func (al *Allocators) txnAllocClusterIPs(service *api.Service, dryRun bool) (transaction, error) {
	// clusterIPs that were allocated may need to be released in case of
	// failure at a higher level.
	allocated, err := al.allocClusterIPs(service, dryRun)
	if err != nil {
		return nil, err
	}

	txn := callbackTransaction{
		revert: func() {
			if dryRun {
				return
			}
			actuallyReleased, err := al.releaseIPs(allocated)