很多人应该只是在物理机或者虚拟机上直接部署过etcd集群，但是基于kubernetes可能未必部署过，接下来我就介绍一下基于kubernetes进行部署etcd集群。
步骤如下：

建立kubernetes命名空间，kubersphere里创建即可，这里忽略。
创建stateful的yaml文件。注意：存储方式，我采用的是NFS的方式，如果是ceph就写：k8s.cloud/storage-type: ceph，如果是本地就写k8s.cloud/storage-type: local-storage。

apiVersion: apps/v1
kind: StatefulSet
metadata:
  labels:
    k8s-app: etcd-cluster
    app: etcd
  name: etcd-cluster
  namespace: etcd
spec:
  replicas: 3
  selector:
    matchLabels:
      k8s-app: etcd-cluster
      app: etcd
  serviceName: etcd-cluster
  template:
    metadata:
      labels:
        k8s-app: etcd-cluster
        app: etcd
      name: etcd-cluster
    spec:
      containers:
      - command:
        - /bin/sh
        - -ec
        - |
          HOSTNAME=$(hostname)
          echo "etcd api version is ${ETCDAPI_VERSION}"

          eps() {
              EPS=""
              for i in $(seq 0 $((${INITIAL_CLUSTER_SIZE} - 1))); do
                  EPS="${EPS}${EPS:+,}http://${SET_NAME}-${i}.${SET_NAME}.${CLUSTER_NAMESPACE}:2379"
              done
              echo ${EPS}
          }

          member_hash() {
              etcdctl member list | grep http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 | cut -d':' -f1 | cut -d'[' -f1
          }

          initial_peers() {
                PEERS=""
                for i in $(seq 0 $((${INITIAL_CLUSTER_SIZE} - 1))); do
                PEERS="${PEERS}${PEERS:+,}${SET_NAME}-${i}=http://${SET_NAME}-${i}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380"
                done
                echo ${PEERS}
          }

          # etcd-SET_ID
          SET_ID=${HOSTNAME##*-}
          # adding a new member to existing cluster (assuming all initial pods are available)
          if [ "${SET_ID}" -ge ${INITIAL_CLUSTER_SIZE} ]; then
              export ETCDCTL_ENDPOINTS=$(eps)

              # member already added?
              MEMBER_HASH=$(member_hash)
              if [ -n "${MEMBER_HASH}" ]; then
                  # the member hash exists but for some reason etcd failed
                  # as the datadir has not be created, we can remove the member
                  # and retrieve new hash
                  if [ "${ETCDAPI_VERSION}" -eq 3 ]; then
                      ETCDCTL_API=3 etcdctl --user=root:${ROOT_PASSWORD} member remove ${MEMBER_HASH}
                  else
                      etcdctl --username=root:${ROOT_PASSWORD} member remove ${MEMBER_HASH}
                  fi
              fi
              echo "Adding new member"
              rm -rf /var/run/etcd/*
              # ensure etcd dir exist
              mkdir -p /var/run/etcd/
              # sleep 60s wait endpoint become ready
              echo "sleep 60s wait endpoint become ready,sleeping..."
              sleep 60

              if [ "${ETCDAPI_VERSION}" -eq 3 ]; then
                  ETCDCTL_API=3 etcdctl --user=root:${ROOT_PASSWORD} member add ${HOSTNAME} --peer-urls=http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 | grep "^ETCD_" > /var/run/etcd/new_member_envs
              else
                  etcdctl --username=root:${ROOT_PASSWORD} member add ${HOSTNAME} http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 | grep "^ETCD_" > /var/run/etcd/new_member_envs
              fi



              if [ $? -ne 0 ]; then
                  echo "member add ${HOSTNAME} error."
                  rm -f /var/run/etcd/new_member_envs
                  exit 1
              fi

              cat /var/run/etcd/new_member_envs
              source /var/run/etcd/new_member_envs

              exec etcd --name ${HOSTNAME} \
                  --initial-advertise-peer-urls http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 \
                  --listen-peer-urls http://0.0.0.0:2380 \
                  --listen-client-urls http://0.0.0.0:2379 \
                  --advertise-client-urls http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2379 \
                  --data-dir /var/run/etcd/default.etcd \
                  --initial-cluster ${ETCD_INITIAL_CLUSTER} \
                  --initial-cluster-state ${ETCD_INITIAL_CLUSTER_STATE}
          fi

          for i in $(seq 0 $((${INITIAL_CLUSTER_SIZE} - 1))); do
              while true; do
                  echo "Waiting for ${SET_NAME}-${i}.${SET_NAME}.${CLUSTER_NAMESPACE} to come up"
                  ping -W 1 -c 1 ${SET_NAME}-${i}.${SET_NAME}.${CLUSTER_NAMESPACE} > /dev/null && break
                  sleep 1s
              done
          done

