Optimized.

Signed-off-by: Bartlomiej Plotka <bwplotka@gmail.com>

prometheus/cache/cache.go

@@ -60,7 +60,7 @@ func (c *CachedTGatherer) Gather() (_ []*dto.MetricFamily, done func(), err erro
 	c.mMu.RLock()
 
 	// BenchmarkCachedTGatherer_Update shows, even for 1 million metrics with 1000 families
-	// this is efficient enough (~250µs 50 kB per op), no need to cache it for now.
+	// this is efficient enough (~300µs and ~50 kB per op), no need to cache it for now.
 	return internal.NormalizeMetricFamilies(c.metricFamilyByName), c.mMu.RUnlock, nil
 }
 
@@ -114,6 +114,11 @@ type Insert struct {
 // Update goes through inserts and deletions and updates current cache in concurrency safe manner.
 // If reset is set to true, all inserts and deletions are working on empty cache. In such case
 // this implementation tries to reuse memory from existing cached item when possible.
+//
+// Update reuses insert struct memory, so after use, Insert slice and its elements cannot be reused
+// outside of this method.
+// TODO(bwplotka): Lack of copying can pose memory safety problems if insert variables are reused. Consider copying if value
+// is different. Yet it gives significant allocation gains.
 func (c *CachedTGatherer) Update(reset bool, inserts []Insert, deletions []Key) error {
 	c.mMu.Lock()
 	defer c.mMu.Unlock()
@@ -126,48 +131,48 @@ func (c *CachedTGatherer) Update(reset bool, inserts []Insert, deletions []Key)
 	}
 
 	errs := prometheus.MultiError{}
-	for _, ins := range inserts {
+	for i := range inserts {
 		// TODO(bwplotka): Validate more about this insert?
-		if err := ins.isValid(); err != nil {
+		if err := inserts[i].isValid(); err != nil {
 			errs.Append(err)
 			continue
 		}
 
 		// Update metric family.
-		mf, ok := c.metricFamilyByName[ins.FQName]
+		mf, ok := c.metricFamilyByName[inserts[i].FQName]
 		if !ok {
 			mf = &dto.MetricFamily{}
-			mf.Name = proto.String(ins.FQName)
+			mf.Name = &inserts[i].FQName
 		} else if reset {
 			// Reset metric slice, since we want to start from scratch.
 			mf.Metric = mf.Metric[:0]
 		}
-		mf.Type = ins.ValueType.ToDTO()
-		mf.Help = proto.String(ins.Help)
+		mf.Type = inserts[i].ValueType.ToDTO()
+		mf.Help = &inserts[i].Help
 
-		currMetricFamilies[ins.FQName] = mf
+		currMetricFamilies[inserts[i].FQName] = mf
 
 		// Update metric pointer.
-		hSum := ins.hash()
+		hSum := inserts[i].hash()
 		m, ok := c.metrics[hSum]
 		if !ok {
-			m = &dto.Metric{Label: make([]*dto.LabelPair, 0, len(ins.LabelNames))}
-			for i := range ins.LabelNames {
+			m = &dto.Metric{Label: make([]*dto.LabelPair, 0, len(inserts[i].LabelNames))}
+			for j := range inserts[i].LabelNames {
 				m.Label = append(m.Label, &dto.LabelPair{
-					Name:  proto.String(ins.LabelNames[i]),
-					Value: proto.String(ins.LabelValues[i]),
+					Name:  &inserts[i].LabelNames[j],
+					Value: &inserts[i].LabelValues[j],
 				})
 			}
-			sort.Sort(labelPairSorter(m.Label))
+			sort.Sort(internal.LabelPairSorter(m.Label))
 		}
 
-		switch ins.ValueType {
+		switch inserts[i].ValueType {
 		case prometheus.CounterValue:
 			v := m.Counter
 			if v == nil {
 				v = &dto.Counter{}
 			}
-			v.Value = proto.Float64(ins.Value)
+			v.Value = &inserts[i].Value
 			m.Counter = v
 			m.Gauge = nil
 			m.Untyped = nil
@@ -176,7 +181,7 @@ func (c *CachedTGatherer) Update(reset bool, inserts []Insert, deletions []Key)
 			if v == nil {
 				v = &dto.Gauge{}
 			}
-			v.Value = proto.Float64(ins.Value)
+			v.Value = &inserts[i].Value
 			m.Counter = nil
 			m.Gauge = v
 			m.Untyped = nil
@@ -185,17 +190,17 @@ func (c *CachedTGatherer) Update(reset bool, inserts []Insert, deletions []Key)
 			if v == nil {
 				v = &dto.Untyped{}
 			}
-			v.Value = proto.Float64(ins.Value)
+			v.Value = &inserts[i].Value
 			m.Counter = nil
 			m.Gauge = nil
 			m.Untyped = v
 		default:
-			return fmt.Errorf("unsupported value type %v", ins.ValueType)
+			return fmt.Errorf("unsupported value type %v", inserts[i].ValueType)
 		}
 
 		m.TimestampMs = nil
-		if ins.Timestamp != nil {
-			m.TimestampMs = proto.Int64(ins.Timestamp.Unix()*1000 + int64(ins.Timestamp.Nanosecond()/1000000))
+		if inserts[i].Timestamp != nil {
+			m.TimestampMs = proto.Int64(inserts[i].Timestamp.Unix()*1000 + int64(inserts[i].Timestamp.Nanosecond()/1000000))
 		}
 		currMetrics[hSum] = m
 
