implement pods reloader on kubernetes

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hi guys, in this article i will give tutorial for implement pods auto reloader on kubernetes, imagine you have config apps on configmap or secret, and have changes, if your service/apps not have hot-reloader you must restart your pods manualy

so in this tutorial i will show you how reloader from stakater can handle hot reload when you have changes on configmap or secret

by default reloader will install on namespace default and watches changes secrets and configmaps in all namespaces, you can run command below for install

kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

in reloader we have 2 methode for restart pods when we have changes on configmap or secret

 

first method

first method will discover deployments/daemonsets/statefulset/rollouts automatically where configmap or secret is being used either via environment variable or from volume mount. And it will perform rolling upgrade on related pods when configmap or secret are updated

for this method you can add annotations on deployment and configmap below

  • deployment: reloader.stakater.com/search: “true”
  • configmap/secret: reloader.stakater.com/match: “true”

sample like below

apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:
    reloader.stakater.com/search: "true"
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        envFrom: 
          - configMapRef:
              name: nginx-configmap
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: ConfigMap
metadata:
  annotations:
    reloader.stakater.com/match: "true"
  name: nginx-configmap
data:
  domain: "sekolahlinux.com"

 

second method

second method will discover deployments/daemonsets/statefulset/rollouts automatically where configmap or secret you set on annotation, even the configmap or secret not use as environment variable or from volume mount. And it will perform rolling upgrade on related pods when configmap or secret are updated

for this method you can add annotations on deployment like below

  • deployment: configmap.reloader.stakater.com/reload: “nginx-configmap”
  • deployment: secret.reloader.stakater.com/reload: “nginx-secret”

and also you can use comma separated list to define multiple secrets or configmap name like below

  • deployment: configmap.reloader.stakater.com/reload: “nginx-configmap,app-configmap”
  • deployment: secret.reloader.stakater.com/reload: “nginx-secret,app-secret”

sample like below

apiVersion: apps/v1
kind: Deployment
metadata:
  annotations:     
    configmap.reloader.stakater.com/reload: "nginx-configmap"
  name: nginx-deployment
  labels:
    app: nginx
spec:
  replicas: 1
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80
---
apiVersion: v1
kind: ConfigMap
metadata:       
  name: nginx-configmap
data:
  domain: "sekolahlinux.com"

reference link: