W have a ConfigMap for our Gorush service (see the Kubernetes: running a push-server with Gorush behind an AWS LoadBalancer post).
The issue is that if change a value in this ConfigMap or Secrets -it will not be applied to already running pods.
There are various solitons like mount data as volumes and re-attach those volumes after data has been changed, or to create a brand new ConfigMap with a new name each time on a new change, and re-map it to the pods.
But let’s try to use the Reloader – it will auto-discover all ConfgiMaps and Secrets and will watch for their changes. Once it will find that a ConfigMap was updated – Reloader will re-create related pods.
Running Reloader in Kubernetes
Create a service and related objects – configs, roles, etc:
$ kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml
deployment.apps/reloader-reloader created
clusterrole.rbac.authorization.k8s.io/reloader-reloader-role created
clusterrolebinding.rbac.authorization.k8s.io/reloader-reloader-role-binding created
serviceaccount/reloader-reloader created
It will be deployed to the в default namespace, and by default will watch for all ConfigMap and Secrets in all namespaces, but you can limit this behavior using object’s annotations, see the full doc here>>>.
Check the service’s pod:
$ kubectl get pod
NAME READY STATUS RESTARTS AGE
reloader-reloader-7684d7d4b5-rwp6x 1/1 Running 0 112s
ConfigMap auto-reload
Now, let’s check an existing value from the Gorush service:
$ curl push.example.com/api/config
...
ios:
enabled: true
key_path: /data/ssl/apns-crt.p12
key_base64: ""
...
And its ConfigMap:
---
apiVersion: v1
kind: ConfigMap
metadata:
name: gorush-config
namespace: gorush
data:
# stat
stat.engine: redis
stat.redis.host: redis:6379
ios.enabled: "true"
ios.key_path: /data/ssl/apns-crt.p12
...
Update its deployment and add to the annotations one of the following string – reloader.stakater.com/auto: "true" or configmap.reloader.stakater.com/reload: "gorush-config", or you’d like to watch only this particular ConfigMap:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: gorush
namespace: gorush
annotations:
configmap.reloader.stakater.com/reload: "gorush-config"
spec:
replicas: 1
template:
metadata:
labels:
app: gorush
tier: frontend
...
Apply the deployment:
$ kubectl apply -f gorush-deployment.yaml
deployment.extensions/gorush configured
Add some changes to the Gorush’ cConfigMap, for example, let’s change ios.enabled: "true" to the ios.enabled: "false":
$ kubectl apply -f gorush-configmap.yaml
configmap/gorush-config configured
configmap/gorush-config-file unchanged
Check events:
$ kubectl get events -n gorush
...
7s Normal ScalingReplicaSet deployment/gorush Scaled up replica set gorush-b85d7dc64 to 1
7s Normal ScalingReplicaSet deployment/gorush Scaled down replica set gorush-7b8695bf6f to 0
Replica-sets:
$ kubectl -n gorush get rs
NAME DESIRED CURRENT READY AGE
gorush-7b8695bf6f 0 0 0 10m
gorush-88cdd9b4d 0 0 0 20m
gorush-b85d7dc64 1 1 1 51s
redis-7d5844c58d 1 1 1 5d
And Gorush’ settings now:
$ curl push.example.com/api/config
...
ios:
enabled: false
key_path: /data/ssl/apns-crt.p12
key_base64: ""
key_type: pem
...
Done.
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