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>
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@ -41,12 +41,12 @@ import (
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"bytes"
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"fmt"
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"io"
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"net/http"
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"reflect"
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"github.com/davecgh/go-spew/spew"
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"github.com/prometheus/common/expfmt"
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dto "github.com/prometheus/client_model/go"
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"github.com/prometheus/common/expfmt"
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"github.com/prometheus/client_golang/prometheus"
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"github.com/prometheus/client_golang/prometheus/internal"
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@ -155,6 +155,34 @@ func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
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return result, nil
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}
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// ScrapeAndCompare calls a remote exporter's endpoint which is expected to return some metrics in
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// plain text format. Then it compares it with the results that the `expected` would return.
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// If the `metricNames` is not empty it would filter the comparison only to the given metric names.
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func ScrapeAndCompare(url string, expected io.Reader, metricNames ...string) error {
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resp, err := http.Get(url)
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if err != nil {
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return fmt.Errorf("scraping metrics failed: %w", err)
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}
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defer resp.Body.Close()
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if resp.StatusCode != http.StatusOK {
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return fmt.Errorf("the scraping target returned a status code other than 200: %d",
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resp.StatusCode)
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}
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scraped, err := convertReaderToMetricFamily(resp.Body)
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if err != nil {
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return err
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}
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wanted, err := convertReaderToMetricFamily(expected)
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if err != nil {
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return err
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}
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return compareMetricFamilies(scraped, wanted, metricNames...)
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}
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// CollectAndCompare registers the provided Collector with a newly created
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// pedantic Registry. It then calls GatherAndCompare with that Registry and with
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// the provided metricNames.
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@ -184,17 +212,35 @@ func TransactionalGatherAndCompare(g prometheus.TransactionalGatherer, expected
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if err != nil {
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return fmt.Errorf("gathering metrics failed: %w", err)
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}
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wanted, err := convertReaderToMetricFamily(expected)
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if err != nil {
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return err
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}
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return compareMetricFamilies(got, wanted, metricNames...)
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}
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// convertReaderToMetricFamily would read from a io.Reader object and convert it to a slice of
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// dto.MetricFamily.
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func convertReaderToMetricFamily(reader io.Reader) ([]*dto.MetricFamily, error) {
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var tp expfmt.TextParser
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notNormalized, err := tp.TextToMetricFamilies(reader)
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if err != nil {
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return nil, fmt.Errorf("converting reader to metric families failed: %w", err)
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}
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return internal.NormalizeMetricFamilies(notNormalized), nil
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}
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// compareMetricFamilies would compare 2 slices of metric families, and optionally filters both of
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// them to the `metricNames` provided.
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func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...string) error {
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if metricNames != nil {
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got = filterMetrics(got, metricNames)
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}
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var tp expfmt.TextParser
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wantRaw, err := tp.TextToMetricFamilies(expected)
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if err != nil {
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return fmt.Errorf("parsing expected metrics failed: %w", err)
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}
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want := internal.NormalizeMetricFamilies(wantRaw)
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return compare(got, want)
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return compare(got, expected)
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}
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// compare encodes both provided slices of metric families into the text format,
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@ -14,6 +14,9 @@
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package testutil
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import (
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"fmt"
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"net/http"
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"net/http/httptest"
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"strings"
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"testing"
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@ -308,6 +311,61 @@ Diff:
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}
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}
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func TestScrapeAndCompare(t *testing.T) {
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const expected = `
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# HELP some_total A value that represents a counter.
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# TYPE some_total counter
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some_total{ label1 = "value1" } 1
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`
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expectedReader := strings.NewReader(expected)
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ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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fmt.Fprintln(w, expected)
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}))
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defer ts.Close()
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if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total"); err != nil {
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t.Errorf("unexpected scraping result:\n%s", err)
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}
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}
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func TestScrapeAndCompareFetchingFail(t *testing.T) {
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err := ScrapeAndCompare("some_url", strings.NewReader("some expectation"), "some_total")
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if err == nil {
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t.Errorf("expected an error but got nil")
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}
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if !strings.HasPrefix(err.Error(), "scraping metrics failed") {
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t.Errorf("unexpected error happened: %s", err)
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}
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}
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func TestScrapeAndCompareBadStatusCode(t *testing.T) {
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const expected = `
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# HELP some_total A value that represents a counter.
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# TYPE some_total counter
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some_total{ label1 = "value1" } 1
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`
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expectedReader := strings.NewReader(expected)
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ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
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w.WriteHeader(http.StatusBadGateway)
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fmt.Fprintln(w, expected)
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}))
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defer ts.Close()
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err := ScrapeAndCompare(ts.URL, expectedReader, "some_total")
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if err == nil {
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t.Errorf("expected an error but got nil")
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}
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if !strings.HasPrefix(err.Error(), "the scraping target returned a status code other than 200") {
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t.Errorf("unexpected error happened: %s", err)
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}
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}
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func TestCollectAndCount(t *testing.T) {
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c := prometheus.NewCounterVec(
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prometheus.CounterOpts{
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