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labels_query_cache.go
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/
labels_query_cache.go
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// SPDX-License-Identifier: AGPL-3.0-only
package querymiddleware
import (
"fmt"
"net/http"
"net/url"
"strconv"
"strings"
"time"
"github.com/go-kit/log"
"github.com/grafana/dskit/cache"
"github.com/pkg/errors"
"github.com/prometheus/client_golang/prometheus"
"github.com/prometheus/prometheus/model/labels"
"github.com/prometheus/prometheus/promql/parser"
v1 "github.com/prometheus/prometheus/web/api/v1"
"golang.org/x/exp/slices"
"github.com/grafana/mimir/pkg/util"
)
const (
labelNamesQueryCachePrefix = "ln:"
labelValuesQueryCachePrefix = "lv:"
stringParamSeparator = rune(0)
)
func newLabelsQueryCacheRoundTripper(
cache cache.Cache,
generator CacheKeyGenerator,
limits Limits,
next http.RoundTripper,
logger log.Logger,
reg prometheus.Registerer,
) http.RoundTripper {
ttl := &labelsQueryTTL{
limits: limits,
}
return newGenericQueryCacheRoundTripper(cache, generator.LabelValues, ttl, next, logger, newResultsCacheMetrics(queryTypeLabels, reg))
}
type labelsQueryTTL struct {
limits Limits
}
func (c *labelsQueryTTL) ttl(userID string) time.Duration {
return c.limits.ResultsCacheTTLForLabelsQuery(userID)
}
func (g DefaultCacheKeyGenerator) LabelValues(r *http.Request) (*GenericQueryCacheKey, error) {
labelValuesReq, err := g.codec.DecodeLabelsQueryRequest(r.Context(), r)
if err != nil {
return nil, err
}
var cacheKeyPrefix string
switch labelValuesReq.(type) {
case *PrometheusLabelNamesQueryRequest:
cacheKeyPrefix = labelNamesQueryCachePrefix
case *PrometheusLabelValuesQueryRequest:
cacheKeyPrefix = labelValuesQueryCachePrefix
}
labelMatcherSets, err := parseRequestMatchersParam(
map[string][]string{"match[]": labelValuesReq.GetLabelMatcherSets()},
"match[]",
)
if err != nil {
return nil, err
}
cacheKey := generateLabelsQueryRequestCacheKey(
labelValuesReq.GetStartOrDefault(),
labelValuesReq.GetEndOrDefault(),
labelValuesReq.GetLabelName(),
labelMatcherSets,
labelValuesReq.GetLimit(),
)
return &GenericQueryCacheKey{
CacheKey: cacheKey,
CacheKeyPrefix: cacheKeyPrefix,
}, nil
}
func generateLabelsQueryRequestCacheKey(startTime, endTime int64, labelName string, matcherSets [][]*labels.Matcher, limit uint64) string {
var (
twoHoursMillis = (2 * time.Hour).Milliseconds()
b = strings.Builder{}
)
// Align start and end times to default block boundaries. The reason is that both TSDB (so the Mimir ingester)
// and Mimir store-gateway query the label names and values out of blocks overlapping within the start and end
// time. This means that for maximum granularity is the block.
if startTime != v1.MinTime.UnixMilli() {
if reminder := startTime % twoHoursMillis; reminder != 0 {
startTime -= reminder
}
}
if endTime != v1.MaxTime.UnixMilli() {
if reminder := endTime % twoHoursMillis; reminder != 0 {
endTime += twoHoursMillis - reminder
}
}
// Add start and end time.
b.WriteString(fmt.Sprintf("%d", startTime))
b.WriteRune(stringParamSeparator)
b.WriteString(fmt.Sprintf("%d", endTime))
// Add label name (if any).
if labelName != "" {
b.WriteRune(stringParamSeparator)
b.WriteString(labelName)
}
// Add matcher sets.
b.WriteRune(stringParamSeparator)
b.WriteString(util.MultiMatchersStringer(matcherSets).String())
// if limit is set, then it will be a positive number
if limit > 0 {
b.WriteRune(stringParamSeparator)
b.WriteString(strconv.Itoa(int(limit)))
}
return b.String()
}
func parseRequestMatchersParam(values url.Values, paramName string) ([][]*labels.Matcher, error) {
matcherSets := make([][]*labels.Matcher, 0, len(values[paramName]))
for _, value := range values[paramName] {
matchers, err := parser.ParseMetricSelector(value)
if err != nil {
return nil, errors.Wrapf(err, "invalid '%s' parameter", paramName)
}
matcherSets = append(matcherSets, matchers)
}
// Ensure stable sorting (improves query results cache hit ratio).
for _, set := range matcherSets {
slices.SortFunc(set, func(a, b *labels.Matcher) int {
return compareLabelMatchers(a, b)
})
}
slices.SortFunc(matcherSets, func(a, b []*labels.Matcher) int {
idx := 0
for ; idx < len(a) && idx < len(b); idx++ {
if c := compareLabelMatchers(a[idx], b[idx]); c != 0 {
return c
}
}
// All label matchers are equal so far. Check which one has fewer matchers.
if idx < len(b) {
return -1
}
if idx < len(a) {
return 1
}
return 0
})
return matcherSets, nil
}
func compareLabelMatchers(a, b *labels.Matcher) int {
if a.Name != b.Name {
return strings.Compare(a.Name, b.Name)
}
if a.Type != b.Type {
return int(b.Type) - int(a.Type)
}
return strings.Compare(a.Value, b.Value)
}