資訊專欄INFORMATION COLUMN
摘要：二總結使用的和的，能夠很好的支持這樣的有狀態服務部署到集群上。部署方式有待優化本次試驗中使用靜態方式部署集群，如果節點變遷時，需要執行等命令手動配置集群，嚴重限制了集群自動故障恢復擴容縮容的能力。
kubernetes通過statefulset為zookeeper、etcd等這類有狀態的應用程序提供完善支持，statefulset具備以下特性：
為pod提供穩定的唯一的網絡標識
穩定值持久化存儲：通過pv/pvc來實現
啟動和停止pod保證有序：優雅的部署和伸縮性
本文闡述了如何在k8s集群上部署zookeeper和etcd有狀態服務，并結合ceph實現數據持久化。
二. 總結使用k8s的statefulset、storageclass、pv、pvc和ceph的rbd，能夠很好的支持zookeeper、etcd這樣的有狀態服務部署到kubernetes集群上。
k8s不會主動刪除已經創建的pv、pvc對象，防止出現誤刪。
如果用戶確定刪除pv、pvc對象，同時還需要手動刪除ceph段的rbd鏡像。
遇到的坑
storageclass中引用的ceph客戶端用戶，必須要有mon rw，rbd rwx權限。如果沒有mon write權限，會導致釋放rbd鎖失敗，無法將rbd鏡像掛載到其他的k8s worker節點。
zookeeper使用探針檢查zookeeper節點的健康狀態，如果節點不健康，k8s將刪除pod，并自動重建該pod，達到自動重啟zookeeper節點的目的。
因zookeeper 3.4版本的集群配置，是通過靜態加載文件zoo.cfg來實現的，所以當zookeeper節點pod ip變動后，需要重啟zookeeper集群中的所有節點。
etcd部署方式有待優化
本次試驗中使用靜態方式部署etcd集群，如果etcd節點變遷時，需要執行etcdctl member remove/add等命令手動配置etcd集群，嚴重限制了etcd集群自動故障恢復、擴容縮容的能力。因此，需要考慮對部署方式優化，改為使用DNS或者etcd descovery的動態方式部署etcd，才能讓etcd更好的運行在k8s上。
三. zookeeper集群部署 1. 下載鏡像docker pull gcr.mirrors.ustc.edu.cn/google_containers/kubernetes-zookeeper:1.0-3.4.10 docker tag gcr.mirrors.ustc.edu.cn/google_containers/kubernetes-zookeeper:1.0-3.4.10 172.16.18.100:5000/gcr.io/google_containers/kubernetes-zookeeper:1.0-3.4.10 docker push 172.16.18.100:5000/gcr.io/google_containers/kubernetes-zookeeper:1.0-3.4.102. 定義ceph secret
cat << EOF | kubectl create -f - apiVersion: v1 data: key: QVFBYy9ndGFRUno4QlJBQXMxTjR3WnlqN29PK3VrMzI1a05aZ3c9PQo= kind: Secret metadata: creationTimestamp: 2017-11-20T10:29:05Z name: ceph-secret namespace: default resourceVersion: "2954730" selfLink: /api/v1/namespaces/default/secrets/ceph-secret uid: a288ff74-cffffd-11e7-81cc-000c29f99475 type: kubernetes.io/rbd EOF3. 定義storageclass rbd存儲
cat << EOF | kubectl create -f - apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: ceph parameters: adminId: admin adminSecretName: ceph-secret adminSecretNamespace: default fsType: ext4 imageFormat: "2" imagefeatures: layering monitors: 172.16.13.223 pool: k8s userId: admin userSecretName: ceph-secret provisioner: kubernetes.io/rbd reclaimPolicy: Delete EOF4. 創建zookeeper集群
使用rbd存儲zookeeper節點數據
cat << EOF | kubectl create -f -
---
apiVersion: v1
kind: Service
metadata:
name: zk-hs
labels:
app: zk
spec:
ports:
- port: 2888
name: server
- port: 3888
name: leader-election
clusterIP: None
selector:
app: zk
---
apiVersion: v1
kind: Service
metadata:
name: zk-cs
labels:
app: zk
spec:
ports:
- port: 2181
name: client
selector:
app: zk
---
apiVersion: policy/v1beta1
kind: PodDisruptionBudget
metadata:
name: zk-pdb
spec:
selector:
matchLabels:
app: zk
maxUnavailable: 1
---
apiVersion: apps/v1beta2 # for versions before 1.8.0 use apps/v1beta1
kind: StatefulSet
metadata:
name: zk
spec:
selector:
matchLabels:
app: zk
serviceName: zk-hs
replicas: 3
updateStrategy:
type: RollingUpdate
podManagementPolicy: Parallel
template:
metadata:
labels:
app: zk
spec:
affinity:
podAntiAffinity:
requiredDuringSchedulingIgnoredDuringExecution:
- labelSelector:
matchExpressions:
- key: "app"
operator: In
values:
- zk
topologyKey: "kubernetes.io/hostname"
containers:
- name: kubernetes-zookeeper
imagePullPolicy: Always
