Merge pull request #573 from prometheus/beorn7/fingerprint

The big and scary fingerprint update.

Godeps/Godeps.json

@@ -29,23 +29,23 @@
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/extraction",
-			"Comment": "0.2.0-3-ga6c5e0f",
-			"Rev": "a6c5e0f955686b0e7bbfd791edecfc65aa72593a"
+			"Comment": "0.3.0",
+			"Rev": "dbbb6c9e1dbb3bf19d0f9a61baa852cbfcee1896"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/model",
-			"Comment": "0.2.0-3-ga6c5e0f",
-			"Rev": "a6c5e0f955686b0e7bbfd791edecfc65aa72593a"
+			"Comment": "0.3.0",
+			"Rev": "dbbb6c9e1dbb3bf19d0f9a61baa852cbfcee1896"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/prometheus",
-			"Comment": "0.2.0-3-ga6c5e0f",
-			"Rev": "a6c5e0f955686b0e7bbfd791edecfc65aa72593a"
+			"Comment": "0.3.0",
+			"Rev": "dbbb6c9e1dbb3bf19d0f9a61baa852cbfcee1896"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_golang/text",
-			"Comment": "0.2.0-3-ga6c5e0f",
-			"Rev": "a6c5e0f955686b0e7bbfd791edecfc65aa72593a"
+			"Comment": "0.3.0",
+			"Rev": "dbbb6c9e1dbb3bf19d0f9a61baa852cbfcee1896"
 		},
 		{
 			"ImportPath": "github.com/prometheus/client_model/go",

Godeps/_workspace/src/github.com/prometheus/client_golang/extraction/metricfamilyprocessor.go

@@ -18,9 +18,11 @@ import (
 	"io"
 	"math"
 
-	"github.com/matttproud/golang_protobuf_extensions/ext"
-	"github.com/prometheus/client_golang/model"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/matttproud/golang_protobuf_extensions/ext"
+
+	"github.com/prometheus/client_golang/model"
 )
 
 type metricFamilyProcessor struct{}

Godeps/_workspace/src/github.com/prometheus/client_golang/model/metric.go

@@ -14,10 +14,8 @@
 package model
 
 import (
-	"encoding/binary"
 	"encoding/json"
 	"fmt"
-	"hash/fnv"
 	"sort"
 	"strings"
 )
@@ -66,37 +64,7 @@ func (m Metric) String() string {
 
 // Fingerprint returns a Metric's Fingerprint.
 func (m Metric) Fingerprint() Fingerprint {
-	labelNames := make([]string, 0, len(m))
-	maxLength := 0
-
-	for labelName, labelValue := range m {
-		labelNames = append(labelNames, string(labelName))
-		if len(labelName) > maxLength {
-			maxLength = len(labelName)
-		}
-		if len(labelValue) > maxLength {
-			maxLength = len(labelValue)
-		}
-	}
-
-	sort.Strings(labelNames)
-
-	summer := fnv.New64a()
-	buf := make([]byte, maxLength)
-
-	for _, labelName := range labelNames {
-		labelValue := m[LabelName(labelName)]
-
-		copy(buf, labelName)
-		summer.Write(buf[:len(labelName)])
-
-		summer.Write(separator)
-
-		copy(buf, labelValue)
-		summer.Write(buf[:len(labelValue)])
-	}
-
-	return Fingerprint(binary.LittleEndian.Uint64(summer.Sum(nil)))
+	return metricToFingerprint(m)
 }
 
 // Clone returns a copy of the Metric.

Godeps/_workspace/src/github.com/prometheus/client_golang/model/metric_test.go

@@ -22,7 +22,7 @@ func testMetric(t testing.TB) {
 	}{
 		{
 			input:       Metric{},
-			fingerprint: 2676020557754725067,
+			fingerprint: 14695981039346656037,
 		},
 		{
 			input: Metric{
@@ -30,31 +30,27 @@ func testMetric(t testing.TB) {
 				"occupation":   "robot",
 				"manufacturer": "westinghouse",
 			},
-			fingerprint: 13260944541294022935,
+			fingerprint: 11310079640881077873,
 		},
 		{
 			input: Metric{
 				"x": "y",
 			},
-			fingerprint: 1470933794305433534,
+			fingerprint: 13948396922932177635,
 		},
-		// The following two demonstrate a bug in fingerprinting. They
-		// should not have the same fingerprint with a sane
-		// fingerprinting function. See
-		// https://github.com/prometheus/client_golang/issues/74 .
 		{
 			input: Metric{
 				"a": "bb",
 				"b": "c",
 			},
-			fingerprint: 3734646176939799877,
+			fingerprint: 3198632812309449502,
 		},
 		{
 			input: Metric{
 				"a":  "b",
 				"bb": "c",
 			},
-			fingerprint: 3734646176939799877,
+			fingerprint: 5774953389407657638,
 		},
 	}
 

