Method ShuffleShardWithLookback

ring/ring.go:976–993

ShuffleShardWithLookback is like ShuffleShard() but the returned subring includes all instances that have been part of the identifier's shard since "now - lookbackPeriod". The returned subring may be unbalanced with regard to zones and should never be used for write operations (read only). This fu

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

// Subring returned by this method does not contain read-only instances that have changed their state
// before the lookback period.
func (r *Ring) ShuffleShardWithLookback(identifier string, size int, lookbackPeriod time.Duration, now time.Time) ReadRing {
	if cached := r.getCachedShuffledSubringWithLookback(identifier, size, lookbackPeriod, now); cached != nil {
		return cached
	}

	var result *Ring
	if size <= 0 {
		result = r.filterOutReadOnlyInstances(lookbackPeriod, now)
	} else {
		result = r.shuffleShard(identifier, size, lookbackPeriod, now)
	}

	if result != r {
		r.setCachedShuffledSubringWithLookback(identifier, size, lookbackPeriod, now, result)
	}

	return result
}

func (r *Ring) shuffleShard(identifier string, size int, lookbackPeriod time.Duration, now time.Time) *Ring {
	lookbackUntil := now.Add(-lookbackPeriod).Unix()