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|
# JSON Patching
[JSON patches]: https://tools.ietf.org/html/rfc6902
[JSON patch]: https://tools.ietf.org/html/rfc6902
A kustomization file supports customizing
resources via [JSON patches].
Make a place to work:
<!-- @placeToWork @testAgainstLatestRelease -->
```
DEMO_HOME=$(mktemp -d)
```
We'll be editting an `Ingress` object:
<!-- @ingress @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/ingress.yaml
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: my-ingress
spec:
rules:
- host: foo.bar.com
http:
paths:
- path: /
backend:
serviceName: homepage
servicePort: 8888
- path: /api
backend:
serviceName: my-api
servicePort: 7701
- path: /test
backend:
serviceName: hello
servicePort: 7702
EOF
```
The edits we want to make are:
- change the value of `host` to _foo.bar.io_
- change the port for `'/'` from _8888_ to _80_
- insert an entirely new serving path `/healthz`
at a particular point in the `paths` list,
rather than at the end or the beginning.
Here's the patch file to do that:
<!-- @addJsonPatch @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/ingress_patch.json
[
{"op": "replace",
"path": "/spec/rules/0/host",
"value": "foo.bar.io"},
{"op": "replace",
"path": "/spec/rules/0/http/paths/0/backend/servicePort",
"value": 80},
{"op": "add",
"path": "/spec/rules/0/http/paths/1",
"value": { "path": "/healthz", "backend": {"servicePort":7700} }}
]
EOF
```
We'll of course need a `kustomization` file
referring to the `Ingress`:
<!-- @kustomization @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/kustomization.yaml
resources:
- ingress.yaml
EOF
```
To this same `kustomization` file, add a
`patches` field refering to
the patch file we just made and
target it to the `Ingress` object:
<!-- @applyJsonPatch @testAgainstLatestRelease -->
```
cat <<EOF >>$DEMO_HOME/kustomization.yaml
patches:
- path: ingress_patch.json
target:
group: networking.k8s.io
version: v1beta1
kind: Ingress
name: my-ingress
EOF
```
Define the expected output:
<!-- @expected @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/out_expected.yaml
apiVersion: networking.k8s.io/v1beta1
kind: Ingress
metadata:
name: my-ingress
spec:
rules:
- host: foo.bar.io
http:
paths:
- backend:
serviceName: homepage
servicePort: 80
path: /
- backend:
servicePort: 7700
path: /healthz
- backend:
serviceName: my-api
servicePort: 7701
path: /api
- backend:
serviceName: hello
servicePort: 7702
path: /test
EOF
```
Run the build:
<!-- @runIt @testAgainstLatestRelease -->
```
kustomize build $DEMO_HOME >$DEMO_HOME/out_actual.yaml
```
Confirm they match:
<!-- @diffShouldExitZero @testAgainstLatestRelease -->
```
diff $DEMO_HOME/out_actual.yaml $DEMO_HOME/out_expected.yaml
```
If you prefer YAML to JSON, the patch can be expressed
in YAML format (nevertheless following [JSON patch] rules):
<!-- @writeYamlPatch @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/ingress_patch.yaml
- op: add
path: /spec/rules/0/http/paths/-
value:
path: '/canada'
backend:
serviceName: hoser
servicePort: 7703
EOF
```
Now add this to the list of patches in the `kustomization` file:
<!-- @addYamlPatch @testAgainstLatestRelease -->
```
cat <<EOF >>$DEMO_HOME/kustomization.yaml
- path: ingress_patch.yaml
target:
group: networking.k8s.io
version: v1beta1
kind: Ingress
name: my-ingress
EOF
```
We expect the following at the end of the output:
<!-- @expected @testAgainstLatestRelease -->
```
cat <<EOF >$DEMO_HOME/out_expected.yaml
- backend:
serviceName: hello
servicePort: 7702
path: /test
- backend:
serviceName: hoser
servicePort: 7703
path: /canada
EOF
```
Try it:
<!-- @runIt @testAgainstLatestRelease -->
```
kustomize build $DEMO_HOME | tail -n 8 |\
diff $DEMO_HOME/out_expected.yaml -
```
To see how to apply one JSON patch to many resources,
see the [multi-patch](patchMultipleObjects.md) demo.
|