Godeps/_workspace/src/github.com/prometheus/client_golang/model/signature.go

@@ -63,10 +63,10 @@ func LabelsToSignature(labels map[string]string) uint64 {
 	hb := getHashAndBuf()
 	defer putHashAndBuf(hb)
 
-	for k, v := range labels {
-		hb.b.WriteString(k)
+	for labelName, labelValue := range labels {
+		hb.b.WriteString(labelName)
 		hb.b.WriteByte(SeparatorByte)
-		hb.b.WriteString(v)
+		hb.b.WriteString(labelValue)
 		hb.h.Write(hb.b.Bytes())
 		result ^= hb.h.Sum64()
 		hb.h.Reset()
@@ -75,10 +75,34 @@ func LabelsToSignature(labels map[string]string) uint64 {
 	return result
 }
 
-// LabelValuesToSignature returns a unique signature (i.e., fingerprint) for the
-// values of a given label set.
-func LabelValuesToSignature(labels map[string]string) uint64 {
-	if len(labels) == 0 {
+// metricToFingerprint works exactly as LabelsToSignature but takes a Metric as
+// parameter (rather than a label map) and returns a Fingerprint.
+func metricToFingerprint(m Metric) Fingerprint {
+	if len(m) == 0 {
+		return Fingerprint(emptyLabelSignature)
+	}
+
+	var result uint64
+	hb := getHashAndBuf()
+	defer putHashAndBuf(hb)
+
+	for labelName, labelValue := range m {
+		hb.b.WriteString(string(labelName))
+		hb.b.WriteByte(SeparatorByte)
+		hb.b.WriteString(string(labelValue))
+		hb.h.Write(hb.b.Bytes())
+		result ^= hb.h.Sum64()
+		hb.h.Reset()
+		hb.b.Reset()
+	}
+	return Fingerprint(result)
+}
+
+// SignatureForLabels works like LabelsToSignature but takes a Metric as
+// parameter (rather than a label map) and only includes the labels with the
+// specified LabelNames into the signature calculation.
+func SignatureForLabels(m Metric, labels LabelNames) uint64 {
+	if len(m) == 0 || len(labels) == 0 {
 		return emptyLabelSignature
 	}
 
@@ -86,8 +110,10 @@ func LabelValuesToSignature(labels map[string]string) uint64 {
 	hb := getHashAndBuf()
 	defer putHashAndBuf(hb)
 
-	for _, v := range labels {
-		hb.b.WriteString(v)
+	for _, label := range labels {
+		hb.b.WriteString(string(label))
+		hb.b.WriteByte(SeparatorByte)
+		hb.b.WriteString(string(m[label]))
 		hb.h.Write(hb.b.Bytes())
 		result ^= hb.h.Sum64()
 		hb.h.Reset()
@@ -95,3 +121,33 @@ func LabelValuesToSignature(labels map[string]string) uint64 {
 	}
 	return result
 }
+
+// SignatureWithoutLabels works like LabelsToSignature but takes a Metric as
+// parameter (rather than a label map) and excludes the labels with any of the
+// specified LabelNames from the signature calculation.
+func SignatureWithoutLabels(m Metric, labels map[LabelName]struct{}) uint64 {
+	if len(m) == 0 {
+		return emptyLabelSignature
+	}
+
+	var result uint64
+	hb := getHashAndBuf()
+	defer putHashAndBuf(hb)
+
+	for labelName, labelValue := range m {
+		if _, exclude := labels[labelName]; exclude {
+			continue
+		}
+		hb.b.WriteString(string(labelName))
+		hb.b.WriteByte(SeparatorByte)
+		hb.b.WriteString(string(labelValue))
+		hb.h.Write(hb.b.Bytes())
+		result ^= hb.h.Sum64()
+		hb.h.Reset()
+		hb.b.Reset()
+	}
+	if result == 0 {
+		return emptyLabelSignature
+	}
+	return result
+}

