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store: label_values: fetch less postings #7814

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merged 6 commits into from
Oct 17, 2024
Merged

store: label_values: fetch less postings #7814

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e355316
label_values: fetch less postings
xBazilio Oct 10, 2024
acb29a8
CHANGELOG.md
xBazilio Oct 10, 2024
bca1cc9
added acceptance test
xBazilio Oct 10, 2024
e17a096
removed redundant comment
xBazilio Oct 10, 2024
f747e39
check if matcher is EQ matcher
xBazilio Oct 11, 2024
6b64e73
Update CHANGELOG.md
xBazilio Oct 11, 2024
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1 change: 1 addition & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ We use *breaking :warning:* to mark changes that are not backward compatible (re
- [#7658](https://github.com/thanos-io/thanos/pull/7658) Store: Fix panic because too small buffer in pool.
- [#7643](https://github.com/thanos-io/thanos/pull/7643) Receive: fix thanos_receive_write_{timeseries,samples} stats
- [#7644](https://github.com/thanos-io/thanos/pull/7644) fix(ui): add null check to find overlapping blocks logic
- [#7814](https://github.com/thanos-io/thanos/pull/7814) Store: label_values: fetch less postings.
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- [#7679](https://github.com/thanos-io/thanos/pull/7679) Query: respect store.limit.* flags when evaluating queries

### Added
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40 changes: 40 additions & 0 deletions pkg/store/acceptance_test.go
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Expand Up @@ -740,6 +740,46 @@ func testStoreAPIsAcceptance(t *testing.T, startStore startStoreFn) {
},
},
},
{
desc: "label_values(kube_pod_info{}, pod) don't fetch postings for pod!=''",
appendFn: func(app storage.Appender) {
_, err := app.Append(0, labels.FromStrings("__name__", "up", "pod", "pod-1"), timestamp.FromTime(now), 1)
testutil.Ok(t, err)
_, err = app.Append(0, labels.FromStrings("__name__", "up", "pod", "pod-2"), timestamp.FromTime(now), 1)
testutil.Ok(t, err)
_, err = app.Append(0, labels.FromStrings("__name__", "kube_pod_info", "pod", "pod-1"), timestamp.FromTime(now), 1)
testutil.Ok(t, err)
testutil.Ok(t, app.Commit())
},
labelNameCalls: []labelNameCallCase{
{
start: timestamp.FromTime(minTime),
end: timestamp.FromTime(maxTime),
expectedNames: []string{"__name__", "pod", "region"},
matchers: []storepb.LabelMatcher{{Type: storepb.LabelMatcher_EQ, Name: "__name__", Value: "kube_pod_info"}},
},
{
start: timestamp.FromTime(minTime),
end: timestamp.FromTime(maxTime),
expectedNames: []string{"__name__", "pod", "region"},
},
},
labelValuesCalls: []labelValuesCallCase{
{
start: timestamp.FromTime(minTime),
end: timestamp.FromTime(maxTime),
label: "pod",
expectedValues: []string{"pod-1"},
matchers: []storepb.LabelMatcher{{Type: storepb.LabelMatcher_EQ, Name: "__name__", Value: "kube_pod_info"}},
},
{
start: timestamp.FromTime(minTime),
end: timestamp.FromTime(maxTime),
label: "pod",
expectedValues: []string{"pod-1", "pod-2"},
},
},
},
} {
t.Run(tc.desc, func(t *testing.T) {
appendFn := tc.appendFn
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30 changes: 27 additions & 3 deletions pkg/store/bucket.go
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Expand Up @@ -1992,6 +1992,14 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR

resHints := &hintspb.LabelValuesResponseHints{}

var hasMetricNameMatcher = false
for _, m := range reqSeriesMatchers {
if m.Name == labels.MetricName {
hasMetricNameMatcher = true
break
}
}

g, gctx := errgroup.WithContext(ctx)

var reqBlockMatchers []*labels.Matcher
Expand All @@ -2015,6 +2023,7 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR
var seriesLimiter = s.seriesLimiterFactory(s.metrics.queriesDropped.WithLabelValues("series", tenant))
var bytesLimiter = s.bytesLimiterFactory(s.metrics.queriesDropped.WithLabelValues("bytes", tenant))
var logger = s.requestLoggerFunc(ctx, s.logger)
var stats = &queryStats{}

for _, b := range s.blocks {
b := b
Expand All @@ -2033,7 +2042,8 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR

// If we have series matchers and the Label is not an external one, add <labelName> != "" matcher
// to only select series that have given label name.
if len(reqSeriesMatchersNoExtLabels) > 0 && !b.extLset.Has(req.Label) {
// We don't need such matcher if matchers already contain __name__ matcher.
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Trying to understand this comment. Why it is specific to the metric name label?
It is just a tradeoff of fetching more postings or series.

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From my experience, if __name__ is specified, it means, user knows, that the metric contains requested label. The method will select all series with such __name__ and they 99% will have the requested label.
As for random queries, where there can be results with the __name__ but without specified labels, normally, they should be rare. Users still can make queries like label_values({}, pod). They will work, but will fetch alot of data.
So the point is, if the user knows what they need and specifies __name__, we don't need to save them from fetching some extra series. But we do save them from fetching all references to all kube_state_metrics from object storage for example.
Other popular labels may be service, application, job, instance. If __name__ is specified, it is guaranteed it'll be less data, but all the label values.

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Not against this. Just hope we have a better way to cover more labels because we have those information from posting cardinality and series size.

if !hasMetricNameMatcher && len(reqSeriesMatchersNoExtLabels) > 0 && !b.extLset.Has(req.Label) {
m, err := labels.NewMatcher(labels.MatchNotEqual, req.Label, "")
if err != nil {
return nil, status.Error(codes.InvalidArgument, err.Error())
Expand Down Expand Up @@ -2101,7 +2111,12 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR
s.metrics.lazyExpandedPostingSeriesOverfetchedSizeBytes,
tenant,
)
defer blockClient.Close()
defer func() {
mtx.Lock()
stats = blockClient.MergeStats(stats)
mtx.Unlock()
blockClient.Close()
}()

if err := blockClient.ExpandPostings(
sortedReqSeriesMatchersNoExtLabels,
Expand Down Expand Up @@ -2130,7 +2145,7 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR
}

val := labelpb.ZLabelsToPromLabels(ls.GetSeries().Labels).Get(req.Label)
if val != "" { // Should never be empty since we added labelName!="" matcher to the list of matchers.
if val != "" {
values[val] = struct{}{}
}
}
Expand All @@ -2154,6 +2169,15 @@ func (s *BucketStore) LabelValues(ctx context.Context, req *storepb.LabelValuesR

s.mtx.RUnlock()

defer func() {
if s.debugLogging {
level.Debug(logger).Log("msg", "stats query processed",
"request", req,
"tenant", tenant,
"stats", fmt.Sprintf("%+v", stats), "err", err)
}
}()

if err := g.Wait(); err != nil {
code := codes.Internal
if s, ok := status.FromError(errors.Cause(err)); ok {
Expand Down
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