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说明
这是一篇非常入门的文章，让你大概了解一下etcd。写这篇文章时使用etcd的版本是3.1.0。
etcd是以实现共享配置和服务发现为目的，提供一致性的键值存储的分布式数据库。kubernetes等项目使用了etcd。下载安装
去下载release包，解压后是一些文档和两个二进制文件etcd和etcdctl。etcd是server端，etcdctl是客户端。将etcd和etcdctl加入PATH路径方便我们执行命令。
运行server
执行命令etcd，即可启动server
ming@ming:/tmp$ etcd2017-02-14 14:04:40.164639 I | etcdmain: etcd Version: 3.1.02017-02-14 14:04:40.164725 I | etcdmain: Git SHA: 8ba28972017-02-14 14:04:40.164736 I | etcdmain: Go Version: go1.7.42017-02-14 14:04:40.164776 I | etcdmain: Go OS/Arch: linux/amd642017-02-14 14:04:40.164784 I | etcdmain: setting maximum number of CPUs to 4, total number of available CPUs is 42017-02-14 14:04:40.164850 W | etcdmain: no data-dir provided, using default data-dir ./default.etcd2017-02-14 14:04:40.164934 I | etcdmain: advertising using detected default host "192.168.1.124"2017-02-14 14:04:40.165855 I | embed: listening for peers on http://localhost:23802017-02-14 14:04:40.167090 I | embed: listening for client requests on localhost:2379......
etcdctl
说明：etcd最新的API版本是v3。与v2相比，v3更高效更清晰。设置环境变量ETCDCTL_API=3。
ming@ming:/tmp$ export ETCDCTL_API=3ming@ming:/tmp$ etcdctl versionetcdctl version: 3.1.0API version: 3.1
键值对命令
put设置key，get取得key
ming@ming:/tmp$ etcdctl put msg "Hello TenxCloud"OKming@ming:/tmp$ etcdctl get msg msgHello TenxCloud
del删除key
ming@ming:/tmp$ etcdctl get msg msgHello TenxCloudming@ming:/tmp$ etcdctl del msg1ming@ming:/tmp$ etcdctl get msgming@ming:/tmp$
txn事务
ming@ming:/tmp$ etcdctl put flag 1OKming@ming:/tmp$ etcdctl txn -icompares:value("flag") = "1"success requests (get, put, delete):put result truefailure requests (get, put, delete):put result falseSUCCESSOKming@ming:/tmp$ etcdctl get resultresulttrue 解释一下：
etcdctl put flag 1设置flag为1
etcdctl txn -i开启事务（-i表示交互模式）
第2步输入命令后回车，终端显示出compares：
输入value("flag") = "1"，此命令是比较flag的值与1是否相等
第4步完成后输入回车，终端会换行显示，此时可以继续输入判断条件（前面说过事务由条件列表组成），再次输入回车表示判断条件输入完毕
第5步连续输入两个回车后，终端显示出success requests (get, put, delete):，表示下面输入判断条件为真时要执行的命令
与输入判断条件相同，连续两个回车表示成功时的执行列表输入完成
终端显示failure requests (get, put, delete):后输入条件判断失败时的执行列表
为了看起来简洁，此实例中条件列表和执行列表只写了一行命令，实际可以输入多行
总结上面的事务，要做的事情就是flag为1时设置result为true，否则设置result为false
事务执行完成后查看result值为true
watch监听
ming@ming:/tmp$ etcdctl watch flagPUTflag2
lease租约
ming@ming:/tmp$ etcdctl lease grant 100lease 38015a3c00490513 granted with TTL(100s)ming@ming:/tmp$ etcdctl put k1 v1 --lease=38015a3c00490513OKming@ming:/tmp$ etcdctl lease timetolive 38015a3c00490513lease 38015a3c00490513 granted with TTL(100s), remaining(67s)ming@ming:/tmp$ etcdctl lease timetolive 38015a3c00490513lease 38015a3c00490513 granted with TTL(100s), remaining(64s)ming@ming:/tmp$ etcdctl lease timetolive 38015a3c00490513 --keyslease 38015a3c00490513 granted with TTL(100s), remaining(59s), attached keys([k1])ming@ming:/tmp$ etcdctl put k2 v2 --lease=38015a3c00490513OKming@ming:/tmp$ etcdctl lease timetolive 38015a3c00490513 --keyslease 38015a3c00490513 granted with TTL(100s), remaining(46s), attached keys([k1 k2])ming@ming:/tmp$ etcdctl lease revoke 38015a3c00490513 lease 38015a3c00490513 revokedming@ming:/tmp$ etcdctl get k1ming@ming:/tmp$ etcdctl get k2ming@ming:/tmp$ ming@ming:/tmp$ etcdctl lease grant 10lease 38015a3c0049051d granted with TTL(10s)ming@ming:/tmp$ etcdctl lease keep-alive 38015a3c0049051dlease 38015a3c0049051d keepalived with TTL(10)lease 38015a3c0049051d keepalived with TTL(10)lease 38015a3c0049051d keepalived with TTL(10)
