ConfigMap Reload

3 minute read

Purpose

ConfigMap or Secret가 변경 될 경우, 이를 인지하여 Deployment의 Pod가 자동으로 재기동 되도록 한다.

사용되는 OpenSource

How to use

1. stakater/Reloader 설치

$ helm install stakater/reloader

Default namespace에 설치 하는 경우, 모든 namspace의 configmap, secrets을 대상으로 동작한다.
특정 namespace에 대해서만 동작하게 하고 싶은 경우, 특정 namespace를 지정하여 설치한다.

2. 소스 코드

  • src/PropertiesConfig.java
    configmap의 data필드의 값을 (@ConfigurationProperties)prefix.Field 형태로 가져와 사용한다.
    아래 코드에서는, console-boot-template-cm Configmap의 data:application.properties: 에서 가져온 값을 사용한다. 
    @Configuration
@ConfigurationProperties(prefix = "bean")
public class PropertiesConfig {

  private String data = "This is default data";
  ... setter & getter
}

  • src/RestController.java ``` java @org.springframework.web.bind.annotation.RestController @RequestMapping(“/test”) public class RestController { @Autowired private PropertiesConfig yamlConfig;

    @GetMapping(“/data”) public String load() { String data = “error”; try { data = String.format(yamlConfig.getData(), “”, “”); } catch (IllegalStateException e) { e.printStackTrace(); } return data; }

}


- resources/application.properties

bean.data=Message from apllication.properties


#### 3. k8s 리소스 생성 및 수정 
- role.yaml   
namespace의 default Role에 configmaps를 get, list, watch 할 수 있는 권한을 부여한다
``` yaml
kind: Role
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  namespace: ayoung
  name: default
rules:
  - apiGroups: ["", "extensions", "apps"]
    resources: ["configmaps", "pods", "services", "endpoints", "secrets"]
    verbs: ["get", "list", "watch"]
---
kind: RoleBinding
apiVersion: rbac.authorization.k8s.io/v1
metadata:
  name: default-binding
  namespace: ayoung
subjects:
  - kind: ServiceAccount
    name: default
    apiGroup: ""
roleRef:
  kind: Role
  name: default
  apiGroup: ""
  • configmap.yaml
    data:application.properties: 필드에 소스코드에서 사용하는 데이터를 입력한다 
    apiVersion: v1
kind: ConfigMap
metadata:
name: console-boot-template-cm         # CHANG IT
namespace: ayoung
data:
application.properties: |-
  bean.data=Testing reload! Message from configmap    # CHANG IT
  • deployment.yaml
    metadata:annoation:configmap.reloader.stakater.com/reload에 감지 대상 ConfigMap의 이름을 지정한다 
    apiVersion: apps/v1
kind: Deployment
metadata:
annotations:
  configmap.reloader.stakater.com/reload: "console-boot-template-cm"     # CHANGE IT
name: console-boot-template
namespace: ayoung
spec:
selector:
  matchLabels:
    app: console-boot-template

replicas: 1
template:
  metadata:
    labels:
      app: console-boot-template
  spec:
    containers:
      - name: console-boot-template
        image: lay126/console-boot-template:latest
        ports:
          - containerPort: 8080
        env:
          - name: env.namespace
            value: ayoung
        volumeMounts:
          - name: config
            mountPath: /config
    volumes:
      - name: config
        configMap:
          name: console-boot-template-cm
  • service.yaml ``` yaml kind: Service apiVersion: v1 metadata: name: console-boot-template-svc namespace: ayoung spec: selector: app: console-boot-template ports:
    • protocol: TCP port: 8080 nodePort: 30083 type: NodePort ```
  • ingress.yaml ``` yaml apiVersion: extensions/v1beta1 kind: Ingress metadata: name: console-boot-template-ing namespace: ayoung spec: rules:
    • host: console-boot-template.cloudzcp.io http: paths:
      • backend: serviceName: console-boot-template-svc servicePort: 8080 tls:
    • hosts:
      • console-boot-template.cloudzcp.io secretName: cloudzcp-io-cert ```

동작

K8S resources

$ kubectl get all
NAME                                           READY   STATUS    RESTARTS   AGE
pod/console-boot-template-57f86b5896-hxtbk     1/1     Running   0          16m
pod/vehement-tapir-reloader-6cfd88bbff-2sszf   1/1     Running   0          13d

NAME                                TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
service/console-boot-template-svc   NodePort   172.21.71.209   <none>        8080:30744/TCP   131m

NAME                                      READY   UP-TO-DATE   AVAILABLE   AGE
deployment.apps/console-boot-template     1/1     1            1           131m
deployment.apps/vehement-tapir-reloader   1/1     1            1           13d

NAME                                                 DESIRED   CURRENT   READY   AGE
replicaset.apps/console-boot-template-57f86b5896     1         1         1       16m
replicaset.apps/vehement-tapir-reloader-6cfd88bbff   1         1         1       13d

$ kubectl get configmap
NAME                       DATA   AGE
console-boot-template-cm   1      131m

configmap edit

$ kubectl edit cm console-boot-template-cm
---
apiVersion: v1
data:
  application.properties: bean.data=Testing reload! Message from cm!    # CHANGE IT
kind: ConfigMap

Pod Reload

$ kgp
NAME                                       READY   STATUS              RESTARTS   AGE
console-boot-template-57f86b5896-hxtbk     1/1     Running             0          19m
# 변경된 cm반영된 Pod 생성
console-boot-template-656575f45f-rt7n6     0/1     ContainerCreating   0          2s
vehement-tapir-reloader-6cfd88bbff-2sszf   1/1     Running             0          13d
...
# 기존 Pod 중지 됨
console-boot-template-57f86b5896-hxtbk     1/1     Terminating   0          20m
  • Configmap 수정 전 Alt text
  • Configmap 수정 후 Alt text

Rolling Update

Deployment replicas를 3개로 조정.

NAME                                       READY   STATUS              RESTARTS   AGE
console-boot-template-74759dcf44-9598r     1/1     Running             0          111s
console-boot-template-74759dcf44-nh9vj     1/1     Running             0          111s
console-boot-template-74759dcf44-xlnbj     1/1     Running             0          111s

Configmap을 수정 한 뒤, Pod의 Rolling Update를 확인.

$ k get pod 
console-boot-template-66686d9df7-svnr9     0/1     ContainerCreating   0          1s
console-boot-template-74759dcf44-9598r     1/1     Running             0          110s
console-boot-template-74759dcf44-nh9vj     1/1     Running             0          110s
console-boot-template-74759dcf44-xlnbj     1/1     Running             0          110s
$ k get pod 
console-boot-template-66686d9df7-pdtxv     0/1     ContainerCreating   0          1s
console-boot-template-66686d9df7-svnr9     1/1     Running             0          10s
console-boot-template-66686d9df7-zwvbl     1/1     Running             0          5s
console-boot-template-74759dcf44-nh9vj     0/1     Terminating         0          119s
console-boot-template-74759dcf44-xlnbj     1/1     Running             0          119s
$ k get pod 
console-boot-template-66686d9df7-pdtxv     1/1     Running   0          10s
console-boot-template-66686d9df7-svnr9     1/1     Running   0          19s
console-boot-template-66686d9df7-zwvbl     1/1     Running   0          14s

Updated: