := NewGauge(name, func() float64 {
+		nLock.Lock()
+		defer nLock.Unlock()
+		n++
+		return n
+	})
+	for i := 0; i < 10; i++ {
+		if nn := g.Get(); nn != n {
+			t.Fatalf("unexpected gauge value; got %v; want %v", nn, n)
+		}
+	}
+
+	// Verify marshalTo
+	testMarshalTo(t, g, "foobar", "foobar 12.23\n")
+
+	// Verify big numbers marshaling
+	n = 1234567899
+	testMarshalTo(t, g, "prefix", "prefix 1234567900\n")
+}
+
+func TestGaugeConcurrent(t *testing.T) {
+	name := "GaugeConcurrent"
+	var n int
+	var nLock sync.Mutex
+	g := NewGauge(name, func() float64 {
+		nLock.Lock()
+		defer nLock.Unlock()
+		n++
+		return float64(n)
+	})
+	err := testConcurrent(func() error {
+		nPrev := g.Get()
+		for i := 0; i < 10; i++ {
+			if n := g.Get(); n <= nPrev {
+				return fmt.Errorf("gauge value must be greater than %v; got %v", nPrev, n)
+			}
+		}
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}

metrics.go

@@ -16,103 +16,15 @@ import (
 	"runtime"
 	"sort"
 	"sync"
-	"sync/atomic"
 	"time"
 
 	"github.com/valyala/histogram"
 )
 
-// NewGauge registers and returns gauge with the given name, which calls f
-// to obtain gauge value.
-//
-// name must be valid Prometheus-compatible metric with possible labels.
-// For instance,
-//
-//     * foo
-//     * foo{bar="baz"}
-//     * foo{bar="baz",aaa="b"}
-//
-// f must be safe for concurrent calls.
-func NewGauge(name string, f func() float64) *Gauge {
-	g := &Gauge{
-		f: f,
-	}
-	registerMetric(name, g)
-	return g
-}
-
-// Gauge is a float64 gauge.
-type Gauge struct {
-	f func() float64
-}
-
-// Get returns the current value for g.
-func (g *Gauge) Get() float64 {
-	return g.f()
-}
-
-func (g *Gauge) marshalTo(prefix string, w io.Writer) {
-	v := g.f()
-	fmt.Fprintf(w, "%s %g\n", prefix, v)
-}
-
-// NewCounter registers and returns new counter with the given name.
-//
-// name must be valid Prometheus-compatible metric with possible lables.
-// For instance,
-//
-//     * foo
-//     * foo{bar="baz"}
-//     * foo{bar="baz",aaa="b"}
-//
-// The returned counter is safe to use from concurrent goroutines.
-func NewCounter(name string) *Counter {
-	c := &Counter{}
-	registerMetric(name, c)
-	return c
-}
-
-// Counter is a counter.
-//
-// It may be used as a gauge if Dec and Set are called.
-type Counter struct {
-	n uint64
-}
-
-// Inc increments c.
-func (c *Counter) Inc() {
-	atomic.AddUint64(&c.n, 1)
-}
-
-// Dec decrements c.
-func (c *Counter) Dec() {
-	atomic.AddUint64(&c.n, ^uint64(0))
-}
-
-// Add adds n to c.
-func (c *Counter) Add(n int) {
-	atomic.AddUint64(&c.n, uint64(n))
-}
-
-// Get returns the current value for c.
-func (c *Counter) Get() uint64 {
-	return atomic.LoadUint64(&c.n)
-}
-
-// Set sets c value to n.
-func (c *Counter) Set(n uint64) {
-	atomic.StoreUint64(&c.n, n)
-}
-
-// marshalTo marshals c with the given prefix to w.
-func (c *Counter) marshalTo(prefix string, w io.Writer) {
-	v := c.Get()
-	fmt.Fprintf(w, "%s %d\n", prefix, v)
-}
-
 var (
 	metricsMapLock sync.Mutex
-	metricsMap     []namedMetric
+	metricsList    []*namedMetric
+	metricsMap     = make(map[string]*namedMetric)
 )
 
 type namedMetric struct {
@@ -120,24 +32,6 @@ type namedMetric struct {
 	metric metric
 }
 