image: "172.16.18.100:5000/gcr.io/google_containers/kubernetes-zookeeper:1.0-3.4.10"
ports:
- containerPort: 2181
name: client
- containerPort: 2888
name: server
- containerPort: 3888
name: leader-election
command:
- sh
- -c
- "start-zookeeper
--servers=3
--data_dir=/var/lib/zookeeper/data
--data_log_dir=/var/lib/zookeeper/data/log
--conf_dir=/opt/zookeeper/conf
--client_port=2181
--election_port=3888
--server_port=2888
--tick_time=2000
--init_limit=10
--sync_limit=5
--heap=512M
--max_client_cnxns=60
--snap_retain_count=3
--purge_interval=12
--max_session_timeout=40000
--min_session_timeout=4000
--log_level=INFO"
readinessProbe:
exec:
command:
- sh
- -c
- "zookeeper-ready 2181"
initialDelaySeconds: 10
timeoutSeconds: 5
livenessProbe:
exec:
command:
- sh
- -c
- "zookeeper-ready 2181"
initialDelaySeconds: 10
timeoutSeconds: 5
volumeMounts:
- name: datadir
mountPath: /var/lib/zookeeper
securityContext:
runAsUser: 1000
fsGroup: 1000
volumeClaimTemplates:
- metadata:
name: datadir
annotations:
volume.beta.kubernetes.io/storage-class: ceph
spec:
accessModes: [ "ReadWriteOnce" ]
resources:
requests:
storage: 1Gi
EOF
查看創建結果
[root@172 zookeeper]# kubectl get no NAME STATUS ROLES AGE VERSION 172.16.20.10 Ready50m v1.8.2 172.16.20.11 Ready 2h v1.8.2 172.16.20.12 Ready 1h v1.8.2 [root@172 zookeeper]# kubectl get po -owide NAME READY STATUS RESTARTS AGE IP NODE zk-0 1/1 Running 0 8m 192.168.5.162 172.16.20.10 zk-1 1/1 Running 0 1h 192.168.2.146 172.16.20.11 [root@172 zookeeper]# kubectl get pv,pvc NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pv/pvc-226cb8f0-d322-11e7-9581-000c29f99475 1Gi RWO Delete Bound default/datadir-zk-0 ceph 1h pv/pvc-22703ece-d322-11e7-9581-000c29f99475 1Gi RWO Delete Bound default/datadir-zk-1 ceph 1h NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE pvc/datadir-zk-0 Bound pvc-226cb8f0-d322-11e7-9581-000c29f99475 1Gi RWO ceph 1h pvc/datadir-zk-1 Bound pvc-22703ece-d322-11e7-9581-000c29f99475 1Gi RWO ceph 1h
zk-0 pod的rbd的鎖信息為
[root@ceph1 ceph]# rbd lock list kubernetes-dynamic-pvc-227b45e5-d322-11e7-90ab-000c29f99475 -p k8s --user admin There is 1 exclusive lock on this image. Locker ID Address client.24146 kubelet_lock_magic_172.16.20.10 172.16.20.10:0/16061523505. 測試pod遷移
嘗試將172.16.20.10節點設置為污點，讓zk-0 pod自動遷移到172.16.20.12
kubectl cordon 172.16.20.10 [root@172 zookeeper]# kubectl get no NAME STATUS ROLES AGE VERSION 172.16.20.10 Ready,SchedulingDisabled58m v1.8.2 172.16.20.11 Ready 2h v1.8.2 172.16.20.12 Ready 1h v1.8.2 kubectl delete po zk-0
觀察zk-0的遷移過程
[root@172 zookeeper]# kubectl get po -owide -w NAME READY STATUS RESTARTS AGE IP NODE zk-0 1/1 Running 0 14m 192.168.5.162 172.16.20.10 zk-1 1/1 Running 0 1h 192.168.2.146 172.16.20.11 zk-0 1/1 Terminating 0 16m 192.168.5.162 172.16.20.10 zk-0 0/1 Terminating 0 16m172.16.20.10 zk-0 0/1 Terminating 0 16m 172.16.20.10 zk-0 0/1 Terminating 0 16m 172.16.20.10 zk-0 0/1 Terminating 0 16m 172.16.20.10 zk-0 0/1 Terminating 0 16m 172.16.20.10 zk-0 0/1 Pending 0 0s zk-0 0/1 Pending 0 0s 172.16.20.12 zk-0 0/1 ContainerCreating 0 0s 172.16.20.12 zk-0 0/1 Running 0 3s 192.168.3.4 172.16.20.12
此時zk-0正常遷移到172.16.20.12
再查看rbd的鎖定信息
