什么是configMap

Kubernetes中的ConfigMap 是用于存储非敏感数据的API对象，用于将配置数据与应用程序的镜像分离。ConfigMap可以包含键值对、文件或者环境变量等配置信息，应用程序可以通过挂载ConfigMap来访问其中的数据，从而实现应用配置的动态管理。ConfigMap的使用有助于提高应用程序的可移植性、可伸缩性和可维护性。

简单来讲， configmap 是用来存储app的配置或者容器的环境变量的， 避免这些配置hard code 在容器内。
但是configMap 并不适合存放敏感数据（例如帐号密码） ， 敏感数据应该存放在secret manager中。

configMap的创建

1. by kubectl command line

我们可以用 kubectl create configMap -h 查看官方的一些示例

Aliases:
configmap, cm

Examples:
  # Create a new config map named my-config based on folder bar
  kubectl create configmap my-config --from-file=path/to/bar
  
  # Create a new config map named my-config with specified keys instead of file basenames on disk
  kubectl create configmap my-config --from-file=key1=/path/to/bar/file1.txt --from-file=key2=/path/to/bar/file2.txt
  
  # Create a new config map named my-config with key1=config1 and key2=config2
  kubectl create configmap my-config --from-literal=key1=config1 --from-literal=key2=config2
  
  # Create a new config map named my-config from the key=value pairs in the file
  kubectl create configmap my-config --from-file=path/to/bar
  
  # Create a new config map named my-config from an env file
  kubectl create configmap my-config --from-env-file=path/to/foo.env --from-env-file=path/to/bar.env

可见， 用命令行创建configMap的都必须提供一个or 若干文件，甚至可以是文件夹， 而且真正的内容都要写在文件中的。
而-from-literal 可以在不提供文件的情况下直接在命令指定key value

例子1 基于文件夹

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI/test$ cd ..
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ ls test/
db1.config  db2.config
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ cat test/db1.config 
db1.hostname=db1
db1.port=3309

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ cat test/db2.config 
db2.hostname=db1
db2.port=3309

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl create cm test-dir-config --from-file=test/
configmap/test-dir-config created

上面我创建了两个config files 在test 文件夹中， 并用folder 名创建了1个configMap item

查看 configMap 的items

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl get cm
NAME                DATA   AGE
kube-root-ca.crt    1      172d
test-dir-config     2      2m28s

可以见到 test-dir-config 被创建出来了

查看 configMap的内容

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl describe cm test-dir-config
Name:         test-dir-config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
db1.config:
----
db1.hostname=db1
db1.port=3309


db2.config:
----
db2.hostname=db1
db2.port=3309



BinaryData
====

Events:  <none>
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ 

可以到这个configMap item 中有两个item, 注意的是
db.hostname 这种细节不是key

keys 只有两个
db1.config
db2.config

里面的内容的整体是key 对应的value！

例子2 基于某个文件

我们在另1个folder test2 created 了1个文件pgsql.yml

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ ls test2
pgsql.yml
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ cat test2/pgsql.yml 
hostname:
  db3.hostname
port:
  3310

注意格式是yaml的

这时我们创建1个configmap item

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl create cm db3.config --from-file=test2/pgsql.yml
configmap/db3.config created

查看configMap item

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl get cm
NAME                DATA   AGE
db3.config          1      67s
kube-root-ca.crt    1      172d
test-dir-config     2      52m

新建的configMap item 名字是db3.config
查看内容

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl describe cm db3.config
Name:         db3.config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
pgsql.yml:
----
hostname:
  db3.hostname
port:
  3310

BinaryData
====

Events:  <none>

key 是 pgsql.yml

这时我们再创建1个configMap item

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl create cm db4.config --from-file=db4-config=test2/pgsql.yml
configmap/db4.config created

注意这里的 --from-fille=db4-config=test2/pgsql.yaml
db4-config 是指定key的名字， overwrite掉 文件名作为key

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl get cm
NAME                DATA   AGE
db3.config          1      5m33s
db4.config          1      85s
kube-root-ca.crt    1      172d
test-dir-config     2      57m
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl describe cm db4.config
Name:         db4.config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
db4-config:
----
hostname:
  db3.hostname
port:
  3310

BinaryData
====

Events:  <none>

再查看内容：
这时的key 已经是 db4-config了

例子3 直接在命令行带上key value 的值

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl create cm db5.config --from-literal=hostname=db5.hostname --from-literal=port=3311
configmap/db5.config created
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl get cm
NAME                DATA   AGE
cloud-user-config   1      33d
db3.config          1      36m
db4.config          1      32m
db5.config          2      3s
kube-root-ca.crt    1      172d
test-dir-config     2      88m
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/CLI$ kubectl describe cm db5.config
Name:         db5.config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
port:
----
3311
hostname:
----
db5.hostname