-func isRegisteredMetric(mm []namedMetric, name string) bool {
-	for _, nm := range mm {
-		if nm.name == name {
-			return true
-		}
-	}
-	return false
-}
-
-func sortMetrics(mm []namedMetric) {
-	lessFunc := func(i, j int) bool {
-		return mm[i].name < mm[j].name
-	}
-	if !sort.SliceIsSorted(mm, lessFunc) {
-		sort.Slice(mm, lessFunc)
-	}
-}
-
 type metric interface {
 	marshalTo(prefix string, w io.Writer)
 }
@@ -154,19 +48,23 @@ type metric interface {
 //     })
 //
 func WritePrometheus(w io.Writer, exposeProcessMetrics bool) {
-	// Export user-defined metrics.
+	lessFunc := func(i, j int) bool {
+		return metricsList[i].name < metricsList[j].name
+	}
 	metricsMapLock.Lock()
-	sortMetrics(metricsMap)
+	if !sort.SliceIsSorted(metricsList, lessFunc) {
-	for _, nm := range metricsMap {
+		sort.Slice(metricsList, lessFunc)
+	}
+	for _, nm := range metricsList {
 		nm.metric.marshalTo(nm.name, w)
 	}
 	metricsMapLock.Unlock()
-
+	if exposeProcessMetrics {
-	if !exposeProcessMetrics {
+		writeProcessMetrics(w)
-		return
+	}
 }
 
-	// Export memory stats.
+func writeProcessMetrics(w io.Writer) {
 	var ms runtime.MemStats
 	runtime.ReadMemStats(&ms)
 	fmt.Fprintf(w, `go_memstats_alloc_bytes %d`+"\n", ms.Alloc)
@@ -225,21 +123,20 @@ var startTime = time.Now()
 
 func registerMetric(name string, m metric) {
 	if err := validateMetric(name); err != nil {
-		// Do not use logger.Panicf here, since it may be uninitialized yet.
 		panic(fmt.Errorf("BUG: invalid metric name %q: %s", name, err))
 	}
 	metricsMapLock.Lock()
-	ok := isRegisteredMetric(metricsMap, name)
+	nm, ok := metricsMap[name]
 	if !ok {
-		nm := namedMetric{
+		nm = &namedMetric{
 			name:   name,
 			metric: m,
 		}
-		metricsMap = append(metricsMap, nm)
+		metricsMap[name] = nm
+		metricsList = append(metricsList, nm)
 	}
 	metricsMapLock.Unlock()
 	if ok {
-		// Do not use logger.Panicf here, since it may be uninitialized yet.
+		panic(fmt.Errorf("BUG: metric %q is already registered", name))
-		panic(fmt.Errorf("BUG: metric with name %q is already registered", name))
 	}
 }

metrics_test.go

@@ -0,0 +1,119 @@
+package metrics
+
+import (
+	"bytes"
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestInvalidName(t *testing.T) {
+	f := func(name string) {
+		t.Helper()
+		expectPanic(t, fmt.Sprintf("NewCounter(%q)", name), func() { NewCounter(name) })
+		expectPanic(t, fmt.Sprintf("GetOrCreateCounter(%q)", name), func() { GetOrCreateCounter(name) })
+		expectPanic(t, fmt.Sprintf("NewGauge(%q)", name), func() { NewGauge(name, func() float64 { return 0 }) })
+		expectPanic(t, fmt.Sprintf("NewSummary(%q)", name), func() { NewSummary(name) })
+	}
+	f("")
+	f("foo{")
+	f("foo}")
+	f("foo{bar")
+	f("foo{bar=")
+	f(`foo{bar="`)
+	f(`foo{bar="baz`)
+	f(`foo{bar="baz"`)
+	f(`foo{bar="baz",`)
+	f(`foo{bar="baz",}`)
+}
+
+func TestDoubleRegister(t *testing.T) {
+	t.Run("NewCounter", func(t *testing.T) {
+		name := "NewCounterDoubleRegister"
+		NewCounter(name)
+		expectPanic(t, name, func() { NewCounter(name) })
+	})
+	t.Run("NewGauge", func(t *testing.T) {
+		name := "NewGaugeDoubleRegister"
+		NewGauge(name, func() float64 { return 0 })
+		expectPanic(t, name, func() { NewGauge(name, func() float64 { return 0 }) })
+	})
+	t.Run("NewSummary", func(t *testing.T) {
+		name := "NewSummaryDoubleRegister"
+		NewSummary(name)
+		expectPanic(t, name, func() { NewSummary(name) })
+	})
+}
+
+func TestGetOrCreateNotCounter(t *testing.T) {
+	name := "GetOrCreateNotCounter"
+	NewSummary(name)
+	expectPanic(t, name, func() { GetOrCreateCounter(name) })
+}
+
+func TestWritePrometheusSerial(t *testing.T) {
+	if err := testWritePrometheus(); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestWritePrometheusConcurrent(t *testing.T) {
+	if err := testConcurrent(testWritePrometheus); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func testWritePrometheus() error {
+	var bb bytes.Buffer
+	WritePrometheus(&bb, false)
+	resultWithoutProcessMetrics := bb.String()
+	bb.Reset()
+	WritePrometheus(&bb, true)
+	resultWithProcessMetrics := bb.String()
+	if len(resultWithProcessMetrics) <= len(resultWithoutProcessMetrics) {
+		return fmt.Errorf("result with process metrics must contain more data than the result without process metrics; got\n%q\nvs\n%q",
+			resultWithProcessMetrics, resultWithoutProcessMetrics)
+	}
+	return nil
+}
+
+func expectPanic(t *testing.T, context string, f func()) {
+	t.Helper()
+	defer func() {
+		if r := recover(); r == nil {
+			t.Fatalf("expecting panic in %s", context)
+		}
+	}()
+	f()
+}
+
+func testConcurrent(f func() error) error {
+	const concurrency = 5
+	resultsCh := make(chan error, concurrency)
+	for i := 0; i < concurrency; i++ {
+		go func() {
+			resultsCh <- f()
+		}()
+	}
+	for i := 0; i < concurrency; i++ {
+		select {
+		case err := <-resultsCh:
+			if err != nil {
+				return fmt.Errorf("unexpected error: %s", err)
+			}
+		case <-time.After(time.Second * 5):
+			return fmt.Errorf("timeout")
+		}
+	}
+	return nil
+}
+
+func testMarshalTo(t *testing.T, m metric, prefix, resultExpected string) {
+	t.Helper()
+	var bb bytes.Buffer
+	m.marshalTo(prefix, &bb)
+	result := bb.String()
+	if result != resultExpected {
+		t.Fatalf("unexpected marshaled metric; got %q; want %q", result, resultExpected)
+	}
+}

