upgrade command add three-way-merge option

[luxurine]

upgrade command add three-way-merge option to show diff for actual state vs desired state #176

prepared resource for testing

1、last release:

---
# Source: base-app/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: base-app-go
  labels:
    app: base-app-go
    team: ops
    owner: somebody
    helm.sh/chart: base-app-1.0.0
    app.kubernetes.io/managed-by: Helm
spec:
  type: ClusterIP
  ports:
    - port: 1323
      targetPort: 1323
      protocol: TCP
      name: http-1323
  selector:
    app: base-app-go
---
# Source: base-app/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: base-app-go
  labels:
    app: base-app-go
    team: ops
    owner: somebody
    helm.sh/chart: base-app-1.0.0
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app: base-app-go
  strategy:
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: base-app-go
        team: ops
        owner: somebody
        helm.sh/chart: base-app-1.0.0
        app.kubernetes.io/managed-by: Helm
    spec:
      imagePullSecrets:
        - name: regcred
      serviceAccountName: default
      initContainers:
      containers:
        - name: base-app-go
          image: xxxxx
          imagePullPolicy: IfNotPresent
          ports:
            - name: http-1323
              containerPort: 1323
              protocol: TCP
          lifecycle:
            preStop:
              exec:
                command:
                  - '/bin/sh'
                  - '-c'
                  - 'sleep 5'
          livenessProbe:
            httpGet:
              path: /healthz
              port: 1323
            initialDelaySeconds: 10
            periodSeconds: 60
          readinessProbe:
            httpGet:
              path: /healthz
              port: 1323
            initialDelaySeconds: 10
            periodSeconds: 3
          volumeMounts:
            - mountPath: /etc/localtime
              name: tz-config
              readOnly: true
            - mountPath: /sock
              name: sock-files
          envFrom:
          env:
            - name: CLUSTER
              value: dev
            - name: COUNT
              value: "3"
      volumes:
        - hostPath:
            path: /etc/localtime
            type: ""
          name: tz-config
        - emptyDir: {}
          name: sock-files

2、target release:

---
# Source: base-app/templates/service.yaml
apiVersion: v1
kind: Service
metadata:
  name: base-app-go
  labels:
    app: base-app-go
    team: ops
    owner: somebody
    helm.sh/chart: base-app-1.0.0
    app.kubernetes.io/managed-by: Helm
spec:
  type: ClusterIP
  ports:
    - port: 1323
      targetPort: 1323
      protocol: TCP
      name: http-1323
  selector:
    app: base-app-go
---
# Source: base-app/templates/deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: base-app-go
  labels:
    app: base-app-go
    team: ops
    owner: somebody
    helm.sh/chart: base-app-1.0.0
    app.kubernetes.io/managed-by: Helm
spec:
  replicas: 1
  selector:
    matchLabels:
      app: base-app-go
  strategy:
    type: RollingUpdate
  template:
    metadata:
      labels:
        app: base-app-go
        team: ops
        owner: somebody
        helm.sh/chart: base-app-1.0.0
        app.kubernetes.io/managed-by: Helm
    spec:
      imagePullSecrets:
        - name: regcred
      serviceAccountName: default
      initContainers:
      containers:
        - name: base-app-go
          image: xxxxx
          imagePullPolicy: IfNotPresent
          ports:
            - name: http-1323
              containerPort: 1323
              protocol: TCP
          lifecycle:
            preStop:
              exec:
                command:
                  - '/bin/sh'
                  - '-c'
                  - 'sleep 5'
          livenessProbe:
            initialDelaySeconds: 10
            periodSeconds: 60
            tcpSocket:
              port: 1323
          readinessProbe:
            httpGet:
              path: /healthz
              port: 1323
            initialDelaySeconds: 10
            periodSeconds: 3
          volumeMounts:
            - mountPath: /etc/localtime
              name: tz-config
              readOnly: true
            - mountPath: /sock
              name: sock-files
          envFrom:
          env:
            - name: CLUSTER
              value: dev
            - name: COUNT
              value: "4"
      volumes:
        - hostPath:
            path: /etc/localtime
            type: ""
          name: tz-config
        - emptyDir: {}
          name: sock-files

normal diff vs diff with --three-way-merge option

1、manual change：

• preStop time from 5 to 10
• delete readinessProbe
• delete Service

2、normal diff output:

default, base-app-go, Deployment (apps) has changed:
...
                    - '-c'
                    - 'sleep 5'
            livenessProbe:
-             httpGet:
-               path: /healthz
-               port: 1323
              initialDelaySeconds: 10
              periodSeconds: 60
+             tcpSocket:
+               port: 1323
            readinessProbe:
              httpGet:
                path: /healthz
...
              - name: CLUSTER
                value: dev
              - name: COUNT
-               value: "3"
+               value: "4"
        volumes:
          - hostPath:
              path: /etc/localtime

3、diff output with --three-way-merge option:

default, base-app-go, Deployment (apps) has changed:
...
      meta.helm.sh/release-name: base-app-01
      meta.helm.sh/release-namespace: default
    creationTimestamp: "2021-09-01T06:29:39Z"
-   generation: 8
+   generation: 9
    labels:
      app: base-app-go
      app.kubernetes.io/managed-by: Helm
...
       - env:
          - name: CLUSTER
             value: dev
          - name: COUNT
-           value: "3"
+           value: "4"
          image: "xxxxx"
          imagePullPolicy: IfNotPresent
          lifecycle:
...
                command:
                - /bin/sh
                - -c
-               - sleep 10
+               - sleep 5
          livenessProbe:
            failureThreshold: 3
-           httpGet:
-             path: /healthz
-             port: 1323
-             scheme: HTTP
            initialDelaySeconds: 10
            periodSeconds: 60
            successThreshold: 1
+           tcpSocket:
+             port: 1323
            timeoutSeconds: 1
          name: base-app-go
          ports:
          - containerPort: 1323
            name: http-1323
            protocol: TCP
+         readinessProbe:
+           failureThreshold: 3
+           httpGet:
+             path: /healthz
+             port: 1323
+             scheme: HTTP
+           initialDelaySeconds: 10
+           periodSeconds: 3
+           successThreshold: 1
+           timeoutSeconds: 1
          resources: {}
          terminationMessagePath: /dev/termination-log
          terminationMessagePolicy: File
...
default, base-app-go, Service (v1) has been added:
- 
+ apiVersion: v1
+ kind: Service
+ metadata:
+   labels:
+     app: base-app-go
+     app.kubernetes.io/managed-by: Helm
+     helm.sh/chart: base-app-1.0.0
+     owner: somebody
+     team: ops
+   name: base-app-go
+   namespace: default
+ spec:
+   ports:
+   - name: http-1323
+     port: 1323
+     protocol: TCP
+     targetPort: 1323
+   selector:
+     app: base-app-go
+   type: ClusterIP

inspired by https://github.com/bacongobbler/helm-patchdiff

[Temikus]

@databus23 @mumoshu can I humbly ask you folks to take a look? 🙏

This might be a step in the right direction to solve #176

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[mumoshu]

Probably L171-L193 doesn't need to be run when we enter the 3-way merge mode?

[mumoshu]

Nevermind. It turned out correct as we still render the chart at L190 to be used when building K8s objects at L207.

[mumoshu]

I have one concern but this looks great for a starter. Thanks a lot for your patience and contribution!

[dudicoco]

Thank you for this addition @luxurine and @mumoshu

When can we expect a new release which contains this change?

[mumoshu]

Yeah maybe in coming weeks.

[mumoshu]

FYI, I've added a feature to enable this via an envvar. See #336 for more information.