etcd 命令含义
`--name`
etcd集群中的节点名，这里可以随意，可区分且不重复就行
`--listen-peer-urls`
监听的用于节点之间通信的url，可监听多个，集群内部将通过这些url进行数据交互(如选举，数据同步等)
`--initial-advertise-peer-urls`
建议用于节点之间通信的url，节点间将以该值进行通信。
`--listen-client-urls`
监听的用于客户端通信的url,同样可以监听多个。
`--advertise-client-urls`
建议使用的客户端通信url,该值用于etcd代理或etcd成员与etcd节点通信。
`--initial-cluster-token etcd-cluster-1`
节点的token值，设置该值后集群将生成唯一id,并为每个节点也生成唯一id,当使用相同配置文件再启动一个集群时，只要该token值不一样，etcd集群就不会相互影响。
-`-initial-cluster`
也就是集群中所有的initial-advertise-peer-urls 的合集
`--initial-cluster-state new`
新建集群的标志，初始化状态使用 new，建立之后改此值为 existing
ETCD安装配置
1.部署架构
192.168.108.128 节点1
192.168.108.129 节点2
192.168.108.130 节点3
2.解压安装：
$ tar -zxvf etcd-v3.2.6-linux-amd64.tar.gz -C /opt/
$ cd /opt
$ mv etcd-v3.2.6-linux-amd64 etcd-v3.2.6
# 创建etcd配置文件目录
$ mkdir /etc/etcd
3.创建etcd配置文件：
$ vi /etc/etcd/conf.yml
节点1，添加如下内容：
name: etcd-1
data-dir: /opt/etcd-v3.2.6/data
listen-client-urls: http://192.168.108.128:2379,http://127.0.0.1:2379
advertise-client-urls: http://192.168.108.128:2379,http://127.0.0.1:2379
listen-peer-urls: http://192.168.108.128:2380
initial-advertise-peer-urls: http://192.168.108.128:2380
initial-cluster: etcd-1=http://192.168.108.128:2380,etcd-2=http://192.168.108.129:2380,etcd-3=http://192.168.108.130:2380
initial-cluster-token: etcd-cluster-token
initial-cluster-state: new
节点2，添加如下内容：
name: etcd-2
data-dir: /opt/etcd-v3.2.6/data
listen-client-urls: http://192.168.108.129:2379,http://127.0.0.1:2379
advertise-client-urls: http://192.168.108.129:2379,http://127.0.0.1:2379
listen-peer-urls: http://192.168.108.129:2380
initial-advertise-peer-urls: http://192.168.108.129:2380
initial-cluster: etcd-1=http://192.168.108.128:2380,etcd-2=http://192.168.108.129:2380,etcd-3=http://192.168.108.130:2380
initial-cluster-token: etcd-cluster-token
initial-cluster-state: new
节点3，添加如下内容：
name: etcd-3
data-dir: /opt/etcd-v3.2.6/data
listen-client-urls: http://192.168.108.130:2379,http://127.0.0.1:2379
advertise-client-urls: http://192.168.108.130:2379,http://127.0.0.1:2379
listen-peer-urls: http://192.168.108.130:2380
initial-advertise-peer-urls: http://192.168.108.130:2380
initial-cluster: etcd-1=http://192.168.108.128:2380,etcd-2=http://192.168.108.129:2380,etcd-3=http://192.168.108.130:2380
initial-cluster-token: etcd-cluster-token
initial-cluster-state: new
4.更新etcd系统默认配置：
当前使用的是etcd v3版本，系统默认的是v2，通过下面命令修改配置。
$ vi /etc/profile
在文件末尾追加：
export ETCDCTL_API=3
使文件生效：
$ source /etc/profile
ETCD命令
$ cd /opt/etcd-v3.2.6
1.创建etcd配置文件：
$ ./etcdctl version
etcdctl version: 3.2.6
API version: 3.2
2.启动命令：
$ ./etcd --config-file=/etc/etcd/conf.yml
3.查看集群成员信息：
$ ./etcdctl member list
2618ce5cd761aa8e: name=etcd-3 peerURLs=http://192.168.108.130:2380 clientURLs=http://127.0.0.1:2379,http://192.168.108.130:2379 isLeader=false
9c359d48a2f34938: name=etcd-1 peerURLs=http://192.168.108.128:2380 clientURLs=http://127.0.0.1:2379,http://192.168.108.128:2379 isLeader=false
f3c45714407d68f3: name=etcd-2 peerURLs=http://192.168.108.129:2380 clientURLs=http://127.0.0.1:2379,http://192.168.108.129:2379 isLeader=true
4.查看集群状态（Leader节点）：
$ ./etcdctl cluster-health
member 2618ce5cd761aa8e is healthy: got healthy result from http://127.0.0.1:2379
member 9c359d48a2f34938 is healthy: got healthy result from http://127.0.0.1:2379
member f3c45714407d68f3 is healthy: got healthy result from http://127.0.0.1:2379
cluster is healthy
ECTD读写操作
基于HTTP协议的API使用起来比较简单，这里主要通过etcdctl和curl两种方式来做简单介绍。
1.下面通过给message key设置Hello值示例：
$ ./etcdctl set /message Hello
Hello
$ curl -X PUT http://127.0.0.1:2379/v2/keys/message -d value="Hello"
{"action":"set","node":{"key":"/message","value":"Hello","modifiedIndex":4,"createdIndex":4}}
2.读取message的值：
$ ./etcdctl get /message
Hello
$ curl http://127.0.0.1:2379/v2/keys/message
{"action":"get","node":{"key":"/message","value":"Hello","modifiedIndex":9,"createdIndex":9}}
3.删除message key：
$ ./etcdctl rm /message
$ curl -X DELETE http://127.0.0.1:2379/v2/keys/message
{"action":"delete","node":{"key":"/message","modifiedIndex":10,"createdIndex":9},"prevNode":{"key":"/message","value":"Hello","modifiedIndex":9,"createdIndex":9}}
说明：因为是集群，所以message在其中一个节点创建后，在集群中的任何节点都可以查询到。
配置ETCD为启动服务
1.编辑/usr/lib/systemd/system/etcd.service，添加下面内容：
[Unit]
Description=Etcd Server
After=network.target
After=network-online.target
Wants=network-online.target
[Service]
Type=notify
WorkingDirectory=/opt/etcd-v3.2.6/
# User=etcd
ExecStart=/opt/etcd-v3.2.6/etcd --config-file=/etc/etcd/conf.yml
Restart=on-failure
LimitNOFILE=65536
[Install]
WantedBy=multi-user.target
2.更新启动：
systemctl daemon-reload
systemctl enable etcd
systemctl start etcd
systemctl restart etcd
systemctl status etcd.service -l