Method setCachedShuffledSubringWithLookback

ring/ring.go:1386–1429

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

}

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

	lookbackWindowStart := now.Add(-lookbackPeriod).Unix()
	validForLookbackWindowsStartingBefore := int64(math.MaxInt64)

	for _, instance := range subring.ringDesc.Ingesters {
		if instance.RegisteredTimestamp >= lookbackWindowStart && instance.RegisteredTimestamp < validForLookbackWindowsStartingBefore {
			validForLookbackWindowsStartingBefore = instance.RegisteredTimestamp
		}
		if instance.ReadOnlyUpdatedTimestamp >= lookbackWindowStart && instance.ReadOnlyUpdatedTimestamp < validForLookbackWindowsStartingBefore {
			validForLookbackWindowsStartingBefore = instance.ReadOnlyUpdatedTimestamp
		}
	}

	r.mtx.Lock()
	defer r.mtx.Unlock()

	// Only cache if *this* ring hasn't changed since computing result
	// (which can happen between releasing the read lock and getting read-write lock).
	// Note that shuffledSubringWithLookbackCache can be only nil when set by test.
	if r.shuffledSubringWithLookbackCache == nil {
		return
	}

	if !r.lastTopologyChange.Equal(subring.lastTopologyChange) {
		return
	}

	// Only update cache if subring's lookback window starts later than the previously cached subring for this identifier,
	// if there is one. This prevents cache thrashing due to different calls competing if their lookback windows start
	// before and after the time of an instance registering.
	key := subringCacheKey{identifier: identifier, shardSize: size, lookbackPeriod: lookbackPeriod}

	if existingEntry, haveCached := r.shuffledSubringWithLookbackCache[key]; !haveCached || existingEntry.validForLookbackWindowsStartingAfter < lookbackWindowStart {
		r.shuffledSubringWithLookbackCache[key] = cachedSubringWithLookback[*Ring]{
			subring:                               subring,
			validForLookbackWindowsStartingAfter:  lookbackWindowStart,
			validForLookbackWindowsStartingBefore: validForLookbackWindowsStartingBefore,
		}
	}
}

func (r *Ring) CleanupShuffleShardCache(identifier string) {
	if r.cfg.SubringCacheDisabled {