Merge c52d495061 into 291b0b0c42

prometheus/promsafe/safe.go

@@ -0,0 +1,387 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package promsafe provides safe labeling - strongly typed labels in prometheus metrics.
+// Enjoy promsafe as you wish!
+package promsafe
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+)
+
+//
+// promsafe configuration: promauto-compatibility, etc
+//
+
+// factory stands for a global promauto.Factory to be used (if any)
+var factory *promauto.Factory
+
+// SetupGlobalPromauto sets a global promauto.Factory to be used for all promsafe metrics.
+// This means that each promsafe.New* call will use this promauto.Factory.
+func SetupGlobalPromauto(factoryArg ...promauto.Factory) {
+	if len(factoryArg) == 0 {
+		f := promauto.With(prometheus.DefaultRegisterer)
+		factory = &f
+	} else {
+		f := factoryArg[0]
+		factory = &f
+	}
+}
+
+// CustomLabelsProvider is an interface that allows to convert anything to a prometheus.Labels
+// It allows to provide your own FAST implementation of Struct->prometheus.Labels conversion
+// without using reflection.
+type CustomLabelsProvider interface {
+	ToPrometheusLabels() prometheus.Labels
+}
+
+// CustomLabelNamesProvider is an interface that allows to convert anything to an order list of label names
+// Result of it is considered to be when registering new metric. As we need proper ORDERED list of label names
+// It allows to provide your own FAST implementation of Struct->[]string conversion without any reflection
+type CustomLabelNamesProvider interface {
+	ToLabelNames() []string
+}
+
+// promsafeTag is the tag name used for promsafe labels inside structs.
+// The tag is optional, as if not present, field is used with snake_cased FieldName.
+// It's useful to use a tag when you want to override the default naming or exclude a field from the metric.
+var promsafeTag = "promsafe"
+
+// SetPromsafeTag sets the tag name used for promsafe labels inside structs.
+func SetPromsafeTag(tag string) {
+	promsafeTag = tag
+}
+
+// labelsProviderMarker is a marker interface for enforcing type-safety of StructLabelProvider.
+type labelsProviderMarker interface {
+	labelsProviderMarker()
+}
+
+// StructLabelProvider should be embedded in any struct that serves as a label provider.
+type StructLabelProvider struct{}
+
+var _ labelsProviderMarker = (*StructLabelProvider)(nil)
+
+func (s StructLabelProvider) labelsProviderMarker() {
+	panic("labelsProviderMarker interface method should never be called")
+}
+
+// newEmptyLabels creates a new empty labels instance of type T
+// It's a bit tricky as we want to support both structs and pointers to structs
+// e.g. &MyLabels{StructLabelProvider} or MyLabels{StructLabelProvider}
+func newEmptyLabels[T labelsProviderMarker]() T {
+	var emptyLabels T
+
+	// Let's Support both Structs or Pointer to Structs given as T
+	val := reflect.ValueOf(&emptyLabels).Elem()
+	if val.Kind() == reflect.Ptr {
+		val.Set(reflect.New(val.Type().Elem()))
+	}
+
+	return emptyLabels
+}
+
+// NewCounterVecT creates a new CounterVecT with type-safe labels.
+func NewCounterVecT[T labelsProviderMarker](opts prometheus.CounterOpts) *CounterVecT[T] {
+	emptyLabels := newEmptyLabels[T]()
+
+	var inner *prometheus.CounterVec
+	if factory != nil {
+		inner = factory.NewCounterVec(opts, extractLabelNames(emptyLabels))
+	} else {
+		inner = prometheus.NewCounterVec(opts, extractLabelNames(emptyLabels))
+	}
+
+	return &CounterVecT[T]{inner: inner}
+}
+
+// CounterVecT is a wrapper around prometheus.CounterVec that allows type-safe labels.
+type CounterVecT[T labelsProviderMarker] struct {
+	inner *prometheus.CounterVec
+}
+
+// GetMetricWithLabelValues covers prometheus.CounterVec.GetMetricWithLabelValues
+// Deprecated: Use GetMetricWith() instead. We can't provide a []string safe implementation in promsafe
+func (c *CounterVecT[T]) GetMetricWithLabelValues(lvs ...string) (prometheus.Counter, error) {
+	panic("There can't be a SAFE GetMetricWithLabelValues(). Use GetMetricWith() instead")
+}
+
+// GetMetricWith behaves like prometheus.CounterVec.GetMetricWith but with type-safe labels.