@@ -254,19 +259,3 @@ func (c *CachedTGatherer) Update(reset bool, inserts []Insert, deletions []Key)
 	c.metricFamilyByName = currMetricFamilies
 	return errs.MaybeUnwrap()
 }
-
-// labelPairSorter implements sort.Interface. It is used to sort a slice of
-// dto.LabelPair pointers.
-type labelPairSorter []*dto.LabelPair
-
-func (s labelPairSorter) Len() int {
-	return len(s)
-}
-
-func (s labelPairSorter) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s labelPairSorter) Less(i, j int) bool {
-	return s[i].GetName() < s[j].GetName()
-}

prometheus/desc.go

@@ -20,6 +20,8 @@ import (
 	"strings"
 
 	"github.com/cespare/xxhash/v2"
+	"github.com/prometheus/client_golang/prometheus/internal"
+
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/model"
@@ -154,7 +156,7 @@ func NewDesc(fqName, help string, variableLabels []string, constLabels Labels) *
 			Value: proto.String(v),
 		})
 	}
-	sort.Sort(labelPairSorter(d.constLabelPairs))
+	sort.Sort(internal.LabelPairSorter(d.constLabelPairs))
 	return d
 }
 

prometheus/internal/metric.go

@@ -19,6 +19,22 @@ import (
 	dto "github.com/prometheus/client_model/go"
 )
 
+// LabelPairSorter implements sort.Interface. It is used to sort a slice of
+// dto.LabelPair pointers.
+type LabelPairSorter []*dto.LabelPair
+
+func (s LabelPairSorter) Len() int {
+	return len(s)
+}
+
+func (s LabelPairSorter) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s LabelPairSorter) Less(i, j int) bool {
+	return s[i].GetName() < s[j].GetName()
+}
+
 // metricSorter is a sortable slice of *dto.Metric.
 type metricSorter []*dto.Metric
 

prometheus/metric.go

@@ -115,22 +115,6 @@ func BuildFQName(namespace, subsystem, name string) string {
 	return name
 }
 
-// labelPairSorter implements sort.Interface. It is used to sort a slice of
-// dto.LabelPair pointers.
-type labelPairSorter []*dto.LabelPair
-
-func (s labelPairSorter) Len() int {
-	return len(s)
-}
-
-func (s labelPairSorter) Swap(i, j int) {
-	s[i], s[j] = s[j], s[i]
-}
-
-func (s labelPairSorter) Less(i, j int) bool {
-	return s[i].GetName() < s[j].GetName()
-}
-
 type invalidMetric struct {
 	desc *Desc
 	err  error

prometheus/registry.go

@@ -891,11 +891,11 @@ func checkMetricConsistency(
 	h.Write(separatorByteSlice)
 	// Make sure label pairs are sorted. We depend on it for the consistency
 	// check.
-	if !sort.IsSorted(labelPairSorter(dtoMetric.Label)) {
+	if !sort.IsSorted(internal.LabelPairSorter(dtoMetric.Label)) {
 		// We cannot sort dtoMetric.Label in place as it is immutable by contract.
 		copiedLabels := make([]*dto.LabelPair, len(dtoMetric.Label))
 		copy(copiedLabels, dtoMetric.Label)
-		sort.Sort(labelPairSorter(copiedLabels))
+		sort.Sort(internal.LabelPairSorter(copiedLabels))
 		dtoMetric.Label = copiedLabels
 	}
 	for _, lp := range dtoMetric.Label {
@@ -942,7 +942,7 @@ func checkDescConsistency(
 			metricFamily.GetName(), dtoMetric, desc,
 		)
 	}
-	sort.Sort(labelPairSorter(lpsFromDesc))
+	sort.Sort(internal.LabelPairSorter(lpsFromDesc))
 	for i, lpFromDesc := range lpsFromDesc {
 		lpFromMetric := dtoMetric.Label[i]
 		if lpFromDesc.GetName() != lpFromMetric.GetName() ||

prometheus/value.go

@@ -22,6 +22,7 @@ import (
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
+	"github.com/prometheus/client_golang/prometheus/internal"
 
 	dto "github.com/prometheus/client_model/go"
 )
@@ -193,7 +194,7 @@ func MakeLabelPairs(desc *Desc, labelValues []string) []*dto.LabelPair {
 		})
 	}
 	labelPairs = append(labelPairs, desc.constLabelPairs...)
-	sort.Sort(labelPairSorter(labelPairs))
+	sort.Sort(internal.LabelPairSorter(labelPairs))
 	return labelPairs
 }
 

prometheus/wrap.go

@@ -20,6 +20,7 @@ import (
 	//nolint:staticcheck // Ignore SA1019. Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
+	"github.com/prometheus/client_golang/prometheus/internal"
 	dto "github.com/prometheus/client_model/go"
 )
 
@@ -182,7 +183,7 @@ func (m *wrappingMetric) Write(out *dto.Metric) error {
 			Value: proto.String(lv),
 		})
 	}
-	sort.Sort(labelPairSorter(out.Label))
+	sort.Sort(internal.LabelPairSorter(out.Label))
 	return nil
 }