Restart pods when configmap updates in Kubernetes?

How do I automatically restart Kubernetes pods and pods associated with deployments when their configmap is changed/updated?

I know there's been talk about the ability to automatically restart pods when a config maps changes but to my knowledge this is not yet available in Kubernetes 1.2.

So what (I think) I'd like to do is a "rolling restart" of the deployment resource associated with the pods consuming the config map. Is it possible, and if so how, to force a rolling restart of a deployment in Kubernetes without changing anything in the actual template? Is this currently the best way to do it or is there a better option?

The current best solution to this problem (referenced deep in https://github.com/kubernetes/kubernetes/issues/22368 linked in the sibling answer) is to use Deployments, and consider your ConfigMaps to be immutable.

When you want to change your config, create a new ConfigMap with the changes you want to make, and point your deployment at the new ConfigMap. If the new config is broken, the Deployment will refuse to scale down your working ReplicaSet. If the new config works, then your old ReplicaSet will be scaled to 0 replicas and deleted, and new pods will be started with the new config.

Not quite as quick as just editing the ConfigMap in place, but much safer.

Signalling a pod on config map update is a feature in the works (https://github.com/kubernetes/kubernetes/issues/22368).

You can always write a custom pid1 that notices the confimap has changed and restarts your app.

You can also eg: mount the same config map in 2 containers, expose a http health check in the second container that fails if the hash of config map contents changes, and shove that as the liveness probe of the first container (because containers in a pod share the same network namespace). The kubelet will restart your first container for you when the probe fails.

Of course if you don't care about which nodes the pods are on, you can simply delete them and the replication controller will "restart" them for you.

The best way I've found to do it is run Reloader

It allows you to define configmaps or secrets to watch, when they get updated, a rolling update of your deployment is performed. Here's an example:

You have a deployment foo and a ConfigMap called foo-configmap. You want to roll the pods of the deployment every time the configmap is changed. You need to run Reloader with:

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

Then specify this annotation in your deployment:

kind: Deployment
metadata:
  annotations:
    configmap.reloader.stakater.com/reload: "foo-configmap"
  name: foo
...