I have a pod in my kubernetes which needed an update to have securityContext. So generated a yaml file using -
kubectl get pod pod_name -o yaml > mypod.yaml
After updating the required securityContext and executing command -
kubectl apply -f mypod.yaml
no changes are observed in pod.
Where as a fresh newly created yaml file works perfectly fine.
new yaml file -
apiVersion: v1
kind: Pod
metadata:
name: mypod
namespace: default
spec:
securityContext:
runAsUser: 1010
containers:
- command:
- sleep
- "4800"
image: ubuntu
name: myubuntuimage
Immutable fields
In Kubernetes you can find information about Immutable fields.
A lot of fields in APIs tend to be immutable, they can't be changed after creation. This is true for example for many of the fields in pods. There is currently no way to declaratively specify that fields are immutable, and one has to rely on either built-in validation for core types, or have to build a validating webhooks for CRDs.
Why ?
There are resources in Kubernetes which have immutable fields by design, i.e. after creation of an object, those fields cannot be mutated anymore. E.g. a pod's specification is mostly unchangeable once it is created. To change the pod, it must be deleted, recreated and rescheduled.
Editing existing pod configuration
If you want to apply new config with security context using kubectl apply you will get error like below:
The Pod "mypod" is invalid: spec: Forbidden: pod updates may not change fields other than `spec.containers[*].image`, `spec.initContainers[*].image`, `spec.activeDeadlineSeconds` or `spec.tolerations` (only additions to existing tolerations)
Same output will be if you would use kubectl patch
kubectl patch pod mypod -p '{"spec":{"securityContext":{"runAsUser":1010}}}'
Also kubectl edit will not change this specific configuration
$ kubectl edit pod
Edit cancelled, no changes made.
Solution
If you need only one pod, you must delete it and create new one with requested configuration.
Better solution is to use resource which will make sure to fulfil some own requirements, like Deployment. After change of the current configuration, deployment will create new Replicaset which will create new pods with new configuration.
by updating the PodTemplateSpec of the Deployment. A new ReplicaSet is created and the Deployment manages moving the Pods from the old ReplicaSet to the new one at a controlled rate. Each new ReplicaSet updates the revision of the Deployment.
I'm working on the manifest of a kubernetes job.
apiVersion: batch/v1
kind: Job
metadata:
name: hello-job
spec:
template:
spec:
containers:
- name: hello
image: hello-image:latest
I then apply the manifest using kubectl apply -f <deployment.yaml> and the job runs without any issue.
The problem comes when i change the image of the running container from latest to something else.
At that point i get a field is immutable exception on applying the manifest.
I get the same exception either if the job is running or completed. The only workaround i found so far is to delete manually the job before applying the new manifest.
How can i update the current job without having to manually delete it first?
I guess you are probably using an incorrect kubernetes resource . Job is a immutable Pod that runs to completion , you cannot update it . As per Kubernetes documentation ..
Say Job old is already running. You want existing Pods to keep running, but you want the rest of the Pods it creates to use a different pod template and for the Job to have a new name. You cannot update the Job because these fields are not updatable. Therefore, you delete Job old but leave its pods running, using kubectl delete jobs/old --cascade=false.
If you intend to update an image you should either use Deployment or Replication controller which supports updates
Say we have this in a deployment.yml
containers:
- name: my_container
imagePullPolicy: Always
image: my_image:latest
and so redeployment might take the form of:
kubectl set image deployment/my-deployment my_container=my_image
which I stole from here:
https://stackoverflow.com/a/40368520/1223975
my question is - is this the right way to do a rolling-update? Will the above always work to make sure the deployment gets the new image? My deployment.yml might never change - it might just be my_image:latest forever, so how to do rolling updates?
I don't expect this to be an accepted answer. But I wanted to make it for the future as there is a command to do this in Kubernetes 1.15.
PR https://github.com/kubernetes/kubernetes/pull/76062 added a command called kubectl rollout restart. It is part of Kubernetes 1.15. In the future you will be able to do:
kubectl rollout restart deployment/my-deployment
We now have scheduled jobs in Kubernetes 1.4- is it possible to do a rolling container update (new image) against the cluster using this? The basic idea is I want a simple way to automatically roll out updates every set interval.
The 'traditional' way to do updates is for the CI to hit a webhook on the Kube master, but I want to avoid exposing services to the public and would rather just check for updates periodically.
