Kubernetes configuration management ConfigMap

Kubernetes configuration management ConfigMap

1. ConfigMaps

1.1 What is configmap

• The kubernetes cluster can use ConfigMap to realize the configuration management of the application in the container .
• Think of ConfigMap as a storage volume mounted to a pod

1.2 4 ways to create ConfigMap

1.2.1 Create by specifying parameters on the command line

Created by specifying the configmap parameter directly on the command line, ie --from-literal=key=value;

[root@k8s-master1 ~]# kubectl create configmap cm1 --from-literal=host=127.0.0.1 --from-literal=port=3306
configmap/cm1 created

[root@k8s-master1 ~]# kubectl get cm
NAME   DATA   AGE
cm1    2      12s

[root@k8s-master1 ~]#  kubectl describe cm cm1
Name:         cm1
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
host:
----
127.0.0.1
port:
----
3306
Events:  <none>

1.2.2 Create from multiple files on the command line

Create by specifying a file, that is, create a configuration file as a ConfigMap --from-file=文件路径;

[root@k8s-master1 ~]#  echo -n 127.0.0.1 > host
[root@k8s-master1 ~]#  echo -n 3306 > port				

[root@k8s-master1 ~]#  kubectl create configmap cm2 --from-file=./host --from-file=./port
configmap/cm2 created

[root@k8s-master1 ~]#  kubectl get cm
NAME   DATA   AGE
cm1    2      3m45s
cm2    2      94s

[root@k8s-master1 ~]#  kubectl describe cm cm2
Name:         cm2
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
host:
----
127.0.0.1
port:
----
3306
Events:  <none>

1.2.3 Create multiple key-value pairs by providing a file on the command line

Through multiple key-value pairs in a file, --from-env-file=文件路径;

[root@k8smaster ~]# vi env.properties
[root@k8smaster ~]# cat env.properties 
host=127.0.0.1
port=3306

[root@k8smaster ~]# kubectl create configmap cm3 --from-env-file=env.properties
configmap/cm3 created
[root@k8smaster ~]# kubectl get cm
NAME   DATA   AGE
cm1    2      76m
cm2    2      4m6s
cm3    2      8s

[root@k8s-master1 ~]#  kubectl describe cm cm3
Name:         cm3
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
host:
----
127.0.0.1
port:
----
3306
Events:  <none>

1.2.4 Create through YAML resource list file

kubectl create/apply -f YMAL文件created by

[root@k8s-master1 ~]#  vim cm4.yml
apiVersion: v1
kind: ConfigMap
metadata:
  name: cm4
data:
  host: 127.0.0.1
  port: "3306"
  
[root@k8s-master1 ~]#  kubectl apply -f cm4.yml
configmap/cm4 created

[root@k8s-master1 ~]#  kubectl get cm
NAME   DATA   AGE
cm1    2      6m18s
cm2    2      4m7s
cm3    2      113s
cm4    2      11s

[root@k8s-master1 ~]#  kubectl describe cm cm4
Name:         cm4
Namespace:    default
Labels:       <none>
Annotations:
Data
====
host:
----
127.0.0.1
port:
----
3306
Events:  <none>

1.3 Two ways to use ConfigMap

1.3.1 passed to the pod through environment variables

[root@k8s-master1 ~]#  vim pod-cm1.yml
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm1
spec:
  containers:
  - name: busybox
    image: busybox
    args: [ "/bin/sh", "-c", "sleep 10000" ]
    envFrom:							# env方式
    - configMapRef:
        name: cm1						# configmap名称

[root@k8s-master1 ~]#  kubectl apply -f pod-cm1.yml
pod/pod-cm1 created

[root@k8s-master1 ~]#  kubectl get pods
NAME               READY   STATUS    RESTARTS   AGE
pod-cm1            1/1     Running   0          9s

