How to create a ConfigMap and use its data in Pods

ConfigMaps allow you to decouple configuration artifacts from image content to keep containerized applications portable. In this notebook we would learn how to create a ConfigMap and also how to use its data in Pods as seen in https://kubernetes.io/docs/tasks/configure-pod-container/configure-pod-configmap/



In [ ]:

    
from kubernetes import client, config
from kubernetes.client.rest import ApiException

Load config from default location



In [ ]:

    
config.load_kube_config()

Create API endpoint instance and API resource instances



In [ ]:

    
api_instance = client.CoreV1Api()
cmap = client.V1ConfigMap()

Create key value pair data for the ConfigMap



In [ ]:

    
cmap.metadata = client.V1ObjectMeta(name="special-config")
cmap.data = {}
cmap.data["special.how"] = "very"
cmap.data["special.type"] = "charm"

Create ConfigMap



In [ ]:

    
api_instance.create_namespaced_config_map(namespace="default", body=cmap)

Create API endpoint instance and API resource instances for test Pod



In [ ]:

    
pod = client.V1Pod()
spec = client.V1PodSpec()
pod.metadata = client.V1ObjectMeta(name="dapi-test-pod")

Initialize test Pod container



In [ ]:

    
container = client.V1Container()
container.name = "test-container"
container.image = "gcr.io/google_containers/busybox"
container.command = ["/bin/sh", "-c", "env"]

Define Pod environment variables with data from ConfigMaps



In [ ]:

    
container.env = [client.V1EnvVar(name="SPECIAL_LEVEL_KEY"), client.V1EnvVar(name="SPECIAL_TYPE_KEY")]
container.env[0].value_from = client.V1EnvVarSource()
container.env[0].value_from.config_map_key_ref = client.V1ConfigMapKeySelector(name="special-config", key="special.how")

container.env[1].value_from = client.V1EnvVarSource()
container.env[1].value_from.config_map_key_ref = client.V1ConfigMapKeySelector(name="special-config", key="special.type")

spec.restart_policy = "Never"
spec.containers = [container]
pod.spec = spec

Create Pod



In [ ]:

    
api_instance.create_namespaced_pod(namespace="default",body=pod)

View ConfigMap data from Pod log



In [ ]:

    
log = ""
try: 
    log = api_instance.read_namespaced_pod_log(name="dapi-test-pod", namespace="default")
except ApiException as e:
    if str(e).find("ContainerCreating") != -1:
        print("Creating Pod container.\nRe-run current cell.")
    else:
        print("Exception when calling CoreV1Api->read_namespaced_pod_log: %s\n" % e)

for line in log.split("\n"):
    if line.startswith("SPECIAL"):
        print(line)

Delete ConfigMap



In [ ]:

    
api_instance.delete_namespaced_config_map(name="special-config", namespace="default", body=cmap)

Delete Pod



In [ ]:

    
api_instance.delete_namespaced_pod(name="dapi-test-pod", namespace="default", body=client.V1DeleteOptions())



In [ ]: