replace remaining usage of hashNew() with xxhash

prometheus/vec.go

@@ -17,9 +17,22 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/prometheus/common/model"
+	"github.com/cespare/xxhash/v2"
 )
 
+// hasher represents the partial API from xxhash, to enable replacing for
+// collision tests
+type hasher interface {
+	WriteString(string) (int, error)
+	Write([]byte) (int, error)
+	Sum64() uint64
+}
+
+// newHasher wraps xxhash.New to satisfy the hasher interface
+func newHasher() hasher {
+	return xxhash.New()
+}
+
 // metricVec is a Collector to bundle metrics of the same name that differ in
 // their label values. metricVec is not used directly (and therefore
 // unexported). It is used as a building block for implementations of vectors of
@@ -30,9 +43,8 @@ type metricVec struct {
 
 	curry []curriedLabelValue
 
-	// hashAdd and hashAddByte can be replaced for testing collision handling.
-	hashAdd     func(h uint64, s string) uint64
-	hashAddByte func(h uint64, b byte) uint64
+	// hasher can be replaced for testing collision handling.
+	newHasher func() hasher
 }
 
 // newMetricVec returns an initialized metricVec.
@@ -43,8 +55,7 @@ func newMetricVec(desc *Desc, newMetric func(lvs ...string) Metric) *metricVec {
 			desc:      desc,
 			newMetric: newMetric,
 		},
-		hashAdd:     hashAdd,
-		hashAddByte: hashAddByte,
+		newHasher: newHasher,
 	}
 }
 
@@ -117,10 +128,9 @@ func (m *metricVec) curryWith(labels Labels) (*metricVec, error) {
 	}
 
 	return &metricVec{
-		metricMap:   m.metricMap,
-		curry:       newCurry,
-		hashAdd:     m.hashAdd,
-		hashAddByte: m.hashAddByte,
+		metricMap: m.metricMap,
+		curry:     newCurry,
+		newHasher: m.newHasher,
 	}, nil
 }
 
@@ -148,21 +158,21 @@ func (m *metricVec) hashLabelValues(vals []string) (uint64, error) {
 	}
 
 	var (
-		h             = hashNew()
+		h             = m.newHasher()
 		curry         = m.curry
 		iVals, iCurry int
 	)
 	for i := 0; i < len(m.desc.variableLabels); i++ {
 		if iCurry < len(curry) && curry[iCurry].index == i {
-			h = m.hashAdd(h, curry[iCurry].value)
+			h.WriteString(curry[iCurry].value)
 			iCurry++
 		} else {
-			h = m.hashAdd(h, vals[iVals])
+			h.WriteString(vals[iVals])
 			iVals++
 		}
-		h = m.hashAddByte(h, model.SeparatorByte)
+		h.Write(separatorByteSlice)
 	}
-	return h, nil
+	return h.Sum64(), nil
 }
 
 func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
@@ -171,7 +181,7 @@ func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
 	}
 
 	var (
-		h      = hashNew()
+		h      = m.newHasher()
 		curry  = m.curry
 		iCurry int
 	)
@@ -181,17 +191,17 @@ func (m *metricVec) hashLabels(labels Labels) (uint64, error) {
 			if ok {
 				return 0, fmt.Errorf("label name %q is already curried", label)
 			}
-			h = m.hashAdd(h, curry[iCurry].value)
+			h.WriteString(curry[iCurry].value)
 			iCurry++
 		} else {
 			if !ok {
 				return 0, fmt.Errorf("label name %q missing in label map", label)
 			}
-			h = m.hashAdd(h, val)
+			h.WriteString(val)
 		}
-		h = m.hashAddByte(h, model.SeparatorByte)
+		h.Write(separatorByteSlice)
 	}
-	return h, nil
+	return h.Sum64(), nil
 }
 
 // metricWithLabelValues provides the metric and its label values for

prometheus/vec_test.go

@@ -20,6 +20,12 @@ import (
 	dto "github.com/prometheus/client_model/go"
 )
 
+type testHasher uint64
+
+func (th testHasher) Write(b []byte) (int, error)       { return len(b), nil }
+func (th testHasher) WriteString(s string) (int, error) { return len(s), nil }
+func (th testHasher) Sum64() uint64                     { return uint64(th) }
+
 func TestDelete(t *testing.T) {
 	vec := NewGaugeVec(
 		GaugeOpts{
@@ -39,8 +45,7 @@ func TestDeleteWithCollisions(t *testing.T) {
 		},
 		[]string{"l1", "l2"},
 	)
-	vec.hashAdd = func(h uint64, s string) uint64 { return 1 }
-	vec.hashAddByte = func(h uint64, b byte) uint64 { return 1 }
+	vec.newHasher = func() hasher { return testHasher(1) }
 	testDelete(t, vec)
 }
 
@@ -93,8 +98,7 @@ func TestDeleteLabelValuesWithCollisions(t *testing.T) {
 		},
 		[]string{"l1", "l2"},
 	)
-	vec.hashAdd = func(h uint64, s string) uint64 { return 1 }
-	vec.hashAddByte = func(h uint64, b byte) uint64 { return 1 }
+	vec.newHasher = func() hasher { return testHasher(1) }
 	testDeleteLabelValues(t, vec)
 }
 
@@ -144,8 +148,7 @@ func TestMetricVecWithCollisions(t *testing.T) {
 		},
 		[]string{"l1", "l2"},
 	)
-	vec.hashAdd = func(h uint64, s string) uint64 { return 1 }
-	vec.hashAddByte = func(h uint64, b byte) uint64 { return 1 }
+	vec.newHasher = func() hasher { return testHasher(1) }
 	testMetricVec(t, vec)
 }
 
@@ -258,8 +261,7 @@ func TestCurryVecWithCollisions(t *testing.T) {
 		},
 		[]string{"one", "two", "three"},
 	)
-	vec.hashAdd = func(h uint64, s string) uint64 { return 1 }
-	vec.hashAddByte = func(h uint64, b byte) uint64 { return 1 }
+	vec.newHasher = func() hasher { return testHasher(1) }
 	testCurryVec(t, vec)
 }