Kubernetes Strategic Merge Patch

External

• https://github.com/kubernetes/community/blob/master/contributors/devel/sig-api-machinery/strategic-merge-patch.md
• https://kubernetes.io/docs/tasks/manage-kubernetes-objects/update-api-object-kubectl-patch/
• https://github.com/kubernetes-sigs/kustomize/blob/master/docs/glossary.md#patchstrategicmerge

Internal

• kubectl kustomize
• kubectl apply
• kubectl edit
• kubectl patch

Overview

A strategic merge patch is a customized version of JSON patch and it looks like an incomplete YAML specification of a Kubernetes resource.

The SMP includes TypeMeta fields to establish the group/version/kind/name of the resource to patch, then just enough remaining fields to step into a nested structure to specify a new field value, e.g. an image tag. By default, an SMP replaces values. This is usually the desired behavior when the target value is a simple string, but may not be desired when the target value is a list. To change this default behavior, add a directive. Recognized directives in YAML patches are:

• replace (the default)
• delete

Example

The following patch updates the amount of memory allocated to a container in a pod and changes it to 1024Mi

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
 containers:
 - name: my-container
   resources:
     limits:
       memory: 1024Mi