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tsdb: Make sure the cache for postings cardinality properly honors the label name (#12653)

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Add a string remembering which label and limit the cache corresponds to.

Signed-off-by: Xiaochao Dong (@damnever) <the.xcdong@gmail.com>
This commit is contained in:
Xiaochao Dong 2023-11-28 21:54:37 +08:00 committed by GitHub
parent 1200c89d0c
commit 28d8f1650c
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GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 36 additions and 4 deletions
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17
tsdb/head.go
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@ -20,6 +20,7 @@ import (
"math"
"path/filepath"
"runtime"
"strconv"
"sync"
"time"
@ -110,7 +111,8 @@ type Head struct {
cardinalityMutex sync.Mutex
cardinalityCache *index.PostingsStats // Posting stats cache which will expire after 30sec.
lastPostingsStatsCall time.Duration // Last posting stats call (PostingsCardinalityStats()) time for caching.
cardinalityCacheKey string
lastPostingsStatsCall time.Duration // Last posting stats call (PostingsCardinalityStats()) time for caching.
// chunkDiskMapper is used to write and read Head chunks to/from disk.
chunkDiskMapper *chunks.ChunkDiskMapper
@ -988,16 +990,23 @@ func (h *Head) DisableNativeHistograms() {
// PostingsCardinalityStats returns highest cardinality stats by label and value names.
func (h *Head) PostingsCardinalityStats(statsByLabelName string, limit int) *index.PostingsStats {
cacheKey := statsByLabelName + ";" + strconv.Itoa(limit)
h.cardinalityMutex.Lock()
defer h.cardinalityMutex.Unlock()
currentTime := time.Duration(time.Now().Unix()) * time.Second
seconds := currentTime - h.lastPostingsStatsCall
if seconds > cardinalityCacheExpirationTime {
if h.cardinalityCacheKey != cacheKey {
h.cardinalityCache = nil
} else {
currentTime := time.Duration(time.Now().Unix()) * time.Second
seconds := currentTime - h.lastPostingsStatsCall
if seconds > cardinalityCacheExpirationTime {
h.cardinalityCache = nil
}
}
if h.cardinalityCache != nil {
return h.cardinalityCache
}
h.cardinalityCacheKey = cacheKey
h.cardinalityCache = h.postings.Stats(statsByLabelName, limit)
h.lastPostingsStatsCall = time.Duration(time.Now().Unix()) * time.Second

23
tsdb/head_test.go
View File

@ -5618,3 +5618,26 @@ func TestStripeSeries_gc(t *testing.T) {
got = s.getByHash(hash, ms2.lset)
require.Nil(t, got)
}
func TestPostingsCardinalityStats(t *testing.T) {
head := &Head{postings: index.NewMemPostings()}
head.postings.Add(1, labels.FromStrings(labels.MetricName, "t", "n", "v1"))
head.postings.Add(2, labels.FromStrings(labels.MetricName, "t", "n", "v2"))
statsForMetricName := head.PostingsCardinalityStats(labels.MetricName, 10)
head.postings.Add(3, labels.FromStrings(labels.MetricName, "t", "n", "v3"))
// Using cache.
require.Equal(t, statsForMetricName, head.PostingsCardinalityStats(labels.MetricName, 10))
statsForSomeLabel := head.PostingsCardinalityStats("n", 10)
// Cache should be evicted because of the change of label name.
require.NotEqual(t, statsForMetricName, statsForSomeLabel)
head.postings.Add(4, labels.FromStrings(labels.MetricName, "t", "n", "v4"))
// Using cache.
require.Equal(t, statsForSomeLabel, head.PostingsCardinalityStats("n", 10))
// Cache should be evicted because of the change of limit parameter.
statsForSomeLabel1 := head.PostingsCardinalityStats("n", 1)
require.NotEqual(t, statsForSomeLabel1, statsForSomeLabel)
// Using cache.
require.Equal(t, statsForSomeLabel1, head.PostingsCardinalityStats("n", 1))
}