简介

etcd是CoreOS团队于2013年6月发起的开源项目，它的目标是构建一个高可用的分布式键值(key-value)数据库。etcd内部采用raft协议作为一致性算法，etcd基于Go语言实现。

etcd作为服务发现系统，有以下的特点

• 简单：安装配置简单，而且提供了HTTP API进行交互，使用也很简单
• 安全：支持SSL证书验证
• 快速：根据官方提供的benchmark数据，单实例支持每秒2k+读操作
• 可靠：采用raft算法，实现分布式系统数据的可用性和一致性
• etcd项目地址：https://github.com/coreos/etcd/

构建镜像

1.创建dockersfile$ sudo touch Dockerfile
2.$ sudo vim Dockerfile编辑Dockerfile文件,写入内容如下:

FROM alpine:latest

ADD etcd /usr/local/bin/
ADD etcdctl /usr/local/bin/
RUN mkdir -p /var/etcd/
RUN mkdir -p /var/lib/etcd/

# Alpine Linux doesn't use pam, which means that there is no /etc/nsswitch.conf,
# but Golang relies on /etc/nsswitch.conf to check the order of DNS resolving
# (see https://github.com/golang/go/commit/9dee7771f561cf6aee081c0af6658cc81fac3918)
# To fix this we just create /etc/nsswitch.conf and add the following line:
RUN echo 'hosts: files mdns4_minimal [NOTFOUND=return] dns mdns4' >> /etc/nsswitch.conf

EXPOSE 2379 2380

# Define default command.
CMD ["/usr/local/bin/etcd"]

3.下载etcd Releases $ wget https://github.com/etcd-io/etcd/releases/download/v3.3.10/etcd-v3.3.10-linux-amd64.tar.gz
4.解压文件:$ tar -zxvf etcd-v3.3.10-linux-amd64.tar.gz
5.将etcd和etcdctl移动到和dockerfile同级目录:$ mv etcd-v3.3.10-linux-amd64/etcd etcd-v3.3.10-linux-amd64/etcdctl -t ./
6.构建etcd镜像docker build -t etcd .
7.查看构建好的镜像docker images

[root@localhost etcd]# docker images;
REPOSITORY                 TAG                 IMAGE ID            CREATED             SIZE
etcd                       latest              dd11f9fc0096        13 seconds ago      39.5 MB

启动etcd(单服务)

docker run -d -v /usr/share/ca-certificates/:/etc/ssl/certs -p 4001:4001 -p 2380:2380 -p 2379:2379 \
 --name etcd etcd /usr/local/bin/etcd \
 -name etcd0 \
 -advertise-client-urls http://192.168.3.3:2379,http://192.168.3.3:4001 \
 -listen-client-urls http://0.0.0.0:2379,http://0.0.0.0:4001 \
 -initial-advertise-peer-urls http://192.168.3.3:2380 \
 -listen-peer-urls http://0.0.0.0:2380 \
 -initial-cluster-token etcd-cluster-1 \
 -initial-cluster etcd0=http://192.168.3.3:2380 \
 -initial-cluster-state new

ETCD参数说明

• **data-dir:**指定节点的数据存储目录，这些数据包括节点ID，集群ID，集群初始化配置，Snapshot文件，若未指定—wal-dir，还会存储WAL文件；
• **wal-dir:**指定节点的was文件的存储目录，若指定了该参数，wal文件会和其他数据文件分开存储。
• name: 节点名称
• initial-advertise-peer-urls: 告知集群其他节点url.(对于集群内提供服务的url)
• listen-peer-urls: 监听URL，用于与其他节点通讯
• advertise-client-urls: 告知客户端url, 也就是服务的url(对外提供服务的utl)
• initial-cluster-token: 集群的ID
• initial-cluster: 集群中所有节点

在docker中运行(集群)

node0

docker run -d -p 2380:2380 -p 2479:2379 --name etcd0 etcd /usr/local/bin/etcd -name etcd0  -advertise-client-urls http://192.168.3.3:2479  -listen-client-urls http://0.0.0.0:2379 -initial-advertise-peer-urls http://192.168.3.3:2380 -listen-peer-urls http://0.0.0.0:2380  -initial-cluster-token etcd-cluster-1 -initial-cluster "etcd0=http://192.168.3.3:2380,etcd1=http://192.168.3.3:2381" -initial-cluster-state new

node1

docker run -d -p 2381:2380 -p 2480:2379 --name etcd1 etcd /usr/local/bin/etcd -name etcd1  -advertise-client-urls http://192.168.3.3:2480  -listen-client-urls http://0.0.0.0:2379 -initial-advertise-peer-urls http://192.168.3.3:2381 -listen-peer-urls http://0.0.0.0:2380  -initial-cluster-token etcd-cluster-1 -initial-cluster "etcd0=http://192.168.3.3:2380,etcd1=http://192.168.3.3:2381" -initial-cluster-state new

这里模拟多端口代表多服务器,需要注意的是-listen-client-urls http://0.0.0.0:2379,-listen-peer-urls http://0.0.0.0:2380,这两个参数是服务内端口号,对应的是-p中的2479:2379中后面的2379,所以这里的监听不需要改变.

集群验证

验证集群members。在集群中的每台机器上查看members，得出的结果应该是相同的

[root@localhost ~]# curl -L http://192.168.3.3:2479/v2/members
{"members":[{"id":"4b316424559e0f9d","name":"etcd0","peerURLs":["http://192.168.3.3:2380"],"clientURLs":["http://192.168.3.3:2479"]},{"id":"6204f98420b429cc","name":"etcd1","peerURLs":["http://192.168.3.3:2381"],"clientURLs":["http://192.168.3.3:2480"]}]}

某台机器上添加数据，其他机器上查看数据，得出的结果应该是相同的

A 服务器中执行

[root@localhost ~]# curl -L http://192.168.3.3:2479/v2/keys/message -XPUT -d value="Hello zhenyuyaodidiao"
{"action":"set","node":{"key":"/message","value":"Hello zhenyuyaodidiao","modifiedIndex":13,"createdIndex":13},"prevNode":{"key":"/message","value":"Hello world1","modifiedIndex":11,"createdIndex":11}}

B 服务上执行

[root@localhost ~]#  curl -L http://192.168.3.3:2480/v2/keys/message
{"action":"get","node":{"key":"/message","value":"Hello zhenyuyaodidiao","modifiedIndex":13,"createdIndex":13}}

原文连接：http://www.artacode.com/posts/etcd/install/