          echo "join member ${HOSTNAME}"
          # join member
          exec etcd --name ${HOSTNAME} \
              --initial-advertise-peer-urls http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 \
              --listen-peer-urls http://0.0.0.0:2380 \
              --listen-client-urls http://0.0.0.0:2379 \
              --advertise-client-urls http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2379 \
              --initial-cluster-token etcd-cluster-1 \
              --data-dir /var/run/etcd/default.etcd \
              --initial-cluster $(initial_peers) \
              --initial-cluster-state new

        env:
        - name: INITIAL_CLUSTER_SIZE
          value: "3"
        - name: CLUSTER_NAMESPACE
          valueFrom:
            fieldRef:
              fieldPath: metadata.namespace
        - name: ETCDAPI_VERSION
          value: "3"
        - name: ROOT_PASSWORD
          value: 'Abc=1234'
        - name: SET_NAME
          value: "etcd-cluster"
        - name: GOMAXPROCS
          value: "4"
        image: gcr.io/etcd-development/etcd:v3.4.9
        imagePullPolicy: Always
        lifecycle:
          preStop:
            exec:
              command:
              - /bin/sh
              - -ec
              - |
                HOSTNAME=$(hostname)

                member_hash() {
                    etcdctl member list | grep http://${HOSTNAME}.${SET_NAME}.${CLUSTER_NAMESPACE}:2380 | cut -d':' -f1 | cut -d'[' -f1
                }

                eps() {
                    EPS=""
                    for i in $(seq 0 $((${INITIAL_CLUSTER_SIZE} - 1))); do
                        EPS="${EPS}${EPS:+,}http://${SET_NAME}-${i}.${SET_NAME}.${CLUSTER_NAMESPACE}:2379"
                    done
                    echo ${EPS}
                }

                export ETCDCTL_ENDPOINTS=$(eps)

                SET_ID=${HOSTNAME##*-}
                # Removing member from cluster
                if [ "${SET_ID}" -ge ${INITIAL_CLUSTER_SIZE} ]; then
                    echo "Removing ${HOSTNAME} from etcd cluster"
                    if [ "${ETCDAPI_VERSION}" -eq 3 ]; then
                        ETCDCTL_API=3 etcdctl --user=root:${ROOT_PASSWORD} member remove $(member_hash)
                    else
                        etcdctl --username=root:${ROOT_PASSWORD} member remove $(member_hash)
                    fi
                    if [ $? -eq 0 ]; then
                        # Remove everything otherwise the cluster will no longer scale-up
                        rm -rf /var/run/etcd/*
                    fi
                fi
        name: etcd-cluster
        ports:
        - containerPort: 2380
          name: peer
          protocol: TCP
        - containerPort: 2379
          name: client
          protocol: TCP
        resources:
          limits:
            cpu: "1"
            memory: 1Gi
          requests:
            cpu: "1"
            memory: 1Gi
        volumeMounts:
        - mountPath: /var/run/etcd
          name: datadir
  updateStrategy:
    type: OnDelete
  volumeClaimTemplates:
  - metadata:
      name: datadir
    spec:
      accessModes:
      - ReadWriteOnce
      resources:
        requests:
          storage: 3Gi
      selector:
        matchLabels:
          k8s.cloud/storage-type: nfs

3.创建service,这个service是为了etcd集群节点之间进行服务注册发现使用的，所以采用clusterip的方式，代码如下
：

apiVersion: v1
kind: Service
metadata:
  labels:
    k8s-app: etcd-cluster
    app: etcd
  name: etcd-cluster
  namespace: etcd
spec:
  clusterIP: None
  ports:
  - name: etcd-cluster-2379
    port: 2379
    protocol: TCP
    targetPort: 2379
  - name: etcd-cluster-2380
    port: 2380
    protocol: TCP
    targetPort: 2380
  selector:
    k8s-app: etcd-cluster
    app: etcd
  type: ClusterIP

4.创建外部访问service，采用nodeport或者loadbalance方式都可以:

apiVersion: v1
kind: Service
metadata:
  labels:
    k8s-app: etcd-cluster-client
    app: etcd
  name: etcd-cluster-client
  namespace: etcd
spec:
  ports:
  - name: etcd-cluster-2379
    port: 2379
    protocol: TCP
    targetPort: 2379
  selector:
    k8s-app: etcd-cluster
    app: etcd
  sessionAffinity: None
  type: NodePort