+func (c *CounterVecT[T]) GetMetricWith(labels T) (prometheus.Counter, error) {
+	return c.inner.GetMetricWith(extractLabelsWithValues(labels))
+}
+
+// WithLabelValues covers like prometheus.CounterVec.WithLabelValues.
+// Deprecated: Use With() instead. We can't provide a []string safe implementation in promsafe
+func (c *CounterVecT[T]) WithLabelValues(lvs ...string) prometheus.Counter {
+	panic("There can't be a SAFE WithLabelValues(). Use With() instead")
+}
+
+// With behaves like prometheus.CounterVec.With but with type-safe labels.
+func (c *CounterVecT[T]) With(labels T) prometheus.Counter {
+	return c.inner.With(extractLabelsWithValues(labels))
+}
+
+// CurryWith behaves like prometheus.CounterVec.CurryWith but with type-safe labels.
+// It still returns a CounterVecT, but it's inner prometheus.CounterVec is curried.
+func (c *CounterVecT[T]) CurryWith(labels T) (*CounterVecT[T], error) {
+	curriedInner, err := c.inner.CurryWith(extractLabelsWithValues(labels))
+	if err != nil {
+		return nil, err
+	}
+	c.inner = curriedInner
+	return c, nil
+}
+
+// MustCurryWith behaves like prometheus.CounterVec.MustCurryWith but with type-safe labels.
+// It still returns a CounterVecT, but it's inner prometheus.CounterVec is curried.
+func (c *CounterVecT[T]) MustCurryWith(labels T) *CounterVecT[T] {
+	c.inner = c.inner.MustCurryWith(extractLabelsWithValues(labels))
+	return c
+}
+
+// Unsafe returns the underlying prometheus.CounterVec
+// it's used to call any other method of prometheus.CounterVec that doesn't require type-safe labels
+func (c *CounterVecT[T]) Unsafe() *prometheus.CounterVec {
+	return c.inner
+}
+
+// NewCounterT simply creates a new prometheus.Counter.
+// As it doesn't have any labels, it's already type-safe.
+// We keep this method just for consistency and interface fulfillment.
+func NewCounterT(opts prometheus.CounterOpts) prometheus.Counter {
+	return prometheus.NewCounter(opts)
+}
+
+// NewCounterFuncT simply creates a new prometheus.CounterFunc.
+// As it doesn't have any labels, it's already type-safe.
+// We keep this method just for consistency and interface fulfillment.
+func NewCounterFuncT(opts prometheus.CounterOpts, function func() float64) prometheus.CounterFunc {
+	return prometheus.NewCounterFunc(opts, function)
+}
+
+//
+// Shorthand for Metrics with a single label
+//
+
+// NewCounterVecT1 creates a new CounterVecT with the only single label
+func NewCounterVecT1(opts prometheus.CounterOpts, labelName string) *CounterVecT1 {
+	var inner *prometheus.CounterVec
+	if factory != nil {
+		inner = factory.NewCounterVec(opts, []string{labelName})
+	} else {
+		inner = prometheus.NewCounterVec(opts, []string{labelName})
+	}
+
+	return &CounterVecT1{inner: inner, labelName: labelName}
+}
+
+// CounterVecT1 is a wrapper around prometheus.CounterVec that allows a single type-safe label.
+type CounterVecT1 struct {
+	labelName string
+	inner     *prometheus.CounterVec
+}
+
+// GetMetricWithLabelValues behaves like prometheus.CounterVec.GetMetricWithLabelValues but with type-safe labels.
+func (c *CounterVecT1) GetMetricWithLabelValues(labelValue string) (prometheus.Counter, error) {
+	return c.inner.GetMetricWithLabelValues(labelValue)
+}
+
+// GetMetricWith behaves like prometheus.CounterVec.GetMetricWith but with type-safe labels.
+// We keep this function for consistency. Actually is useless and it's the same as GetMetricWithLabelValues
+func (c *CounterVecT1) GetMetricWith(labelValue string) (prometheus.Counter, error) {
+	return c.inner.GetMetricWith(prometheus.Labels{c.labelName: labelValue})
+}
+
+// WithLabelValues behaves like prometheus.CounterVec.WithLabelValues but with type-safe labels.