Godeps/_workspace/src/github.com/prometheus/client_golang/model/signature_test.go

@@ -18,7 +18,7 @@ import (
 	"testing"
 )
 
-func testLabelsToSignature(t testing.TB) {
+func TestLabelsToSignature(t *testing.T) {
 	var scenarios = []struct {
 		in  map[string]string
 		out uint64
@@ -42,57 +42,112 @@ func testLabelsToSignature(t testing.TB) {
 	}
 }
 
-func TestLabelToSignature(t *testing.T) {
-	testLabelsToSignature(t)
-}
-
-func TestEmptyLabelSignature(t *testing.T) {
-	input := []map[string]string{nil, {}}
-
-	var ms runtime.MemStats
-	runtime.ReadMemStats(&ms)
-
-	alloc := ms.Alloc
-
-	for _, labels := range input {
-		LabelsToSignature(labels)
+func TestMetricToFingerprint(t *testing.T) {
+	var scenarios = []struct {
+		in  Metric
+		out Fingerprint
+	}{
+		{
+			in:  Metric{},
+			out: 14695981039346656037,
+		},
+		{
+			in:  Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			out: 12952432476264840823,
+		},
 	}
 
-	runtime.ReadMemStats(&ms)
+	for i, scenario := range scenarios {
+		actual := metricToFingerprint(scenario.in)
 
-	if got := ms.Alloc; alloc != got {
-		t.Fatal("expected LabelsToSignature with empty labels not to perform allocations")
-	}
-}
-
-func BenchmarkLabelToSignature(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		testLabelsToSignature(b)
-	}
-}
-
-func benchmarkLabelValuesToSignature(b *testing.B, l map[string]string, e uint64) {
-	for i := 0; i < b.N; i++ {
-		if a := LabelValuesToSignature(l); a != e {
-			b.Fatalf("expected signature of %d for %s, got %d", e, l, a)
+		if actual != scenario.out {
+			t.Errorf("%d. expected %d, got %d", i, scenario.out, actual)
 		}
 	}
 }
 
-func BenchmarkLabelValuesToSignatureScalar(b *testing.B) {
-	benchmarkLabelValuesToSignature(b, nil, 14695981039346656037)
+func TestSignatureForLabels(t *testing.T) {
+	var scenarios = []struct {
+		in     Metric
+		labels LabelNames
+		out    uint64
+	}{
+		{
+			in:     Metric{},
+			labels: nil,
+			out:    14695981039346656037,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: LabelNames{"fear", "name"},
+			out:    12952432476264840823,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough", "foo": "bar"},
+			labels: LabelNames{"fear", "name"},
+			out:    12952432476264840823,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: LabelNames{},
+			out:    14695981039346656037,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: nil,
+			out:    14695981039346656037,
+		},
+	}
+
+	for i, scenario := range scenarios {
+		actual := SignatureForLabels(scenario.in, scenario.labels)
+
+		if actual != scenario.out {
+			t.Errorf("%d. expected %d, got %d", i, scenario.out, actual)
+		}
+	}
 }
 
-func BenchmarkLabelValuesToSignatureSingle(b *testing.B) {
-	benchmarkLabelValuesToSignature(b, map[string]string{"first-label": "first-label-value"}, 2653746141194979650)
-}
+func TestSignatureWithoutLabels(t *testing.T) {
+	var scenarios = []struct {
+		in     Metric
+		labels map[LabelName]struct{}
+		out    uint64
+	}{
+		{
+			in:     Metric{},
+			labels: nil,
+			out:    14695981039346656037,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: map[LabelName]struct{}{"fear": struct{}{}, "name": struct{}{}},
+			out:    14695981039346656037,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough", "foo": "bar"},
+			labels: map[LabelName]struct{}{"foo": struct{}{}},
+			out:    12952432476264840823,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: map[LabelName]struct{}{},
+			out:    12952432476264840823,
+		},
+		{
+			in:     Metric{"name": "garland, briggs", "fear": "love is not enough"},
+			labels: nil,
+			out:    12952432476264840823,
+		},
+	}
 
