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// Copyright 2018 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 prometheus
import (
"errors"
"fmt"
"strings"
"unicode/utf8"
"github.com/prometheus/common/model"
)
// Labels represents a collection of label name -> value mappings. This type is
// commonly used with the With(Labels) and GetMetricWith(Labels) methods of
// metric vector Collectors, e.g.:
//
// myVec.With(Labels{"code": "404", "method": "GET"}).Add(42)
//
// The other use-case is the specification of constant label pairs in Opts or to
// create a Desc.
type Labels map[string]string
// LabelConstraint normalizes label values.
type LabelConstraint func(string) string
// ConstrainedLabels represents a label name and its constrain function
// to normalize label values. This type is commonly used when constructing
// metric vector Collectors.
type ConstrainedLabel struct {
Name string
Constraint LabelConstraint
}
// ConstrainableLabels is an interface that allows creating of labels that can
// be optionally constrained.
//
// prometheus.V2().NewCounterVec(CounterVecOpts{
// CounterOpts: {...}, // Usual CounterOpts fields
// VariableLabels: []ConstrainedLabels{
// {Name: "A"},
// {Name: "B", Constraint: func(v string) string { ... }},
// },
// })
type ConstrainableLabels interface {
compile() *compiledLabels
labelNames() []string
}
// ConstrainedLabels represents a collection of label name -> constrain function
// to normalize label values. This type is commonly used when constructing
// metric vector Collectors.
type ConstrainedLabels []ConstrainedLabel
func (cls ConstrainedLabels) compile() *compiledLabels {
compiled := &compiledLabels{
names: make([]string, len(cls)),
labelConstraints: map[string]LabelConstraint{},
}
for i, label := range cls {
compiled.names[i] = label.Name
if label.Constraint != nil {
compiled.labelConstraints[label.Name] = label.Constraint
}
}
return compiled
}
func (cls ConstrainedLabels) labelNames() []string {
names := make([]string, len(cls))
for i, label := range cls {
names[i] = label.Name
}
return names
}
// UnconstrainedLabels represents collection of label without any constraint on
// their value. Thus, it is simply a collection of label names.
//
// UnconstrainedLabels([]string{ "A", "B" })
//
// is equivalent to
//
// ConstrainedLabels {
// { Name: "A" },
// { Name: "B" },
// }
type UnconstrainedLabels []string
func (uls UnconstrainedLabels) compile() *compiledLabels {
return &compiledLabels{
names: uls,
}
}
func (uls UnconstrainedLabels) labelNames() []string {
return uls
}
type compiledLabels struct {
names []string
labelConstraints map[string]LabelConstraint
}
func (cls *compiledLabels) compile() *compiledLabels {
return cls
}
func (cls *compiledLabels) labelNames() []string {
return cls.names
}
func (cls *compiledLabels) constrain(labelName, value string) string {
if fn, ok := cls.labelConstraints[labelName]; ok && fn != nil {
return fn(value)
}
return value
}
// reservedLabelPrefix is a prefix which is not legal in user-supplied
// label names.
const reservedLabelPrefix = "__"
var errInconsistentCardinality = errors.New("inconsistent label cardinality")
func makeInconsistentCardinalityError(fqName string, labels, labelValues []string) error {
return fmt.Errorf(
"%w: %q has %d variable labels named %q but %d values %q were provided",
errInconsistentCardinality, fqName,
len(labels), labels,
len(labelValues), labelValues,
)
}
func validateValuesInLabels(labels Labels, expectedNumberOfValues int) error {
if len(labels) != expectedNumberOfValues {
return fmt.Errorf(
"%w: expected %d label values but got %d in %#v",
errInconsistentCardinality, expectedNumberOfValues,
len(labels), labels,
)
}
for name, val := range labels {
if !utf8.ValidString(val) {
return fmt.Errorf("label %s: value %q is not valid UTF-8", name, val)
}
}
return nil
}
func validateLabelValues(vals []string, expectedNumberOfValues int) error {
if len(vals) != expectedNumberOfValues {
// The call below makes vals escape, copy them to avoid that.
vals := append([]string(nil), vals...)
return fmt.Errorf(
"%w: expected %d label values but got %d in %#v",
errInconsistentCardinality, expectedNumberOfValues,
len(vals), vals,
)
}
for _, val := range vals {
if !utf8.ValidString(val) {
return fmt.Errorf("label value %q is not valid UTF-8", val)
}
}
return nil
}
func checkLabelName(l string) bool {
return model.LabelName(l).IsValid() && !strings.HasPrefix(l, reservedLabelPrefix)
}
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