[root@k8s-master1 ~]#  kubectl exec pod-cm1 -- env
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
HOSTNAME=pod-cm1
host=127.0.0.1								 # 我们创建的configmap传进去的env
port=3306									 # 我们创建的configmap传进去的env
DEPLOY_NGINX_PORT_80_TCP=tcp://10.2.205.160:80
DEPLOY_NGINX_PORT_80_TCP_ADDR=10.2.205.160
KUBERNETES_PORT=tcp://10.2.0.1:443
KUBERNETES_PORT_443_TCP=tcp://10.2.0.1:443
MY_SERVICE_SERVICE_HOST=10.2.52.46
MY_SERVICE_PORT_80_TCP_ADDR=10.2.52.46
KUBERNETES_SERVICE_HOST=10.2.0.1
KUBERNETES_PORT_443_TCP_PROTO=tcp
KUBERNETES_PORT_443_TCP_ADDR=10.2.0.1
MY_SERVICE_SERVICE_PORT=80
MY_SERVICE_PORT=tcp://10.2.52.46:80
MY_SERVICE_PORT_80_TCP=tcp://10.2.52.46:80
DEPLOY_NGINX_SERVICE_HOST=10.2.205.160
DEPLOY_NGINX_SERVICE_PORT=80
KUBERNETES_PORT_443_TCP_PORT=443
MY_SERVICE_PORT_80_TCP_PORT=80
DEPLOY_NGINX_PORT=tcp://10.2.205.160:80
DEPLOY_NGINX_PORT_80_TCP_PROTO=tcp
DEPLOY_NGINX_PORT_80_TCP_PORT=80
KUBERNETES_SERVICE_PORT=443
KUBERNETES_SERVICE_PORT_HTTPS=443
MY_SERVICE_PORT_80_TCP_PROTO=tcp
HOME=/root

1.3.2 Mount to pod by volume

[root@k8s-master1 ~]#  vim pod-cm2.yml
apiVersion: v1
kind: Pod
metadata:
  name: pod-cm2
spec:
  containers:
  - name: busybox
    image: busybox
    args: [ "/bin/sh", "-c", "sleep 10000" ]
    volumeMounts:                               # 用volume挂载方式
    - name: vol-cm                              # 对应下面的volume名
      mountPath: "/etc/mysql"                   # 挂载到容器内部的路径
      readOnly: true                            # 只读

  volumes:
  - name: vol-cm                                # 卷名称
    configMap:
      name: cm2                                 # configmap的名称

[root@k8s-master1 ~]#  kubectl apply -f pod-cm2.yml
pod/pod-cm2 created

[root@k8s-master1 ~]#  kubectl get pod
NAME      READY   STATUS    RESTARTS   AGE
pod-cm1   1/1     Running   0          3m51s
pod-cm2   1/1     Running   0          49s

[root@k8s-master1 ~]#  kubectl exec pod-cm2 -- ls /etc/mysql
host
port
[root@k8s-master1 ~]#  kubectl exec pod-cm2 -- cat /etc/mysql/host
127.0.0.1

[root@k8s-master1 ~]#  kubectl exec pod-cm2 -- cat /etc/mysql/port
3306

1.4 Hot update of ConfigMap

1.4.1 ConfigMap hot update method

If the value is modified, will the inside of the container be updated?

• Passed to the pod through environment variables. This method will not be hot updated
• Mount it to the pod by volume. This method will be hot updated, which takes about half a minute.

1.4.2 ConfigMap hot update verification

1.4.2.1 Through environment variables

This method will not be hot updated

1. Edit and modify the corresponding configmap

[root@k8s-master1 ~]# kubectl edit cm cm1
apiVersion: v1
data:
  host: 127.0.0.1
  port: "3307"								3306修改成3307
kind: ConfigMap
metadata:
  creationTimestamp: "2020-11-07T12:07:04Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {
    
    }
        f:host: {
    
    }
        f:port: {
    
    }
    manager: kubectl
    operation: Update
    time: "2020-11-07T12:07:04Z"
  name: cm1
  namespace: default
  resourceVersion: "169386"
  selfLink: /api/v1/namespaces/default/configmaps/cm1
  uid: f06cd44d-2ef9-48f2-9ccc-995f9d9ea2ad

2. Verify the changes in the corresponding pod and find that it will not change for a long time ( environment variable method )

[root@k8s-master1 ~]#  kubectl exec pod-cm1 -- env |grep port
port=3306									仍然为3306

1.4.2.2 Through the volume method

1. Edit and modify the corresponding configmap

[root@k8s-master1 ~]#  kubectl edit cm cm2
apiVersion: v1
data:
  host: 127.0.0.1
  port: "3308"							 		 修改成3308
kind: ConfigMap
metadata:
  creationTimestamp: "2020-11-07T12:09:15Z"
  managedFields:
  - apiVersion: v1
    fieldsType: FieldsV1
    fieldsV1:
      f:data:
        .: {
    
    }
        f:host: {
    
    }
        f:port: {
    
    }
    manager: kubectl
    operation: Update
    time: "2020-11-07T12:09:15Z"
  name: cm2
  namespace: default
  resourceVersion: "169707"
  selfLink: /api/v1/namespaces/default/configmaps/cm2

2. Verify the changes in the corresponding pod, which will change after a period of time ( volume mount method )

[root@k8s-master1 ~]#  kubectl exec pod-cm2 -- cat /etc/mysql/port
3308										     大概半分钟后更新