-func BenchmarkLabelValuesToSignatureDouble(b *testing.B) {
-	benchmarkLabelValuesToSignature(b, map[string]string{"first-label": "first-label-value", "second-label": "second-label-value"}, 8893559499616767364)
-}
+	for i, scenario := range scenarios {
+		actual := SignatureWithoutLabels(scenario.in, scenario.labels)
 
-func BenchmarkLabelValuesToSignatureTriple(b *testing.B) {
-	benchmarkLabelValuesToSignature(b, map[string]string{"first-label": "first-label-value", "second-label": "second-label-value", "third-label": "third-label-value"}, 1685970066862087833)
+		if actual != scenario.out {
+			t.Errorf("%d. expected %d, got %d", i, scenario.out, actual)
+		}
+	}
 }
 
 func benchmarkLabelToSignature(b *testing.B, l map[string]string, e uint64) {
@@ -118,3 +173,46 @@ func BenchmarkLabelToSignatureDouble(b *testing.B) {
 func BenchmarkLabelToSignatureTriple(b *testing.B) {
 	benchmarkLabelToSignature(b, map[string]string{"first-label": "first-label-value", "second-label": "second-label-value", "third-label": "third-label-value"}, 15738406913934009676)
 }
+
+func benchmarkMetricToFingerprint(b *testing.B, m Metric, e Fingerprint) {
+	for i := 0; i < b.N; i++ {
+		if a := metricToFingerprint(m); a != e {
+			b.Fatalf("expected signature of %d for %s, got %d", e, m, a)
+		}
+	}
+}
+
+func BenchmarkMetricToFingerprintScalar(b *testing.B) {
+	benchmarkMetricToFingerprint(b, nil, 14695981039346656037)
+}
+
+func BenchmarkMetricToFingerprintSingle(b *testing.B) {
+	benchmarkMetricToFingerprint(b, Metric{"first-label": "first-label-value"}, 5147259542624943964)
+}
+
+func BenchmarkMetricToFingerprintDouble(b *testing.B) {
+	benchmarkMetricToFingerprint(b, Metric{"first-label": "first-label-value", "second-label": "second-label-value"}, 18269973311206963528)
+}
+
+func BenchmarkMetricToFingerprintTriple(b *testing.B) {
+	benchmarkMetricToFingerprint(b, Metric{"first-label": "first-label-value", "second-label": "second-label-value", "third-label": "third-label-value"}, 15738406913934009676)
+}
+
+func TestEmptyLabelSignature(t *testing.T) {
+	input := []map[string]string{nil, {}}
+
+	var ms runtime.MemStats
+	runtime.ReadMemStats(&ms)
+
+	alloc := ms.Alloc
+
+	for _, labels := range input {
+		LabelsToSignature(labels)
+	}
+
+	runtime.ReadMemStats(&ms)
+
+	if got := ms.Alloc; alloc != got {
+		t.Fatal("expected LabelsToSignature with empty labels not to perform allocations")
+	}
+}

Godeps/_workspace/src/github.com/prometheus/client_golang/model/timestamp.go

@@ -88,6 +88,7 @@ func (t Timestamp) String() string {
 	return strconv.FormatFloat(float64(t)/float64(second), 'f', -1, 64)
 }
 
+// MarshalJSON implements the json.Marshaler interface.
 func (t Timestamp) MarshalJSON() ([]byte, error) {
 	return []byte(t.String()), nil
 }

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/desc.go

@@ -11,8 +11,9 @@ import (
 
 	"github.com/prometheus/client_golang/model"
 
-	"github.com/golang/protobuf/proto"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/golang/protobuf/proto"
 )
 
 var (

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/example_selfcollector_test.go

@@ -17,8 +17,10 @@ import (
 	"runtime"
 
 	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/prometheus"
+
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 func NewCallbackMetric(desc *prometheus.Desc, callback func() float64) *CallbackMetric {

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/examples_test.go

@@ -21,9 +21,11 @@ import (
 	"runtime"
 	"sort"
 
-	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/golang/protobuf/proto"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 func ExampleGauge() {

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/expvar_test.go

@@ -19,8 +19,9 @@ import (
 	"sort"
 	"strings"
 
-	"github.com/prometheus/client_golang/prometheus"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/prometheus"
 )
 
 func ExampleExpvarCollector() {

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/histogram.go

@@ -21,6 +21,7 @@ import (
 	"sync/atomic"
 
