Porting promlint from prometheus/prometheus

prometheus/testutil/promlint/promlint.go

@@ -0,0 +1,368 @@
+// 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 (
+	"fmt"
+	"io"
+	"regexp"
+	"sort"
+	"strings"
+
+	"github.com/prometheus/common/expfmt"
+
+	dto "github.com/prometheus/client_model/go"
+)
+
+// 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 {
+	r io.Reader
+}
+
+// A Problem is an issue detected by a Linter.
+type Problem struct {
+	// The name of the metric indicated by this Problem.
+	Metric string
+
+	// A description of the issue for this Problem.
+	Text string
+}
+
+// newProblem is helper function to create a Problem.
+func newProblem(mf dto.MetricFamily, text string) Problem {
+	return Problem{
+		Metric: mf.GetName(),
+		Text:   text,
+	}
+}
+
+// New creates a new Linter that reads an input stream of Prometheus metrics.
+// Only the Prometheus text exposition format is supported.
+func New(r io.Reader) *Linter {
+	return &Linter{
+		r: r,
+	}
+}
+
+// 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) {
+	// TODO(mdlayher): support for protobuf exposition format?
+	d := expfmt.NewDecoder(l.r, expfmt.FmtText)
+
+	var problems []Problem
+
+	var mf dto.MetricFamily
+	for {
+		if err := d.Decode(&mf); err != nil {
+			if err == io.EOF {
+				break
+			}
+
+			return nil, err
+		}
+
+		problems = append(problems, 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 lint(mf dto.MetricFamily) []Problem {
+	fns := []func(mf dto.MetricFamily) []Problem{
+		lintHelp,
+		lintMetricUnits,
+		lintCounter,
+		lintHistogramSummaryReserved,
+		lintMetricTypeInName,
+		lintReservedChars,
+		lintCamelCase,
+		lintUnitAbbreviations,
+	}
+
+	var problems []Problem
+	for _, fn := range fns {
+		problems = append(problems, fn(mf)...)
+	}
+
+	// TODO(mdlayher): lint rules for specific metrics types.
+	return problems
+}
+
+// lintHelp detects issues related to the help text for a metric.
+func lintHelp(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+
+	// Expect all metrics to have help text available.
+	if mf.Help == nil {
+		problems = append(problems, newProblem(mf, "no help text"))
+	}
+
+	return problems
+}
+
+// lintMetricUnits detects issues with metric unit names.
+func lintMetricUnits(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+
+	unit, base, ok := metricUnits(*mf.Name)
+	if !ok {
+		// No known units detected.
+		return nil
+	}
+
+	// Unit is already a base unit.
+	if unit == base {
+		return nil
+	}
+
+	problems = append(problems, newProblem(mf, fmt.Sprintf("use base unit %q instead of %q", base, unit)))
+
+	return problems
+}
+
+// lintCounter detects issues specific to counters, as well as patterns that should
+// only be used with counters.
+func lintCounter(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+
+	isCounter := mf.GetType() == dto.MetricType_COUNTER
+	isUntyped := mf.GetType() == dto.MetricType_UNTYPED
+	hasTotalSuffix := strings.HasSuffix(mf.GetName(), "_total")
+
+	switch {
+	case isCounter && !hasTotalSuffix:
+		problems = append(problems, newProblem(mf, `counter metrics should have "_total" suffix`))
+	case !isUntyped && !isCounter && hasTotalSuffix:
+		problems = append(problems, newProblem(mf, `non-counter metrics should not have "_total" suffix`))
+	}
+
+	return problems
+}
+
+// lintHistogramSummaryReserved detects when other types of metrics use names or labels
+// reserved for use by histograms and/or summaries.
+func lintHistogramSummaryReserved(mf dto.MetricFamily) []Problem {
+	// These rules do not apply to untyped metrics.
+	t := mf.GetType()
+	if t == dto.MetricType_UNTYPED {
+		return nil
+	}
+
+	var problems []Problem
+
+	isHistogram := t == dto.MetricType_HISTOGRAM
+	isSummary := t == dto.MetricType_SUMMARY
+
+	n := mf.GetName()
+
+	if !isHistogram && strings.HasSuffix(n, "_bucket") {
+		problems = append(problems, newProblem(mf, `non-histogram metrics should not have "_bucket" suffix`))
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_count") {
+		problems = append(problems, newProblem(mf, `non-histogram and non-summary metrics should not have "_count" suffix`))
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_sum") {
+		problems = append(problems, newProblem(mf, `non-histogram and non-summary metrics should not have "_sum" suffix`))
+	}
+
+	for _, m := range mf.GetMetric() {
+		for _, l := range m.GetLabel() {
+			ln := l.GetName()
+
+			if !isHistogram && ln == "le" {
+				problems = append(problems, newProblem(mf, `non-histogram metrics should not have "le" label`))
+			}
+			if !isSummary && ln == "quantile" {
+				problems = append(problems, newProblem(mf, `non-summary metrics should not have "quantile" label`))
+			}
+		}
+	}
+
+	return problems
+}
+
+// lintMetricTypeInName detects when metric types are included in the metric name.
