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fix(logql): Make LabelSampleExtractor work as expected when label doesn't exist in logline #6766

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merged 10 commits into from
Aug 3, 2022
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fix(logql): Make LabelSampleExtractor work as expected when label doesn't exist in logline #6766

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d0fbf3c
fix(logql): Make `StringLabelfilter` work as expected
kavirajk Jul 25, 2022
a83da68
Add it on changelog
kavirajk Jul 25, 2022
8120941
Fix linter
kavirajk Jul 25, 2022
bab6ca0
Add more tests and fix the edge case with equality to empty strings
kavirajk Jul 27, 2022
a50c635
typo on the comment
kavirajk Jul 27, 2022
40c5953
handle this edge case during metric extraction. Not in label filter
kavirajk Aug 1, 2022
b915271
Fix linter
kavirajk Aug 1, 2022
b24112a
Remove commented code
kavirajk Aug 1, 2022
6568360
Merge branch 'main' into kavirajk/logql-label-check-bug
kavirajk Aug 1, 2022
2f9b01e
Update changelog
kavirajk Aug 3, 2022
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Expand Up @@ -27,6 +27,7 @@
* [6395](https://github.com/grafana/loki/pull/6395) **DylanGuedes**: Add encoding support

##### Fixes
* [6766](https://github.com/grafana/loki/pull/6766) **kavirajk**: fix(logql): Make `StringLabelfilter` work as expected

##### Changes

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19 changes: 18 additions & 1 deletion pkg/logql/log/label_filter.go
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Expand Up @@ -342,7 +342,24 @@ func (s *StringLabelFilter) Process(_ int64, line []byte, lbs *LabelsBuilder) ([
if s.Name == logqlmodel.ErrorLabel {
return line, s.Matches(lbs.GetErr())
}
v, _ := lbs.Get(s.Name)
v, ok := lbs.Get(s.Name)
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this is the real fix.


// NOTE(kavi): whether the `label` exists in logline matters when doing `!=` or `!~`.
// Because, consider following long lines
// ```
// 1.msg="hello" subqueries=5
// 2.msg="hello" subqueries=0
// 3.msg="hello"
// 4.msg="hello" subqueries=""
//```

// Now when quering like `{...}|logfmt|subqueries=""` should consider lines 3 and 4.
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@cyriltovena cyriltovena Jul 28, 2022 •
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Not sure about this, it doesn't really make it easier to understand for the end user as this make it more obscure:

  • when using equality we consider non existent label empty
  • but for inequality we don't.

Honestly in #6713 I think the expectations were wrong.

sum(sum_over_time({job="loki-ops/query-frontend"}
  |= "metrics.go"
  | logfmt
  | subqueries!="0"
  | unwrap subqueries
  [5m]
))

When subqueries doesn't exist then subqueries!="0" is true.

What is weird was that empty labels does transform into a 0 integer.

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@kavirajk kavirajk Jul 28, 2022 •
edited
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When subqueries doesn't exist then subqueries!="0" is true.

So you saying subqueries!=0 and subqueries!="0" ok to return different log lines?. But that's unexpected behaviour to end-user IMHO. Both should return exactly same results IMO.

What is weird was that empty labels does transform into a 0 integer.

That's because, we don't mutate the log line if label is not present. So treat it as if label="" during label filter, But still log line doesn't contain actual label, which breaks when doing unwrap on same label during metrics extraction.

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What is weird was that empty labels does transform into a 0 integer.

I agree with @cyriltovena. This is the part I think we need to address.

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May be we discard empty values ? If that is possible.

Yes that's possible. We can skip empty values during metrics extraction when using unwrap without changing any of the existing label filter behavior.

Also the more I think about it, subqueries!="0" and subqueries!=0 are two different label filters and should be treated as such. And former can indeed match log lines that doesn't have subqueries label at all (we are assuming it has default empty string substring=" when doesn't exist).

I have change the PR like it's mentioned here.

// But when doing queries like `{...}|logfmt|subqueries!="0"` (also with !~), then line 3 shouldn't be considered.
// https://github.com/grafana/loki/pull/6766
// https://github.com/grafana/loki/issues/6713
if !ok && (s.Type == labels.MatchNotEqual || s.Type == labels.MatchNotRegexp) {
return line, false
}
return line, s.Matches(v)
}

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68 changes: 68 additions & 0 deletions pkg/logql/log/label_filter_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ import (
"time"

"github.com/prometheus/prometheus/model/labels"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"

