Why Aren't My Environment Variables Set in Kubernetes Pods From ConfigMap? - express

Question

I have the following configmap spec:
apiVersion: v1
data:
MY_NON_SECRET: foo
MY_OTHER_NON_SECRET: bar
kind: ConfigMap
metadata:
name: web-configmap
namespace: default
$ kubectl describe configmap web-configmap
Name: web-configmap
Namespace: default
Labels: <none>
Annotations: <none>
Data
====
MY_NON_SECRET:
----
foo
MY_OTHER_NON_SECRET:
----
bar
Events: <none>
And the following pod spec:
apiVersion: v1
kind: Pod
metadata:
name: web-pod
spec:
containers:
- name: web
image: kahunacohen/hello-kube:latest
envFrom:
- configMapRef:
name: web-configmap
ports:
- containerPort: 3000
$ kubectl describe pod web-deployment-5bb9d846b6-8k2s9
Name: web-deployment-5bb9d846b6-8k2s9
Namespace: default
Priority: 0
Node: minikube/192.168.49.2
Start Time: Mon, 12 Jul 2021 12:22:24 +0300
Labels: app=web-pod
pod-template-hash=5bb9d846b6
service=web-service
Annotations: <none>
Status: Running
IP: 172.17.0.5
IPs:
IP: 172.17.0.5
Controlled By: ReplicaSet/web-deployment-5bb9d846b6
Containers:
web:
Container ID: docker://8de5472c9605e5764276c345865ec52f9ec032e01ed58bc9a02de525af788acf
Image: kahunacohen/hello-kube:latest
Image ID: docker-pullable://kahunacohen/hello-kube#sha256:930dc2ca802bff72ee39604533342ef55e24a34b4a42b9074e885f18789ea736
Port: 3000/TCP
Host Port: 0/TCP
State: Running
Started: Mon, 12 Jul 2021 12:22:27 +0300
Ready: True
Restart Count: 0
Environment: <none>
Mounts:
/var/run/secrets/kubernetes.io/serviceaccount from kube-api-access-tcqwz (ro)
Conditions:
Type Status
Initialized True
Ready True
ContainersReady True
PodScheduled True
Volumes:
kube-api-access-tcqwz:
Type: Projected (a volume that contains injected data from multiple sources)
TokenExpirationSeconds: 3607
ConfigMapName: kube-root-ca.crt
ConfigMapOptional: <nil>
DownwardAPI: true
QoS Class: BestEffort
Node-Selectors: <none>
Tolerations: node.kubernetes.io/not-ready:NoExecute op=Exists for 300s
node.kubernetes.io/unreachable:NoExecute op=Exists for 300s
Events:
Type Reason Age From Message
---- ------ ---- ---- -------
Normal Scheduled 19m default-scheduler Successfully assigned default/web-deployment-5bb9d846b6-8k2s9 to minikube
Normal Pulling 19m kubelet Pulling image "kahunacohen/hello-kube:latest"
Normal Pulled 19m kubelet Successfully pulled image "kahunacohen/hello-kube:latest" in 2.3212119s
Normal Created 19m kubelet Created container web
Normal Started 19m kubelet Started container web
The pod has container that is running expressjs with this code which is trying to print out the env vars set in the config map:
const process = require("process");
const express = require("express");
const app = express();
app.get("/", (req, res) => {
res.send(`<h1>Kubernetes Expressjs Example 0.3</h2>
<h2>Non-Secret Configuration Example</h2>
<p>This uses ConfigMaps as env vars.</p>
<ul>
<li>MY_NON_SECRET: "${process.env.MY_NON_SECRET}"</li>
<li>MY_OTHER_NON_SECRET: "${process.env.MY_OTHER_NON_SECRET}"</li>
</ul>
`);
});
app.listen(3000, () => {
console.log("Listening on http://localhost:3000");
})
When I deploy these pods, the env vars are undefined
When I do $ kubectl exec {POD_NAME} -- env
I don't see my env vars.
What am I doing wrong? I've tried killing the pods, waiting till they restart then check again to no avail.

Answer 1

It looks like your pods are managed by web-deployment deployment. You cannot patch such pods directly.
If you run kubectl get pod <pod-name> -n <namespace> -oyaml, you'll see a block called ownerReferences under the metadata section. This tells you who is the owner/manager of this pod.
In case of a deployment, here is the ownership hierarchy:
Deployment -> ReplicaSet -> Pod
i.e. A deployment creates replicaset and replicaset in turn creates pod.
So, if you want to change anything in the pod Spec, you should make that change in the deployment, not in the replicaset or the pod directly as they will get overwritten.
Patch your deployment either by running and edit the environment field there:
kubectl edit deployment.apps <deployment-name> -n <namespace>
or update the deployment yaml with your changes and run
kubectl apply -f <deployment-yaml-file>