[root@ceph1 ceph]# rbd lock list kubernetes-dynamic-pvc-227b45e5-d322-11e7-90ab-000c29f99475 -p k8s --user admin There is 1 exclusive lock on this image. Locker ID Address client.24146 kubelet_lock_magic_172.16.20.10 172.16.20.10:0/1606152350 [root@ceph1 ceph]# rbd lock list kubernetes-dynamic-pvc-227b45e5-d322-11e7-90ab-000c29f99475 -p k8s --user admin There is 1 exclusive lock on this image. Locker ID Address client.24154 kubelet_lock_magic_172.16.20.12 172.16.20.12:0/3715989358
之前在另外一個ceph集群測試這個zk pod遷移的時候，總是報錯無法釋放lock，經分析應該是使用的ceph賬號沒有相應的權限，所以導致釋放lock失敗。記錄的報錯信息如下：
Nov 27 10:45:55 172 kubelet: W1127 10:45:55.551768 11556 rbd_util.go:471] rbd: no watchers on kubernetes-dynamic-pvc-f35a411e-d317-11e7-90ab-000c29f99475 Nov 27 10:45:55 172 kubelet: I1127 10:45:55.694126 11556 rbd_util.go:181] remove orphaned locker kubelet_lock_magic_172.16.20.12 from client client.171490: err exit status 13, output: 2017-11-27 10:45:55.570483 7fbdbe922d40 -1 did not load config file, using default settings. Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.600816 7fbdbe922d40 -1 Errors while parsing config file! Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.600824 7fbdbe922d40 -1 parse_file: cannot open /etc/ceph/ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.600825 7fbdbe922d40 -1 parse_file: cannot open ~/.ceph/ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.600825 7fbdbe922d40 -1 parse_file: cannot open ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.602492 7fbdbe922d40 -1 Errors while parsing config file! Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.602494 7fbdbe922d40 -1 parse_file: cannot open /etc/ceph/ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.602495 7fbdbe922d40 -1 parse_file: cannot open ~/.ceph/ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.602496 7fbdbe922d40 -1 parse_file: cannot open ceph.conf: (2) No such file or directory Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.651594 7fbdbe922d40 -1 auth: unable to find a keyring on /etc/ceph/ceph.client.k8s.keyring,/etc/ceph/ceph.keyring,/etc/ceph/keyring,/etc/ceph/keyring.bin,: (2) No such file or directory Nov 27 10:45:55 172 kubelet: rbd: releasing lock failed: (13) Permission denied Nov 27 10:45:55 172 kubelet: 2017-11-27 10:45:55.682470 7fbdbe922d40 -1 librbd: unable to blacklist client: (13) Permission denied
k8s rbd volume的實現代碼：
if lock {
// check if lock is already held for this host by matching lock_id and rbd lock id
if strings.Contains(output, lock_id) {
// this host already holds the lock, exit
glog.V(1).Infof("rbd: lock already held for %s", lock_id)
return nil
}
// clean up orphaned lock if no watcher on the image
used, statusErr := util.rbdStatus(&b)
if statusErr == nil && !used {
re := regexp.MustCompile("client.* " + kubeLockMagic + ".*")
locks := re.FindAllStringSubmatch(output, -1)
for _, v := range locks {
if len(v) > 0 {
lockInfo := strings.Split(v[0], " ")
if len(lockInfo) > 2 {
args := []string{"lock", "remove", b.Image, lockInfo[1], lockInfo[0], "--pool", b.Pool, "--id", b.Id, "-m", mon}
args = append(args, secret_opt...)
cmd, err = b.exec.Run("rbd", args...)
