K
Q

k8s - trigger new pod creation via config map update

3/22/2019

I have a deployment for which the env variables for pod are set via config map.

    envFrom:
    - configMapRef:
        name: map

My config map will look like this

apiVersion: v1
data:
  HI: HELLO
  PASSWORD: PWD
  USERNAME: USER
kind: ConfigMap
metadata:
  name: map

all the pods have these env variables set from map. Now If I change the config map file and apply - kubectl apply -f map.yaml i get the confirmation that map is configured. However it does not trigger new pods creation with updated env variables.

Interestingly this one works

kubectl set env deploy/mydeploy PASSWORD=NEWPWD

But not this one

kubectl set env deploy/mydeploy --from=cm/map

But I am looking for the way for new pods creation with updated env variables via config map!

-- KitKarson
kubernetes

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2 Answers

3/25/2019

The simple answer is NO.

In case you are not using helm & looking for a hack, after updating the configMap, just use an dummy env variable - keep updating the value just to trigger the rolling update.

kubectl set env deploy/mydeploy DUMMY_ENV_FOR_ROLLING_UPDATE=dummyval
-- KitKarson
Source: StackOverflow
3/22/2019

Interestingly this one works

kubectl set env deploy/mydeploy PASSWORD=NEWPWD

But not this one

kubectl set env deploy/mydeploy --from=cm/map

This is expected behavior. Your pod manifest hasn't changed in second command (when you use the cm), that's why Kubernetes not recreating it.

There are several ways to deal with that. Basically what you can do is artificially change Pod manifest every time ConfigMap changes, e.g. adding annotation to the Pod with sha256sum of ConfigMap content. This is actually what Helm suggests you do. If you are using Helm it can be done as:

kind: Deployment
spec:
  template:
    metadata:
      annotations:
        checksum/config: {{ include (print $.Template.BasePath "/configmap.yaml") . | sha256sum }}
[...]

From here: https://github.com/helm/helm/blob/master/docs/charts_tips_and_tricks.md#automatically-roll-deployments-when-configmaps-or-secrets-change

Just make sure you add annotation to Pod (template) object, not the Deployment itself.

-- Grigory Ignatyev
Source: StackOverflow