add time factor

Signed-off-by: Mauro Stettler <mauro.stettler@gmail.com>

tsdb/chunks/chunk_write_queue.go

@@ -16,13 +16,17 @@ package chunks
 import (
 	"errors"
 	"sync"
+	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/prometheus/prometheus/tsdb/chunkenc"
 )
 
-const chunkRefMapFreeThreshold = 10
+const (
+	chunkRefMapFreeThreshold   = 10
+	chunkRefMapMinFreeInterval = 10 * time.Minute
+)
 
 type chunkWriteJob struct {
 	cutFile   bool
@@ -40,9 +44,10 @@ type chunkWriteJob struct {
 type chunkWriteQueue struct {
 	jobs chan chunkWriteJob
 
-	chunkRefMapMtx  sync.RWMutex
-	chunkRefMap     map[ChunkDiskMapperRef]chunkenc.Chunk
-	chunkRefMapPeak int
+	chunkRefMapMtx      sync.RWMutex
+	chunkRefMap         map[ChunkDiskMapperRef]chunkenc.Chunk
+	chunkRefMapPeak     int
+	chunkRefMapLastFree time.Time
 
 	isRunningMtx sync.Mutex // Protects the isRunning property.
 	isRunning    bool       // Used to prevent that new jobs get added to the queue when the chan is already closed.
@@ -71,9 +76,10 @@ func newChunkWriteQueue(reg prometheus.Registerer, size int, writeChunk writeChu
 	)
 
 	q := &chunkWriteQueue{
-		jobs:        make(chan chunkWriteJob, size),
-		chunkRefMap: make(map[ChunkDiskMapperRef]chunkenc.Chunk),
-		writeChunk:  writeChunk,
+		jobs:                make(chan chunkWriteJob, size),
+		chunkRefMap:         make(map[ChunkDiskMapperRef]chunkenc.Chunk),
+		chunkRefMapLastFree: time.Now(),
+		writeChunk:          writeChunk,
 
 		adds:      counters.WithLabelValues("add"),
 		gets:      counters.WithLabelValues("get"),
@@ -116,12 +122,13 @@ func (c *chunkWriteQueue) processJob(job chunkWriteJob) {
 
 	c.completed.Inc()
 
-	if len(c.chunkRefMap) == 0 && c.chunkRefMapPeak > chunkRefMapFreeThreshold {
+	if len(c.chunkRefMap) == 0 && c.chunkRefMapPeak > chunkRefMapFreeThreshold && time.Since(c.chunkRefMapLastFree) > chunkRefMapMinFreeInterval {
 		// Re-initialize the chunk ref map to half of the peak size that was in use since the last re-init event.
 		// By setting it to half of the peak we try to minimize the number of allocations required for a "normal" usage
 		// while ensuring that if its usage has decreased we shrink it over time.
 		c.chunkRefMap = make(map[ChunkDiskMapperRef]chunkenc.Chunk, c.chunkRefMapPeak/2)
 		c.chunkRefMapPeak = 0
+		c.chunkRefMapLastFree = time.Now()
 	}
 }