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testutil compareMetricFamilies: make less error-prone (#1424) 

* testutil compareMetricFamilies: make less error-prone

The functions `GatherAndCompare`, `ScrapeAndCompare` and others that use
`compareMetricFamilies` under the hood can return no error if
`metricNames` includes none of the names found in the scraped/gathered
results. To avoid false Positves (an error being the negative case), we
can return an error if there is is at least one name in `metricNames`
that is not in the filtered results.

Fixes: https://github.com/prometheus/client_golang/issues/1351

Signed-off-by: leonnicolas <leonloechner@gmx.de>

* Add missing metricNames to error

In to see which metric names are missing, we can add them to the error
message.

Signed-off-by: leonnicolas <leonloechner@gmx.de>

* Apply suggestions from code review

- remove if nil check
- use two nested loops instead of map
- use new function `hasMetricByName` for readability

Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
Signed-off-by: leonnicolas <60091705+leonnicolas@users.noreply.github.com>

* prometheus/testutil/testutil_test.go: compare complete error

Before we would only compare the error prefix in `TestScrapeAndCompare`.

Signed-off-by: leonnicolas <leonloechner@gmx.de>

---------

Signed-off-by: leonnicolas <leonloechner@gmx.de>
Signed-off-by: leonnicolas <60091705+leonnicolas@users.noreply.github.com>
Co-authored-by: Bartlomiej Plotka <bwplotka@gmail.com>
This commit is contained in:
leonnicolas 2024-05-15 11:50:24 +02:00 committed by GitHub
parent 36b9f46811
commit c7c7509669
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GPG Key ID: B5690EEEBB952194
2 changed files with 110 additions and 48 deletions
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18
prometheus/testutil/testutil.go
View File

@ -277,6 +277,15 @@ func compareMetricFamilies(got, expected []*dto.MetricFamily, metricNames ...str
if metricNames != nil {
got = filterMetrics(got, metricNames)
expected = filterMetrics(expected, metricNames)
if len(metricNames) > len(got) {
var missingMetricNames []string
for _, name := range metricNames {
if ok := hasMetricByName(got, name); !ok {
missingMetricNames = append(missingMetricNames, name)
}
}
return fmt.Errorf("expected metric name(s) not found: %v", missingMetricNames)
}
}
return compare(got, expected)
@ -318,3 +327,12 @@ func filterMetrics(metrics []*dto.MetricFamily, names []string) []*dto.MetricFam
}
return filtered
}
func hasMetricByName(metrics []*dto.MetricFamily, name string) bool {
for _, mf := range metrics {
if mf.GetName() == name {
return true
}
}
return false
}

140
prometheus/testutil/testutil_test.go
View File

@ -328,27 +328,32 @@ func TestMetricNotFound(t *testing.T) {
}
func TestScrapeAndCompare(t *testing.T) {
const expected = `
scenarios := map[string]struct {
want string
metricNames []string
// expectedErr if empty, means no fail is expected for the comparison.
expectedErr string
}{
"empty metric Names": {
want: `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
some_total{ label1 = "value1" } 1
`
`,
metricNames: []string{},
},
"one metric": {
want: `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
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 TestScrapeAndCompareWithMultipleExpected(t *testing.T) {
const expected = `
some_total{ label1 = "value1" } 1
`,
metricNames: []string{"some_total"},
},
"multiple expected": {
want: `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
@ -358,53 +363,92 @@ func TestScrapeAndCompareWithMultipleExpected(t *testing.T) {
# TYPE some_total2 counter
some_total2{ label2 = "value2" } 1
`
`,
metricNames: []string{"some_total2"},
},
"expected metric name is not scraped": {
want: `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
expectedReader := strings.NewReader(expected)
some_total{ label1 = "value1" } 1
ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, expected)
}))
defer ts.Close()
# HELP some_total2 A value that represents a counter.
# TYPE some_total2 counter
if err := ScrapeAndCompare(ts.URL, expectedReader, "some_total2"); err != nil {
t.Errorf("unexpected scraping result:\n%s", err)
some_total2{ label2 = "value2" } 1
`,
metricNames: []string{"some_total3"},
expectedErr: "expected metric name(s) not found: [some_total3]",
},
"one of multiple expected metric names is not scraped": {
want: `
# HELP some_total A value that represents a counter.
# TYPE some_total counter
some_total{ label1 = "value1" } 1
# HELP some_total2 A value that represents a counter.
# TYPE some_total2 counter
some_total2{ label2 = "value2" } 1
`,
metricNames: []string{"some_total1", "some_total3"},
expectedErr: "expected metric name(s) not found: [some_total1 some_total3]",
},
}
}
for name, scenario := range scenarios {
t.Run(name, func(t *testing.T) {
expectedReader := strings.NewReader(scenario.want)
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")
ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
fmt.Fprintln(w, scenario.want)
}))
defer ts.Close()
if err := ScrapeAndCompare(ts.URL, expectedReader, scenario.metricNames...); err != nil {
if scenario.expectedErr == "" || err.Error() != scenario.expectedErr {
t.Errorf("unexpected error happened: %s", err)
}
} else if scenario.expectedErr != "" {
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 = `
t.Run("fetching fail", func(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)
}
})
t.Run("bad status code", func(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)
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()
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)
}
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) {