add operation with Kustomize only if not exists - kubernetes

Question

I want to add a resource limit and request using Kustomize if and only if it's not already configured. Problem is that the deployment is in fact a list of deployments, so I cannot use default values:
values.yaml
myDeployments:
- name: deployment1
- name: deployment2
resources:
limits:
cpu: 150
memory: 200
kustomize.yaml
- target:
kind: Deployment
patch: |-
- op: add
path: "/spec/template/spec/containers/0/resources"
value:
limits:
cpu: 300
memory: 400
Problem here is that it's replaces both deployments' resources, ignoring the resources defined in values.yaml.

Answer 1

You can't make Kustomize conditionally apply a patch based on whether or not the resource limits already exists. You could use labels to identify deployments that should receive the default resource limits, e.g. given something like:
apiVersion: apps/v1
kind: Deployment
metadata:
name: example
spec:
replicas: 1
template:
spec:
metadata:
labels:
example.com/default_limits: "true"
[...]
You could do something like this in your kustomization.yaml:
- target:
kind: Deployment
labelSelector: example.com/default_limits=true
patch: |-
- op: add
path: "/spec/template/spec/containers/0/resources"
value:
limits:
cpu: 300
memory: 400
However, you could also simply set a default resource limits in your target namespace. See "Configure Default CPU Requests and Limits for a Namespace" for details. You would create a LimitRange resource in your namespace:
apiVersion: v1
kind: LimitRange
metadata:
name: cpu-limit-range
spec:
limits:
- type: container
default:
cpu: 150
memory: 200
This would be applied to any containers that don't declare their own resource limits, which is I think the behavior you're looking for.