BinaryData
====

Events:  <none>

注意这句命令创建了 1个 configmap item, 但是里面有两对KV
分别是
key： hostname
key: port

2. by yaml file

在项目中， 更常用定义资源应该是yaml file 格式

为了实现与上面命令同样的效果， 我们创建了1个yaml file, 内容如下

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/yaml$ ls
db6-config.yaml
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/yaml$ cat db6-config.yaml 
apiVersion: v1
kind: ConfigMap
metadata:
  name: db6.config
data:
  hostname: db6.hostname
  port: "3311"g

apply 资源

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/yaml$ kubectl apply -f db6-config.yaml 
configmap/db6.config created

查看configMap items

configmap/db6.config created
gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/yaml$ kubectl get cm
NAME                DATA   AGE
db3.config          1      85m
db4.config          1      81m
db5.config          2      48m
db6.config          2      33s
kube-root-ca.crt    1      172d
test-dir-config     2      137m

查看内容

gateman@MoreFine-S500:~/projects/coding/k8s-s/configMap/yaml$ kubectl describe cm db6.config
Name:         db6.config
Namespace:    default
Labels:       <none>
Annotations:  <none>

Data
====
hostname:
----
db6.hostname
port:
----
3311

BinaryData
====

Events:  <none>

可见 效果时间一样的

configMap的使用

在yaml 里大概有两种使用方法

1. 利用configMapKeyRef 读取配置
2. 利用volumes 把配置写入1个文件

1. 利用configMapKeyRef 读取配置

例子：

我们首先准备1个springboot serice - cloud order
令其的actuator/info 接口可以return 当前环境的所有环境变量

@Component
@Slf4j
public class AppVersionInfo implements InfoContributor {

    @Value("${pom.version}") // https://stackoverflow.com/questions/3697449/retrieve-version-from-maven-pom-xml-in-code
    private String appVersion;

    @Autowired
    private String hostname;

    @Autowired
    private InfoService infoservice;

    @Value("${spring.datasource.url}")
    private String dbUrl;

    @Override
    // https://docs.spring.io/spring-boot/docs/current/reference/html/production-ready-features.html#production-ready-endpoints-info
    public void contribute(Info.Builder builder) {
        log.info("AppVersionInfo: contribute ...");
        builder.withDetail("app", "Cloud Order Service")
                .withDetail("version", appVersion)
                .withDetail("hostname",hostname)
                .withDetail("dbUrl", dbUrl)
                .withDetail("description", "This is a simple Spring Boot application to for cloud order.")
                .withDetail("SystemVariables", infoservice.getSystemVariables());

    }
}

@Service
public class InfoService {

        public String getHostName() {
            return "unknown";
        }

        public HashMap<String, String> getSystemVariables() {
            Map<String, String> envVariables = System.getenv();

            //envVariables.forEach((key, value) -> systemVariables.put(key, value));
            return new HashMap<>(envVariables);
        }
}

然后我们利用yaml 创建1个configMap
cloud-order-configmap.yaml

apiVersion: v1
kind: ConfigMap
metadata:
  name: cloud-order-app-tag-config
data:
  APP_TAG: cloud-order-app-tag

里面指定一了1个KV 对

部署

kubectl apply -f cloud-order-configmap.yaml

然后再编写 deployment 的yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels: # label of this deployment
    app: cloud-order # custom defined
    author: nvd11
  name: deployment-cloud-order # name of this deployment
  namespace: default
spec:
  replicas: 3            # desired replica count, Please note that the replica Pods in a Deployment are typically distributed across multiple nodes.
  revisionHistoryLimit: 10 # The number of old ReplicaSets to retain to allow rollback
  selector: # label of the Pod that the Deployment is managing,, it's mandatory, without it , we will get this error 
            # error: error validating data: ValidationError(Deployment.spec.selector): missing required field "matchLabels" in io.k8s.apimachinery.pkg.apis.meta.v1.LabelSelector ..
    matchLabels:
      app: cloud-order
  strategy: # Strategy of upodate
    type: RollingUpdate # RollingUpdate or Recreate
    rollingUpdate:
      maxSurge: 25% # The maximum number of Pods that can be created over the desired number of Pods during the update
      maxUnavailable: 25% # The maximum number of Pods that can be unavailable during the update
  template: # Pod template
    metadata:
      labels:
        app: cloud-order # label of the Pod that the Deployment is managing. must match the selector, otherwise, will get the error Invalid value: map[string]string{"app":"bq-api-xxx"}: `selector` does not match template `labels`
    spec: # specification of the Pod
      containers:
      - image: europe-west2-docker.pkg.dev/jason-hsbc/my-docker-repo/cloud-order:1.0.2 # image of the container
        imagePullPolicy: IfNotPresent
        name: container-cloud-order
        env: # set env varaibles
        - name: APP_ENVIRONMENT # name of the environment variable
          value: prod # value of the environment variable
        - name: APP_TAG 
          valueFrom: # value from config map
            configMapKeyRef: 
              name: cloud-order-app-tag-config # name of the configMap item
              key: APP_TAG # key from the config map item
            
