上篇文章etcd 入门 中已经介绍了etcd基本功能，单节点服务的安装和使用。
本文将介绍etcd 分布式多节点的安装、配置和使用。
由于资源限制，本文以单机多节点服务为例进行阐述。
在实际应用场景中，为了高可用和容灾，是需要多机器安装的。
1.多节点服务集群搭建
操作系统使用的 centos 6.8。
默认情况下，端口2379用于提供HTTP API服务，端口2380用于节点间通信。
在单机情况下，多节点服务需要使用不同端口。
三节点集群信息如下：
| name | ip | port |
|---|---|---|
| etcd-01 | 127.0.0.1 | 2379,2380 |
| etcd-02 | 127.0.0.1 | 2479,2480 |
| etcd-03 | 127.0.0.1 | 2579,2580 |
启动节点1
定义启动脚本start_etcd1.sh
TOKEN=token-01
CLUSTER_STATE=new
NAME_1=etcd-01
NAME_2=etcd-02
NAME_3=etcd-03
HOST_1=127.0.0.1
HOST_2=127.0.0.1
HOST_3=127.0.0.1
PORT_API_1=2379
PORT_PEER_1=2380
PORT_API_2=2479
PORT_PEER_2=2480
PORT_API_3=2579
PORT_PEER_3=2580
CLUSTER=${NAME_1}=http://${HOST_1}:${PORT_PEER_1},${NAME_2}=http://${HOST_2}:${PORT_PEER_2},${NAME_3}=http://${HOST_3}:${PORT_PEER_3}
# For every machine
THIS_NAME=${NAME_1}
THIS_IP=${HOST_1}
THIS_PORT_API=${PORT_API_1}
THIS_PORT_PEER=${PORT_PEER_1}
./etcd --data-dir=data.${THIS_NAME} --name ${THIS_NAME}
--initial-advertise-peer-urls http://${THIS_IP}:${THIS_PORT_PEER} --listen-peer-urls http://${THIS_IP}:${THIS_PORT_PEER}
--advertise-client-urls http://${THIS_IP}:${THIS_PORT_API} --listen-client-urls http://${THIS_IP}:${THIS_PORT_API}
--initial-cluster ${CLUSTER}
--initial-cluster-state ${CLUSTER_STATE} --initial-cluster-token ${TOKEN}
启动
bash start_etcd2.sh
启动节点2
定义启动脚本start_etcd2.sh,
只需将启动脚本start_etcd1.sh中的配置项修改：
THIS_NAME=${NAME_2}
THIS_IP=${HOST_2}
THIS_PORT_API=${PORT_API_2}
THIS_PORT_PEER=${PORT_PEER_2}
启动
bash start_etcd2.sh
启动节点3
定义启动脚本start_etcd3.sh，
只需将启动脚本start_etcd1.sh中的配置项修改：
THIS_NAME=${NAME_3}
THIS_IP=${HOST_3}
THIS_PORT_API=${PORT_API_3}
THIS_PORT_PEER=${PORT_PEER_3}
启动
bash start_etcd3.sh
2.使用
查看节点信息
export ETCDCTL_API=3
HOST_1=127.0.0.1
HOST_2=127.0.0.1
HOST_3=127.0.0.1
PORT_API_1=2379
PORT_API_2=2479
PORT_API_3=2579
ENDPOINTS=$HOST_1:${PORT_API_1},$HOST_2:${PORT_API_2},$HOST_3:${PORT_API_3}
./etcdctl --endpoints=$ENDPOINTS member list
$ ./etcdctl --endpoints=$ENDPOINTS member list
264ae6bc59e99892, started, etcd-01, http://127.0.0.1:2380, http://127.0.0.1:2379, false
dbafe5ad6b652eda, started, etcd-02, http://127.0.0.1:2480, http://127.0.0.1:2479, false
f570ae41f524bdcb, started, etcd-03, http://127.0.0.1:2580, http://127.0.0.1:2579, false
或者
$ ./etcdctl --endpoints=$ENDPOINTS --write-out=table member list
+------------------+---------+---------+-----------------------+-----------------------+------------+
| ID | STATUS | NAME | PEER ADDRS | CLIENT ADDRS | IS LEARNER |
+------------------+---------+---------+-----------------------+-----------------------+------------+
| 264ae6bc59e99892 | started | etcd-01 | http://127.0.0.1:2380 | http://127.0.0.1:2379 | false |
| dbafe5ad6b652eda | started | etcd-02 | http://127.0.0.1:2480 | http://127.0.0.1:2479 | false |
| f570ae41f524bdcb | started | etcd-03 | http://127.0.0.1:2580 | http://127.0.0.1:2579 | false |
集群状态
$ ./etcdctl --endpoints=$ENDPOINTS endpoint status
127.0.0.1:2379, 264ae6bc59e99892, 3.4.13, 20 kB, false, false, 8, 10, 10,
127.0.0.1:2479, dbafe5ad6b652eda, 3.4.13, 33 kB, true, false, 8, 10, 10,
127.0.0.1:2579, f570ae41f524bdcb, 3.4.13, 20 kB, false, false, 8, 10, 10,
$ ./etcdctl --endpoints=$ENDPOINTS --write-out=table endpoint status
+----------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| ENDPOINT | ID | VERSION | DB SIZE | IS LEADER | IS LEARNER | RAFT TERM | RAFT INDEX | RAFT APPLIED INDEX | ERRORS |
+----------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
| 127.0.0.1:2379 | 264ae6bc59e99892 | 3.4.13 | 20 kB | false | false | 8 | 10 | 10 | |
| 127.0.0.1:2479 | dbafe5ad6b652eda | 3.4.13 | 33 kB | true | false | 8 | 10 | 10 | |
| 127.0.0.1:2579 | f570ae41f524bdcb | 3.4.13 | 20 kB | false | false | 8 | 10 | 10 | |
+----------------+------------------+---------+---------+-----------+------------+-----------+------------+--------------------+--------+
可以看到，127.0.0.1:2479 这个节点是leader。
查看节点健康状况
$ ./etcdctl --endpoints=$ENDPOINTS endpoint health
127.0.0.1:2379 is healthy: successfully committed proposal: took = 5.843376ms
127.0.0.1:2479 is healthy: successfully committed proposal: took = 4.92724ms
127.0.0.1:2579 is healthy: successfully committed proposal: took = 7.661623ms
$ ./etcdctl --endpoints=$ENDPOINTS --write-out=table endpoint health
+----------------+--------+------------+-------+
| ENDPOINT | HEALTH | TOOK | ERROR |
+----------------+--------+------------+-------+
| 127.0.0.1:2379 | true | 8.470348ms | |
| 127.0.0.1:2479 | true | 4.540441ms | |
| 127.0.0.1:2579 | true | 8.666543ms | |
+----------------+--------+------------+-------+
键值对 读写
$ ./etcdctl --endpoints=$ENDPOINTS put foo "Hello World"
OK
$ ./etcdctl --endpoints=$ENDPOINTS get foo
foo
Hello World
分布式锁
在终端1中获取锁
$ ./etcdctl --endpoints=$ENDPOINTS lock mutex1
mutex1/3dcb7516bf48a904
在终端2中获取同一把锁，会被卡住
$ ./etcdctl --endpoints=$ENDPOINTS lock mutex1
此时，停止终端1的操作，释放锁，终端2才可以获取到锁:
$ ./etcdctl --endpoints=$ENDPOINTS lock mutex1
mutex1/3dcb7516bf48a907