[docker] 使用docker搭建etcd集群

kubernetes使用etcd做配置中心，要对它加深一些了解。

etcd is a strongly consistent, distributed key-value store that provides a reliable way to store data that needs to be accessed by a distributed system or cluster of machines. It gracefully handles leader elections during network partitions and can tolerate machine failure, even in the leader node.

1. 下载etcd docker
   发布仓库见：https://github.com/etcd-io/etcd/releases

$ docker pull quay.io/coreos/etcd

2. 编辑etcd-compose.yml
   推荐养成用compose管理container的习惯

$ cat etcd-compose.yml
version: '3'
services:
  etcd-node1:
    image: "quay.io/coreos/etcd"
    container_name: "etcd-node1"
    ports:
      - "12379:2379"
      - "12380:2380"
    command: 'etcd -name etcd-node1 -advertise-client-urls http://0.0.0.0:2379 -listen-client-urls http://0.0.0.0:2379 -listen-peer-urls http://0.0.0.0:2380 -initial-cluster-token etcd-cluster -initial-cluster "etcd-node1=http://etcd-node1:2380,etcd-node2=http://etcd-node2:2380,etcd-node3=http://etcd-node3:2380" -initial-cluster-state new'
    networks:
      - "etcd"

  etcd-node2:
    image: "quay.io/coreos/etcd"
    container_name: "etcd-node2"
    ports:
      - "22379:2379"
      - "22380:2380"
    command: 'etcd -name etcd-node2 -advertise-client-urls http://0.0.0.0:2379 -listen-client-urls http://0.0.0.0:2379 -listen-peer-urls http://0.0.0.0:2380 -initial-cluster-token etcd-cluster -initial-cluster "etcd-node1=http://etcd-node1:2380,etcd-node2=http://etcd-node2:2380,etcd-node3=http://etcd-node3:2380" -initial-cluster-state new'
    networks:
      - "etcd"

  etcd-node3:
    image: "quay.io/coreos/etcd"
    container_name: "etcd-node3"
    ports:
      - "32379:2379"
      - "32380:2380"
    command: 'etcd -name etcd-node3 -advertise-client-urls http://0.0.0.0:2379 -listen-client-urls http://0.0.0.0:2379 -listen-peer-urls http://0.0.0.0:2380 -initial-cluster-token etcd-cluster -initial-cluster "etcd-node1=http://etcd-node1:2380,etcd-node2=http://etcd-node2:2380,etcd-node3=http://etcd-node3:2380" -initial-cluster-state new'
    networks:
      - "etcd"

networks:
  etcd:

3.启动docker-compose

$ docker-compose -f etcd-compose.yml up -d

4.检查容器状态查询节点成员

$ docker-compose -f etcd-compose.yml ps                                                                                                                                        
   Name                 Command               State                        Ports
------------------------------------------------------------------------------------------------------
etcd-node1   etcd -name etcd-node1 -adv ...   Up      0.0.0.0:12379->2379/tcp, 0.0.0.0:12380->2380/tcp
etcd-node2   etcd -name etcd-node2 -adv ...   Up      0.0.0.0:22379->2379/tcp, 0.0.0.0:22380->2380/tcp
etcd-node3   etcd -name etcd-node3 -adv ...   Up      0.0.0.0:32379->2379/tcp, 0.0.0.0:32380->2380/tcp

# 查询每台的成员，结果是一致的
# curl http://127.0.0.1:12379/v2/members | json_pp
# curl http://127.0.0.1:22379/v2/members | json_pp
# curl http://127.0.0.1:32379/v2/members | json_pp
{
   "members" : [
      {
         "id" : "5b926f852fa1811",
         "peerURLs" : [
            "http://etcd-node1:2380"
         ],
         "clientURLs" : [
            "http://0.0.0.0:2379"
         ],
         "name" : "etcd-node1"
      },
      {
         "peerURLs" : [
            "http://etcd-node2:2380"
         ],
         "clientURLs" : [
            "http://0.0.0.0:2379"
         ],
         "name" : "etcd-node2",
         "id" : "9b3cd975d37c44ce"
      },
      {
         "id" : "9e13ad3ed0f8a26b",
         "peerURLs" : [
            "http://etcd-node3:2380"
         ],
         "clientURLs" : [
            "http://0.0.0.0:2379"
         ],
         "name" : "etcd-node3"
      }
   ]
}

5.销毁测试环境

$ docker-compose -f etcd-compose.yml down
Stopping etcd-node2 ... done
Stopping etcd-node1 ... done
Stopping etcd-node3 ... done
Removing etcd-node2 ... done
Removing etcd-node1 ... done
Removing etcd-node3 ... done
Removing network docker-compose_etcd