      restartPolicy: Always # Restart policy for all containers within the Pod
      terminationGracePeriodSeconds: 10 # The period of time in seconds given to the Pod to terminate gracefully

注意， 我们在环境变量那里 新增了1个item ， 环境变量的名字是 APP_TAG, 而 环境变量的value 是从 configmap 里获取的
部署成功后

测试api /actuator/info

ateman@MoreFine-S500:~/projects/coding/k8s-s/service-case/cloud-order$ curl http://www.jp-gcp-vms.cloud:8085/cloud-order/actuator/info | jq .
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100  1777    0  1777    0     0   3067      0 --:--:-- --:--:-- --:--:--  3063
{
  "app": "Cloud Order Service",
  "version": "1.0.2",
  "hostname": "deployment-cloud-order-c56db7848-lt5wc",
  "dbUrl": "jdbc:mysql://192.168.0.42:3306/demo_cloud_order?useUnicode=true&characterEncoding=utf-8&useSSL=false&allowPublicKeyRetrieval=true",
  "description": "This is a simple Spring Boot application to for cloud order.",
  "SystemVariables": {
    "PATH": "/usr/java/openjdk-17/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
    "CLUSTERIP_CLOUD_ORDER_SERVICE_HOST": "10.98.117.97",
    "CLUSTERIP_BQ_API_SERVICE_SERVICE_PORT": "8080",
    "KUBERNETES_PORT": "tcp://10.96.0.1:443",
    "JAVA_HOME": "/usr/java/openjdk-17",
    "KUBERNETES_SERVICE_HOST": "10.96.0.1",
    "LANG": "C.UTF-8",
    "CLUSTERIP_CLOUD_ORDER_PORT": "tcp://10.98.117.97:8080",
    "CLUSTERIP_BQ_API_SERVICE_PORT_8080_TCP": "tcp://10.100.68.154:8080",
    "CLUSTERIP_CLOUD_ORDER_PORT_8080_TCP": "tcp://10.98.117.97:8080",
    "CLUSTERIP_BQ_API_SERVICE_PORT_8080_TCP_PROTO": "tcp",
    "PWD": "/app",
    "JAVA_VERSION": "17.0.2",
    "_": "/usr/java/openjdk-17/bin/java",
    "CLUSTERIP_CLOUD_ORDER_PORT_8080_TCP_ADDR": "10.98.117.97",
    "KUBERNETES_PORT_443_TCP": "tcp://10.96.0.1:443",
    "KUBERNETES_PORT_443_TCP_ADDR": "10.96.0.1",
    "CLUSTERIP_CLOUD_ORDER_PORT_8080_TCP_PORT": "8080",
    "CLUSTERIP_BQ_API_SERVICE_PORT": "tcp://10.100.68.154:8080",
    "CLUSTERIP_BQ_API_SERVICE_PORT_8080_TCP_PORT": "8080",
    "KUBERNETES_PORT_443_TCP_PROTO": "tcp",
    "APP_ENVIRONMENT": "prod",
    "KUBERNETES_SERVICE_PORT": "443",
    "CLUSTERIP_CLOUD_ORDER_SERVICE_PORT": "8080",
    "CLUSTERIP_BQ_API_SERVICE_PORT_8080_TCP_ADDR": "10.100.68.154",
    "APP_TAG": "cloud-order-app-tag",
    "HOSTNAME": "deployment-cloud-order-c56db7848-lt5wc",
    "CLUSTERIP_CLOUD_ORDER_PORT_8080_TCP_PROTO": "tcp",
    "CLUSTERIP_BQ_API_SERVICE_SERVICE_HOST": "10.100.68.154",
    "KUBERNETES_PORT_443_TCP_PORT": "443",
    "KUBERNETES_SERVICE_PORT_HTTPS": "443",
    "SHLVL": "1",
    "HOME": "/root"
  }
}

