Kustomize Hash Annotator

Kustomize plugin to add annotations with the hash value of specified resources.

Background

At the time of writing, for ConfigMap and Secret declared from ConfigMapGenerator or SecretGenerator, Kustomize can append a hash suffix to trigger a rolling update when there is a change in the ConfigMap or Secret.

This plugin allows you to annotate any resources with the hash values of any other resources (including themselves), as long as they are all managed by Kustomize.

Requirements

• Go
• Kustomize

# Verify Go is installed and your $GOPATH is set
go env

# Verify Kustomize is installed and your $XDG_CONFIG_HOME is set
kustomize version
echo $XDG_CONFIG_HOME # should be ~/.config or your custom path

# Set up your $XDG_CONFIG_HOME if it is unset
echo "export XDG_CONFIG_HOME=\$HOME/.config" >> $HOME/.bashrc

Installation

Remotely Download the Latest Release

mkdir -p $XDG_CONFIG_HOME/kustomize/plugin/pcjun97/v1/hashannotator/v1
wget -c https://github.com/pcjun97/kustomize-hash-annotator/releases/latest/download/hashannotator_latest_$(uname -s)_$(uname -m).tar.gz -O hashannotator_latest.tar.gz
tar -xzf hashannotator_latest.tar.gz -C $XDG_CONFIG_HOME/kustomize/plugin/pcjun97/v1/hashannotator/

Run make install with the cloned repo Locally

git clone https://github.com/pcjun97/kustomize-hash-annotator.git
cd kustomize-hash-annotator
make install

Usage

1. Create your resources

deployment.yaml

apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: example
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: example
  template:
    metadata:
      labels:
        app.kubernetes.io/name: example
    spec:
      containers:
        - name: example
          image: hello-world
          envFrom:
            - configMapRef:
                name: example

configmap.yaml

apiVersion: v1beta1
kind: ConfigMap
metadata:
  name: example
data:
  FOO: bar

2. Add the HashAnnotator transformer

hashannotator.yaml

apiVersion: pcjun97/v1
kind: HashAnnotator
metadata:
  name: not-important-to-example
targets:
  - kind: Deployment
resources:
  - kind: ConfigMap
fieldSpecs:
  - path: spec/template/metadata/annotations
    create: true

3. Create your kustomization.yaml

kustomization.yaml

apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

resources:
  - deployment.yaml
  - configmap.yaml

transformers:
  - hashannotator.yaml

4. Build with kustomize

kustomize build --enable-alpha-plugins

Output

apiVersion: v1beta1
data:
  FOO: bar
kind: ConfigMap
metadata:
  name: example
---
apiVersion: apps/v1beta1
kind: Deployment
metadata:
  name: example
spec:
  selector:
    matchLabels:
      app.kubernetes.io/name: example
  template:
    metadata:
      annotations:
        kustomize.config.k8s.io/hash-configmap-example: 59m54fbgh2
      labels:
        app.kubernetes.io/name: example
    spec:
      containers:
      - envFrom:
        - configMapRef:
            name: example
        image: hello-world
        name: example

Transformer Options

Targets

Select targets to add the annotations.

E.g. select resources with name matching foo*:

targets:
  - name: foo*

Select all resources of kind Deployment:

targets:
  - kind: Deployment

Using multiple fields just makes the target more specific. The following selects only Deployments that also have the label app=hello (full label/annotation selector rules):

targets:
  - kind: Deployment
    labelSelector: app=hello

Resources

Select resources to hash. Uses the same selector rules as targets.

E.g.

resources:
  - kind: ConfigMap
    labelSelector: app=hello

FieldSpecs

Represents paths to fields in resources. Determines which resource types and which fields within those types the transformer can modify.

fieldSpecs:
- kind: Deployment
  path: spec/template/metadata/annotations
- kind: Pod
  path: metadata/annotations