"github.com/grafana/loki/pkg/logqlmodel"
Expand Down Expand Up @@ -350,3 +351,70 @@ func TestReduceAndLabelFilter(t *testing.T) {
})
}
}

func TestStringLabelFilter(t *testing.T) {
// NOTE: https://github.com/grafana/loki/issues/6713

tests := []struct {
name string
filter *StringLabelFilter
labels labels.Labels
shouldMatch bool
}{
{
name: `logfmt|subqueries!="0" (without label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchNotEqual, "subqueries", "0")),
labels: labels.Labels{{Name: "msg", Value: "hello"}}, // no label `subqueries`
shouldMatch: false,
},
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{
name: `logfmt|subqueries!="0" (with label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchNotEqual, "subqueries", "0")),
labels: labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: "2"}}, // label `subqueries` exist
shouldMatch: true,
},
{
name: `logfmt|subqueries!~"0" (without label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchNotRegexp, "subqueries", "0")),
labels: labels.Labels{{Name: "msg", Value: "hello"}}, // no label `subqueries`
shouldMatch: false,
},
{
name: `logfmt|subqueries!~"0" (with label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchNotRegexp, "subqueries", "0")),
labels: labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: "2"}}, // label `subqueries` exist
shouldMatch: true,
},
{
name: `logfmt|subqueries="0" (without label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "subqueries", "")),
labels: labels.Labels{{Name: "msg", Value: "hello"}}, // no label `subqueries`
shouldMatch: true,
},
{
name: `logfmt|subqueries="0" (with label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchEqual, "subqueries", "")),
labels: labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: ""}}, // label `subqueries` exist
shouldMatch: true,
},
{
name: `logfmt|subqueries=~"0" (without label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "subqueries", "")),
labels: labels.Labels{{Name: "msg", Value: "hello"}}, // no label `subqueries`
shouldMatch: true,
},
{
name: `logfmt|subqueries=~"0" (with label)`,
filter: NewStringLabelFilter(labels.MustNewMatcher(labels.MatchRegexp, "subqueries", "")),
labels: labels.Labels{{Name: "msg", Value: "hello"}, {Name: "subqueries", Value: ""}}, // label `subqueries` exist
shouldMatch: true,
},
}

for _, tc := range tests {
t.Run(tc.name, func(t *testing.T) {
_, ok := tc.filter.Process(0, []byte("sample log line"), NewBaseLabelsBuilder().ForLabels(tc.labels, tc.labels.Hash()))
assert.Equal(t, tc.shouldMatch, ok)
})
}
}
64 changes: 64 additions & 0 deletions pkg/logql/log/metrics_extraction_test.go
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Expand Up @@ -6,6 +6,7 @@ import (
"time"

"github.com/prometheus/prometheus/model/labels"
"github.com/stretchr/testify/assert"
"github.com/stretchr/testify/require"
)

Expand Down Expand Up @@ -152,6 +153,69 @@ func Test_Extract_ExpectedLabels(t *testing.T) {
require.True(t, ok)
require.Equal(t, (20 * time.Millisecond).Seconds(), f)
require.Equal(t, labels.Labels{{Name: "foo", Value: "json"}}, lbs.Labels())

}
func TestLabelExtractorWithStages(t *testing.T) {

// A helper type to check if particular logline should be skipped
// during `ProcessLine` or got correct sample value extracted.
type checkLine struct {
logLine string
skip bool
sample float64
}

tests := []struct {
name string
extractor SampleExtractor
checkLines []checkLine
shouldFail bool
}{
{
name: "with just logfmt and stringlabelfilter",
// {foo="bar"} | logfmt | subqueries != "0" (note: "0", a stringlabelfilter)
extractor: mustSampleExtractor(
LabelExtractorWithStages("subqueries", ConvertFloat, []string{"foo"}, false, false, []Stage{NewLogfmtParser(), NewStringLabelFilter(labels.MustNewMatcher(labels.MatchNotEqual, "subqueries", "0"))}, NoopStage),
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),
checkLines: []checkLine{
{logLine: "msg=hello subqueries=5", skip: false, sample: 5},
{logLine: "msg=hello subqueries=0", skip: true},
{logLine: "msg=hello ", skip: true}, // log lines doesn't contain the `subqueries` label
},
},
{
name: "with just logfmt and numeric labelfilter",
// {foo="bar"} | logfmt | subqueries != 0 (note: "0", a numericLabelFilter)
extractor: mustSampleExtractor(
LabelExtractorWithStages("subqueries", ConvertFloat, []string{"foo"}, false, false, []Stage{NewLogfmtParser(), NewNumericLabelFilter(LabelFilterNotEqual, "subqueries", 0)}, NoopStage),
),
checkLines: []checkLine{
{logLine: "msg=hello subqueries=5", skip: false, sample: 5},
{logLine: "msg=hello subqueries=0", skip: true},
{logLine: "msg=hello ", skip: true}, // log lines doesn't contain the `subqueries` label
},
},
}

for _, tc := range tests {
t.Run(tc.name, func(t *testing.T) {
for _, line := range tc.checkLines {
v, lbs, ok := tc.extractor.ForStream(labels.Labels{{Name: "bar", Value: "foo"}}).ProcessString(0, line.logLine)
skipped := !ok
assert.Equal(t, line.skip, skipped, "line", line.logLine)
if !skipped {
assert.Equal(t, line.sample, v)

// lbs shouldn't have __error__ = SampleExtractionError
assert.Empty(t, lbs.Labels())
return
}

// if line is skipped, `lbs` will be nil.
assert.Nil(t, lbs, "line", line.logLine)
}
})
}
}

func mustSampleExtractor(ex SampleExtractor, err error) SampleExtractor {
Expand Down