# 執行rbd lock remove命令時返回了錯誤信息
glog.Infof("remove orphaned locker %s from client %s: err %v, output: %s", lockInfo[1], lockInfo[0], err, string(cmd))
}
}
}
}
// hold a lock: rbd lock add
args := []string{"lock", "add", b.Image, lock_id, "--pool", b.Pool, "--id", b.Id, "-m", mon}
args = append(args, secret_opt...)
cmd, err = b.exec.Run("rbd", args...)
}
可以看到，rbd lock remove操作被拒絕了，原因是沒有權限rbd: releasing lock failed: (13) Permission denied。
6. 測試擴容zookeeper集群節點數從2個擴為3個。
集群節點數為2時，zoo.cfg的配置中定義了兩個實例
zookeeper@zk-0:/opt/zookeeper/conf$ cat zoo.cfg #This file was autogenerated DO NOT EDIT clientPort=2181 dataDir=/var/lib/zookeeper/data dataLogDir=/var/lib/zookeeper/data/log tickTime=2000 initLimit=10 syncLimit=5 maxClientCnxns=60 minSessionTimeout=4000 maxSessionTimeout=40000 autopurge.snapRetainCount=3 autopurge.purgeInteval=12 server.1=zk-0.zk-hs.default.svc.cluster.local:2888:3888 server.2=zk-1.zk-hs.default.svc.cluster.local:2888:3888
使用kubectl edit statefulset zk命令修改replicas=3，start-zookeeper --servers=3,
此時觀察pod的變化
[root@172 zookeeper]# kubectl get po -owide -w NAME READY STATUS RESTARTS AGE IP NODE zk-0 1/1 Running 0 1h 192.168.5.170 172.16.20.10 zk-1 1/1 Running 0 1h 192.168.3.12 172.16.20.12 zk-2 0/1 Pending 0 0szk-2 0/1 Pending 0 0s 172.16.20.11 zk-2 0/1 ContainerCreating 0 0s 172.16.20.11 zk-2 0/1 Running 0 1s 192.168.2.154 172.16.20.11 zk-2 1/1 Running 0 11s 192.168.2.154 172.16.20.11 zk-1 1/1 Terminating 0 1h 192.168.3.12 172.16.20.12 zk-1 0/1 Terminating 0 1h 172.16.20.12 zk-1 0/1 Terminating 0 1h 172.16.20.12 zk-1 0/1 Terminating 0 1h 172.16.20.12 zk-1 0/1 Terminating 0 1h 172.16.20.12 zk-1 0/1 Pending 0 0s zk-1 0/1 Pending 0 0s 172.16.20.12 zk-1 0/1 ContainerCreating 0 0s 172.16.20.12 zk-1 0/1 Running 0 2s 192.168.3.13 172.16.20.12 zk-1 1/1 Running 0 20s 192.168.3.13 172.16.20.12 zk-0 1/1 Terminating 0 1h 192.168.5.170 172.16.20.10 zk-0 0/1 Terminating 0 1h 172.16.20.10 zk-0 0/1 Terminating 0 1h 172.16.20.10 zk-0 0/1 Terminating 0 1h 172.16.20.10 zk-0 0/1 Terminating 0 1h 172.16.20.10 zk-0 0/1 Pending 0 0s zk-0 0/1 Pending 0 0s 172.16.20.10 zk-0 0/1 ContainerCreating 0 0s 172.16.20.10 zk-0 0/1 Running 0 2s 192.168.5.171 172.16.20.10 zk-0 1/1 Running 0 12s 192.168.5.171 172.16.20.10
可以看到zk-0/zk-1都重啟了，這樣可以加載新的zoo.cfg配置文件，保證集群正確配置。
新的zoo.cfg配置文件記錄了3個實例：
[root@172 ~]# kubectl exec zk-0 -- cat /opt/zookeeper/conf/zoo.cfg #This file was autogenerated DO NOT EDIT clientPort=2181 dataDir=/var/lib/zookeeper/data dataLogDir=/var/lib/zookeeper/data/log tickTime=2000 initLimit=10 syncLimit=5 maxClientCnxns=60 minSessionTimeout=4000 maxSessionTimeout=40000 autopurge.snapRetainCount=3 autopurge.purgeInteval=12 server.1=zk-0.zk-hs.default.svc.cluster.local:2888:3888 server.2=zk-1.zk-hs.default.svc.cluster.local:2888:3888 server.3=zk-2.zk-hs.default.svc.cluster.local:2888:38887. 測試縮容