lease grant <ttl>
lease revoke <lease ID> 删除lease，并删除所有关联的key lease timetolive <lease ID> 取得lease的总时间和剩余时间 lease keep-alive <lease ID> 此命令不会只更新一次lease时间，而是周期性地刷新，保证它不会过期。 集群管理命令
TODO
并发控制命令
lock <lock name>
使用Ctrl+C正常退出lock命令，退出码为0，第二次能正常lock：ming@ming:/tmp$ etcdctl lock testtest/38015a3fd6795e04^Cming@ming:/tmp$ echo $?0ming@ming:/tmp$ etcdctl lock testtest/38015a3fd6795e0akill掉lock命令，退出码不为0，第二次lock被阻塞：终端1，第一次正常锁住test：ming@ming:/tmp$ etcdctl lock testtest/38015a3fd6795e11终端2，kill掉lock命令：ming@ming:~$ ps aux|grep 'etcdctl lock'ming 44546 0.5 0.5 19876 11436 pts/5 Sl+ 11:42 0:00 etcdctl lock testming 44560 0.0 0.0 14224 1084 pts/6 S+ 11:43 0:00 grep --color=auto etcdctl lockming@ming:~$ kill -9 44546 终端1，退出码不为0，第二次锁test被阻塞ming@ming:/tmp$ etcdctl lock testtest/38015a3fd6795e1eKilledming@ming:/tmp$ echo $?137ming@ming:/tmp$ etcdctl lock test
elect
TODO权限命令
user
add 添加用户
delete 删除用户
get 取得用户详情
list 列出所有用户
passwd 修改用户密码
grant-role 给用户分配角色
revoke-role 给用户移除角色
role
add 添加角色
delete 删除角色
get 取得角色信息
list 列出所有角色
grant-permission 为角色设置某个key的权限
revoke-permission 为角色移除某个key的权限
auth
示例
下面以示例来学习这三个命令root用户存在时才能开启权限控制ming@ming:/tmp$ etcdctl auth enableError: etcdserver: root user does not existming@ming:/tmp$ etcdctl user add rootPassword of root: Type password of root again for confirmation: User root createdming@ming:/tmp$ etcdctl auth enableAuthentication Enabled 开启权限控制后需要用--user指定用户ming@ming:/tmp$ etcdctl user listError: etcdserver: user name not foundming@ming:/tmp$ etcdctl user list --user=rootPassword: rootming@ming:/tmp$ etcdctl user get root --user=rootPassword: User: rootRoles: root 添加用户，前两个密码是新用户的，后一个密码是root的ming@ming:/tmp$ etcdctl user add mengyuan --user=rootPassword of mengyuan: Type password of mengyuan again for confirmation: Password: User mengyuan created 使用新用户执行put命令，提示没有权限ming@ming:/tmp$ etcdctl put key1 v1 --user=mengyuanPassword: Error: etcdserver: permission denied创建名为rw_key_的role，添加对字符串"key"做为前缀的key的读写权限，为mengyuan添加角色ming@ming:/tmp$ etcdctl role add rw_key_ --user=rootPassword: Role rw_key_ createdming@ming:/tmp$ etcdctl --user=root role grant-permission rw_key_ readwrite key --prefix=truePassword: Role rw_key_ updatedming@ming:/tmp$ etcdctl --user=root user grant-role mengyuan rw_key_Password: Role rw_key_ is granted to user mengyuan 添加权限成功后执行put key1成功，执行put k1失败（因为上面只给前缀为"key"的key添加了权限）ming@ming:/tmp$ etcdctl put key1 v1 --user=mengyuanPassword: OKming@ming:/tmp$ etcdctl put k1 v1 --user=mengyuanPassword: Error: etcdserver: permission denied 执行user list命令失败，没有权限ming@ming:/tmp$ etcdctl user list --user=mengyuanPassword: Error: etcdserver: permission denied为新用户添加root的角色后就能执行user list命令了，注意命令中第一个root是角色，第二个root是用户ming@ming:/tmp$ etcdctl user grant-role mengyuan root --user=rootPassword: Role root is granted to user mengyuanming@ming:/tmp$ etcdctl user list --user=mengyuanPassword: mengyuanroot
进一步学习
etcdctl <command> -h查看子命令的帮助（例：etcdctl watch -h）
是网页版集群环境
etcdctl能够设置--prefix=true来操作多个指定前缀的key