func (q *quota) Admit(a admission.Attributes) (err error) {
	if a.GetOperation() == "DELETE" {
		return nil
	}

	key := &api.ResourceQuota{
		ObjectMeta: api.ObjectMeta{
			Namespace: a.GetNamespace(),
			Name:      "",
		},
	}
	items, err := q.indexer.Index("namespace", key)
	if err != nil {
		return admission.NewForbidden(a, fmt.Errorf("Unable to %s %s at this time because there was an error enforcing quota", a.GetOperation(), a.GetResource()))
	}
	if len(items) == 0 {
		return nil
	}

	for i := range items {
		quota := items[i].(*api.ResourceQuota)

		// we cannot modify the value directly in the cache, so we copy
		status := &api.ResourceQuotaStatus{
			Hard: api.ResourceList{},
			Used: api.ResourceList{},
		}
		for k, v := range quota.Status.Hard {
			status.Hard[k] = *v.Copy()
		}
		for k, v := range quota.Status.Used {
			status.Used[k] = *v.Copy()
		}

		dirty, err := IncrementUsage(a, status, q.client)
		if err != nil {
			return admission.NewForbidden(a, err)
		}

		if dirty {
			// construct a usage record
			usage := api.ResourceQuota{
				ObjectMeta: api.ObjectMeta{
					Name:            quota.Name,
					Namespace:       quota.Namespace,
					ResourceVersion: quota.ResourceVersion,
					Labels:          quota.Labels,
					Annotations:     quota.Annotations},
			}
			usage.Status = *status
			_, err = q.client.ResourceQuotas(usage.Namespace).UpdateStatus(&usage)
			if err != nil {
				return admission.NewForbidden(a, fmt.Errorf("Unable to %s %s at this time because there was an error enforcing quota", a.GetOperation(), a.GetResource()))
			}
		}
	}
	return nil
}

// ValidateResourceQuotaUpdate tests to see if the update is legal for an end user to make.
// newResourceQuota is updated with fields that cannot be changed.
func ValidateResourceQuotaUpdate(newResourceQuota, oldResourceQuota *api.ResourceQuota) errs.ValidationErrorList {
	allErrs := errs.ValidationErrorList{}
	allErrs = append(allErrs, ValidateObjectMetaUpdate(&oldResourceQuota.ObjectMeta, &newResourceQuota.ObjectMeta).Prefix("metadata")...)
	for k := range newResourceQuota.Spec.Hard {
		allErrs = append(allErrs, validateResourceName(string(k), string(newResourceQuota.TypeMeta.Kind))...)
	}
	newResourceQuota.Status = oldResourceQuota.Status
	return allErrs
}

// ValidateResourceQuotaStatusUpdate tests to see if the status update is legal for an end user to make.
// newResourceQuota is updated with fields that cannot be changed.
func ValidateResourceQuotaStatusUpdate(newResourceQuota, oldResourceQuota *api.ResourceQuota) errs.ValidationErrorList {
	allErrs := errs.ValidationErrorList{}
	allErrs = append(allErrs, ValidateObjectMetaUpdate(&oldResourceQuota.ObjectMeta, &newResourceQuota.ObjectMeta).Prefix("metadata")...)
	if newResourceQuota.ResourceVersion == "" {
		allErrs = append(allErrs, fmt.Errorf("ResourceVersion must be specified"))
	}
	for k := range newResourceQuota.Status.Hard {
		allErrs = append(allErrs, validateResourceName(string(k), string(newResourceQuota.TypeMeta.Kind))...)
	}
	for k := range newResourceQuota.Status.Used {
		allErrs = append(allErrs, validateResourceName(string(k), string(newResourceQuota.TypeMeta.Kind))...)
	}
	newResourceQuota.Spec = oldResourceQuota.Spec
	return allErrs
}

func (q *quota) Admit(a admission.Attributes) (err error) {
	if a.GetSubresource() != "" {
		return nil
	}

	if a.GetOperation() == "DELETE" {
		return nil
	}

	key := &api.ResourceQuota{
		ObjectMeta: api.ObjectMeta{
			Namespace: a.GetNamespace(),
			Name:      "",
		},
	}

	// concurrent operations that modify quota tracked resources can cause a conflict when incrementing usage
	// as a result, we will attempt to increment quota usage per request up to numRetries limit
	// we fuzz each retry with an interval period to attempt to improve end-user experience during concurrent operations
	numRetries := 10
	interval := time.Duration(rand.Int63n(90)+int64(10)) * time.Millisecond

	items, err := q.indexer.Index("namespace", key)
	if err != nil {
		return admission.NewForbidden(a, fmt.Errorf("Unable to %s %s at this time because there was an error enforcing quota", a.GetOperation(), a.GetResource()))
	}
	if len(items) == 0 {
		return nil
	}

	for i := range items {

		quota := items[i].(*api.ResourceQuota)

		for retry := 1; retry <= numRetries; retry++ {

			// we cannot modify the value directly in the cache, so we copy
			status := &api.ResourceQuotaStatus{
				Hard: api.ResourceList{},
				Used: api.ResourceList{},
			}
			for k, v := range quota.Status.Hard {
				status.Hard[k] = *v.Copy()
			}
			for k, v := range quota.Status.Used {
				status.Used[k] = *v.Copy()
			}

			dirty, err := IncrementUsage(a, status, q.client)
			if err != nil {
				return admission.NewForbidden(a, err)
			}

			if dirty {
				// construct a usage record
				usage := api.ResourceQuota{
					ObjectMeta: api.ObjectMeta{
						Name:            quota.Name,
						Namespace:       quota.Namespace,
						ResourceVersion: quota.ResourceVersion,
						Labels:          quota.Labels,
						Annotations:     quota.Annotations},
				}
				usage.Status = *status
				_, err = q.client.ResourceQuotas(usage.Namespace).UpdateStatus(&usage)
				if err == nil {
					break
				}

				// we have concurrent requests to update quota, so look to retry if needed
				if retry == numRetries {
					return admission.NewForbidden(a, fmt.Errorf("Unable to %s %s at this time because there are too many concurrent requests to increment quota", a.GetOperation(), a.GetResource()))
				}
				time.Sleep(interval)
				// manually get the latest quota
				quota, err = q.client.ResourceQuotas(usage.Namespace).Get(quota.Name)
				if err != nil {
					return admission.NewForbidden(a, err)
				}
			}
		}
	}
	return nil
}