k8s-reloader

wang alan

發佈於Develop

2023/04/24閱讀時間約 11 分鐘

👨‍💻簡介

有時候修改掛載的config檔，無法即時更新，需要重啟pod才會生效，為了解決這個問題，k8s-reloader因此而誕生，透過觀察掛載的configmap或是secret的變化自動對掛載的物件做滾動更新。

以下為在minikube環境下，透過掛載nginx-config檔並搭配reloader這個插件進行熱部署。

🔗github-repo : stakater/Reloader: A Kubernetes controller to watch changes in ConfigMap and Secrets and do rolling upgrades on Pods with their associated Deployment, StatefulSet, DaemonSet and DeploymentConfig – [✩Star] if you’re using it! (github.com)

🔰基礎介紹

運作原理

Reloader偵測所有資源變化，對有變化的資源使用SHA1計算資源的哈西值
Reloader查看是否有設定相關的annotation，並查看有設定annotation資源的特殊環境變量
對有設定annotation的資源比對其哈希值，如果環境變量中哈希值不同，則更新環境變量，如果環境變量不存在，則創建一個

環境變量名稱

ConfigMap：STAKATER_{configmap_name}_CONFIGMAP ，比如 ConfigMap 的名稱為 foo，則生成的環境變量的名稱為：STAKATER_FOO_CONFIGMAP。
Secret：STAKATER_{secret_name}_SECRET ，比如 Secret 的名稱為 foo，則生成的環境變量的名稱為：STAKATER_FOO_SECRET。

環境變量的值

使用 SHA1 計算的 ConfigMap 或者 Secret 的哈希值。

版本需求

k8s版本需 >= 1.9

安裝方式

使用Manifests安裝

kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

使用Kustomize安裝

kubectl apply -k https://github.com/stakater/Reloader/deployments/kubernetes
apiVersion: kustomize.config.k8s.io/v1beta1
kind: Kustomization

bases:
  - https://github.com/stakater/Reloader/deployments/kubernetes

namespace: reloader

使用Helm安裝

helm repo add stakater https://stakater.github.io/stakater-charts

helm repo update

helm install stakater/reloader # For helm3 add --generate-name flag or set the release name

預設情況下，reloader會偵測所有namespace的資源，如果要針對單一namespace可使用--set reloader.watchGlobally為false，以下範例為安裝在test namespace並只偵測test namespace底下的資源

helm install stakater/reloader --set reloader.watchGlobally=false --namespace test # For helm3 add --generate-name flag or set the release name

使用方式

自動偵測所有資源

設定reloader.stakater.com/auto: "true"

kind: Deployment
metadata:
  annotations:
    reloader.stakater.com/auto: "true"
spec:
  template:
    metadata:

限制只偵測有設定annotations的資源

deploy設定reloader.stakater.com/search: "true"，configmap等資源設定reloader.stakater.com/match: "true"

kind: Deployment
metadata:
  annotations:
    reloader.stakater.com/search: "true"
spec:
  template:
---
kind: ConfigMap
metadata:
  annotations:
    reloader.stakater.com/match: "true"
data:
  key: value

reloader.stakater.com/auto與reloader.stakater.com/search不能同時使用如果使用reloader.stakater.com/auto，則reloader.stakater.com/match不管有沒有設定都會被偵測

只偵測特定資源

資源使用,做分隔

Configmap

kind: Deployment
metadata:
  annotations:
    configmap.reloader.stakater.com/reload: "foo-configmap"
spec:
  template:
    metadata:

Secret

kind: Deployment
metadata:
  annotations:
    secret.reloader.stakater.com/reload: "foo-secret,bar-secret,baz-secret"
spec:
  template: 
    metadata:

🎯setup

部署reloader

kubectl apply -f https://raw.githubusercontent.com/stakater/Reloader/master/deployments/kubernetes/reloader.yaml

部署nginx服務建立以下檔案


apiVersion: v1
kind: ConfigMap
metadata:
  name: nginx-map
  annotations:
	reloader.stakater.com/match: "true"
data:
  test.conf: |
	server {
	  listen       80;
	  server_name  abc.com;

	  location / {
		  root  /usr/share/nginx/html ;
		  index index.html index.htm;
	  }
	}
---
apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  annotations:
	configmap.reloader.stakater.com/reload: "nginx-map"
spec:
  replicas: 2
  selector:
	matchLabels:
	  service: http-server
  template:
	metadata:
	  labels:
		service: http-server
	spec:
	  containers:
	  - name: nginx
		image: sz9751210/nginx-reloader:v1
		imagePullPolicy: IfNotPresent
		ports:
		- containerPort: 80
		volumeMounts:
		- mountPath: /etc/nginx/conf.d # mount nginx-conf volumn to /etc/nginx/conf.d
		  readOnly: true
		  name: deployment-nginx-conf
	  volumes:
		- name: deployment-nginx-conf
		  configMap:
			name: nginx-map # place ConfigMap `nginx-conf` on /etc/nginx
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  selector:
	service: http-server
  ports:
  - port: 80
	targetPort: 80
部署
kubectl apply -f k8s-reloader-demo.yaml