summary.go

@@ -3,6 +3,7 @@ package metrics
 import (
 	"fmt"
 	"io"
+	"math"
 	"sync"
 	"time"
 
@@ -50,6 +51,7 @@ func NewSummary(name string) *Summary {
 //
 // The returned summary is safe to use from concurrent goroutines.
 func NewSummaryExt(name string, window time.Duration, quantiles []float64) *Summary {
+	validateQuantiles(quantiles)
 	s := &Summary{
 		curr:           histogram.NewFast(),
 		next:           histogram.NewFast(),
@@ -57,7 +59,7 @@ func NewSummaryExt(name string, window time.Duration, quantiles []float64) *Summ
 		quantileValues: make([]float64, len(quantiles)),
 	}
 	registerSummary(s, window)
-	registerMetric(fmt.Sprintf("\x00%s", name), s)
+	registerMetric(name, s)
 	for i, q := range quantiles {
 		quantileValueName := addTag(name, fmt.Sprintf(`quantile="%g"`, q))
 		qv := &quantileValue{
@@ -69,6 +71,14 @@ func NewSummaryExt(name string, window time.Duration, quantiles []float64) *Summ
 	return s
 }
 
+func validateQuantiles(quantiles []float64) {
+	for _, q := range quantiles {
+		if q < 0 || q > 1 {
+			panic(fmt.Errorf("BUG: quantile must be in the range [0..1]; got %v", q))
+		}
+	}
+}
+
 // Update updates the summary.
 func (s *Summary) Update(v float64) {
 	s.mu.Lock()
@@ -104,8 +114,10 @@ func (qv *quantileValue) marshalTo(prefix string, w io.Writer) {
 	qv.s.mu.Lock()
 	v := qv.s.quantileValues[qv.idx]
 	qv.s.mu.Unlock()
+	if !math.IsNaN(v) {
 		fmt.Fprintf(w, "%s %g\n", prefix, v)
 	}
+}
 
 func addTag(name, tag string) string {
 	if len(name) == 0 || name[len(name)-1] != '}' {