+func (c *CounterVecT1) WithLabelValues(labelValue string) prometheus.Counter {
+	return c.inner.WithLabelValues(labelValue)
+}
+
+// With behaves like prometheus.CounterVec.With but with type-safe labels.
+// We keep this function for consistency. Actually is useless and it's the same as WithLabelValues
+func (c *CounterVecT1) With(labelValue string) prometheus.Counter {
+	return c.inner.With(prometheus.Labels{c.labelName: labelValue})
+}
+
+// CurryWith behaves like prometheus.CounterVec.CurryWith but with type-safe labels.
+// It still returns a CounterVecT, but it's inner prometheus.CounterVec is curried.
+func (c *CounterVecT1) CurryWith(labelValue string) (*CounterVecT1, error) {
+	curriedInner, err := c.inner.CurryWith(prometheus.Labels{c.labelName: labelValue})
+	if err != nil {
+		return nil, err
+	}
+	c.inner = curriedInner
+	return c, nil
+}
+
+// MustCurryWith behaves like prometheus.CounterVec.MustCurryWith but with type-safe labels.
+// It still returns a CounterVecT, but it's inner prometheus.CounterVec is curried.
+func (c *CounterVecT1) MustCurryWith(labelValue string) *CounterVecT1 {
+	c.inner = c.inner.MustCurryWith(prometheus.Labels{c.labelName: labelValue})
+	return c
+}
+
+// Unsafe returns the underlying prometheus.CounterVec
+// it's used to call any other method of prometheus.CounterVec that doesn't require type-safe labels
+func (c *CounterVecT1) Unsafe() *prometheus.CounterVec {
+	return c.inner
+}
+
+//
+// Promauto compatibility
+//
+
+// Factory is a promauto-like factory that allows type-safe labels.
+// We have to duplicate promauto.Factory logic here, because promauto.Factory's registry is private.
+type Factory[T labelsProviderMarker] struct {
+	r prometheus.Registerer
+}
+
+// WithAuto is a helper function that allows to use promauto.With with promsafe.With
+func WithAuto[T labelsProviderMarker](r prometheus.Registerer) Factory[T] {
+	return Factory[T]{r: r}
+}
+
+// NewCounterVecT works like promauto.NewCounterVec but with type-safe labels
+func (f Factory[T]) NewCounterVecT(opts prometheus.CounterOpts) *CounterVecT[T] {
+	c := NewCounterVecT[T](opts)
+	if f.r != nil {
+		f.r.MustRegister(c.inner)
+	}
+	return c
+}
+
+// NewCounterT wraps promauto.NewCounter.
+// As it doesn't require any labels, it's already type-safe, and we keep it for consistency.
+func (f Factory[T]) NewCounterT(opts prometheus.CounterOpts) prometheus.Counter {
+	return promauto.With(f.r).NewCounter(opts)
+}
+
+// NewCounterFuncT wraps promauto.NewCounterFunc.
+// As it doesn't require any labels, it's already type-safe, and we keep it for consistency.
