了解etcd

1. etcd流程
   

   etcd集群是一个分布式系统，使用Raft协议来维护集群内部各个节点状态的一致性。
   主机状态leader，follower、candidate
   当集群初始化时候，每个节点都是follower角色
   通过心跳与其他节点同步数据
   当follower在一定时间内没有收到来自主节点的心跳，将会自己角色改变为candidate，并发起一次选主投票
   配置etcd集群，建议尽可能满足奇数个节点

2. 部署单节点etcd集群

   [root@vms51 ~]# yum isntall etcd -y
   [root@vms51 ~]# vim /etc/etcd/etcd.conf
     [Member]
     ETCD_DATA_DIR="/var/lib/etcd/default.etcd"
     ETCD_LISTEN_PEER_URLS="http://192.168.108.51:2380,http://localhost:2380"
     ETCD_LISTEN_CLIENT_URLS="http://192.168.108.51:2379,http://localhost:2379"
     ETCD_NAME="default"
     #[Clustering]
     ETCD_ADVERTISE_CLIENT_URLS="http://localhost:2379"
   [root@vms51 ~]# systemctl restart etcd
   [root@vms51 ~]# etcdctl member list
   [root@vms51 ~]# etcdctl cluster-health
   [root@vms51 ~]# etcdctl ls /
   [root@vms51 ~]# etcdctl mkdir /aa
   [root@vms51 ~]# etcdctl ls /
   /aa

3. 部署etcd多节点集群

   三节点都要装 yum isntall etcd -y
   
   [root@vms51 ~]# cat /etc/etcd/etcd.conf 
   ETCD_DATA_DIR="/var/lib/etcd/cluster.etcd"
   ETCD_LISTEN_PEER_URLS="http://192.168.108.51:2380,http://localhost:2380"
   ETCD_LISTEN_CLIENT_URLS="http://192.168.108.51:2379,http://localhost:2379"
   ETCD_NAME="etcd-51"
   ETCD_INITIAL_ADVERTISE_PEER_URLS="http://192.168.108.51:2380"
   ETCD_ADVERTISE_CLIENT_URLS="http://192.168.108.51:2379,http://localhost:2379"
   ETCD_INITIAL_CLUSTER="etcd-51=http://192.168.108.51:2380,etcd-52=http://192.168.108.52:2380,etcd-53=http://192.168.108.53:2380"
   ETCD_INITIAL_CLUSTER_TOKEN="etcd-cluster"
   ETCD_INITIAL_CLUSTER_STATE="new"
   
   [root@vms52 ~]# cat /etc/etcd/etcd.conf 
   ETCD_DATA_DIR="/var/lib/etcd/cluster.etcd"
   ETCD_LISTEN_PEER_URLS="http://192.168.108.52:2380,http://localhost:2380"
   ETCD_LISTEN_CLIENT_URLS="http://192.168.108.52:2379,http://localhost:2379"
   ETCD_NAME="etcd-52"
   ETCD_INITIAL_ADVERTISE_PEER_URLS="http://192.168.108.52:2380"
   ETCD_ADVERTISE_CLIENT_URLS="http://192.168.108.52:2379,http://localhost:2379"
   ETCD_INITIAL_CLUSTER="etcd-51=http://192.168.108.51:2380,etcd-52=http://192.168.108.52:2380,etcd-53=http://192.168.108.53:2380"
   ETCD_INITIAL_CLUSTER_TOKEN="etcd-cluster"
   ETCD_INITIAL_CLUSTER_STATE="new"
   
   [root@vms53 ~]# cat /etc/etcd/etcd.conf 
   ETCD_DATA_DIR="/var/lib/etcd/cluster.etcd"
   ETCD_LISTEN_PEER_URLS="http://192.168.108.53:2380,http://localhost:2380"
   ETCD_LISTEN_CLIENT_URLS="http://192.168.108.53:2379,http://localhost:2379"
   ETCD_NAME="etcd-53"
   ETCD_INITIAL_ADVERTISE_PEER_URLS="http://192.168.108.53:2380"
   ETCD_ADVERTISE_CLIENT_URLS="http://192.168.108.53:2379,http://localhost:2379"
   ETCD_INITIAL_CLUSTER="etcd-51=http://192.168.108.51:2380,etcd-52=http://192.168.108.52:2380,etcd-53=http://192.168.108.53:2380"
   ETCD_INITIAL_CLUSTER_TOKEN="etcd-cluster"
   ETCD_INITIAL_CLUSTER_STATE="new"
   
   systemctl restart etcd
   etcdctl cluster-health
   etcdctl member list
   
   

