configmap-attacher

configmap-attacher

Overview

This container was built to provide the ability to work with revisioned configmaps while performing Canary deployment with Argo Rollouts on Kubernetes. It supports only Rollout objects and not deployment objects with workloadRef

This Job is part of the following Helm chart

Configmaps and Canary Deployment:

When performing a Canary deployment, there will be a new ReplicaSet and an old ReplicaSet. Based on the Canary strategy, pods will be migrated from the old ReplicaSet to the new ReplicaSet. By default, when a Canary deployment is triggered due to a change in a configmap link, the old configmap will be replaced with the new one, and Pods that will be migrated to the new ReplicaSet will load the new configmap.

The problem:

During the Canary rollout, one of the pods from the old ReplicaSet is recreated or restarted due to infra-related causes like Spot replacement; that pod will load the new configmap although it's located on the old ReplicaSet.

The solution

On every deploy, attach the revisioned configmaps to the new ReplicaSets, and utilize the K8S garbage collector to delete old configmaps.

CLI

• -rollout - Rollout that will be the ownerReference
• -namespace - The namespace of the rollout and configmaps
• -configmaps - Configmaps to add the ownerReference, for multiple configmaps use ',' as a separator

Environment Variables

Permissions

To make the configmap-attacher work on any namespace, it's better to deploy it in kube-system with ClusterRole permissions; you can use the following:

---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRole
metadata:
  name: configmap-attacher-job
rules:
- apiGroups:
  - argoproj.io
  resources:
  - rollouts
  - rollouts/status
  - rollouts/finalizers
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - apps
  resources:
  - replicasets
  verbs:
  - get
  - list
  - watch
- apiGroups:
  - ""
  resources:
  - configmaps
  verbs:
  - get
  - list
  - watch
  - patch
---
apiVersion: v1
kind: ServiceAccount
metadata:
  name: configmap-attacher-job
  namespace: kube-system
---
apiVersion: rbac.authorization.k8s.io/v1
kind: ClusterRoleBinding
metadata:
  name: configmap-attacher-job
roleRef:
  apiGroup: rbac.authorization.k8s.io
  kind: ClusterRole
  name: configmap-attacher-job
subjects:
- kind: ServiceAccount
  name: configmap-attacher-job
  namespace: kube-system

Job example:

apiVersion: batch/v1
kind: Job
metadata:
  namespace: kube-system
  annotations:
    argocd.argoproj.io/hook: Sync
  name: configmap-attacher-job
spec:
  backoffLimit: 3
  template:
    metadata:
      name: configmap-attacher-job
      annotations:
    spec:
      containers:
      - name: configmap-attacher-job
        args: ["-rollout", "<Rollout Name>", "-namespace", "<Namespace>", "-configmaps", <Configmap name>]
        image: quay.io/liorfranko/configmap-attacher:1.0.1
        resources:
          limits:
            cpu: 0.1
            memory: 100Mi
          requests:
            cpu: 0.1
            memory: 100Mi
        env:
          - name: VERSION
            value: "1.0.1"
          - name: JOB_NAME
            value: "configmap-attacher-job"
      restartPolicy: OnFailure
      serviceAccountName: configmap-attacher-job