+func (f Factory[T]) NewCounterFuncT(opts prometheus.CounterOpts, function func() float64) prometheus.CounterFunc {
+	return promauto.With(f.r).NewCounterFunc(opts, function)
+}
+
+// TODO: we can't use Factory with NewCounterT1. If we need, then we need a new type-less Factory
+
+//
+// Helpers
+//
+
+// extractLabelsWithValues extracts labels names+values from a given labelsProviderMarker (parent instance of a StructLabelProvider)
+func extractLabelsWithValues(labelProvider labelsProviderMarker) prometheus.Labels {
+	if any(labelProvider) == nil {
+		return nil
+	}
+
+	if clp, ok := labelProvider.(CustomLabelsProvider); ok {
+		return clp.ToPrometheusLabels()
+	}
+
+	// Here, then, it can be only a struct, that is a parent of StructLabelProvider
+	return extractLabelFromStruct(labelProvider)
+}
+
+// extractLabelNames extracts labels names from a given labelsProviderMarker (parent instance of aStructLabelProvider)
+func extractLabelNames(labelProvider labelsProviderMarker) []string {
+	if any(labelProvider) == nil {
+		return nil
+	}
+
+	// If custom implementation is done, just do it
+	if clp, ok := labelProvider.(CustomLabelNamesProvider); ok {
+		return clp.ToLabelNames()
+	}
+
+	// Fallback to slow implementation via reflect
+	// We'll return label values in order of fields in the struct
+	val := reflect.Indirect(reflect.ValueOf(labelProvider))
+	typ := val.Type()
+
+	labelNames := make([]string, 0, typ.NumField())
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+		if field.Anonymous {
+			continue
+		}
+
+		var fieldName string
+		if ourTag := field.Tag.Get(promsafeTag); ourTag == "-" {
+			continue
+		} else if ourTag != "" {
+			fieldName = ourTag
+		} else {
+			fieldName = toSnakeCase(field.Name)
+		}
+
+		labelNames = append(labelNames, fieldName)
+	}
+
+	return labelNames
+}
+
+// extractLabelFromStruct extracts labels names+values from a given StructLabelProvider
+func extractLabelFromStruct(structWithLabels any) prometheus.Labels {
+	labels := prometheus.Labels{}
+
+	val := reflect.Indirect(reflect.ValueOf(structWithLabels))
+	typ := val.Type()
+
+	for i := 0; i < typ.NumField(); i++ {
+		field := typ.Field(i)
+		if field.Anonymous {
+			continue
+		}
+
+		var labelName string
+		if ourTag := field.Tag.Get(promsafeTag); ourTag != "" {
+			if ourTag == "-" { // tag="-" means "skip this field"
+				continue
+			}
+			labelName = ourTag
+		} else {
+			labelName = toSnakeCase(field.Name)
+		}
+
+		labels[labelName] = stringifyLabelValue(val.Field(i))
+	}
+	return labels
+}
+
+// stringifyLabelValue makes up a valid string value from a given field's value
+// It's used ONLY in fallback reflect mode
+// Field value might be a pointer, that's why we do reflect.Indirect()
+// Note: in future we can handle default values here as well
+func stringifyLabelValue(v reflect.Value) string {
+	return fmt.Sprintf("%v", reflect.Indirect(v).Interface())
+}
+
+// Convert struct field names to snake_case for Prometheus label compliance.
+func toSnakeCase(s string) string {
+	s = strings.TrimSpace(s)
+	var result []rune
+	for i, r := range s {
+		if i > 0 && r >= 'A' && r <= 'Z' {
+			result = append(result, '_')
+		}
+		result = append(result, r)
+	}
+	return strings.ToLower(string(result))
+}

prometheus/promsafe/safe_test.go

@@ -0,0 +1,197 @@
+// Copyright 2024 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package promsafe_test
+
+import (
+	"log"
+
+	"github.com/prometheus/client_golang/prometheus"
+	"github.com/prometheus/client_golang/prometheus/promauto"
+	"github.com/prometheus/client_golang/prometheus/promsafe"
+)
+
+// Important: This is not a test file. These are only examples!
+//            These can be considered smoke tests, but nothing more.
