diff --git a/prometheus/promsafe/safe.go b/prometheus/promsafe/safe.go new file mode 100644 index 0000000..019210b --- /dev/null +++ b/prometheus/promsafe/safe.go @@ -0,0 +1,307 @@ +// 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 + } +} + +// 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 +} + +// labelProviderMarker is a marker interface for enforcing type-safety. +// With its help we can force our label-related functions to only accept SingleLabelProvider or StructLabelProvider. +type labelProviderMarker interface { + marker() +} + +// SingleLabelProvider is a type used for declaring a single label. +// When used as labelProviderMarker it provides just a label name. +// It's meant to be used with single-label metrics only! +// Use StructLabelProvider for multi-label metrics. +type SingleLabelProvider string + +var _ labelProviderMarker = SingleLabelProvider("") + +func (s SingleLabelProvider) marker() { + panic("marker interface method should never be called") +} + +// StructLabelProvider should be embedded in any struct that serves as a label provider. +type StructLabelProvider struct{} + +var _ labelProviderMarker = (*StructLabelProvider)(nil) + +func (s StructLabelProvider) marker() { + panic("marker interface method should never be called") +} + +// handler is a helper struct that helps us to handle type-safe labels +// It holds a label name in case if it's the only label (when SingleLabelProvider is used). +type handler[T labelProviderMarker] struct { + theOnlyLabelName string +} + +func newHandler[T labelProviderMarker](labelProvider T) handler[T] { + var h handler[T] + if s, ok := any(labelProvider).(SingleLabelProvider); ok { + h.theOnlyLabelName = string(s) + } + return h +} + +// extractLabelsWithValues extracts labels names+values from a given labelProviderMarker (SingleLabelProvider or StructLabelProvider) +func (h handler[T]) extractLabels(labelProvider T) []string { + if any(labelProvider) == nil { + return nil + } + if s, ok := any(labelProvider).(SingleLabelProvider); ok { + return []string{string(s)} + } + + // Here, then, it can be only a struct, that is a parent of StructLabelProvider + labels := extractLabelFromStruct(labelProvider) + labelNames := make([]string, 0, len(labels)) + for k := range labels { + labelNames = append(labelNames, k) + } + return labelNames +} + +// extractLabelsWithValues extracts labels names+values from a given labelProviderMarker (SingleLabelProvider or StructLabelProvider) +func (h handler[T]) extractLabelsWithValues(labelProvider T) prometheus.Labels { + if any(labelProvider) == nil { + return nil + } + + // TODO: let's handle defaults as well, why not? + + if s, ok := any(labelProvider).(SingleLabelProvider); ok { + return prometheus.Labels{h.theOnlyLabelName: string(s)} + } + + // Here, then, it can be only a struct, that is a parent of StructLabelProvider + return extractLabelFromStruct(labelProvider) +} + +// extractLabelValues extracts label string values from a given labelProviderMarker (SingleLabelProvider or StructLabelProvider) +func (h handler[T]) extractLabelValues(labelProvider T) []string { + m := h.extractLabelsWithValues(labelProvider) + + labelValues := make([]string, 0, len(m)) + for _, v := range m { + labelValues = append(labelValues, v) + } + return labelValues +} + +// NewCounterVecT creates a new CounterVecT with type-safe labels. +func NewCounterVecT[T labelProviderMarker](opts prometheus.CounterOpts, labels T) *CounterVecT[T] { + h := newHandler(labels) + + var inner *prometheus.CounterVec + + if factory != nil { + inner = factory.NewCounterVec(opts, h.extractLabels(labels)) + } else { + inner = prometheus.NewCounterVec(opts, h.extractLabels(labels)) + } + + return &CounterVecT[T]{ + handler: h, + inner: inner, + } +} + +// CounterVecT is a wrapper around prometheus.CounterVecT that allows type-safe labels. +type CounterVecT[T labelProviderMarker] struct { + handler[T] + inner *prometheus.CounterVec +} + +// GetMetricWithLabelValues behaves like prometheus.CounterVec.GetMetricWithLabelValues but with type-safe labels. +func (c *CounterVecT[T]) GetMetricWithLabelValues(labels T) (prometheus.Counter, error) { + return c.inner.GetMetricWithLabelValues(c.handler.extractLabelValues(labels)...) +} + +// 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(c.handler.extractLabelsWithValues(labels)) +} + +// WithLabelValues behaves like prometheus.CounterVec.WithLabelValues but with type-safe labels. +func (c *CounterVecT[T]) WithLabelValues(labels T) prometheus.Counter { + return c.inner.WithLabelValues(c.handler.extractLabelValues(labels)...) +} + +// With behaves like prometheus.CounterVec.With but with type-safe labels. +func (c *CounterVecT[T]) With(labels T) prometheus.Counter { + return c.inner.With(c.handler.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(c.handler.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(c.handler.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) +} + +// +// 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 labelProviderMarker] struct { + r prometheus.Registerer +} + +// WithAuto is a helper function that allows to use promauto.With with promsafe.With +func WithAuto(r prometheus.Registerer) Factory[labelProviderMarker] { + return Factory[labelProviderMarker]{r: r} +} + +// NewCounterVecT works like promauto.NewCounterVec but with type-safe labels +func (f Factory[T]) NewCounterVecT(opts prometheus.CounterOpts, labels T) *CounterVecT[T] { + c := NewCounterVecT(opts, labels) + 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) +} + +// +// Helpers +// + +// 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) + } + + // Note: we don't handle defaults values for now + // so it can have "nil" values, if you had *string fields, etc + fieldVal := fmt.Sprintf("%v", val.Field(i).Interface()) + + labels[labelName] = fieldVal + } + return labels +} + +// 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)) +} diff --git a/prometheus/promsafe/safe_test.go b/prometheus/promsafe/safe_test.go new file mode 100644 index 0000000..d0f65c2 --- /dev/null +++ b/prometheus/promsafe/safe_test.go @@ -0,0 +1,131 @@ +// 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/promsafe" +) + +func ExampleNewCounterVecT_single_label_manual() { + // Manually registering with a single label + + c := promsafe.NewCounterVecT(prometheus.CounterOpts{ + Name: "items_counted_by_status", + }, promsafe.SingleLabelProvider("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: +} + +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(prometheus.CounterOpts{ + Name: "items_counted_detailed", + }, &MyCounterLabels{}) + + // 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 TicketReservationAttemptsLabels struct { + promsafe.StructLabelProvider + EventType string + Source string + } + c := promsafe.WithAuto(myReg).NewCounterVecT(counterOpts, &TicketReservationAttemptsLabels{}) + + c.With(&TicketReservationAttemptsLabels{ + 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() + + 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 TicketReservationAttemptsLabels struct { + promsafe.StructLabelProvider + Status string + Source string + } + c := promsafe.NewCounterVecT(counterOpts, &TicketReservationAttemptsLabels{}) + + c.With(&TicketReservationAttemptsLabels{ + Status: "active", Source: "source1", + }).Inc() + + // Output: +}