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// Copyright 2020 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 promlint provides a linter for Prometheus metrics.
package promlint
import (
"errors"
"io"
"sort"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
)
// A Linter is a Prometheus metrics linter. It identifies issues with metric
// names, types, and metadata, and reports them to the caller.
type Linter struct {
// The linter will read metrics in the Prometheus text format from r and
// then lint it, _and_ it will lint the metrics provided directly as
// MetricFamily proto messages in mfs. Note, however, that the current
// constructor functions New and NewWithMetricFamilies only ever set one
// of them.
r io.Reader
mfs []*dto.MetricFamily
customValidations []Validation
}
// New creates a new Linter that reads an input stream of Prometheus metrics in
// the Prometheus text exposition format.
func New(r io.Reader) *Linter {
return &Linter{
r: r,
}
}
// NewWithMetricFamilies creates a new Linter that reads from a slice of
// MetricFamily protobuf messages.
func NewWithMetricFamilies(mfs []*dto.MetricFamily) *Linter {
return &Linter{
mfs: mfs,
}
}
// AddCustomValidations adds custom validations to the linter.
func (l *Linter) AddCustomValidations(vs ...Validation) {
if l.customValidations == nil {
l.customValidations = make([]Validation, 0, len(vs))
}
l.customValidations = append(l.customValidations, vs...)
}
// Lint performs a linting pass, returning a slice of Problems indicating any
// issues found in the metrics stream. The slice is sorted by metric name
// and issue description.
func (l *Linter) Lint() ([]Problem, error) {
var problems []Problem
if l.r != nil {
d := expfmt.NewDecoder(l.r, expfmt.NewFormat(expfmt.TypeTextPlain))
mf := &dto.MetricFamily{}
for {
if err := d.Decode(mf); err != nil {
if errors.Is(err, io.EOF) {
break
}
return nil, err
}
problems = append(problems, l.lint(mf)...)
}
}
for _, mf := range l.mfs {
problems = append(problems, l.lint(mf)...)
}
// Ensure deterministic output.
sort.SliceStable(problems, func(i, j int) bool {
if problems[i].Metric == problems[j].Metric {
return problems[i].Text < problems[j].Text
}
return problems[i].Metric < problems[j].Metric
})
return problems, nil
}
// lint is the entry point for linting a single metric.
func (l *Linter) lint(mf *dto.MetricFamily) []Problem {
var problems []Problem
for _, fn := range defaultValidations {
errs := fn(mf)
for _, err := range errs {
problems = append(problems, newProblem(mf, err.Error()))
}
}
if l.customValidations != nil {
for _, fn := range l.customValidations {
errs := fn(mf)
for _, err := range errs {
problems = append(problems, newProblem(mf, err.Error()))
}
}
}
// TODO(mdlayher): lint rules for specific metrics types.
return problems
}
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