I feel like this should be an already asked question, but I'm having difficulties finding a concrete answer. I'm deploying Jenkins through ArgoCD by defining the deployment via kustomize (kubernetes yaml). I want to inject a prefix to have Jenkins start on /jenkins, but I don't see a way to add it. I saw online that I can have a env tag, but no full example of this was available. Where would I inject a prefix value if using kubernetes yaml for a Jenkins deployment?
So, I solved this issue myself, and I'd like to post the answer as this is the top searched question when searching "Kustomize Jenkins_opts".
In your project, assuming you are using Kustomize to deploy Jenkins (This will work with any app deployment where you want to inject values when deploying), you should have a project structure similar to this:
ProjectA
|
|---> app.yaml //contains the yaml definitions for your deployment
|---> kustomize.yaml //entry file to run Kustomize to deploy your app
Add a new file to your project structure. Name it whatever you want, I named mine something like app-env.yaml. It will look something like:
apiVersion: apps/v1
kind: Deployment
metadata:
name: jenkins
spec:
template:
spec:
containers:
- name: jenkins
env:
- name: JENKINS_OPTS
value: --prefix=/jenkins
This will specifically inject the --prefix flag to assign the prefix value for the URL to Jenkins on deployment to the Jenkins container. You can add multiple env variables. You can inject any value you want. My example is using Jenkins specific flags as this question centered around Jenkins, but it works for any app. Add this file to your Kustomize file from earlier:
namePrefix: kustomize-
resources:
- app.yaml
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization
patchesStrategicMerge:
- app-env.yaml
When your app is deployed via K8s, it will run the startup process for your app, while passing the values defined in your env file. Hope this helps anyone else.
I have a configmap.yaml file as below :
apiVersion: v1
kind: ConfigMap
metadata:
name: abc
namespace: monitoring
labels:
app: abc
version: 0.17.0
data:
application.yml: |-
myjava:
security:
enabled: true
abc:
server:
access-log:
enabled: ${myvar}. ## this is not working
"myvar" value is available in pod as shell environment variable from secretkeyref field in deployment file.
Now I want to replace myvar shell environment variable in configmap above i.e before application.yml file is available in pod it should have replaced myvar value. which is not working i tried ${myvar} and $(myvar) and "#{ENV['myvar']}"
Is that possible in kubernetes configmap to reference with in data section pod's environment variable if yes how or should i need to write a script to replace with sed -i application.yml etc.
Is that possible in kubernetes configmap to reference with in data section pod's environment variable
That's not possible. A ConfigMap is not associated with a particular pod, so there's no way to perform the sort of variable substitution you're asking about. You would need to implement this logic inside your containers (fetch the ConfigMap, perform variable substitution yourself, then consume the data).
I'm working with a Pod (Shiny Proxy) that talks to Kubernetes API to start other pods. I'm wanting to make this generic, and so don't want to hardcode the namespace (because I intend to have multiple of these, deployed probably as an OpenShift Template or similar).
I am using Kustomize to set the namespace on all objects. Here's what my kustomization.yaml looks like for my overlay:
bases:
- ../../base
namespace: shiny
commonAnnotations:
technical_contact: A Local Developer <somedev#example.invalid>
Running Shiny Proxy and having it start the pods I need it to (I have service accounts and RBAC already sorted) works, so long as as in the configuration for Shiny Proxy I specify (hard-code) the namespace that the new pods should be generated in. The default namespace that Shiny Proxy will use is (unfortunately) 'default', which is inappropriate for my needs.
Currently for the configuration I'm using a ConfigMap (perhaps I should move to a Kustomize ConfigMapGenerator)
The ConfigMap in question is currently like the following:
apiVersion: v1
kind: ConfigMap
metadata:
name: shiny-proxy
data:
application_yml: |
...
container-backend: kubernetes
kubernetes:
url: https://kubernetes.default.svc.cluster.local:443
namespace: shiny
...
The above works, but 'shiny' is hardcoded; I would like to be able to do something like the following:
namespace: { .metadata.namespace }
But this doesn't appear to work in a ConfigMap, and I don't see anything in the documentation that would lead to believe that it would, or that a similar thing appears possible within the ConfigMap machinery.
Looking over the Kustomize documentation doesn't fill me with clarity either, particularly as the configuration file is essentially plain-text (and not a YAML document as far as the ConfigMap is concerned). I've seen some use of Vars, but https://github.com/kubernetes-sigs/kustomize/issues/741 leads to believe that's a non-starter.
Is there a nice declarative way of handling this? Or should I be looking to have the templating smarts happen within the container, which seems kinda wrong to me, but I am still new to Kubernetes (and OpenShift)
I'm using CodeReady Containers 1.24 (OpenShift 4.7.2) which is essentially Kubernetes 1.20 (IIRC). I'm preferring to keep this fairly well aligned with Kubernetes without getting too OpenShift specific, but this is still early days.
Thanks,
Cameron
If you don't want to hard-code a specific data in your manifest file, you can consider using Kustomize plugins. In this case, the sedtransformer plugin may be useful. This is an example plugin, maintained and tested by the kustomize maintainers, but not built-in to kustomize.
