Method shrinkChunkRefMap

tsdb/chunks/chunk_write_queue.go:151–178

shrinkChunkRefMap checks whether the conditions to shrink the chunkRefMap are met, if so chunkRefMap is reinitialized. The chunkRefMapMtx must be held when calling this method. We do this because Go runtime doesn't release internal memory used by map after map has been emptied. To achieve that we c

()

// We do this because Go runtime doesn't release internal memory used by map after map has been emptied.
// To achieve that we create new map instead and throw the old one away.
func (c *chunkWriteQueue) shrinkChunkRefMap() {
	if len(c.chunkRefMap) > 0 {
		// Can't shrink it while there is data in it.
		return
	}

	if c.chunkRefMapPeakSize < chunkRefMapShrinkThreshold {
		// Not shrinking it because it has not grown to the minimum threshold yet.
		return
	}

	now := time.Now()

	if now.Sub(c.chunkRefMapLastShrink) < chunkRefMapMinShrinkInterval {
		// Not shrinking it because the minimum duration between shrink-events has not passed yet.
		return
	}

	// Re-initialize the chunk ref map to half of the peak size that it has grown to since the last re-init event.
	// We are trying to hit the sweet spot in the trade-off between initializing it to a very small size
	// potentially resulting in many allocations to re-grow it, and initializing it to a large size potentially
	// resulting in unused allocated memory.
	c.chunkRefMap = make(map[ChunkDiskMapperRef]chunkenc.Chunk, c.chunkRefMapPeakSize/2)

	c.chunkRefMapPeakSize = 0
	c.chunkRefMapLastShrink = now
	c.shrink.Inc()
}

func (c *chunkWriteQueue) addJob(job chunkWriteJob) (err error) {
	defer func() {