Migrating from Helm v2 to Helm v3

You can use Helm 2to3 plugin to migrate Helm 2 GitLab releases to Helm 3: 

helm 2to3 convert YOUR-GITLAB-RELEASE

Known Issues

After migration the subsequent upgrades may fail with an error similar to the following: 

Error: UPGRADE FAILED: cannot patch "..." with kind Deployment: Deployment.apps "..." is invalid: spec.selector:
Invalid value: v1.LabelSelector{...}: field is immutable

or 

Error: UPGRADE FAILED: cannot patch "..." with kind StatefulSet: StatefulSet.apps "..." is invalid:
spec: Forbidden: updates to statefulset spec for fields other than 'replicas', 'template', and 'updateStrategy' are forbidden

This is due to known issues with Helm 2 to 3 migration in Cert Manager and Redis dependencies. In a nutshell, the heritage label on some Deployments and StatefulSets are immutable and can not be changed from Tiller (set by Helm 2) to Helm (set by Helm 3). So they must be replaced forcefully.

To work around this use the following instructions:

Note: These instructions forcefully replace resources, notably Redis StatefulSet. You need to ensure that the attached data volume to this StatefulSet is safe and remains intact.
  1. Replace cert-manager Deployments (when enabled). 
kubectl get deployments -l app=cert-manager -o yaml | sed "s/Tiller/Helm/g" | kubectl replace --force=true -f -
kubectl get deployments -l app=cainjector -o yaml | sed "s/Tiller/Helm/g" | kubectl replace --force=true -f -
  1. (Optional) Set persistentVolumeReclaimPolicy to Retain on the PV that is claimed by Redis StatefulSet. This is to ensure that the PV won’t be deleted inadvertently. 
kubectl patch pv <PV-NAME> -p '{"spec":{"persistentVolumeReclaimPolicy":"Retain"}}'
  1. Set heritage label of the existing Redis PVC to Helm. 
kubectl label pvc -l app=redis --overwrite heritage=Helm
  1. Replace Redis StatefulSet without cascading. 
kubectl get statefulsets.apps -l app=redis -o yaml | sed "s/Tiller/Helm/g" | kubectl replace --force=true --cascade=false -f -