 	"github.com/golang/protobuf/proto"
+
 	"github.com/prometheus/client_golang/model"
 	dto "github.com/prometheus/client_model/go"
 )

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/registry.go

@@ -35,9 +35,11 @@ import (
 
 	"bitbucket.org/ww/goautoneg"
 	"github.com/golang/protobuf/proto"
+
+	dto "github.com/prometheus/client_model/go"
+
 	"github.com/prometheus/client_golang/model"
 	"github.com/prometheus/client_golang/text"
-	dto "github.com/prometheus/client_model/go"
 )
 
 var (

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/summary.go

@@ -22,8 +22,10 @@ import (
 
 	"github.com/beorn7/perks/quantile"
 	"github.com/golang/protobuf/proto"
-	"github.com/prometheus/client_golang/model"
+
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/prometheus/client_golang/model"
 )
 
 // A Summary captures individual observations from an event or sample stream and

Godeps/_workspace/src/github.com/prometheus/client_golang/prometheus/value.go

@@ -20,8 +20,9 @@ import (
 	"sort"
 	"sync/atomic"
 
-	"github.com/golang/protobuf/proto"
 	dto "github.com/prometheus/client_model/go"
+
+	"github.com/golang/protobuf/proto"
 )
 
 // ValueType is an enumeration of metric types that represent a simple value.

Godeps/_workspace/src/github.com/prometheus/client_golang/text/bench_test.go

@@ -16,11 +16,12 @@ package text
 import (
 	"bytes"
 	"compress/gzip"
-	"github.com/matttproud/golang_protobuf_extensions/ext"
-	dto "github.com/prometheus/client_model/go"
 	"io"
 	"io/ioutil"
 	"testing"
+	dto "github.com/prometheus/client_model/go"
+
+	"github.com/matttproud/golang_protobuf_extensions/ext"
 )
 
 // Benchmarks to show how much penalty text format parsing actually inflicts.

Godeps/_workspace/src/github.com/prometheus/client_golang/text/parse.go

@@ -22,9 +22,10 @@ import (
 	"strconv"
 	"strings"
 
+	dto "github.com/prometheus/client_model/go"
+
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/client_golang/model"
-	dto "github.com/prometheus/client_model/go"
 )
 
 // A stateFn is a function that represents a state in a state machine. By

Godeps/_workspace/src/github.com/prometheus/client_golang/text/parse_test.go

@@ -385,7 +385,7 @@ request_duration_microseconds_count 2693
 					},
 				},
 			},
-		},
+                },
 	}
 
 	for i, scenario := range scenarios {

Godeps/_workspace/src/github.com/prometheus/client_golang/text/proto.go

@@ -19,6 +19,7 @@ import (
 
 	"github.com/golang/protobuf/proto"
 	"github.com/matttproud/golang_protobuf_extensions/ext"
+
 	dto "github.com/prometheus/client_model/go"
 )
 

rules/ast/ast.go

@@ -17,7 +17,6 @@ import (
 	"errors"
 	"flag"
 	"fmt"
-	"hash/fnv"
 	"math"
 	"time"
 
@@ -383,23 +382,6 @@ func (node *ScalarFunctionCall) Eval(timestamp clientmodel.Timestamp) clientmode
 	return node.function.callFn(timestamp, node.args).(clientmodel.SampleValue)
 }
 