   [root@vms51 ~]# etcdctl ls /
   [root@vms51 ~]# etcdctl mkdir /aa
   [root@vms51 ~]# etcdctl ls /
   /aa
   
   数据会在集群内的三个节点实时同步！

4. 参数的意义

   ETCD_NAME 节点名称，默认为default
   ETCD_DATA_DIR 服务运行数据保存路径
   ETCD_LISTEN_PEER_URLS 监听同伴通讯地址，比如http://ip:2380，如果有多个，使用逗号分隔。需要所有节点都能狗访问，所以不要使用localhost！
   ETCD_LISTEN_CLIENT_URLS 监听的客户端服务地址
   ETCD_ADVERTISE_CLIENT_URLS 对外公告的该节点客户端监听地址，这个值会告诉集群中其他节点。
   ETCD_INITIAL_ADVERTISE_PEER_URLS 对外公告的该节点同伴监听地址，这个值会告诉集群中其他节点。
   ETCD_INITIAL_CLUSTER 集群中所有节点的信息
   ETCD_INITIAL_CLUSTER_STATE 新建集群的时候，这个值为new，假如加入已经存在的集群，这个值为existing。
   ETCD_INITIAL_CLUSTER_TOKEN 集群的ID，多个集群的时候，每个集群的ID必须保持唯一。
   etcdctl member add etcd-54 http://192.168.108.54:2380

5. 版本

   etcd有两个版本，2和3，不做配置，默认为,2版本
   export ETCDCTL_API=3 设置为3版本
   做快照必须在版本3上做
   集群内节点的版本必须一致，否则看不到数据

6. 添加节点

   添加新节点需要在版本2下操作，版本3会报错
   [root@vms54 ~]# yum install etcd -y
   
   [root@vms54 ~]# cat /etc/etcd/etcd.conf 
   ETCD_DATA_DIR="/var/lib/etcd/cluster.etcd"
   ETCD_LISTEN_PEER_URLS="http://192.168.108.54:2380,http://localhost:2380"
   ETCD_LISTEN_CLIENT_URLS="http://192.168.108.54:2379,http://localhost:2379"
   ETCD_NAME="etcd-54"
   ETCD_INITIAL_ADVERTISE_PEER_URLS="http://192.168.108.54:2380"
   ETCD_ADVERTISE_CLIENT_URLS="http://192.168.108.54:2379,http://localhost:2379"
   ETCD_INITIAL_CLUSTER="etcd-51=http://192.168.108.51:2380,etcd-52=http://192.168.108.52:2380,etcd-53=http://192.168.108.53:2380,etcd-54=http://192.168.108.54:2380"
   ETCD_INITIAL_CLUSTER_TOKEN="etcd-cluster"
   ETCD_INITIAL_CLUSTER_STATE="existing"
   
   [root@vms51 ~]# etcdctl member add etcd-54 http://192.168.108.54:2380 #在leader节点上添加
   Added member named etcd-54 with ID 16407f9d3e09c96 to cluster
   ETCD_NAME="etcd-54"
   ETCD_INITIAL_CLUSTER="etcd-54=http://192.168.108.54:2380,etcd-53=http://192.168.108.53:2380,etcd-51=http://192.168.108.51:2380,etcd-52=http://192.168.108.52:2380"
   ETCD_INITIAL_CLUSTER_STATE="existing"
   
   [root@vms51 ~]# etcdctl member list
   16407f9d3e09c96: name=etcd-54 peerURLs=http://192.168.108.54:2380 clientURLs=http://192.168.108.54:2379,http://localhost:2379 isLeader=false
   cd338f95176e7eb5: name=etcd-53 peerURLs=http://192.168.108.53:2380 clientURLs=http://192.168.108.53:2379,http://localhost:2379 isLeader=false
   d13555f74ecbefa7: name=etcd-51 peerURLs=http://192.168.108.51:2380 clientURLs=http://192.168.108.51:2379,http://localhost:2379 isLeader=true
   f709fac2d2871b31: name=etcd-52 peerURLs=http://192.168.108.52:2380 clientURLs=http://192.168.108.52:2379,http://localhost:2379 isLeader=false
   
   [root@vms54 ~]# systemctl start etcd