I think it's generally safe to expose your master server and send updates to it from your CI system, but you could definitely set up a scheduled job to update a Deployment to it's latest version. Kubernetes has a concept called Service Accounts for authentication with the API from within the cluster and are integrated well with kubectl (i.e. it will use the service account info automatically to auth). The cluster also provides a kubernetes service for the master API. So you can deploy a container with kubectl and a script and use it to update the Deployment periodically.
You will need a mechanism to figure out what the latest version is. Maybe you could store the latest version info in a text file or something written to GCS or S3 and pull that file to get the latest version.
Say you have a deploy.yaml like this:
apiVersion: extensions/v1beta1
kind: Deployment
metadata:
name: myapp
spec:
template:
spec:
containers:
- name: myapp
image: myapp:<latest-ver>
And then you can generate and update the Deployment in a script like so:
#!/bin/sh
wget -o VERSION http://url/to/VERSION
sed "s/<latest-ver>/$(cat VERSION)/" deploy.yaml | kubectl apply -f -
And build that into an image and run it as your scheduled job.
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
...
Helm 3 doc page
Often times configmaps or secrets are injected as configuration files in containers. Depending on the application a restart may be required should those be updated with a subsequent helm upgrade, but if the deployment spec itself didn't change the application keeps running with the old configuration resulting in an inconsistent deployment.
The sha256sum function can be used together with the include function to ensure a deployments template section is updated if another spec changes:
kind: Deployment
spec:
template:
metadata:
annotations:
checksum/config: {{ include (print $.Template.BasePath "/secret.yaml") . | sha256sum }}
[...]
In my case, for some reasons, $.Template.BasePath didn't work but $.Chart.Name does:
spec:
replicas: 1
template:
metadata:
labels:
app: admin-app
annotations:
checksum/config: {{ include (print $.Chart.Name "/templates/" $.Chart.Name "-configmap.yaml") . | sha256sum }}
You can update a metadata annotation that is not relevant for your deployment. it will trigger a rolling-update
for example:
spec:
template:
metadata:
annotations:
configmap-version: 1
If k8>1.15; then doing a rollout restart worked best for me as part of CI/CD with App configuration path hooked up with a volume-mount. A reloader plugin or setting restartPolicy: Always in deployment manifest YML did not work for me. No application code changes needed, worked for both static assets as well as Microservice.
kubectl rollout restart deployment/<deploymentName> -n <namespace>
Had this problem where the Deployment was in a sub-chart and the values controlling it were in the parent chart's values file. This is what we used to trigger restart:
spec:
template:
metadata:
annotations:
checksum/config: {{ tpl (toYaml .Values) . | sha256sum }}
Obviously this will trigger restart on any value change but it works for our situation. What was originally in the child chart would only work if the config.yaml in the child chart itself changed:
checksum/config: {{ include (print $.Template.BasePath "/config.yaml") . | sha256sum }}
Consider using kustomize (or kubectl apply -k) and then leveraging it's powerful configMapGenerator feature. For example, from: https://kubectl.docs.kubernetes.io/references/kustomize/kustomization/configmapgenerator/
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
# Just one example of many...
- name: my-app-config
literals:
- JAVA_HOME=/opt/java/jdk
- JAVA_TOOL_OPTIONS=-agentlib:hprof
# Explanation below...
- SECRETS_VERSION=1
Then simply reference my-app-config in your deployments. When building with kustomize, it'll automatically find and update references to my-app-config with an updated suffix, e.g. my-app-config-f7mm6mhf59.
Bonus, updating secrets: I also use this technique for forcing a reload of secrets (since they're affected in the same way). While I personally manage my secrets completely separately (using Mozilla sops), you can bundle a config map alongside your secrets, so for example in your deployment:
# ...
spec:
template:
spec:
containers:
- name: my-app
image: my-app:tag
envFrom:
# For any NON-secret environment variables. Name is automatically updated by Kustomize
- configMapRef:
name: my-app-config
# Defined separately OUTSIDE of Kustomize. Just modify SECRETS_VERSION=[number] in the my-app-config ConfigMap
# to trigger an update in both the config as well as the secrets (since the pod will get restarted).
- secretRef:
name: my-app-secrets
Then, just add a variable like SECRETS_VERSION into your ConfigMap like I did above. Then, each time you change my-app-secrets, just increment the value of SECRETS_VERSION, which serves no other purpose except to trigger a change in the kustomize'd ConfigMap name, which should also result in a restart of your pod. So then it becomes:
I also banged my head around this problem for some time and wished to solve this in an elegant but quick way.