As you can see in the Kustomize plugins guide:
Kustomize offers a plugin framework allowing people to write their own resource generators and transformers.
For more information on creating and using Kustomize plugins, see Extending Kustomize.
I will create an example to illustrate how you can use the sedtransformer plugin in your case.
Suppose I have a shiny-proxy ConfigMap:
NOTE: I don't specify a namespace, I use namespace: NAMESPACE instead.
$ cat cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: shiny-proxy
data:
application_yml: |
container-backend: kubernetes
kubernetes:
url: https://kubernetes.default.svc.cluster.local:443
namespace: NAMESPACE
something_else:
something: something
To use the sedtransformer plugin, we first need to create the plugin’s configuration file which contains a YAML configuration object:
NOTE: In argsOneLiner: I specify that NAMESPACE should be replaced with shiny.
$ cat sedTransformer.yaml
apiVersion: someteam.example.com/v1
kind: SedTransformer
metadata:
name: sedtransformer
argsOneLiner: s/NAMESPACE/shiny/g
Next, we need to put the SedTransformer Bash script in the right place.
When loading, kustomize will first look for an executable file called
$XDG_CONFIG_HOME/kustomize/plugin/${apiVersion}/LOWERCASE(${kind})/${kind}
I create the necessary directories and download the SedTransformer script from the Github:
NOTE: The downloaded script need to be executable.
$ mkdir -p $HOME/.config/kustomize/plugin/someteam.example.com/v1/sedtransformer
$ cd $HOME/.config/kustomize/plugin/someteam.example.com/v1/sedtransformer
$ wget https://raw.githubusercontent.com/kubernetes-sigs/kustomize/master/plugin/someteam.example.com/v1/sedtransformer/SedTransformer
$ chmod a+x SedTransformer
Finally, we can check if it works as expected:
NOTE: To use this plugin, you need to provide the --enable-alpha-plugins flag.
$ tree
.
├── cm.yaml
├── kustomization.yaml
└── sedTransformer.yaml
0 directories, 3 files
$ cat kustomization.yaml
resources:
- cm.yaml
transformers:
- sedTransformer.yaml
$ kustomize build --enable-alpha-plugins .
apiVersion: v1
data:
application_yml: |
container-backend: kubernetes
kubernetes:
url: https://kubernetes.default.svc.cluster.local:443
namespace: shiny
something_else:
something: something
kind: ConfigMap
metadata:
name: shiny-proxy
Using the sedtransformer plugin can be especially useful if you want to replace NAMESPACE in a number of places.
I found the easiest way of doing this was to use an entrypoint script in the container that harvested the downward API (?) service credentials (specifically the namespace secret) that get mounted in the container, and exposes that as an environment variable.
export SHINY_K8S_NAMESPACE=`cat /run/secrets/kubernetes.io/serviceaccount/namespace`
cd /opt/shiny-proxy/working
exec java ${JVM_OPTIONS} -jar /opt/shiny-proxy/shiny-proxy.jar
Within the application configuration (shiny-proxy), it supports the use of environment variables in its configuration file, so I can refer to the pod's namespace using ${SHINY_K8S_NAMESPACE}
Although, I've just now seen the idea of a fieldRef (from https://docs.openshift.com/enterprise/3.2/dev_guide/downward_api.html), and would be generalisable to things other than just namespace.
apiVersion: v1
kind: Pod
metadata:
name: dapi-env-test-pod
spec:
containers:
- name: env-test-container
image: gcr.io/google_containers/busybox
command: ["/bin/sh", "-c", "env"]
env:
- name: MY_NAMESPACE
valueFrom:
fieldRef:
fieldPath: metadata.namespace
restartPolicy: Never
i am running a statefulset where i use volumeClaimTemplates. everything's fine there.
i also have a configmap where i would like to essentially replace some entries with the name of the pod for each pod that this config file is projected onto; eg, if the configmap data is:
ThisHost=<hostname -s>
OtherConfig1=1
OtherConfig1=2
...
then for the statefulset pod named mypod-0, the config file should contain ThisHost=mypod-0 and ThisHost=mypod-1 for mypod-1.
how could i do this?
The hostnames are contained in environment variables within the pod by default called HOSTNAME.
It is possible to modify the configmap itself if you first:
mount the configmap and set it to ThisHost=hostname -s (this will create a file in the pod's filesystem with that text)
pass a substitution command to the pod when starting (something like $ sed 's/hostname/$HOSTNAME/g' -i /path/to/configmapfile)
Basically, you mount the configmap and then replace it with the environment variable information that is available within the pod. It's just a substitution operation.
Look at the example below:
apiVersion: v1
kind: Pod
metadata:
name: command-demo
labels:
purpose: demonstrate-command
spec:
containers:
- name: command-demo-container
image: debian
command: ["sed"]
args: ["'s/hostname/$HOSTNAME'", "-i", "/path/to/config/map/mount/point"]
restartPolicy: OnFailure
The args' syntax might need some adjustments but you get the idea.
Please let me know if that helped.
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)