縮容的時候，zk集群也自動重啟了所有的zk節點，縮容過程如下：
[root@172 ~]# kubectl get po -owide -w NAME READY STATUS RESTARTS AGE IP NODE zk-0 1/1 Running 0 5m 192.168.5.171 172.16.20.10 zk-1 1/1 Running 0 6m 192.168.3.13 172.16.20.12 zk-2 1/1 Running 0 7m 192.168.2.154 172.16.20.11 zk-2 1/1 Terminating 0 7m 192.168.2.154 172.16.20.11 zk-1 1/1 Terminating 0 7m 192.168.3.13 172.16.20.12 zk-2 0/1 Terminating 0 8m四. etcd集群部署 1. 創建etcd集群172.16.20.11 zk-1 0/1 Terminating 0 7m 172.16.20.12 zk-2 0/1 Terminating 0 8m 172.16.20.11 zk-1 0/1 Terminating 0 7m 172.16.20.12 zk-1 0/1 Terminating 0 7m 172.16.20.12 zk-1 0/1 Terminating 0 7m 172.16.20.12 zk-1 0/1 Pending 0 0s zk-1 0/1 Pending 0 0s 172.16.20.12 zk-1 0/1 ContainerCreating 0 0s 172.16.20.12 zk-1 0/1 Running 0 2s 192.168.3.14 172.16.20.12 zk-2 0/1 Terminating 0 8m 172.16.20.11 zk-2 0/1 Terminating 0 8m 172.16.20.11 zk-1 1/1 Running 0 19s 192.168.3.14 172.16.20.12 zk-0 1/1 Terminating 0 7m 192.168.5.171 172.16.20.10 zk-0 0/1 Terminating 0 7m 172.16.20.10 zk-0 0/1 Terminating 0 7m 172.16.20.10 zk-0 0/1 Terminating 0 7m 172.16.20.10 zk-0 0/1 Pending 0 0s zk-0 0/1 Pending 0 0s 172.16.20.10 zk-0 0/1 ContainerCreating 0 0s 172.16.20.10 zk-0 0/1 Running 0 3s 192.168.5.172 172.16.20.10 zk-0 1/1 Running 0 13s 192.168.5.172 172.16.20.10
cat << EOF | kubectl create -f -
apiVersion: v1
kind: Service
metadata:
name: "etcd"
annotations:
# Create endpoints also if the related pod isn"t ready
service.alpha.kubernetes.io/tolerate-unready-endpoints: "true"
spec:
ports:
- port: 2379
name: client
- port: 2380
name: peer
clusterIP: None
selector:
component: "etcd"
---
apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
name: "etcd"
labels:
component: "etcd"
spec:
serviceName: "etcd"
# changing replicas value will require a manual etcdctl member remove/add
# command (remove before decreasing and add after increasing)
replicas: 3
template:
metadata:
name: "etcd"
labels:
component: "etcd"
spec:
containers:
- name: "etcd"
image: "172.16.18.100:5000/quay.io/coreos/etcd:v3.2.3"
ports:
- containerPort: 2379
name: client
- containerPort: 2380
name: peer
env:
- name: CLUSTER_SIZE
value: "3"
- name: SET_NAME
value: "etcd"
volumeMounts:
- name: data
mountPath: /var/run/etcd
command:
- "/bin/sh"
- "-ecx"
- |
IP=$(hostname -i)
for i in $(seq 0 $((${CLUSTER_SIZE} - 1))); do
while true; do
echo "Waiting for ${SET_NAME}-${i}.${SET_NAME} to come up"
ping -W 1 -c 1 ${SET_NAME}-${i}.${SET_NAME}.default.svc.cluster.local > /dev/null && break
sleep 1s
done
done
PEERS=""
for i in $(seq 0 $((${CLUSTER_SIZE} - 1))); do
PEERS="${PEERS}${PEERS:+,}${SET_NAME}-${i}=http://${SET_NAME}-${i}.${SET_NAME}.default.svc.cluster.local:2380"