+//            TODO: Write real tests
+
+func ExampleNewCounterVecT_multiple_labels_manual() {
+	// Manually registering with multiple labels
+
+	type MyCounterLabels struct {
+		promsafe.StructLabelProvider
+		EventType string
+		Success   bool
+		Position  uint8 // yes, it's a number, but be careful with high-cardinality labels
+
+		ShouldNotBeUsed string `promsafe:"-"`
+	}
+
+	c := promsafe.NewCounterVecT[MyCounterLabels](prometheus.CounterOpts{
+		Name: "items_counted_detailed",
+	})
+
+	// Manually register the counter
+	if err := prometheus.Register(c.Unsafe()); err != nil {
+		log.Fatal("could not register: ", err.Error())
+	}
+
+	// and now, because of generics we can call Inc() with filled struct of labels:
+	counter := c.With(MyCounterLabels{
+		EventType: "reservation", Success: true, Position: 1,
+	})
+	counter.Inc()
+
+	// Output:
+}
+
+func ExampleNewCounterVecT_promauto_migrated() {
+	// Examples on how to migrate from promauto to promsafe
+	// When promauto was using a custom factory with custom registry
+
+	myReg := prometheus.NewRegistry()
+
+	counterOpts := prometheus.CounterOpts{
+		Name: "items_counted_detailed_auto",
+	}
+
+	// Old unsafe code
+	// promauto.With(myReg).NewCounterVec(counterOpts, []string{"event_type", "source"})
+	// becomes:
+
+	type MyLabels struct {
+		promsafe.StructLabelProvider
+		EventType string
+		Source    string
+	}
+	c := promsafe.WithAuto[MyLabels](myReg).NewCounterVecT(counterOpts)
+
+	c.With(MyLabels{
+		EventType: "reservation", Source: "source1",
+	}).Inc()
+
+	// Output:
+}
+
+func ExampleNewCounterVecT_promauto_global_migrated() {
+	// Examples on how to migrate from promauto to promsafe
+	// when promauto public API was used (with default registry)
+
+	// Setup so every NewCounter* call will use default registry
+	// like promauto does
+	// Note: it actually accepts other registry to become a default one
+	promsafe.SetupGlobalPromauto()
+	defer func() {
+		// cleanup for other examples
+		promsafe.SetupGlobalPromauto(promauto.With(nil))
+	}()
+
+	counterOpts := prometheus.CounterOpts{
+		Name: "items_counted_detailed_auto_global",
+	}
+
+	// Old code:
+	//c := promauto.NewCounterVec(counterOpts, []string{"status", "source"})
+	//c.With(prometheus.Labels{
+	//	"status": "active",
+	//	"source": "source1",
+	//}).Inc()
+	// becomes:
+
+	type MyLabels struct {
+		promsafe.StructLabelProvider
+		Status string
+		Source string
+	}
+	c := promsafe.NewCounterVecT[*MyLabels](counterOpts)
+
+	c.With(&MyLabels{
+		Status: "active", Source: "source1",
+	}).Inc()
+
+	// Output:
+}
+
+func ExampleNewCounterVecT_pointer_to_labels_promauto() {
+	// It's possible to use pointer to labels struct
+	myReg := prometheus.NewRegistry()
+
+	counterOpts := prometheus.CounterOpts{
+		Name: "items_counted_detailed_ptr",
+	}
+
+	type MyLabels struct {
+		promsafe.StructLabelProvider
+		EventType string
+		Source    string
+	}
+	c := promsafe.WithAuto[*MyLabels](myReg).NewCounterVecT(counterOpts)
+
+	c.With(&MyLabels{
+		EventType: "reservation", Source: "source1",
+	}).Inc()
+
+	// Output:
+}
+
+// FastMyLabels is a struct that will have a custom method that converts to prometheus.Labels
+type FastMyLabels struct {
+	promsafe.StructLabelProvider
+	EventType string
+	Source    string
+}
+
+// ToPrometheusLabels does a superfast conversion to labels. So no reflection is involved.
+func (f FastMyLabels) ToPrometheusLabels() prometheus.Labels {
+	return prometheus.Labels{"event_type": f.EventType, "source": f.Source}
+}
+
+// ToLabelNames does a superfast label names list. So no reflection is involved.
+func (f FastMyLabels) ToLabelNames() []string {
+	return []string{"event_type", "source"}
+}
+
+func ExampleNewCounterVecT_fast_safe_labels_provider() {
+	// It's possible to use pointer to labels struct
+	myReg := prometheus.NewRegistry()
+
+	counterOpts := prometheus.CounterOpts{
+		Name: "items_counted_fast",
+	}
+
+	c := promsafe.WithAuto[FastMyLabels](myReg).NewCounterVecT(counterOpts)
+
+	c.With(FastMyLabels{
+		EventType: "reservation", Source: "source1",
+	}).Inc()
+
+	// Output:
+}
+
+func ExampleNewCounterVecT_single_label_manual() {
+	// Manually registering with a single label
+	// Example of usage of shorthand: no structs no generics, but one string only
+
+	c := promsafe.NewCounterVecT1(prometheus.CounterOpts{
+		Name: "items_counted_by_status",
+	}, "status")
+
+	// Manually register the counter
+	if err := prometheus.Register(c.Unsafe()); err != nil {
+		log.Fatal("could not register: ", err.Error())
+	}
+
+	c.With("active").Inc()
+
+	// Output:
+}