Kubernetes and Configmap

Kubernetes ConfigMap

kubectl create -f web-cm.yaml

root@kuberm:~/kube1.6config/deploy/configmap# cat web-cm.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: hadoop-env
data:
  CORE_CONF_fs_defaultFS: "hdfs://namenode:8020"
  CORE_CONF_hadoop_http_staticuser_user: "root"

kubectl create -f web-cm2.yaml

root@kuberm:~/kube1.6config/deploy/configmap# cat web-cm2.yaml
apiVersion: v1
kind: ConfigMap
metadata:
  name: special-config
  namespace: default
data:
  special.how: very
  special.type: charm

###kubectl create -f web-controller.yaml

apiVersion: extensions/v1beta1
kind: Deployment
metadata:
  name: webconfig
  namespace: default
  labels:
    app: webconfig
spec:
  replicas: 1
  selector:
    matchLabels:
      app: webconfig
  template:
    metadata:
      labels:
        app:  webconfig
        group: lb
    spec:
      terminationGracePeriodSeconds: 60
      containers:
      - name:  webconfig
        # Any image is permissable as long as: 1. It serves a 404 page at /
        # and 2. It serves 200 on a /healthz endpoint
        image: 172.16.155.136:5000/uwebserverv6
        env:
          - name: SPECIAL_LEVEL_KEY
            valueFrom:
              configMapKeyRef:
                name: special-config
                key: special.how
          - name: SPECIAL_TYPE_KEY
            valueFrom:
              configMapKeyRef:
                name: special-config
                key: special.type
        envFrom:
        - configMapRef:
            name: hadoop-env
        ports:
        - containerPort: 8000
        resources:
          limits:
            cpu: 10m
            memory: 20Mi
          requests:
            cpu: 10m
            memory: 20Mi

Reuslt

You will see the result.

• if you use envFrom, you can directly use the parameter mapped from configmap you defined
• if you use env, you can redefine the key to the value that you defined in configmap. It's quite convinuence, if every body defined in different key but with same value. You can now adding the env and valuefrom parameter to trasfer the key-value pair.

root@webconfig-3249689838-fglf7:/# env
HOSTNAME=webconfig-3249689838-fglf7
KUBERNETES_PORT_443_TCP_PORT=443
KUBERNETES_PORT=tcp://172.18.0.1:443
CORE_CONF_fs_defaultFS=hdfs://namenode:8020
KUBERNETES_SERVICE_PORT=443
KUBERNETES_SERVICE_HOST=172.18.0.1
LS_COLORS=
SPECIAL_TYPE_KEY=charm
SPECIAL_LEVEL_KEY=very
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
PWD=/
SHLVL=1
HOME=/root
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_SERVICE_PORT_HTTPS=443
CORE_CONF_hadoop_http_staticuser_user=root
LESSOPEN=| /usr/bin/lesspipe %s
KUBERNETES_PORT_443_TCP_ADDR=172.18.0.1
KUBERNETES_PORT_443_TCP=tcp://172.18.0.1:443
LESSCLOSE=/usr/bin/lesspipe %s %s
_=/usr/bin/env