-// hashForLabels returns a hash value taken from the label/value pairs of the
-// specified labels in the metric.
-func hashForLabels(metric clientmodel.Metric, labels clientmodel.LabelNames) uint64 {
-	var result uint64
-	s := fnv.New64a()
-
-	for _, label := range labels {
-		s.Write([]byte(label))
-		s.Write([]byte{clientmodel.SeparatorByte})
-		s.Write([]byte(metric[label]))
-		result ^= s.Sum64()
-		s.Reset()
-	}
-
-	return result
-}
-
 // EvalVectorInstant evaluates a VectorNode with an instant query.
 func EvalVectorInstant(node VectorNode, timestamp clientmodel.Timestamp, storage local.Storage, queryStats *stats.TimerGroup) (Vector, error) {
 	totalEvalTimer := queryStats.GetTimer(stats.TotalEvalTime).Start()
@@ -503,7 +485,7 @@ func (node *VectorAggregation) Eval(timestamp clientmodel.Timestamp) Vector {
 	vector := node.vector.Eval(timestamp)
 	result := map[uint64]*groupedAggregation{}
 	for _, sample := range vector {
-		groupingKey := hashForLabels(sample.Metric.Metric, node.groupBy)
+		groupingKey := clientmodel.SignatureForLabels(sample.Metric.Metric, node.groupBy)
 		if groupedResult, ok := result[groupingKey]; ok {
 			if node.keepExtraLabels {
 				groupedResult.labels = labelIntersection(groupedResult.labels, sample.Metric)
@@ -879,7 +861,7 @@ func (node *VectorArithExpr) evalVectors(timestamp clientmodel.Timestamp, lhs, r
 			metric := node.resultMetric(ls, rs)
 			// Check if the same label set has been added for a many-to-one matching before.
 			if node.matchCardinality == MatchManyToOne || node.matchCardinality == MatchOneToMany {
-				insHash := hashForLabels(metric.Metric, node.includeLabels)
+				insHash := clientmodel.SignatureForLabels(metric.Metric, node.includeLabels)
 				if ihs, exists := added[hash]; exists {
 					for _, ih := range ihs {
 						if ih == insHash {
@@ -971,7 +953,7 @@ func (node *VectorArithExpr) hashForMetric(metric clientmodel.Metric) uint64 {
 			}
 		}
 	}
-	return hashForLabels(metric, labels)
+	return clientmodel.SignatureForLabels(metric, labels)
 }
 
 // Eval implements the MatrixNode interface and returns the value of

rules/ast/functions.go

@@ -504,7 +504,7 @@ func histogramQuantileImpl(timestamp clientmodel.Timestamp, args []Node) interfa
 	q := args[0].(ScalarNode).Eval(timestamp)
 	inVec := args[1].(VectorNode).Eval(timestamp)
 	outVec := Vector{}
-	fpToMetricWithBuckets := map[clientmodel.Fingerprint]*metricWithBuckets{}
+	signatureToMetricWithBuckets := map[uint64]*metricWithBuckets{}
 	for _, el := range inVec {
 		upperBound, err := strconv.ParseFloat(
 			string(el.Metric.Metric[clientmodel.BucketLabel]), 64,
@@ -514,18 +514,18 @@ func histogramQuantileImpl(timestamp clientmodel.Timestamp, args []Node) interfa
 			// TODO(beorn7): Issue a warning somehow.
 			continue
 		}
-		fp := bucketFingerprint(el.Metric.Metric)
-		mb, ok := fpToMetricWithBuckets[fp]
+		signature := clientmodel.SignatureWithoutLabels(el.Metric.Metric, excludedLabels)
+		mb, ok := signatureToMetricWithBuckets[signature]
 		if !ok {
 			el.Metric.Delete(clientmodel.BucketLabel)
 			el.Metric.Delete(clientmodel.MetricNameLabel)
 			mb = &metricWithBuckets{el.Metric, nil}
-			fpToMetricWithBuckets[fp] = mb
+			signatureToMetricWithBuckets[signature] = mb
 		}
 		mb.buckets = append(mb.buckets, bucket{upperBound, el.Value})
 	}
 
-	for _, mb := range fpToMetricWithBuckets {
+	for _, mb := range signatureToMetricWithBuckets {
 		outVec = append(outVec, &Sample{
 			Metric:    mb.metric,
 			Value:     clientmodel.SampleValue(quantile(q, mb.buckets)),

rules/ast/quantile.go

@@ -14,8 +14,6 @@
 package ast
 
 import (
-	"encoding/binary"
-	"hash/fnv"
 	"math"
 	"sort"
 
@@ -24,6 +22,13 @@ import (
 
 // Helpers to calculate quantiles.
 
+// excludedLabels are the labels to exclude from signature calculation for
+// quantiles.
+var excludedLabels = map[clientmodel.LabelName]struct{}{
+	clientmodel.MetricNameLabel: struct{}{},
+	clientmodel.BucketLabel:     struct{}{},
+}
+
 type bucket struct {
 	upperBound float64
 	count      clientmodel.SampleValue
@@ -99,46 +104,3 @@ func quantile(q clientmodel.SampleValue, buckets buckets) float64 {
 	}
 	return bucketStart + (bucketEnd-bucketStart)*float64(rank/count)
 }
-
-// bucketFingerprint works like the Fingerprint method of Metric, but ignores
-// the name and the bucket label.
-func bucketFingerprint(m clientmodel.Metric) clientmodel.Fingerprint {
-	numLabels := 0
-	if len(m) > 2 {
-		numLabels = len(m) - 2
-	}
-	labelNames := make([]string, 0, numLabels)
-	maxLength := 0
-
-	for labelName, labelValue := range m {
-		if labelName == clientmodel.MetricNameLabel || labelName == clientmodel.BucketLabel {
-			continue
-		}
-		labelNames = append(labelNames, string(labelName))
-		if len(labelName) > maxLength {
-			maxLength = len(labelName)
-		}
-		if len(labelValue) > maxLength {
-			maxLength = len(labelValue)
-		}
-	}
-
-	sort.Strings(labelNames)
-
-	summer := fnv.New64a()
-	buf := make([]byte, maxLength)
-
-	for _, labelName := range labelNames {
-		labelValue := m[clientmodel.LabelName(labelName)]
-
-		copy(buf, labelName)
-		summer.Write(buf[:len(labelName)])
-		summer.Write([]byte{clientmodel.SeparatorByte})
-
-		copy(buf, labelValue)
-		summer.Write(buf[:len(labelValue)])
-		summer.Write([]byte{clientmodel.SeparatorByte})
-	}
-
-	return clientmodel.Fingerprint(binary.LittleEndian.Uint64(summer.Sum(nil)))
-}

storage/local/persistence.go

@@ -18,9 +18,12 @@ import (
 	"encoding/binary"
 	"fmt"
 	"io"
+	"io/ioutil"
 	"os"
 	"path"
 	"path/filepath"
+	"strconv"
+	"strings"
 	"sync"
 	"time"
 
@@ -36,6 +39,11 @@ import (
 )
 
 const (
+	// Version of the storage as it can be found in the version file.
+	// Increment to protect against incompatible changes.
+	Version         = 1
+	versionFileName = "VERSION"
+
 	seriesFileSuffix     = ".db"
 	seriesTempFileSuffix = ".db.tmp"
 	seriesDirNameLen     = 2 // How many bytes of the fingerprint in dir name.
@@ -114,10 +122,42 @@ type persistence struct {
 
 // newPersistence returns a newly allocated persistence backed by local disk storage, ready to use.
 func newPersistence(basePath string, chunkLen int, dirty bool) (*persistence, error) {
-	if err := os.MkdirAll(basePath, 0700); err != nil {
+	dirtyPath := filepath.Join(basePath, dirtyFileName)
+	versionPath := filepath.Join(basePath, versionFileName)
+
+	if versionData, err := ioutil.ReadFile(versionPath); err == nil {
+		if persistedVersion, err := strconv.Atoi(strings.TrimSpace(string(versionData))); err != nil {
+			return nil, fmt.Errorf("cannot parse content of %s: %s", versionPath, versionData)
+		} else if persistedVersion != Version {
+			return nil, fmt.Errorf("found storage version %d on disk, need version %d - please wipe storage or run a version of Prometheus compatible with storage version %d", persistedVersion, Version, persistedVersion)
+		}
+	} else if os.IsNotExist(err) {
+		// No version file found. Let's create the directory (in case
+		// it's not there yet) and then check if it is actually
+		// empty. If not, we have found an old storage directory without
+		// version file, so we have to bail out.
+		if err := os.MkdirAll(basePath, 0700); err != nil {
+			return nil, err
+		}
+		fis, err := ioutil.ReadDir(basePath)
+		if err != nil {
+			return nil, err
+		}
+		if len(fis) > 0 {
+			return nil, fmt.Errorf("could not detect storage version on disk, assuming version 0, need version %d - please wipe storage or run a version of Prometheus compatible with storage version 0", Version)
+		}
+		// Finally we can write our own version into a new version file.
+		file, err := os.Create(versionPath)
+		if err != nil {
+			return nil, err
+		}
+		defer file.Close()
+		if _, err := fmt.Fprintf(file, "%d\n", Version); err != nil {
+			return nil, err
+		}
+	} else {
 		return nil, err
 	}
-	dirtyPath := filepath.Join(basePath, dirtyFileName)
 
 	fLock, dirtyfileExisted, err := flock.New(dirtyPath)
 	if err != nil {