client_golang/prometheus/testutil/testutil.go

359 lines
12 KiB
Go
Raw Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

// 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 testutil provides helpers to test code using the prometheus package
// of client_golang.
//
// While writing unit tests to verify correct instrumentation of your code, it's
// a common mistake to mostly test the instrumentation library instead of your
// own code. Rather than verifying that a prometheus.Counter's value has changed
// as expected or that it shows up in the exposition after registration, it is
// in general more robust and more faithful to the concept of unit tests to use
// mock implementations of the prometheus.Counter and prometheus.Registerer
// interfaces that simply assert that the Add or Register methods have been
// called with the expected arguments. However, this might be overkill in simple
// scenarios. The ToFloat64 function is provided for simple inspection of a
// single-value metric, but it has to be used with caution.
//
// End-to-end tests to verify all or larger parts of the metrics exposition can
// be implemented with the CollectAndCompare or GatherAndCompare functions. The
// most appropriate use is not so much testing instrumentation of your code, but
// testing custom prometheus.Collector implementations and in particular whole
// exporters, i.e. programs that retrieve telemetry data from a 3rd party source
// and convert it into Prometheus metrics.
//
// In a similar pattern, CollectAndLint and GatherAndLint can be used to detect
// metrics that have issues with their name, type, or metadata without being
// necessarily invalid, e.g. a counter with a name missing the “_total” suffix.
package testutil
import (
"bytes"
"fmt"
"io"
"net/http"
"reflect"
"github.com/davecgh/go-spew/spew"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
"google.golang.org/protobuf/proto"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/internal"
)
// ToFloat64 collects all Metrics from the provided Collector. It expects that
// this results in exactly one Metric being collected, which must be a Gauge,
// Counter, or Untyped. In all other cases, ToFloat64 panics. ToFloat64 returns
// the value of the collected Metric.
//
// The Collector provided is typically a simple instance of Gauge or Counter, or
// less commonly a GaugeVec or CounterVec with exactly one element. But any
// Collector fulfilling the prerequisites described above will do.
//
// Use this function with caution. It is computationally very expensive and thus
// not suited at all to read values from Metrics in regular code. This is really
// only for testing purposes, and even for testing, other approaches are often
// more appropriate (see this package's documentation).
//
// A clear anti-pattern would be to use a metric type from the prometheus
// package to track values that are also needed for something else than the
// exposition of Prometheus metrics. For example, you would like to track the
// number of items in a queue because your code should reject queuing further
// items if a certain limit is reached. It is tempting to track the number of
// items in a prometheus.Gauge, as it is then easily available as a metric for
// exposition, too. However, then you would need to call ToFloat64 in your
// regular code, potentially quite often. The recommended way is to track the
// number of items conventionally (in the way you would have done it without
// considering Prometheus metrics) and then expose the number with a
// prometheus.GaugeFunc.
func ToFloat64(c prometheus.Collector) float64 {
var (
m prometheus.Metric
mCount int
mChan = make(chan prometheus.Metric)
done = make(chan struct{})
)
go func() {
for m = range mChan {
mCount++
}
close(done)
}()
c.Collect(mChan)
close(mChan)
<-done
if mCount != 1 {
panic(fmt.Errorf("collected %d metrics instead of exactly 1", mCount))
}
pb := &dto.Metric{}
if err := m.Write(pb); err != nil {
panic(fmt.Errorf("error happened while collecting metrics: %w", err))
}
if pb.Gauge != nil {
return pb.Gauge.GetValue()
}
if pb.Counter != nil {
return pb.Counter.GetValue()
}
if pb.Untyped != nil {
return pb.Untyped.GetValue()
}
panic(fmt.Errorf("collected a non-gauge/counter/untyped metric: %s", pb))
}
// CollectAndCount registers the provided Collector with a newly created
// pedantic Registry. It then calls GatherAndCount with that Registry and with
// the provided metricNames. In the unlikely case that the registration or the
// gathering fails, this function panics. (This is inconsistent with the other
// CollectAnd… functions in this package and has historical reasons. Changing
// the function signature would be a breaking change and will therefore only
// happen with the next major version bump.)
func CollectAndCount(c prometheus.Collector, metricNames ...string) int {
reg := prometheus.NewPedanticRegistry()
if err := reg.Register(c); err != nil {
panic(fmt.Errorf("registering collector failed: %w", err))
}
result, err := GatherAndCount(reg, metricNames...)
if err != nil {
panic(err)
}
return result
}
// GatherAndCount gathers all metrics from the provided Gatherer and counts
// them. It returns the number of metric children in all gathered metric
// families together. If any metricNames are provided, only metrics with those
// names are counted.
func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
got, err := g.Gather()
if err != nil {
return 0, fmt.Errorf("gathering metrics failed: %w", err)
}
if metricNames != nil {
got = filterMetrics(got, metricNames)
}
result := 0
for _, mf := range got {
result += len(mf.GetMetric())
}
return result, nil
}
// ScrapeAndCompare calls a remote exporter's endpoint which is expected to return some metrics in
// plain text format. Then it compares it with the results that the `expected` would return.
// If the `metricNames` is not empty it would filter the comparison only to the given metric names.
func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) error {
resp, err := http.Get(url)
if err != nil {
return fmt.Errorf("scraping metrics failed: %w", err)
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return fmt.Errorf("the scraping target returned a status code other than 200: %d",
resp.StatusCode)
}
scraped, err := convertReaderToMetricFamily(resp.Body)
if err != nil {
return err
}
wanted, err := convertReaderToMetricFamily(expected)
if err != nil {
return err
}
return compareMetricFamilies(scraped, wanted, metricNames...)
