How would I assign ConfigMap to a pod that is already running? - docker

Question

I cannot get a ConfigMap loaded into a pod that is currently running nginx.
I tried by creating a simple pod definition and added to it a simple read ConfigMap shown below:
apiVersion: v1
kind: Pod
metadata:
name: testpod
spec:
containers:
- name: testcontainer
image: nginx
env:
- name: MY_VAR
valueFrom:
configMapKeyRef:
name: configmap1
key: data1
This ran successfully and its YAML file was saved and then deleted.
Here's what I got:
apiVersion: v1
kind: Pod
metadata:
annotations:
kubectl.kubernetes.io/last-applied-configuration: |
{"apiVersion":"v1","kind":"Pod","metadata":{"annotations":{},"name":"testpod","namespace":"default"},"spec":{"containers":[{"env":[{"name":"MY_VAR","valueFrom":{"configMapKeyRef":{"key":"data1","name":"configmap1"}}}],"image":"nginx","name":"testcontainer"}]}}
creationTimestamp: null
name: testpod
selfLink: /api/v1/namespaces/default/pods/testpod
spec:
containers:
- env:
- name: MY_VAR
valueFrom:
configMapKeyRef:
key: data1
name: configmap1
image: nginx
imagePullPolicy: Always
name: testcontainer
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-27x4x
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: ip-10-0-1-103
priority: 0
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- name: default-token-27x4x
secret:
defaultMode: 420
secretName: default-token-27x4x
status:
phase: Pending
qosClass: BestEffort
I then tried copying its syntax into what was another pod which was running.
This is what I got using kubectl edit pod po?
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: "2019-08-17T18:15:22Z"
labels:
run: pod1
name: pod1
namespace: default
resourceVersion: "12167"
selfLink: /api/v1/namespaces/default/pods/pod1
uid: fa297c13-c11a-11e9-9a5f-02ca4f0dcea0
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: pod1
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-27x4x
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: ip-10-0-1-102
priority: 0
restartPolicy: Never
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- name: default-token-27x4x
secret:
defaultMode: 420
secretName: default-token-27x4x
status:
conditions:
- lastProbeTime: null
lastTransitionTime: "2019-08-17T18:15:22Z"
status: "True"
type: Initialized
- lastProbeTime: null
lastTransitionTime: "2019-08-17T18:15:27Z"
status: "True"
type: Ready
- lastProbeTime: null
lastTransitionTime: "2019-08-17T18:15:27Z"
status: "True"
type: ContainersReady
- lastProbeTime: null
lastTransitionTime: "2019-08-17T18:15:22Z"
status: "True"
type: PodScheduled
containerStatuses:
- containerID: docker://99bfded0d69f4ed5ed854e59b458acd8a9197f9bef6d662a03587fe2ff61b128
image: nginx:latest
imageID: docker-pullable://nginx#sha256:53ddb41e46de3d63376579acf46f9a41a8d7de33645db47a486de9769201fec9
lastState: {}
name: pod1
ready: true
restartCount: 0
state:
running:
startedAt: "2019-08-17T18:15:27Z"
hostIP: 10.0.1.102
phase: Running
podIP: 10.244.2.2
qosClass: BestEffort
startTime: "2019-08-17T18:15:22Z"
And also k get po pod1 -o yaml --export
apiVersion: v1
kind: Pod
metadata:
creationTimestamp: null
labels:
run: pod1
name: pod1
selfLink: /api/v1/namespaces/default/pods/pod1
spec:
containers:
- image: nginx
imagePullPolicy: Always
name: pod1
resources: {}
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /var/run/secrets/kubernetes.io/serviceaccount
name: default-token-27x4x
readOnly: true
dnsPolicy: ClusterFirst
enableServiceLinks: true
nodeName: ip-10-0-1-102
priority: 0
restartPolicy: Never
schedulerName: default-scheduler
securityContext: {}
serviceAccount: default
serviceAccountName: default
terminationGracePeriodSeconds: 30
tolerations:
- effect: NoExecute
key: node.kubernetes.io/not-ready
operator: Exists
tolerationSeconds: 300
- effect: NoExecute
key: node.kubernetes.io/unreachable
operator: Exists
tolerationSeconds: 300
volumes:
- name: default-token-27x4x
secret:
defaultMode: 420
secretName: default-token-27x4x
status:
phase: Pending
qosClass: BestEffort
What am I doing wrong or have I missed something?

Answer 1

You can't add configuration to a running pod, that's something inherent to containers.
To put it simply: a container is running with a service, the state of the service defines the state of the container. As you know, nginx needs to reload it's configuration if you change it, but that's not really a good idea in this context, so you need to stop/start the container with the new configuration.
So what you are getting is normal, the service state is still running so it's keeping the old file configuration it has from before even if you make change inside the file.
If you need the service to be reloading without downtime, set multiple replicas and create a rolling update rule for no downtime during update.
There are some special cases to this, like grafana, where it can go check if files have been changed from the last modification.