func SelectZonesForVolume()

in volume/helpers/zones.go [106:184]
59 lines of code
22 McCabe index (conditional complexity)

func SelectZonesForVolume(zoneParameterPresent, zonesParameterPresent bool, zoneParameter string, zonesParameter, zonesWithNodes sets.String, node *v1.Node, allowedTopologies []v1.TopologySelectorTerm, pvcName string, numReplicas uint32) (sets.String, error) {
	if zoneParameterPresent && zonesParameterPresent {
		return nil, fmt.Errorf("both zone and zones StorageClass parameters must not be used at the same time")
	}

	var zoneFromNode string
	// pick one zone from node if present
	if node != nil {
		// VolumeScheduling implicit since node is not nil
		if zoneParameterPresent || zonesParameterPresent {
			return nil, fmt.Errorf("zone[s] cannot be specified in StorageClass if VolumeBindingMode is set to WaitForFirstConsumer. Please specify allowedTopologies in StorageClass for constraining zones")
		}

		// pick node's zone for one of the replicas
		var ok bool
		zoneFromNode, ok = node.ObjectMeta.Labels[v1.LabelTopologyZone]
		if !ok {
			zoneFromNode, ok = node.ObjectMeta.Labels[v1.LabelFailureDomainBetaZone]
			if !ok {
				return nil, fmt.Errorf("Either %s or %s Label for node missing", v1.LabelTopologyZone, v1.LabelFailureDomainBetaZone)
			}
		}
		// if single replica volume and node with zone found, return immediately
		if numReplicas == 1 {
			return sets.NewString(zoneFromNode), nil
		}
	}

	// pick zone from allowedZones if specified
	allowedZones, err := ZonesFromAllowedTopologies(allowedTopologies)
	if err != nil {
		return nil, err
	}

	if (len(allowedTopologies) > 0) && (allowedZones.Len() == 0) {
		return nil, fmt.Errorf("no matchLabelExpressions with %s key found in allowedTopologies. Please specify matchLabelExpressions with %s key", v1.LabelTopologyZone, v1.LabelTopologyZone)
	}

	if allowedZones.Len() > 0 {
		// VolumeScheduling implicit since allowedZones present
		if zoneParameterPresent || zonesParameterPresent {
			return nil, fmt.Errorf("zone[s] cannot be specified in StorageClass if allowedTopologies specified")
		}
		// scheduler will guarantee if node != null above, zoneFromNode is member of allowedZones.
		// so if zoneFromNode != "", we can safely assume it is part of allowedZones.
		zones, err := chooseZonesForVolumeIncludingZone(allowedZones, pvcName, zoneFromNode, numReplicas)
		if err != nil {
			return nil, fmt.Errorf("cannot process zones in allowedTopologies: %v", err)
		}
		return zones, nil
	}

	// pick zone from parameters if present
	if zoneParameterPresent {
		if numReplicas > 1 {
			return nil, fmt.Errorf("zone cannot be specified if desired number of replicas for pv is greather than 1. Please specify zones or allowedTopologies to specify desired zones")
		}
		return sets.NewString(zoneParameter), nil
	}

	if zonesParameterPresent {
		if uint32(zonesParameter.Len()) < numReplicas {
			return nil, fmt.Errorf("not enough zones found in zones parameter to provision a volume with %d replicas. Found %d zones, need %d zones", numReplicas, zonesParameter.Len(), numReplicas)
		}
		// directly choose from zones parameter; no zone from node need to be considered
		return ChooseZonesForVolume(zonesParameter, pvcName, numReplicas), nil
	}

	// pick zone from zones with nodes
	if zonesWithNodes.Len() > 0 {
		// If node != null (and thus zoneFromNode != ""), zoneFromNode will be member of zonesWithNodes
		zones, err := chooseZonesForVolumeIncludingZone(zonesWithNodes, pvcName, zoneFromNode, numReplicas)
		if err != nil {
			return nil, fmt.Errorf("cannot process zones where nodes exist in the cluster: %v", err)
		}
		return zones, nil
	}
	return nil, fmt.Errorf("cannot determine zones to provision volume in")
}