查看 APP_TAG 的那一行， 的确能正确地获取configmap 里的配置信息！

2. 利用volumes 把配置写入1个文件

在这个例子中
我们再利用yaml 创建另1个configMap

apiVersion: v1
kind: ConfigMap
metadata:
  name: cloud-order-os-version-config
data:
  OS_VERSION: ubuntu-x.x

部署

gateman@MoreFine-S500:~/projects/coding/k8s-s/service-case/cloud-order$ kubectl apply -f cloud-order-configmap2.yaml
configmap/cloud-order-os-version-config created

修改 cloud order service 的deployment yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  labels: # label of this deployment
    app: cloud-order # custom defined
    author: nvd11
  name: deployment-cloud-order # name of this deployment
  namespace: default
spec:
  replicas: 3            # desired replica count, Please note that the replica Pods in a Deployment are typically distributed across multiple nodes.
  revisionHistoryLimit: 10 # The number of old ReplicaSets to retain to allow rollback
  selector: # label of the Pod that the Deployment is managing,, it's mandatory, without it , we will get this error 
            # error: error validating data: ValidationError(Deployment.spec.selector): missing required field "matchLabels" in io.k8s.apimachinery.pkg.apis.meta.v1.LabelSelector ..
    matchLabels:
      app: cloud-order
  strategy: # Strategy of upodate
    type: RollingUpdate # RollingUpdate or Recreate
    rollingUpdate:
      maxSurge: 25% # The maximum number of Pods that can be created over the desired number of Pods during the update
      maxUnavailable: 25% # The maximum number of Pods that can be unavailable during the update
  template: # Pod template
    metadata:
      labels:
        app: cloud-order # label of the Pod that the Deployment is managing. must match the selector, otherwise, will get the error Invalid value: map[string]string{"app":"bq-api-xxx"}: `selector` does not match template `labels`
    spec: # specification of the Pod
      containers:
      - image: europe-west2-docker.pkg.dev/jason-hsbc/my-docker-repo/cloud-order:1.0.2 # image of the container
        imagePullPolicy: IfNotPresent
        name: container-cloud-order
        env: # set env varaibles
        - name: APP_ENVIRONMENT # name of the environment variable
          value: prod # value of the environment variable
        - name: APP_TAG 
          valueFrom: # value from config map
            configMapKeyRef: 
              name: cloud-order-app-tag-config # name of the configMap item
              key: APP_TAG # key from the config map item
        volumeMounts: # volume mount
          - name: config-volume
            mountPath: /app/config
      volumes:
        - name: config-volume
          configMap:
            name: cloud-order-os-version-config # name of the config map
            items:
              - key: OS_VERSION # key of the config map item
                path: os-version.conf # name of the file, it will only contain the content of the key
            
            
      restartPolicy: Always # Restart policy for all containers within the Pod
      terminationGracePeriodSeconds: 10 # The period of time in seconds given to the Pod to terminate gracefully

注意我们在这里新增了1个卷 把configmap cloud-order-os-version-config 指定某个key的value 保存到1个文件中 os-version.conf
而在container 的配置中， 我们 吧这个卷mount 在 /app/config 路径下

重新部署：

gateman@MoreFine-S500:~/projects/coding/k8s-s/service-case/cloud-order$ kubectl apply -f deployment-cloud-order.yaml 
deployment.apps/deployment-cloud-order configured
gateman@MoreFine-S500:~/projects/coding/k8s-s/service-case/cloud-order$ kubectl get pods
NAME                                         READY   STATUS    RESTARTS         AGE
deployment-bq-api-service-6f6ffc7866-8djx9   1/1     Running   0                26h
deployment-bq-api-service-6f6ffc7866-g4854   1/1     Running   9 (3d21h ago)    45d
deployment-bq-api-service-6f6ffc7866-lwxt7   1/1     Running   11 (3d21h ago)   47d
deployment-bq-api-service-6f6ffc7866-mxwcq   1/1     Running   8 (3d21h ago)    45d
deployment-cloud-order-7cb8466d48-2kcnn      1/1     Running   0                8s
deployment-cloud-order-7cb8466d48-57w6n      1/1     Running   0                7s
deployment-cloud-order-7cb8466d48-d6jk7      1/1     Running   0                5s

进入容器：

gateman@MoreFine-S500:~$ kubectl exec -it deployment-cloud-order-7cb8466d48-d6jk7 /bin/bash
kubectl exec [POD] [COMMAND] is DEPRECATED and will be removed in a future version. Use kubectl exec [POD] -- [COMMAND] instead.
bash-4.4# cd /app/config
bash-4.4# ls
os-version.conf
bash-4.4# cat os-version.conf 
ubuntu-x.x

可以见到configmap的内容的确放入了 容器内的对应的目录下