summary_test.go

@@ -0,0 +1,101 @@
+package metrics
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+	"time"
+)
+
+func TestSummarySerial(t *testing.T) {
+	name := `TestSummarySerial`
+	s := NewSummary(name)
+
+	// Verify that the summary isn't visible in the output of WritePrometheus,
+	// since it doesn't contain any values yet.
+	var bb bytes.Buffer
+	WritePrometheus(&bb, false)
+	result := bb.String()
+	if strings.Contains(result, name) {
+		t.Fatalf("summary %s shouldn't be visible in the WritePrometheus output; got\n%s", name, result)
+	}
+
+	// Write data to summary
+	for i := 0; i < 2000; i++ {
+		s.Update(float64(i))
+		t := time.Now()
+		s.UpdateDuration(t.Add(-time.Millisecond * time.Duration(i)))
+	}
+
+	// Make sure the summary doesn't print anything on marshalTo call
+	// and updates s.quantileValues.
+	testMarshalTo(t, s, "prefix", "")
+
+	// Verify s.quantileValues
+	if s.quantileValues[len(s.quantileValues)-1] != 1999 {
+		t.Fatalf("unexpected quantileValues[last]; got %v; want %v", s.quantileValues[len(s.quantileValues)-1], 1999)
+	}
+
+	// Make sure the summary becomes visible in the output of WritePrometheus,
+	// since now it contains values.
+	bb.Reset()
+	WritePrometheus(&bb, false)
+	result = bb.String()
+	if !strings.Contains(result, name) {
+		t.Fatalf("missing summary %s in the WritePrometheus output; got\n%s", name, result)
+	}
+}
+
+func TestSummaryConcurrent(t *testing.T) {
+	name := "SummaryConcurrent"
+	s := NewSummary(name)
+	err := testConcurrent(func() error {
+		for i := 0; i < 10; i++ {
+			s.Update(float64(i))
+		}
+		testMarshalTo(t, s, "prefix", "")
+		return nil
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestSummaryWithTags(t *testing.T) {
+	name := `TestSummary{tag="foo"}`
+	s := NewSummary(name)
+	s.Update(123)
+
+	var bb bytes.Buffer
+	WritePrometheus(&bb, false)
+	result := bb.String()
+	namePrefixWithTag := `TestSummary{tag="foo",quantile="`
+	if !strings.Contains(result, namePrefixWithTag) {
+		t.Fatalf("missing summary prefix %s in the WritePrometheus output; got\n%s", namePrefixWithTag, result)
+	}
+}
+
+func TestSummaryInvalidQuantiles(t *testing.T) {
+	name := "SummaryInvalidQuantiles"
+	expectPanic(t, name, func() {
+		NewSummaryExt(name, time.Minute, []float64{123, -234})
+	})
+}
+
+func TestSummarySmallWindow(t *testing.T) {
+	name := "SummarySmallWindow"
+	window := time.Millisecond * 20
+	quantiles := []float64{0.1, 0.2, 0.3}
+	s := NewSummaryExt(name, window, quantiles)
+	for i := 0; i < 2000; i++ {
+		s.Update(123)
+	}
+	// Wait for window update and verify that the summary has been cleared.
+	time.Sleep(5 * window)
+	var bb bytes.Buffer
+	WritePrometheus(&bb, false)
+	result := bb.String()
+	if strings.Contains(result, name) {
+		t.Fatalf("summary %s cannot be present in the WritePrometheus output; got\n%s", name, result)
+	}
+}

validator.go

@@ -10,10 +10,6 @@ func validateMetric(s string) error {
 	if len(s) == 0 {
 		return fmt.Errorf("metric cannot be empty")
 	}
-	if s[0] == 0 {
-		// Skip special case metrics. See Histogram for details.
-		return nil
-	}
 	n := strings.IndexByte(s, '{')
 	if n < 0 {
 		return validateIdent(s)
@@ -67,10 +63,17 @@ func validateTags(s string) error {
 		if !strings.HasPrefix(s, ",") {
 			return fmt.Errorf("missing `,` after %q value; tail=%q", ident, s)
 		}
-		s = s[2:]
+		s = skipSpace(s[1:])
 	}
 }
 
+func skipSpace(s string) string {
+	for len(s) > 0 && s[0] == ' ' {
+		s = s[1:]
+	}
+	return s
+}
+
 func validateIdent(s string) error {
 	if !identRegexp.MatchString(s) {
 		return fmt.Errorf("invalid identifier %q", s)

validator_test.go

@@ -17,6 +17,7 @@ func TestValidateMetricSuccess(t *testing.T) {
 	f(`a{foo="bar"}`)
 	f(`foo{bar="baz", x="y\"z"}`)
 	f(`foo{bar="b}az"}`)
+	f(`:foo:bar{bar="a",baz="b"}`)
 }
 
 func TestValidateMetricError(t *testing.T) {
@@ -41,7 +42,6 @@ func TestValidateMetricError(t *testing.T) {
 	f(`a{foo= "bar"}`)
 	f(`a{foo="bar" }`)
 	f(`a{foo="bar" ,baz="a"}`)
-	f(`a{foo="bar" ,baz="a"}`)
 
 	// invalid tags
 	f("a{foo}")