+func lintMetricTypeInName(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+	n := strings.ToLower(mf.GetName())
+
+	for i, t := range dto.MetricType_name {
+		if i == int32(dto.MetricType_UNTYPED) {
+			continue
+		}
+
+		typename := strings.ToLower(t)
+		if strings.Contains(n, "_"+typename+"_") || strings.HasSuffix(n, "_"+typename) {
+			problems = append(problems, newProblem(mf, fmt.Sprintf(`metric name should not include type '%s'`, typename)))
+		}
+	}
+	return problems
+}
+
+// lintReservedChars detects colons in metric names.
+func lintReservedChars(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+	if strings.Contains(mf.GetName(), ":") {
+		problems = append(problems, newProblem(mf, "metric names should not contain ':'"))
+	}
+	return problems
+}
+
+var camelCase = regexp.MustCompile(`[a-z][A-Z]`)
+
+// lintCamelCase detects metric names and label names written in camelCase.
+func lintCamelCase(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+	if camelCase.FindString(mf.GetName()) != "" {
+		problems = append(problems, newProblem(mf, "metric names should be written in 'snake_case' not 'camelCase'"))
+	}
+
+	for _, m := range mf.GetMetric() {
+		for _, l := range m.GetLabel() {
+			if camelCase.FindString(l.GetName()) != "" {
+				problems = append(problems, newProblem(mf, "label names should be written in 'snake_case' not 'camelCase'"))
+			}
+		}
+	}
+	return problems
+}
+
+// lintUnitAbbreviations detects abbreviated units in the metric name.
+func lintUnitAbbreviations(mf dto.MetricFamily) []Problem {
+	var problems []Problem
+	n := strings.ToLower(mf.GetName())
+	for _, s := range unitAbbreviations {
+		if strings.Contains(n, "_"+s+"_") || strings.HasSuffix(n, "_"+s) {
+			problems = append(problems, newProblem(mf, "metric names should not contain abbreviated units"))
+		}
+	}
+	return problems
+}
+
+// metricUnits attempts to detect known unit types used as part of a metric name,
+// e.g. "foo_bytes_total" or "bar_baz_milligrams".
+func metricUnits(m string) (unit string, base string, ok bool) {
+	ss := strings.Split(m, "_")
+
+	for unit, base := range units {
+		// Also check for "no prefix".
+		for _, p := range append(unitPrefixes, "") {
+			for _, s := range ss {
+				// Attempt to explicitly match a known unit with a known prefix,
+				// as some words may look like "units" when matching suffix.
+				//
+				// As an example, "thermometers" should not match "meters", but
+				// "kilometers" should.
+				if s == p+unit {
+					return p + unit, base, true
+				}
+			}
+		}
+	}
+
+	return "", "", false
+}
+
+// Units and their possible prefixes recognized by this library.  More can be
+// added over time as needed.
+var (
+	// map a unit to the appropriate base unit.
+	units = map[string]string{
+		// Base units.
+		"amperes": "amperes",
+		"bytes":   "bytes",
+		"celsius": "celsius", // Celsius is more common in practice than Kelvin.
+		"grams":   "grams",
+		"joules":  "joules",
+		"meters":  "meters", // Both American and international spelling permitted.
+		"metres":  "metres",
+		"seconds": "seconds",
+		"volts":   "volts",
+
+		// Non base units.
+		// Time.
+		"minutes": "seconds",
+		"hours":   "seconds",
+		"days":    "seconds",
+		"weeks":   "seconds",
+		// Temperature.
+		"kelvin":     "celsius",
+		"kelvins":    "celsius",
+		"fahrenheit": "celsius",
+		"rankine":    "celsius",
+		// Length.
+		"inches": "meters",
+		"yards":  "meters",
+		"miles":  "meters",
+		// Bytes.
+		"bits": "bytes",
+		// Energy.
+		"calories": "joules",
+		// Mass.
+		"pounds": "grams",
+		"ounces": "grams",
+	}
+
+	unitPrefixes = []string{
+		"pico",
+		"nano",
+		"micro",
+		"milli",
+		"centi",
+		"deci",
+		"deca",
+		"hecto",
+		"kilo",
+		"kibi",
+		"mega",
+		"mibi",
+		"giga",
+		"gibi",
+		"tera",
+		"tebi",
+		"peta",
+		"pebi",
+	}
+
+	// Common abbreviations that we'd like to discourage.
+	unitAbbreviations = []string{
+		"s",
+		"ms",
+		"us",
+		"ns",
+		"sec",
+		"b",
+		"kb",
+		"mb",
+		"gb",
+		"tb",
+		"pb",
+		"m",
+		"h",
+		"d",
+	}
+)