func()

in v1storage/storage.go [1174:1214]

• 27 lines of code
• 6 McCabe index (conditional complexity)

func (s *MemorySeriesStorage) maybeEvict() {
	ms := runtime.MemStats{}
	runtime.ReadMemStats(&ms)
	numChunksToEvict := s.calculatePersistUrgency(&ms)

	if numChunksToEvict <= 0 {
		return
	}

	chunkDescsToEvict := make([]*chunk.Desc, numChunksToEvict)
	for i := range chunkDescsToEvict {
		e := s.evictList.Front()
		if e == nil {
			break
		}
		cd := e.Value.(*chunk.Desc)
		cd.EvictListElement = nil
		chunkDescsToEvict[i] = cd
		s.evictList.Remove(e)
	}
	// Do the actual eviction in a goroutine as we might otherwise deadlock,
	// in the following way: A chunk was Unpinned completely and therefore
	// scheduled for eviction. At the time we actually try to evict it,
	// another goroutine is pinning the chunk. The pinning goroutine has
	// currently locked the chunk and tries to send the evict request (to
	// remove the chunk from the evict list) to the evictRequests
	// channel. The send blocks because evictRequests is full. However, the
	// goroutine that is supposed to empty the channel is waiting for the
	// Chunk.Desc lock to try to evict the chunk.
	go func() {
		for _, cd := range chunkDescsToEvict {
			if cd == nil {
				break
			}
			cd.MaybeEvict()
			// We don't care if the eviction succeeds. If the chunk
			// was pinned in the meantime, it will be added to the
			// evict list once it gets Unpinned again.
		}
	}()
}