func determineScaleClusterOpLockIfNecessary()

in controllers/solr_cluster_ops_util.go [153:209]
39 lines of code
15 McCabe index (conditional complexity)

func determineScaleClusterOpLockIfNecessary(ctx context.Context, r *SolrCloudReconciler, instance *solrv1beta1.SolrCloud, statefulSet *appsv1.StatefulSet, scaleDownOpIsQueued bool, podList []corev1.Pod, blockReconciliationOfStatefulSet bool, logger logr.Logger) (clusterOp *SolrClusterOp, retryLaterDuration time.Duration, err error) {
	desiredPods := int(*instance.Spec.Replicas)
	configuredPods := int(*statefulSet.Spec.Replicas)
	if desiredPods != configuredPods {
		// We do not do a "managed" scale-to-zero operation.
		// Only do a managed scale down if the desiredPods is positive.
		// The VacatePodsOnScaleDown option is enabled by default, so treat "nil" like "true"
		if desiredPods < configuredPods && desiredPods > 0 &&
			(instance.Spec.Scaling.VacatePodsOnScaleDown == nil || *instance.Spec.Scaling.VacatePodsOnScaleDown) {
			if len(podList) > configuredPods {
				// There are too many pods, the statefulSet controller has yet to delete unwanted pods.
				// Do not start the scale down until these extra pods are deleted.
				return nil, time.Second * 5, nil
			}
			clusterOp = &SolrClusterOp{
				Operation: ScaleDownLock,
				Metadata:  strconv.Itoa(configuredPods - 1),
			}
		} else if desiredPods > configuredPods && (instance.Spec.Scaling.PopulatePodsOnScaleUp == nil || *instance.Spec.Scaling.PopulatePodsOnScaleUp) {
			// We need to wait for all pods to become healthy to scale up in a managed fashion, otherwise
			// the balancing will skip some pods
			if len(podList) < configuredPods {
				// There are not enough pods, the statefulSet controller has yet to create the previously desired pods.
				// Do not start the scale up until these missing pods are created.
				return nil, time.Second * 5, nil
			}
			// If Solr nodes are advertised by their individual node services (through an ingress)
			// then make sure that the host aliases are set for all desired pods before starting a scale-up.
			// If the host aliases do not already include the soon-to-be created pods, then Solr might not be able to balance
			// replicas onto the new hosts.
			// We need to make sure that the StatefulSet is updated with these new hostAliases before the scale up occurs.
			if instance.UsesIndividualNodeServices() && instance.Spec.SolrAddressability.External.UseExternalAddress {
				for _, pod := range podList {
					if len(pod.Spec.HostAliases) < desiredPods {
						return nil, time.Second * 5, nil
					}
				}
			}

			clusterOp = &SolrClusterOp{
				Operation: ScaleUpLock,
				Metadata:  strconv.Itoa(desiredPods),
			}
		} else {
			err = scaleCloudUnmanaged(ctx, r, statefulSet, desiredPods, logger)
		}
	} else if scaleDownOpIsQueued {
		// If the statefulSet and the solrCloud have the same number of pods configured, and the queued operation is a scaleDown,
		// that means the scaleDown was reverted. So there's no reason to change the number of pods.
		// However, a Replica Balancing should be done just in case, so start it via a new ClusterOperation.
		clusterOp = &SolrClusterOp{
			Operation: BalanceReplicasLock,
			Metadata:  "UndoFailedScaleDown",
		}
	}
	return
}