Configmaps
Environment Variables
We are going to use some environment variables in this tutorial. Please make sure you have set them correctly.
# check if the environment variables are set if not set them
export NAMESPACE=<namespace>
echo $NAMESPACE
Similar to environment variables, ConfigsMaps allow you to separate the configuration for an application from the image. Pods can access those variables at runtime which allows maximum portability for applications running in containers. In this lab, you will learn how to create and use ConfigMaps.
A ConfigMap can be created using the kubectl create configmap command as follows:
kubectl create configmap <name> <data-source> --namespace $NAMESPACE
Where the <data-source> can be a file, directory, or command line input.
Task 1: Create a ConfigMap for Java properties
A classic example for ConfigMaps are properties files of Java applications which can’t be configured with environment variables.
First, create a file called java.properties with the following content:
JAVA_OPTS=-Xmx512m
key=value
key2=value2
Now you can create a ConfigMap based on that file:
kubectl create configmap javaconfiguration --from-file=./java.properties --namespace $NAMESPACE
Verify that the ConfigMap was created successfully:
kubectl get configmaps --namespace $NAMESPACE
The output should look like this:
NAME DATA AGE
javaconfiguration 1 2m
Have a look at its content:
kubectl get configmap javaconfiguration -o yaml --namespace $NAMESPACE
The output should look like this:
apiVersion: v1
kind: ConfigMap
metadata:
name: javaconfiguration
data:
java.properties: |
JAVA_OPTS=-Xmx512m
key=value
key2=value2
Task 2: Create a Pod that uses the ConfigMap
Next, we want to make a ConfigMap accessible for a container. There are basically the following possibilities to achieve this:
- ConfigMap properties as environment variables in a Deployment
- Command line arguments via environment variables
- Mounted as volumes in the container
In this example, we want the file to be mounted as a volume inside the container.
Basically, a Deployment has to be extended with the following config:
...
volumeMounts:
- mountPath: /etc/config
name: config-volume
...
volumes:
- configMap:
defaultMode: 420
name: javaconfiguration
name: config-volume
...
The volumeMounts section defines the mount point inside the container. The volumes section defines the volume that should be mounted. The name property of the volume has to match the name property of the volumeMounts section.
Create a file called java-deployment.yaml with the following content:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: spring-boot-example
name: spring-boot-example
spec:
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 10
selector:
matchLabels:
app: spring-boot-example
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
labels:
app: spring-boot-example
spec:
containers:
- image: appuio/example-spring-boot
imagePullPolicy: Always
name: example-spring-boot
resources:
limits:
cpu: 1
memory: 768Mi
requests:
cpu: 20m
memory: 32Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /etc/config
name: config-volume
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
volumes:
- configMap:
defaultMode: 420
name: javaconfiguration
name: config-volume
Deploy it:
kubectl apply -f java-deployment.yaml --namespace $NAMESPACE
This means that the container should now be able to access the ConfigMap’s content in /etc/config/java.properties. Let’s check:
export POD_NAME=$(kubectl get pods --namespace $NAMESPACE -l "app=spring-boot-example" -o jsonpath="{.items[0].metadata.name}")
kubectl exec -it $POD_NAME --namespace $NAMESPACE -- cat /etc/config/java.properties
Note
On Windows, you can use Git Bash with winpty kubectl exec -it <pod> --namespace $NAMESPACE -- cat //etc/config/java.properties.
The output should look like this:
JAVA_OPTS=-Xmx512m
key=value
key2=value2
Like this, the property file can be read and used by the application inside the container. The image stays portable to other environments.
Task 3: Create a ConfigMap for environment variables
In the previous task, we created a ConfigMap for a Java properties file. Now we want to create a ConfigMap for environment variables.
Use a ConfigMap to define the environment variables JAVA_OPTS and JAVA_TOOL_OPTIONS.
You can refer to the official documentation for more information.
solutions
kubectl create configmap javaenv --from-literal=JAVA_OPTS=-Xmx512m --from-literal=JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF-8 --namespace $NAMESPACE
Update the java-deployment.yaml file with the following content:
apiVersion: apps/v1
kind: Deployment
metadata:
labels:
app: spring-boot-example
name: spring-boot-example
spec:
progressDeadlineSeconds: 600
replicas: 1
revisionHistoryLimit: 10
selector:
matchLabels:
app: spring-boot-example
strategy:
rollingUpdate:
maxSurge: 25%
maxUnavailable: 25%
type: RollingUpdate
template:
metadata:
labels:
app: spring-boot-example
spec:
containers:
- image: appuio/example-spring-boot
imagePullPolicy: Always
name: example-spring-boot
resources:
limits:
cpu: 1
memory: 768Mi
requests:
cpu: 20m
memory: 32Mi
terminationMessagePath: /dev/termination-log
terminationMessagePolicy: File
volumeMounts:
- mountPath: /etc/config
name: config-volume
envFrom:
- configMapRef:
name: javaenv
dnsPolicy: ClusterFirst
restartPolicy: Always
schedulerName: default-scheduler
securityContext: {}
terminationGracePeriodSeconds: 30
volumes:
- configMap:
defaultMode: 420
name: javaconfiguration
name: config-volume
Make sure you delete the old deployment first:
kubectl delete deployment spring-boot-example --namespace $NAMESPACE
Then, create the new deployment:
kubectl create -f java-deployment.yaml --namespace $NAMESPACE
Check the environment variables of the container:
export POD_NAME=$(kubectl get pods --namespace $NAMESPACE -l "app=spring-boot-example" -o jsonpath="{.items[0].metadata.name}")
kubectl exec -it $POD_NAME --namespace $NAMESPACE -- env
The output should look like this:
...
JAVA_OPTS=-Xmx512m
JAVA_TOOL_OPTIONS=-Dfile.encoding=UTF-8
...