Here are my 20 cents:
The answer using labels as mentioned here won't work if you are updating labels. But would work if you always add labels. More details here.
The answer mentioned here is the most elegant way to do this quickly according to me but had the problem of handling deletes. I am adding on to this answer:
Solution
I am doing this in one of the Kubernetes Operator where only a single task is performed in one reconcilation loop.
Compute the hash of the config map data. Say it comes as v2.
Create ConfigMap cm-v2 having labels: version: v2 and product: prime if it does not exist and RETURN. If it exists GO BELOW.
Find all the Deployments which have the label product: prime but do not have version: v2, If such deployments are found, DELETE them and RETURN. ELSE GO BELOW.
Delete all ConfigMap which has the label product: prime but does not have version: v2 ELSE GO BELOW.
Create Deployment deployment-v2 with labels product: prime and version: v2 and having config map attached as cm-v2 and RETURN, ELSE Do nothing.
That's it! It looks long, but this could be the fastest implementation and is in principle with treating infrastructure as Cattle (immutability).
Also, the above solution works when your Kubernetes Deployment has Recreate update strategy. Logic may require little tweaks for other scenarios.
How do I automatically restart Kubernetes pods and pods associated
with deployments when their configmap is changed/updated?
If you are using configmap as Environment you have to use the external option.
Reloader
Kube watcher
Configurator
Kubernetes auto-reload the config map if it's mounted as volume (If subpath there it won't work with that).
When a ConfigMap currently consumed in a volume is updated, projected
keys are eventually updated as well. The kubelet checks whether the
mounted ConfigMap is fresh on every periodic sync. However, the
kubelet uses its local cache for getting the current value of the
ConfigMap. The type of the cache is configurable using the
ConfigMapAndSecretChangeDetectionStrategy field in the
KubeletConfiguration struct. A ConfigMap can be either propagated by
watch (default), ttl-based, or by redirecting all requests directly to
the API server. As a result, the total delay from the moment when the
ConfigMap is updated to the moment when new keys are projected to the
Pod can be as long as the kubelet sync period + cache propagation
delay, where the cache propagation delay depends on the chosen cache
type (it equals to watch propagation delay, ttl of cache, or zero
correspondingly).
Official document : https://kubernetes.io/docs/concepts/configuration/configmap/#mounted-configmaps-are-updated-automatically
ConfigMaps consumed as environment variables are not updated automatically and require a pod restart.
Simple example Configmap
apiVersion: v1
kind: ConfigMap
metadata:
name: config
namespace: default
data:
foo: bar
POD config
spec:
containers:
- name: configmaptestapp
image: <Image>
volumeMounts:
- mountPath: /config
name: configmap-data-volume
ports:
- containerPort: 8080
volumes:
- name: configmap-data-volume
configMap:
name: config
Example : https://medium.com/#harsh.manvar111/update-configmap-without-restarting-pod-56801dce3388
Adding the immutable property to the config map totally avoids the problem. Using config hashing helps in a seamless rolling update but it does not help in a rollback. You can take a look at this open-source project - 'Configurator' - https://github.com/gopaddle-io/configurator.git .'Configurator' works by the following using the custom resources :
Configurator ties the deployment lifecycle with the configMap. When
the config map is updated, a new version is created for that
configMap. All the deployments that were attached to the configMap
get a rolling update with the latest configMap version tied to it.
When you roll back the deployment to an older version, it bounces to
configMap version it had before doing the rolling update.
This way you can maintain versions to the config map and facilitate rolling and rollback to your deployment along with the config map.
Another way is to stick it into the command section of the Deployment:
...
command: [ "echo", "
option = value\n
other_option = value\n
" ]
...
Alternatively, to make it more ConfigMap-like, use an additional Deployment that will just host that config in the command section and execute kubectl create on it while adding an unique 'version' to its name (like calculating a hash of the content) and modifying all the deployments that use that config:
...
command: [ "/usr/sbin/kubectl-apply-config.sh", "
option = value\n
other_option = value\n
" ]
...
I'll probably post kubectl-apply-config.sh if it ends up working.
(don't do that; it looks too bad)