Purge expired postings cache items due inactivity (#6502)

* Purge expired postings cache items due inactivity

Signed-off-by: alanprot <alanprot@gmail.com>

* Fix comments

Signed-off-by: alanprot <alanprot@gmail.com>

---------

Signed-off-by: alanprot <alanprot@gmail.com>

Author: alanprot

pkg/ingester/ingester.go

@@ -878,6 +878,14 @@ func (i *Ingester) starting(ctx context.Context) error {
 		servs = append(servs, closeIdleService)
 	}
 
+	if i.expandedPostingsCacheFactory != nil {
+		interval := i.cfg.BlocksStorageConfig.TSDB.ExpandedCachingExpireInterval
+		if interval == 0 {
+			interval = cortex_tsdb.ExpandedCachingExpireInterval
+		}
+		servs = append(servs, services.NewTimerService(interval, nil, i.expirePostingsCache, nil))
+	}
+
 	var err error
 	i.TSDBState.subservices, err = services.NewManager(servs...)
 	if err == nil {
@@ -2794,6 +2802,18 @@ func (i *Ingester) closeAndDeleteIdleUserTSDBs(ctx context.Context) error {
 	return nil
 }
 
+func (i *Ingester) expirePostingsCache(ctx context.Context) error {
+	for _, userID := range i.getTSDBUsers() {
+		if ctx.Err() != nil {
+			return nil
+		}
+		userDB := i.getTSDB(userID)
+		userDB.postingCache.PurgeExpiredItems()
+	}
+
+	return nil
+}
+
 func (i *Ingester) closeAndDeleteUserTSDBIfIdle(userID string) tsdbCloseCheckResult {
 	userDB := i.getTSDB(userID)
 	if userDB == nil || userDB.shipper == nil {

pkg/ingester/ingester_test.go

@@ -5525,6 +5525,7 @@ func TestExpendedPostingsCacheIsolation(t *testing.T) {
 
 func TestExpendedPostingsCache(t *testing.T) {
 	cfg := defaultIngesterTestConfig(t)
+	cfg.BlocksStorageConfig.TSDB.ExpandedCachingExpireInterval = time.Second
 	cfg.BlocksStorageConfig.TSDB.BlockRanges = []time.Duration{2 * time.Hour}
 
 	runQuery := func(t *testing.T, ctx context.Context, i *Ingester, matchers []*client.LabelMatcher) []client.TimeSeriesChunk {
@@ -5540,9 +5541,10 @@ func TestExpendedPostingsCache(t *testing.T) {
 	}
 
 	tc := map[string]struct {
-		cacheConfig              cortex_tsdb.TSDBPostingsCacheConfig
-		expectedBlockPostingCall int
-		expectedHeadPostingCall  int
+		cacheConfig               cortex_tsdb.TSDBPostingsCacheConfig
+		expectedBlockPostingCall  int
+		expectedHeadPostingCall   int
+		shouldExpireDueInactivity bool
 	}{
 		"cacheDisabled": {
 			expectedBlockPostingCall: 0,
@@ -5594,6 +5596,23 @@ func TestExpendedPostingsCache(t *testing.T) {
 				},
 			},
 		},
+		"expire due inactivity": {
+			expectedBlockPostingCall:  1,
+			expectedHeadPostingCall:   1,
+			shouldExpireDueInactivity: true,
+			cacheConfig: cortex_tsdb.TSDBPostingsCacheConfig{
+				Blocks: cortex_tsdb.PostingsCacheConfig{
+					Ttl:      time.Second,
+					MaxBytes: 1024 * 1024 * 1024,
+					Enabled:  true,
+				},
+				Head: cortex_tsdb.PostingsCacheConfig{
+					Ttl:      time.Second,
+					MaxBytes: 1024 * 1024 * 1024,
+					Enabled:  true,
+				},
+			},
+		},
 	}
 