done
# start etcd. If cluster is already initialized the `--initial-*` options will be ignored.
exec etcd --name ${HOSTNAME}
--listen-peer-urls http://${IP}:2380
--listen-client-urls http://${IP}:2379,http://127.0.0.1:2379
--advertise-client-urls http://${HOSTNAME}.${SET_NAME}:2379
--initial-advertise-peer-urls http://${HOSTNAME}.${SET_NAME}:2380
--initial-cluster-token etcd-cluster-1
--initial-cluster ${PEERS}
--initial-cluster-state new
--data-dir /var/run/etcd/default.etcd
## We are using dynamic pv provisioning using the "standard" storage class so
## this resource can be directly deployed without changes to minikube (since
## minikube defines this class for its minikube hostpath provisioner). In
## production define your own way to use pv claims.
volumeClaimTemplates:
- metadata:
name: data
annotations:
volume.beta.kubernetes.io/storage-class: ceph
spec:
accessModes:
- "ReadWriteOnce"
resources:
requests:
storage: 1Gi
EOF
創建完成之后的po,pv,pvc清單如下：
[root@172 etcd]# kubectl get po -owide NAME READY STATUS RESTARTS AGE IP NODE etcd-0 1/1 Running 0 15m 192.168.5.174 172.16.20.10 etcd-1 1/1 Running 0 15m 192.168.3.16 172.16.20.12 etcd-2 1/1 Running 0 5s 192.168.5.176 172.16.20.102. 測試縮容
kubectl scale statefulset etcd --replicas=2 [root@172 ~]# kubectl get po -owide -w NAME READY STATUS RESTARTS AGE IP NODE etcd-0 1/1 Running 0 17m 192.168.5.174 172.16.20.10 etcd-1 1/1 Running 0 17m 192.168.3.16 172.16.20.12 etcd-2 1/1 Running 0 1m 192.168.5.176 172.16.20.10 etcd-2 1/1 Terminating 0 1m 192.168.5.176 172.16.20.10 etcd-2 0/1 Terminating 0 1m172.16.20.10
檢查集群健康
kubectl exec etcd-0 -- etcdctl cluster-health failed to check the health of member 42c8b94265b9b79a on http://etcd-2.etcd:2379: Get http://etcd-2.etcd:2379/health: dial tcp: lookup etcd-2.etcd on 10.96.0.10:53: no such host member 42c8b94265b9b79a is unreachable: [http://etcd-2.etcd:2379] are all unreachable member 9869f0647883a00d is healthy: got healthy result from http://etcd-1.etcd:2379 member c799a6ef06bc8c14 is healthy: got healthy result from http://etcd-0.etcd:2379 cluster is healthy
發現縮容后，etcd-2并沒有從etcd集群中自動刪除，可見這個etcd鏡像對自動擴容縮容的支持并不夠好。
我們手工刪除掉etcd-2
[root@172 etcd]# kubectl exec etcd-0 -- etcdctl member remove 42c8b94265b9b79a Removed member 42c8b94265b9b79a from cluster [root@172 etcd]# kubectl exec etcd-0 -- etcdctl cluster-health member 9869f0647883a00d is healthy: got healthy result from http://etcd-1.etcd:2379 member c799a6ef06bc8c14 is healthy: got healthy result from http://etcd-0.etcd:2379 cluster is healthy3. 測試擴容
從etcd.yaml的啟動腳本中可以看出，擴容時新啟動一個etcd pod時參數--initial-cluster-state new，該etcd鏡像并不支持動態擴容，可以考慮使用基于dns動態部署etcd集群的方式來修改啟動腳本，這樣才能支持etcd cluster動態擴容。
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