The newbie cloud architect diary

We want to override chart repository (and later ingres domain) configuration at cluster level. In this case we will use a JSONPatch which is very handy when something applies to any helmrelease.
$ cat <<EOF >project/config/local/cluster-patch.json
[
 {"op": "replace",
 "path": "/spec/chart/repository",
 "value": "http://chartmuseum.kube-system:8080"}
]
EOF

We may now create a new kind of kustomization.yaml

$ ./genOverlayKust.sh project/config/local/
INFO: OVERLAY_DIR set to project/config/local/
INFO: Found 1 resource patch(es).
INFO: Found ../../base/kustomization.yaml
INFO: project/config/local/kustomization.yaml written successfully.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
bases:
- ../../base
patches:
- path: cluster-patch.json
  target:
    group: helm.fluxcd.io
    version: v1
    kind: HelmRelease
As we can see, the script searches for base kustomization.yaml in parent hierarchy, and then "hooks" itself there. Also, our JSON patch has been automatically found and referenced.
Note that JSON Patch is not yet supported by kubectl kustomize. Therefore you have to use the standalone version of the tool to be able to render results. Note that this is also the version integrated by FluxCD.
$ kustomize build project/config/local/ | grep "releasename\|repository"
    repository: http://chartmuseum:8080
  releasename: chart-a
    repository: http://chartmuseum:8080
  releasename: chart-b
    repository: http://chartmuseum:8080
  releasename: chart-c

We want to deploy our portal into different namespaces, and if necessary, automatically create the target namespace as part of the deployment. We will create a new resource object for that.
$ cat > project/config/local/releases/arch/arch-ns.yaml  <<- "EOF"
---
apiVersion: v1
kind: Namespace
metadata:
  name: arch
  labels:
    name: arch
EOF
While generating corresponding kustomization, we will take the opportunity to update our HelmResources with this namespace using the -n parameter.
$ ./genOverlayKust.sh -n arch project/config/local/releases/arch
INFO: Target namespace set to arch
INFO: OVERLAY_DIR set to project/config/local/releases/arch
INFO: Found ../../../../base/kustomization.yaml
INFO: Found 1 YAML resource(s).
INFO: Found 1 JSON patch(es).
INFO: project/config/local/releases/arch/kustomization.yaml written successfully.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: arch
bases:
- ../../../../base
resources:
- arch-ns.yaml
patches:
- path: cluster-patch-inherited.json
  target:
    group: helm.fluxcd.io
    version: v1
    kind: HelmRelease

$ kustomize build project/config/local/releases/arch | grep namespace | sort -u
  namespace: arch

• Multiple overlays not supported i.e. bases cannot reference another kustomization.yaml containing bases (error: cycle detected) --> an overlay must directly point to a base of HelmRelease(s)
• Refering resource or patch from parent structure not supported (security: file is not in or below) --> parent resources and patches to inherit via file copy
• Symbolic links not supported (error: file not found) --> cannot help working around above limitations

• we may select the chart to modify from the YAML vs. for JSON it has to be done as part of kustomization.yaml
• there is no values node defined from the base object and therefore it would need to be created first for the path to be valid.

$ cat > project/config/local/releases/arch/portal/chart-c-replica-patch.yaml <<- "EOF"
---
apiVersion: helm.fluxcd.io/v1
kind: HelmRelease
metadata:
  name: chart-c
spec:
  values:
    replicaCount: 2
EOF

$ ./genOverlayKust.sh -p true project/config/local/releases/arch/portal/
INFO: Name prefix activated
INFO: OVERLAY_DIR set to project/config/local/releases/arch/portal/
INFO: Removing previously inherited patches
rm: cannot remove '/mnt/HDD2TB/Repository/tncad/k8s-app-cpd/026-fluxhelm-kustomize/project/config/local/releases/arch/portal/*-inherited.*': No such file or directory
INFO: Found ../../../../../base/kustomization.yaml
INFO: Found 1 YAML resource(s).
INFO: Found 2 YAML or JSON patch(es).
INFO: project/config/local/releases/arch/portal/kustomization.yaml written successfully.

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
namespace: arch
namePrefix: portal-
bases:
- ../../../../../base
resources:
- arch-ns-inherited.yaml
patches:
-path: chart-c-replica-patch.yaml
- path: cluster-patch-inherited.json
  target:
    group: helm.fluxcd.io
    version: v1
    kind: HelmRelease

$ kustomize build project/config/local/releases/arch/portal | grep "portal-\|replicaCount"
  name: portal-arch
  name: portal-chart-a
  name: portal-chart-b
  name: portal-chart-c
    replicaCount: 2