patchMultipleObjects.md

Demo: applying a patch to multiple resources

A kustomization file supports customizing resources via both Strategic Merge Patch and JSON patches. Now one patch can be applied to multiple resources.

This can be done by specifying a patch and a target selector as follows:

patches:
- path: <PatchFile>
  target:
    group: <Group>
    version: <Version>
    kind: <Kind>
    name: <Name>
    namespace: <Namespace>
    labelSelector: <LabelSelector>
    annotationSelector: <AnnotationSelector>

Both labelSelector and annotationSelector should follow the convention in label selector. Kustomize selects the targets which match all the fields in target to apply the patch.

The example below shows how to inject a sidecar container for all deployment resources.

Make a kustomization containing a Deployment resource.

DEMO_HOME=$(mktemp -d)

cat <<EOF >$DEMO_HOME/kustomization.yaml
resources:
- deployments.yaml
EOF

cat <<EOF >$DEMO_HOME/deployments.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy1
spec:
  template:
    metadata:
      labels:
        old-label: old-value
    spec:
      containers:
        - name: nginx
          image: nginx
          args:
          - one
          - two
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy2
spec:
  template:
    metadata:
      labels:
        key: value
    spec:
      containers:
        - name: busybox
          image: busybox
EOF

Declare a Strategic Merge Patch file to inject a sidecar container:

cat <<EOF >$DEMO_HOME/patch.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: not-important
spec:
  template:
    spec:
      containers:
        - name: istio-proxy
          image: docker.io/istio/proxyv2
          args:
          - proxy
          - sidecar
EOF

Apply the patch by adding patches field in kustomization.yaml

cat <<EOF >>$DEMO_HOME/kustomization.yaml
patches:
- path: patch.yaml
  target:
    kind: Deployment
EOF

Running kustomize build $DEMO_HOME, in the output confirm that both Deployment resources are patched correctly.

test 2 == \
  $(kustomize build $DEMO_HOME | grep "image: docker.io/istio/proxyv2" | wc -l); \
  echo $?

The output is as follows:

apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy1
spec:
  template:
    metadata:
      labels:
        old-label: old-value
    spec:
      containers:
      - args:
        - proxy
        - sidecar
        image: docker.io/istio/proxyv2
        name: istio-proxy
      - args:
        - one
        - two
        image: nginx
        name: nginx
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: deploy2
spec:
  template:
    metadata:
      labels:
        key: value
    spec:
      containers:
      - args:
        - proxy
        - sidecar
        image: docker.io/istio/proxyv2
        name: istio-proxy
      - image: busybox
        name: busybox

Target selector

• Select resources with name matching name*

  target:
    name: name*

• Select all Deployment resources

  target:
    kind: Deployment

• Select resources matching label app=hello

  target:
    labelSelector: app=hello

• Select resources matching annotation app=hello

  target:
    annotationSelector: app=hello

• Select all Deployment resources matching label app=hello

  target:
    kind: Deployment
    labelSelector: app=hello