}
// CollectAndCompare registers the provided Collector with a newly created
// pedantic Registry. It then calls GatherAndCompare with that Registry and with
// the provided metricNames.
func CollectAndCompare(c prometheus.Collector, expected io.Reader, metricNames ...string) error {
reg := prometheus.NewPedanticRegistry()
if err := reg.Register(c); err != nil {
return fmt.Errorf("registering collector failed: %w", err)
}
return GatherAndCompare(reg, expected, metricNames...)
}
// GatherAndCompare gathers all metrics from the provided Gatherer and compares
// it to an expected output read from the provided Reader in the Prometheus text
// exposition format. If any metricNames are provided, only metrics with those
// names are compared.
func GatherAndCompare(g prometheus.Gatherer, expected io.Reader, metricNames ...string) error {
return TransactionalGatherAndCompare(prometheus.ToTransactionalGatherer(g), expected, metricNames...)
}
// TransactionalGatherAndCompare gathers all metrics from the provided Gatherer and compares
// it to an expected output read from the provided Reader in the Prometheus text
// exposition format. If any metricNames are provided, only metrics with those
// names are compared.
func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected io.Reader, metricNames ...string) error {
got, done, err := g.Gather()
defer done()
if err != nil {
return fmt.Errorf("gathering metrics failed: %w", err)
}
wanted, err := convertReaderToMetricFamily(expected)
if err != nil {
return err
}
return compareMetricFamilies(got, wanted, metricNames...)
}
// convertReaderToMetricFamily would read from a io.Reader object and convert it to a slice of
// dto.MetricFamily.
func convertReaderToMetricFamily(reader io.Reader) ([]*dto.MetricFamily, error) {
var tp expfmt.TextParser
notNormalized, err := tp.TextToMetricFamilies(reader)
if err != nil {
return nil, fmt.Errorf("converting reader to metric families failed: %w", err)
}
// The text protocol handles empty help fields inconsistently. When
// encoding, any non-nil value, include the empty string, produces a
// "# HELP" line. But when decoding, the help field is only set to a
// non-nil value if the "# HELP" line contains a non-empty value.
//
// Because metrics in a registry always have non-nil help fields, populate
// any nil help fields in the parsed metrics with the empty string so that
// when we compare text encodings, the results are consistent.
for _, metric := range notNormalized {
if metric.Help == nil {
metric.Help = proto.String("")
}
}
return internal.NormalizeMetricFamilies(notNormalized), nil
}
// compareMetricFamilies would compare 2 slices of metric families, and optionally filters both of
// them to the `metricNames` provided.
func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...string) error {
if metricNames != nil {
got = filterMetrics(got, metricNames)
expected = filterMetrics(expected, metricNames)
}
return compare(got, expected)
}
// compare encodes both provided slices of metric families into the text format,
// compares their string message, and returns an error if they do not match.
// The error contains the encoded text of both the desired and the actual
// result.
func compare(got, want []*dto.MetricFamily) error {
var gotBuf, wantBuf bytes.Buffer
enc := expfmt.NewEncoder(&gotBuf, expfmt.NewFormat(expfmt.TypeTextPlain))
for _, mf := range got {
if err := enc.Encode(mf); err != nil {
return fmt.Errorf("encoding gathered metrics failed: %w", err)
}
}
enc = expfmt.NewEncoder(&wantBuf, expfmt.NewFormat(expfmt.TypeTextPlain))
for _, mf := range want {
if err := enc.Encode(mf); err != nil {
return fmt.Errorf("encoding expected metrics failed: %w", err)
}
}
if diffErr := diff(wantBuf, gotBuf); diffErr != "" {
return fmt.Errorf(diffErr)
}
return nil
}
// diff returns a diff of both values as long as both are of the same type and
// are a struct, map, slice, array or string. Otherwise it returns an empty string.
func diff(expected, actual interface{}) string {
if expected == nil || actual == nil {
return ""
}
et, ek := typeAndKind(expected)
at, _ := typeAndKind(actual)
if et != at {
return ""
}
if ek != reflect.Struct && ek != reflect.Map && ek != reflect.Slice && ek != reflect.Array && ek != reflect.String {
return ""
}
var e, a string
c := spew.ConfigState{
Indent: " ",
DisablePointerAddresses: true,
DisableCapacities: true,
SortKeys: true,
}
if et != reflect.TypeOf("") {
e = c.Sdump(expected)
a = c.Sdump(actual)
} else {
e = reflect.ValueOf(expected).String()
a = reflect.ValueOf(actual).String()
}
diff, _ := internal.GetUnifiedDiffString(internal.UnifiedDiff{
A: internal.SplitLines(e),
B: internal.SplitLines(a),
FromFile: "metric output does not match expectation; want",
FromDate: "",
ToFile: "got:",
ToDate: "",
Context: 1,
})
if diff == "" {
return ""
}
return "\n\nDiff:\n" + diff
}
// typeAndKind returns the type and kind of the given interface{}
func typeAndKind(v interface{}) (reflect.Type, reflect.Kind) {
t := reflect.TypeOf(v)
k := t.Kind()
if k == reflect.Ptr {
t = t.Elem()
k = t.Kind()
}
return t, k
}
func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFamily {
var filtered []*dto.MetricFamily
for _, m := range metrics {
for _, name := range names {
if m.GetName() == name {
filtered = append(filtered, m)
break
}
}
}
return filtered
}