Method getCachedShuffledSubringWithLookback

ring/ring.go:1345–1384

(identifier string, size int, lookbackPeriod time.Duration, now time.Time)

}

func (r *Ring) getCachedShuffledSubringWithLookback(identifier string, size int, lookbackPeriod time.Duration, now time.Time) *Ring {
	if r.cfg.SubringCacheDisabled {
		return nil
	}

	r.mtx.RLock()
	defer r.mtx.RUnlock()

	cached, ok := r.shuffledSubringWithLookbackCache[subringCacheKey{identifier: identifier, shardSize: size, lookbackPeriod: lookbackPeriod}]
	if !ok {
		return nil
	}

	lookbackWindowStart := now.Add(-lookbackPeriod).Unix()
	if lookbackWindowStart < cached.validForLookbackWindowsStartingAfter || lookbackWindowStart > cached.validForLookbackWindowsStartingBefore {
		// The cached subring is not valid for the lookback window that has been requested.
		return nil
	}

	cachedSubring := cached.subring

	// No need to update the cached subring if it is the original ring itself.
	if r == cachedSubring {
		return cachedSubring
	}

	cachedSubring.mtx.Lock()
	defer cachedSubring.mtx.Unlock()

	// Update instance states and timestamps. We know that the topology is the same,
	// so zones and tokens are equal.
	for name, cachedIng := range cachedSubring.ringDesc.Ingesters {
		ing := r.ringDesc.Ingesters[name]
		cachedIng.State = ing.State
		cachedIng.Timestamp = ing.Timestamp
		cachedSubring.ringDesc.Ingesters[name] = cachedIng
	}

	return cachedSubring
}

func (r *Ring) setCachedShuffledSubringWithLookback(identifier string, size int, lookbackPeriod time.Duration, now time.Time, subring *Ring) {
	if subring == nil || r.cfg.SubringCacheDisabled {