Method ShuffleShardWithLookback

ring/partition_ring.go:217–229

ShuffleShardWithLookback is like ShuffleShard() but the returned subring includes all instances that have been part of the identifier's shard in [now - lookbackPeriod, now] time window. This function can return a mix of ACTIVE and INACTIVE partitions. INACTIVE partitions are only included if they w

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

// This function supports caching, but the cache will only be effective if successive calls for the
// same identifier are with the same lookbackPeriod and increasing values of now.
func (r *PartitionRing) ShuffleShardWithLookback(identifier string, size int, lookbackPeriod time.Duration, now time.Time) (*PartitionRing, error) {
	if cached := r.shuffleShardCache.getSubringWithLookback(identifier, size, lookbackPeriod, now); cached != nil {
		return cached, nil
	}

	subring, err := r.shuffleShard(identifier, size, lookbackPeriod, now)
	if err != nil {
		return nil, err
	}

	r.shuffleShardCache.setSubringWithLookback(identifier, size, lookbackPeriod, now, subring)
	return subring, nil
}

func (r *PartitionRing) shuffleShard(identifier string, size int, lookbackPeriod time.Duration, now time.Time) (*PartitionRing, error) {
	// If the size is too small or too large, run with a size equal to the total number of partitions.