Method nextSequence

db/sequence_allocator.go:175–188

Returns the next available sequence. If previously reserved sequences are available (s.last < s.max), returns one and increments s.last. If no previously reserved sequences are available, reserves new batch.

(ctx context.Context)

// and increments s.last.
// If no previously reserved sequences are available, reserves new batch.
func (s *sequenceAllocator) nextSequence(ctx context.Context) (sequence uint64, err error) {
	s.mutex.Lock()
	sequence, sequencesReserved, err := s._nextSequence(ctx)
	s.mutex.Unlock()
	if err != nil {
		return 0, err
	}
	// If sequences were reserved, send notification to the release sequence monitor, to start the clock for releasing these sequences.
	// Must be done after mutex is released.
	if sequencesReserved {
		s.reserveNotify <- struct{}{}
	}
	return sequence, nil
}

// _releaseCurrentBatch releases any unused sequences currently held by the allocator.
// Writes unused sequence document while holding s.lock, shouldn't be used by high-throughput operations.