ConfigMa

Stable Kubernetes ConfigMaps in an unstable world

ConfigMa enables you to present a persistent ConfigMap to your application using the data from the latest instance of an immutable ConfigMap.

For example, let's imagine your pipeline produces ConfigMaps with the following naming convention:

$ kubectl get cm
NAME                              DATA   AGE
network-conf-be1c2b               1      10m
network-conf-89fea1               1      12m
network-conf-c5b12f               1      15m

This presents a difficulty if you wish to use this data in a Pod:

apiVersion: v1
kind: Pod
metadata:
  name: network-pod
spec:
  containers:
    - name: net-container
      image: network-image
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
  volumes:
    - name: config-volume
      configMap:
        name: network-conf-be1c2b

Although our application can read the data as it changes in the ConfigMap, we need to find a way to update the ConfigMap reference in the pod each time a new version of the ConfigMap is generated with the latest network configuration data.

This is the problem ConfigMa aims to solve. Using the ConfigMatcher custom resource we now do the following:

apiVersion: util.phoban.io/v1alpha1
kind: ConfigMatch
metadata:
  name: configmatch-sample
spec:
  sourceRef:
    kind: ConfigMap
    pattern: ^network-conf-*$
    matchGroup: config
  target:
    kind: ConfigMap
    name: network-conf
    namespace: default

We must also add the following label to our ConfigMaps: configma.io/group: config.

With this in place ConfigMa will now generate a ConfigMap named network-conf in the default namespace and keep it's data in sync with the latest version of the ConfigMap matching .spec.sourceRef.pattern with the matchGroup label.

Your workload can now use this stable reference:

apiVersion: v1
kind: Pod
metadata:
  name: network-pod
spec:
  containers:
    - name: net-container
      image: network-image
      volumeMounts:
      - name: config-volume
        mountPath: /etc/config
  volumes:
    - name: config-volume
      configMap:
        name: network-conf

Inspired by https://github.com/gopaddle-io/configurator