promlint: initial copy from github.com/prometheus/prometheus/util/pro…

promlint/promlint.go

@@ -0,0 +1,268 @@
+// Copyright 2017 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"
+	"sort"
+	"strings"
+
+	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 {
+	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
+}
+
+// problems is a slice of Problems with a helper method to easily append
+// additional Problems to the slice.
+type problems []Problem
+
+// Add appends a new Problem to the slice for the specified metric, with
+// the specified issue text.
+func (p *problems) Add(mf dto.MetricFamily, text string) {
+	*p = append(*p, Problem{
+		Metric: mf.GetName(),
+		Text:   text,
+	})
+}
+
+// New creates a new Linter that reads an input stream of Prometheus metrics.
+// Only the 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 true
+		}
+
+		return problems[i].Text < problems[j].Text
+	})
+
+	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,
+	}
+
+	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 problems
+
+	// Expect all metrics to have help text available.
+	if mf.Help == nil {
+		problems.Add(mf, "no help text")
+	}
+
+	return problems
+}
+
+// lintMetricUnits detects issues with metric unit names.
+func lintMetricUnits(mf dto.MetricFamily) []Problem {
+	var problems problems
+
+	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.Add(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 problems
+
+	isCounter := mf.GetType() == dto.MetricType_COUNTER
+	isUntyped := mf.GetType() == dto.MetricType_UNTYPED
+	hasTotalSuffix := strings.HasSuffix(mf.GetName(), "_total")
+
+	switch {
+	case isCounter && !hasTotalSuffix:
+		problems.Add(mf, `counter metrics should have "_total" suffix`)
+	case !isUntyped && !isCounter && hasTotalSuffix:
+		problems.Add(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 problems
+
+	isHistogram := t == dto.MetricType_HISTOGRAM
+	isSummary := t == dto.MetricType_SUMMARY
+
+	n := mf.GetName()
+
+	if !isHistogram && strings.HasSuffix(n, "_bucket") {
+		problems.Add(mf, `non-histogram metrics should not have "_bucket" suffix`)
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_count") {
+		problems.Add(mf, `non-histogram and non-summary metrics should not have "_count" suffix`)
+	}
+	if !isHistogram && !isSummary && strings.HasSuffix(n, "_sum") {
+		problems.Add(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.Add(mf, `non-histogram metrics should not have "le" label`)
+			}
+			if !isSummary && ln == "quantile" {
+				problems.Add(mf, `non-summary metrics should not have "quantile" label`)
+			}
+		}
+	}
+
+	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 _, u := range baseUnits {
+		// 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+u {
+					return p + u, u, true
+				}
+			}
+		}
+	}
+
+	return "", "", false
+}
+
+// Units and their possible prefixes recognized by this library.  More can be
+// added over time as needed.
+var (
+	baseUnits = []string{
+		"amperes",
+		"bytes",
+		"candela",
+		"grams",
+		"kelvin", // Both plural and non-plural form allowed.
+		"kelvins",
+		"meters", // Both American and international spelling permitted.
+		"metres",
+		"moles",
+		"seconds",
+	}
+
+	unitPrefixes = []string{
+		"pico",
+		"nano",
+		"micro",
+		"milli",
+		"centi",
+		"deci",
+		"deca",
+		"hecto",
+		"kilo",
+		"kibi",
+		"mega",
+		"mibi",
+		"giga",
+		"gibi",
+		"tera",
+		"tebi",
+		"peta",
+		"pebi",
+	}
+)