etcd 是基于 raft算法的分布式键值数据库，生来就为集群化而设计的，由于Raft算法在做决策时需要超半数节点的投票，所以etcd集群一般推荐奇数节点，如3、5或者7个节点构成一个集群。
member操作
现有3节点集群(存储已持久化)
一个节点宕机，重启后无法加入集群
1将节点关闭(副本数置为0)，并将数据删除
2删除崩溃节点
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| etcdctl --endpoints=172.16.176.179:2379 member remove <崩溃节点id>
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3添加 member 节点
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| etcdctl --endpoints=172.16.176.179:2379 member add etcd-0 --peer-urls=http://etcd-headless-0.apisix-etcd.svc.nbugs.local:2380
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4查询 member 节点列表信息
5启动节点
ETCD_INITIAL_CLUSTER_STATE 须设置为 existing
6节点出现Error: etcdserver: re-configuration failed due to not enough started members
7删除节点
8等待节点加入集群
报错处理
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2
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| Error: etcdserver: re-configuration failed due to not enough started members
member remove <崩溃节点id>
这个出现一般是节点初始化后无法加入集群，用命令删掉节点等待节点加入集群即可，不用删数据
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2
| Error: bad member ID arg (strconv.ParseUint: parsing "": invalid syntax), expecting ID in Hex
重新初始化节点
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2
| failed to publish local member to cluster through raft
重新初始化节点
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2
| member 2d9c4bf1e501bb91 has already been bootstrapped
重新初始化节点
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2
| discovery failed","error":"couldn't find local name \"etcd-1\" in the initial cluster configuration
重新初始化节点
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etcdctl命令
因为etcd配置了证书，所以所有的命令都要带上证书访问，如：
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| ETCDCTL_API=3 ./etcdctl --endpoints=https://0:2379,https://1:2379,https://2:2379 --cacert /etc/etcd/ssl/ca.pem --cert /etc/etcd/ssl/etcd.pem --key /etc/etcd/ssl/etcd-key.pem endpoint status -w=table
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- version: 查看版本
- member list: 查看节点
- endpoint status: 节点状态，leader 情况
- endpoint health: 健康状态与耗时
- set app demo: 写入
- get app: 获取
- update app demo1:更新
- rm app: 删除
- mkdir demo 创建文件夹
- rmdir dir 删除文件夹
- backup 备份
- watch key 监测 key 变化
- get / –prefix –keys-only: 查看所有 key