Etcd是一个高可用的、开源的、分布式的Key/value存储系统，提供共享配置、服务的注册和发现、数据TTL失效、数据改变监视、多值、目录监听、分布式原子锁操作等功能。通常，k8s使用etcd进行数据存储，本文将部署etcd集群用做应用的存储。

一、前提

        部署好k8s，最好有3个及以上worker节点，部署好StorageClass可以动态创建PVC。本文k8s版本v1.24.8，StorageClass使用nfs-client，使用命名空间gv-public，以部署apisix为例，说明etcd集群部署的过程。

二、yaml文件

        以下yaml文件是使用命名空间:gv-public（已创建），sc:nfs-client为例，部署根据实际情况修改。

1）svc.yaml

        etcd集群用到两个svc，apisix-etcd-headless和apisix-etcd。

apiVersion: v1
kind: Service
metadata:
  name: apisix-etcd-headless
  namespace: gv-public
  labels:
    app.kubernetes.io/instance: apisix-etcd
    app.kubernetes.io/name: apisix-etcd
spec:
  ports:
  - name: client
    port: 2379
    protocol: TCP
    targetPort: 2379
  - name: peer
    port: 2380
    protocol: TCP
    targetPort: 2380
  clusterIP: None
  selector:
    app.kubernetes.io/instance: apisix-etcd
    app.kubernetes.io/name: apisix-etcd
  publishNotReadyAddresses: true
--- 
apiVersion: v1
kind: Service
metadata:
  name: apisix-etcd
  namespace: gv-public
  labels:
    app.kubernetes.io/instance: apisix-etcd
    app.kubernetes.io/name: apisix-etcd
spec:
  ports:
  - name: client
    port: 2379
    protocol: TCP
    targetPort: 2379
  - name: peer
    port: 2380
    protocol: TCP
    targetPort: 2380
  selector:
    app.kubernetes.io/instance: apisix-etcd
    app.kubernetes.io/name: apisix-etcd

