### zookeeper

- PodDisruptionBudget：

k8s可以为每个应用程序创建 `PodDisruptionBudget` 对象（PDB）。PDB 将限制在同一时间因资源干扰导致的复制应用程序中宕机的 pod 数量。

可以通过两个参数来配置PodDisruptionBudget：

```a
MinAvailable：表示最小可用Pod数，表示应用Pod集群处于运行状态的最小Pod数量，或者是运行状态的Pod数同总Pod数的最小百分比

MaxUnavailable：表示最大不可用Pod数，表示应用Pod集群处于不可用状态的最大Pod数，或者是不可用状态的Pod数同总Pod数的最大百分比
```

需要注意的是，`MinAvailable`参数和`MaxUnavailable`参数只能同时配置一个。

- 部署：

```bash
kubectl apply -f ./

kubectl get svc -n public-service

NAME         TYPE        CLUSTER-IP      EXTERNAL-IP   PORT(S)             AGE
kubernetes   ClusterIP   10.96.0.1       <none>        443/TCP             25d
zk-cs        ClusterIP   10.107.243.77   <none>        2181/TCP            29s
zk-hs        ClusterIP   None            <none>        2888/TCP,3888/TCP   29s

kubectl get pod -n public-service

NAME   READY   STATUS    RESTARTS   AGE
zk-0   1/1     Running   0          92s
zk-1   1/1     Running   0          73s
zk-2   1/1     Running   0          48s
```

- 查看zookeeper配置：

```bash
kubectl exec zk-0 -n public-service -- cat /opt/zookeeper/conf/zoo.cfg

#This file was autogenerated by k8szk DO NOT EDIT
clientPort=2181
dataDir=/var/lib/zookeeper/data
dataLogDir=/var/lib/zookeeper/log
tickTime=2000
initLimit=10
syncLimit=2000
maxClientCnxns=60
minSessionTimeout= 4000
maxSessionTimeout= 40000
autopurge.snapRetainCount=3
autopurge.purgeInteval=1
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:2888:3888
```

- 查看集群状态：

```bash
kubectl exec zk-0 -n public-service -- zkServer.sh status

ZooKeeper JMX enabled by default
Using config: /usr/bin/../etc/zookeeper/zoo.cfg
Mode: follower


kubectl exec zk-1 -n public-service -- zkServer.sh status

ZooKeeper JMX enabled by default
Using config: /usr/bin/../etc/zookeeper/zoo.cfg
Mode: leader

kubectl exec zk-2 -n public-service -- zkServer.sh status

ZooKeeper JMX enabled by default
Using config: /usr/bin/../etc/zookeeper/zoo.cfg
Mode: follower
```

可以看到：zk-1 是集群leader，zk-0 和 zk-2 是集群follower。

```bash
kubectl exec zk-0 -n public-service -- cat /var/lib/zookeeper/data/myid
1

kubectl exec zk-1 -n public-service -- cat /var/lib/zookeeper/data/myid
2

kubectl exec zk-2 -n public-service -- cat /var/lib/zookeeper/data/myid
3
```

- 集群测试：

```bash
kubectl exec zk-0 -n public-service -- zkCli.sh create /hello world

WATCHER::

WatchedEvent state:SyncConnected type:None path:null
Created /hello

kubectl exec zk-1 -n public-service -- zkCli.sh get /hello

WATCHER::

WatchedEvent state:SyncConnected type:None path:null
cZxid = 0x100000002
world
ctime = Sat Jun 06 07:11:23 UTC 2020
mZxid = 0x100000002
mtime = Sat Jun 06 07:11:23 UTC 2020
pZxid = 0x100000002
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0

kubectl exec zk-2 -n public-service -- zkCli.sh get /hello

WATCHER::

WatchedEvent state:SyncConnected type:None path:null
world
cZxid = 0x100000002
ctime = Sat Jun 06 07:11:23 UTC 2020
mZxid = 0x100000002
mtime = Sat Jun 06 07:11:23 UTC 2020
pZxid = 0x100000002
cversion = 0
dataVersion = 0
aclVersion = 0
ephemeralOwner = 0x0
dataLength = 5
numChildren = 0
```

在 zk-0 创建的数据在集群中所有的服务上都是可用的。k8s部署zookeeper集群完成。

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