testutil: Add ScrapeAndCompare (#1043)

* testutil: Add ScrapeAndCompare

Signed-off-by: sazary <soroosh@azary.ir>

* testutil: Use %w verb wherever we're using an error in fmt.Errorf

Signed-off-by: sazary <soroosh@azary.ir>

* Format

Signed-off-by: Kemal Akkoyun <kakkoyun@gmail.com>

Co-authored-by: Kemal Akkoyun <kakkoyun@users.noreply.github.com>
Co-authored-by: Kemal Akkoyun <kakkoyun@gmail.com>
This commit is contained in:
Soroosh Azary Marhabi 2022-08-05 18:57:47 +04:30 committed by GitHub
parent c576b951ad
commit 1638da9ae4
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 113 additions and 9 deletions

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@ -41,12 +41,12 @@ import (
"bytes"
"fmt"
"io"
"net/http"
"reflect"
"github.com/davecgh/go-spew/spew"
"github.com/prometheus/common/expfmt"
dto "github.com/prometheus/client_model/go"
"github.com/prometheus/common/expfmt"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/client_golang/prometheus/internal"
@ -155,6 +155,34 @@ func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
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.
@ -184,17 +212,35 @@ func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected
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)
}
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)
}
var tp expfmt.TextParser
wantRaw, err := tp.TextToMetricFamilies(expected)
if err != nil {
return fmt.Errorf("parsing expected metrics failed: %w", err)
}
want := internal.NormalizeMetricFamilies(wantRaw)
return compare(got, want)
return compare(got, expected)
}
// compare encodes both provided slices of metric families into the text format,

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@ -14,6 +14,9 @@
package testutil
import (
"fmt"
"net/http"
"net/http/httptest"
"strings"
"testing"
@ -308,6 +311,61 @@ Diff:
}
}
func TestScrapeAndCompare(t *testing.T) {
const expected = `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
some_total{ label1 = "value1" } 1
`
expectedReader := strings.NewReader(expected)
ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, expected)
}))
defer ts.Close()
if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total"); err != nil {
t.Errorf("unexpected scraping result:\n%s", err)
}
}
func TestScrapeAndCompareFetchingFail(t *testing.T) {
err := ScrapeAndCompare("some_url", strings.NewReader("some expectation"), "some_total")
if err == nil {
t.Errorf("expected an error but got nil")
}
if !strings.HasPrefix(err.Error(), "scraping metrics failed") {
t.Errorf("unexpected error happened: %s", err)
}
}
func TestScrapeAndCompareBadStatusCode(t *testing.T) {
const expected = `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
some_total{ label1 = "value1" } 1
`
expectedReader := strings.NewReader(expected)
ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
w.WriteHeader(http.StatusBadGateway)
fmt.Fprintln(w, expected)
}))
defer ts.Close()
err := ScrapeAndCompare(ts.URL, expectedReader, "some_total")
if err == nil {
t.Errorf("expected an error but got nil")
}
if !strings.HasPrefix(err.Error(), "the scraping target returned a status code other than 200") {
t.Errorf("unexpected error happened: %s", err)
}
}
func TestCollectAndCount(t *testing.T) {
c := prometheus.NewCounterVec(
prometheus.CounterOpts{