Invalid spec selector after upgrading helm template

Question

I've upgraded helm templates (by hand)

Fragment of previous depoloyment.yaml:

apiVersion: apps/v1beta2 kind: Deployment metadata:   name: {{ template "measurement-collector.fullname" . }}   labels:     app: {{ template "measurement-collector.name" . }}     chart: {{ template "measurement-collector.chart" . }}     release: {{ .Release.Name }}     heritage: {{ .Release.Service }} spec:   replicas: {{ .Values.replicaCount }}   selector:     matchLabels:       app: {{ template "measurement-collector.name" . }}       release: {{ .Release.Name }} 

New one:

apiVersion: apps/v1beta2 kind: Deployment metadata:   name: {{ include "measurement-collector.fullname" . }}   labels:     app.kubernetes.io/name: {{ include "measurement-collector.name" . }}     helm.sh/chart: {{ include "measurement-collector.chart" . }}     app.kubernetes.io/instance: {{ .Release.Name }}     app.kubernetes.io/managed-by: {{ .Release.Service }} spec:   replicas: {{ .Values.replicaCount }}   selector:     matchLabels:       app.kubernetes.io/name: {{ include "measurement-collector.name" . }}       app.kubernetes.io/instance: {{ .Release.Name }} 

new service.yaml:

  name: {{ include "measurement-collector.fullname" . }}   labels:     app.kubernetes.io/name: {{ include "measurement-collector.name" . }}     helm.sh/chart: {{ include "measurement-collector.chart" . }}     app.kubernetes.io/instance: {{ .Release.Name }}     app.kubernetes.io/managed-by: {{ .Release.Service }} spec:   type: {{ .Values.service.type }}   ports:       protocol: TCP       name: http   selector:     app.kubernetes.io/name: {{ include "measurement-collector.name" . }}     app.kubernetes.io/instance: {{ .Release.Name }} 

Then after running: helm upgrade -i measurement-collector chart/measurement-collector --namespace prod --wait

I get:

Error: UPGRADE FAILED: Deployment.apps "measurement-collector" is invalid: spec.selector: Invalid value:  v1.LabelSelector{MatchLabels:map[string]string{"app.kubernetes.io/name":"measurement-collector", "app.kubernetes.io/instance":"measurement-collector"},          MatchExpressions:[]v1.LabelSelectorRequirement(nil)}: field is immutable 

Answer 1

If you change the selector label, then you will need to purge the release first before deploying.

Answer 2

Though @TigerBear answer is correct, I think I need to explain it in a little bit more details. This problem is caused by a simple reason - immutability of the selectors. You cannot update selectors for (I am not sure this is the complete list, feel free to correct me):

1. ReplicasSets
2. Deployments
3. DaemonSets

In other words, for example if you have a Deployment with label 'my-app: ABC' within selectors, after that you have updated label inside selector onto this: 'my-app: XYZ', and then simply applied this changes, e.g. like this:

kubectl apply -f deployment-file-name.yml 

it will not work - you have to recreate the deployment.

Related github k8s issue, also there is a little note about it in the Deployment doc