 	for name, c := range tc {
@@ -5790,6 +5809,17 @@ func TestExpendedPostingsCache(t *testing.T) {
 			require.Len(t, runQuery(t, ctx, i, []*client.LabelMatcher{{Type: client.EQUAL, Name: "extra", Value: "1"}}), 1)
 			// Return cached value from block and bypass head
 			require.Equal(t, int64(0), postingsForMatchersCalls.Load())
+
+			if c.shouldExpireDueInactivity {
+				test.Poll(t, c.cacheConfig.Blocks.Ttl+c.cacheConfig.Head.Ttl+cfg.BlocksStorageConfig.TSDB.ExpandedCachingExpireInterval, 0, func() interface{} {
+					size := 0
+					for _, userID := range i.getTSDBUsers() {
+						userDB := i.getTSDB(userID)
+						size += userDB.postingCache.Size()
+					}
+					return size
+				})
+			}
 		})
 	}
 }

pkg/storage/tsdb/config.go

@@ -30,6 +30,9 @@ const (
 	// How often are open TSDBs checked for being idle and closed.
 	DefaultCloseIdleTSDBInterval = 5 * time.Minute
 
+	// How often expired items are cleaned from the PostingsCache
+	ExpandedCachingExpireInterval = 5 * time.Minute
+
 	// How often to check for tenant deletion mark.
 	DeletionMarkCheckInterval = 1 * time.Hour
 
@@ -156,6 +159,9 @@ type TSDBConfig struct {
 	// How often to check for idle TSDBs for closing. DefaultCloseIdleTSDBInterval is not suitable for testing, so tests can override.
 	CloseIdleTSDBInterval time.Duration `yaml:"-"`
 
+	// How often expired items are cleaned from the PostingsCache. ExpandedCachingExpireInterval is not suitable for testing, so tests can override.
+	ExpandedCachingExpireInterval time.Duration `yaml:"-"`
+
 	// Positive value enables experimental support for exemplars. 0 or less to disable.
 	MaxExemplars int `yaml:"max_exemplars"`
 

pkg/storage/tsdb/expanded_postings_cache.go

@@ -124,6 +124,8 @@ func (f *ExpandedPostingsCacheFactory) NewExpandedPostingsCache(userId string, m
 type ExpandedPostingsCache interface {
 	PostingsForMatchers(ctx context.Context, blockID ulid.ULID, ix tsdb.IndexReader, ms ...*labels.Matcher) (index.Postings, error)
 	ExpireSeries(metric labels.Labels)
+	PurgeExpiredItems()
+	Size() int
 }
 
 type blocksPostingsForMatchersCache struct {
@@ -166,6 +168,15 @@ func (c *blocksPostingsForMatchersCache) ExpireSeries(metric labels.Labels) {
 	c.seedByHash.incrementSeed(c.userId, metricName)
 }
 
+func (c *blocksPostingsForMatchersCache) PurgeExpiredItems() {
+	c.headCache.expire()
+	c.blocksCache.expire()
+}
+
+func (c *blocksPostingsForMatchersCache) Size() int {
+	return c.headCache.size() + c.blocksCache.size()
+}
+
 func (c *blocksPostingsForMatchersCache) PostingsForMatchers(ctx context.Context, blockID ulid.ULID, ix tsdb.IndexReader, ms ...*labels.Matcher) (index.Postings, error) {
 	return c.fetchPostings(blockID, ix, ms...)(ctx)
 }
@@ -365,6 +376,12 @@ func (c *fifoCache[V]) expire() {
 	}
 }
 
+func (c *fifoCache[V]) size() int {
+	c.cachedMtx.RLock()
+	defer c.cachedMtx.RUnlock()
+	return c.cached.Len()
+}
+
 func (c *fifoCache[V]) getPromiseForKey(k string, fetch func() (V, int64, error)) (*cacheEntryPromise[V], bool) {
 	r := &cacheEntryPromise[V]{
 		done: make(chan struct{}),