2)etcd.yaml

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: apisix-etcd
  namespace: gv-public
  labels:
    app.kubernetes.io/instance: apisix-etcd
    app.kubernetes.io/name: apisix-etcd
spec:
  podManagementPolicy: Parallel
  replicas: 3
  serviceName: apisix-etcd-headless
  selector:
    matchLabels:
      app.kubernetes.io/instance: apisix-etcd
      app.kubernetes.io/name: apisix-etcd
  template:
    metadata:
      labels:
        app.kubernetes.io/instance: apisix-etcd
        app.kubernetes.io/name: apisix-etcd
    spec:
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - podAffinityTerm:
              labelSelector:
                matchLabels:
                  app.kubernetes.io/instance: apisix-etcd
                  app.kubernetes.io/name: apisix-etcd
              topologyKey: kubernetes.io/hostname
            weight: 1
      containers:
      - name: apisix-etcd-app
        image: bitnami/etcd:3.4.24
        imagePullPolicy: IfNotPresent
        ports:
        - containerPort: 2379
          name: client
          protocol: TCP
        - containerPort: 2380
          name: peer
          protocol: TCP
        env:
        - name: BITNAMI_DEBUG
          value: 'false'
        - name: MY_POD_IP
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: status.podIP
        - name: MY_POD_NAME
          valueFrom:
            fieldRef:
              apiVersion: v1
              fieldPath: metadata.name
        - name: MY_STS_NAME
          value: apisix-etcd
        - name: ETCDCTL_API
          value: '3'
        - name: ETCD_ON_K8S
          value: 'yes'
        - name: ETCD_START_FROM_SNAPSHOT
          value: 'no'
        - name: ETCD_DISASTER_RECOVERY
          value: 'no'
        - name: ETCD_NAME
          value: $(MY_POD_NAME)
        - name: ETCD_DATA_DIR
          value: /bitnami/etcd/data
        - name: ETCD_LOG_LEVEL
          value: info
        - name: ALLOW_NONE_AUTHENTICATION
          value: 'yes'
        - name: ETCD_ADVERTISE_CLIENT_URLS
          value: http://$(MY_POD_NAME).apisix-etcd-headless.gv-public.svc.cluster.local:2379
        - name: ETCD_LISTEN_CLIENT_URLS
          value: http://0.0.0.0:2379
        - name: ETCD_INITIAL_ADVERTISE_PEER_URLS
          value: http://$(MY_POD_NAME).apisix-etcd-headless.gv-public.svc.cluster.local:2380
        - name: ETCD_LISTEN_PEER_URLS
          value: http://0.0.0.0:2380
        - name: ETCD_INITIAL_CLUSTER_TOKEN
          value: apisix-etcd-cluster-k8s
        - name: ETCD_INITIAL_CLUSTER_STATE
          value: new
        - name: ETCD_INITIAL_CLUSTER
          value: apisix-etcd-0=http://apisix-etcd-0.apisix-etcd-headless.gv-public.svc.cluster.local:2380,apisix-etcd-1=http://apisix-etcd-1.apisix-etcd-headless.gv-public.svc.cluster.local:2380,apisix-etcd-2=http://apisix-etcd-2.apisix-etcd-headless.gv-public.svc.cluster.local:2380
        - name: ETCD_CLUSTER_DOMAIN
          value: apisix-etcd-headless.gv-public.svc.cluster.local
        volumeMounts:
        - name: data
          mountPath: /bitnami/etcd
        lifecycle:
          preStop:
            exec:
              command:
              - /opt/bitnami/scripts/etcd/prestop.sh
        livenessProbe:
          exec:
            command:
            - /opt/bitnami/scripts/etcd/healthcheck.sh
          initialDelaySeconds: 60
          timeoutSeconds: 5
          periodSeconds: 30
          successThreshold: 1
          failureThreshold: 5
        readinessProbe:
          exec:
            command:
            - /opt/bitnami/scripts/etcd/healthcheck.sh
          initialDelaySeconds: 60
          timeoutSeconds: 5
          periodSeconds: 10
          successThreshold: 1
          failureThreshold: 5
      securityContext:
        fsGroup: 1001
  volumeClaimTemplates:
  - metadata:
      name: data
    spec:
      accessModes: 
      - ReadWriteOnce
      storageClassName: nfs-client
      resources:
        requests:
          storage: 1Gi

三、执行yaml

分别执行如下命令，创建etcd集群：

#kubectl create -f svc.yaml

[root@k8s-master apisix]# kubectl get svc -n gv-public | grep etcd
apisix-etcd            ClusterIP   10.43.141.181   <none>        2379/TCP,2380/TCP                     58m
apisix-etcd-headless   ClusterIP   None            <none>        2379/TCP,2380/TCP                     58m

#kubectl create -f etcd.yaml

[root@k8s-master apisix]# kubectl get pod -n gv-public | grep etcd
apisix-etcd-0                       1/1     Running   0             59m
apisix-etcd-1                       1/1     Running   0             59m
apisix-etcd-2                       1/1     Running   0             59m

进入etcd集群的一个pod容器：

#kubectl exec -it apisix-etcd-0 -n gv-public -- /bin/bash

查看集群信息：

I have no name!@apisix-etcd-0:/opt/bitnami/etcd$ etcdctl endpoint status --cluster -w table
+----------------------------------------------------------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
|                                  ENDPOINT                                  |        ID        | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+----------------------------------------------------------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| http://apisix-etcd-2.apisix-etcd-headless.gv-public.svc.cluster.local:2379 | a13daea6a7c5a0ed |  3.4.24 |   49 kB |     false |      false |         5 |         50 |                 50 |        |
| http://apisix-etcd-0.apisix-etcd-headless.gv-public.svc.cluster.local:2379 | c3f10b3f6f66b949 |  3.4.24 |   49 kB |     false |      false |         5 |         50 |                 50 |        |
| http://apisix-etcd-1.apisix-etcd-headless.gv-public.svc.cluster.local:2379 | c6a5a0cbfafa2786 |  3.4.24 |   49 kB |      true |      false |         5 |         50 |                 50 |        |
+----------------------------------------------------------------------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+