1. 简介

ETCD 是一个高可用的分布式键值数据库，可用于服务发现。ETCD 采用 raft 一致性算法，基于 Go 语言实现。

特点

简单：安装配置使用简单，提供 HTTP API

安全：支持 SSL 证书

可靠：采用 raft 算法，实现分布式系统数据的可用性和一致性

2. 用法

通过 etcdctl 可以使用 ETCD。假设使用 v3 版本，且集群设置如下：

export ETCDCTL_API=3

HOST_1=10.240.0.17

HOST_2=10.240.0.18

HOST_3=10.240.0.19

ENDPOINTS=$HOST_1:2379,$HOST_2:2379,$HOST_3:2379

etcdctl --endpoints=$ENDPOINTS member list

版本设置

ETCD v2 和 v3 两个版本不兼容，且 v2 已经停止支持。如果一个系统上同时按照了两个版本，需要通过环境变量来切换：

export ETCDCTL_API=3

读写数据

put 命令写数据：

etcdctl --endpoints=$ENDPOINTS put foo "Hello World!"

get 命令读数据：

etcdctl --endpoints=$ENDPOINTS get foo

etcdctl --endpoints=$ENDPOINTS --write-out="json" get foo

通过 --write-out="json" 选项读数据时，会读包括元数据在内的所有数据，并以 JSON 格式输出。

通过 prefix 选项读数据

etcdctl --endpoints=$ENDPOINTS put web1 value1

etcdctl --endpoints=$ENDPOINTS put web2 value2

etcdctl --endpoints=$ENDPOINTS put web3 value3

etcdctl --endpoints=$ENDPOINTS get web --prefix

删除数据

etcdctl --endpoints=$ENDPOINTS put key myvalue

etcdctl --endpoints=$ENDPOINTS del key

etcdctl --endpoints=$ENDPOINTS put k1 value1

etcdctl --endpoints=$ENDPOINTS put k2 value2

etcdctl --endpoints=$ENDPOINTS del k --prefix

事务性写入 txn

通过 txn 可以将多个请求放入一个事务：

etcdctl --endpoints=$ENDPOINTS put user1 bad

etcdctl --endpoints=$ENDPOINTS txn --interactive

compares:

value("user1") = "bad"      

success requests (get, put, delete):

del user1  

failure requests (get, put, delete):

put user1 good

监控数据变化 watch

通过 watch 选项，可以在将来发生改变时获得通知：

etcdctl --endpoints=$ENDPOINTS watch stock1

etcdctl --endpoints=$ENDPOINTS put stock1 1000

etcdctl --endpoints=$ENDPOINTS watch stock --prefix

etcdctl --endpoints=$ENDPOINTS put stock1 10

etcdctl --endpoints=$ENDPOINTS put stock2 20

安全写入 lease

lease 选项可以通过 TTL 写入数据：

etcdctl --endpoints=$ENDPOINTS lease grant 300

# lease 2be7547fbc6a5afa granted with TTL(300s)

etcdctl --endpoints=$ENDPOINTS put sample value --lease=2be7547fbc6a5afa

etcdctl --endpoints=$ENDPOINTS get sample

etcdctl --endpoints=$ENDPOINTS lease keep-alive 2be7547fbc6a5afa

etcdctl --endpoints=$ENDPOINTS lease revoke 2be7547fbc6a5afa

# or after 300 seconds

etcdctl --endpoints=$ENDPOINTS get sample

分布式锁 lock

etcdctl --endpoints=$ENDPOINTS lock mutex1

# another client with the same name blocks

etcdctl --endpoints=$ENDPOINTS lock mutex1

集群状态

为每台机器指定初始群集配置：

etcdctl --write-out=table --endpoints=$ENDPOINTS endpoint status

+------------------+------------------+---------+---------+-----------+-----------+------------+

|     ENDPOINT     |        ID        | VERSION | DB SIZE | IS LEADER | RAFT TERM | RAFT INDEX |

+------------------+------------------+---------+---------+-----------+-----------+------------+

| 10.240.0.17:2379 | 4917a7ab173fabe7 | 3.0.0   | 45 kB   | true      |         4 |      16726 |

| 10.240.0.18:2379 | 59796ba9cd1bcd72 | 3.0.0   | 45 kB   | false     |         4 |      16726 |

| 10.240.0.19:2379 | 94df724b66343e6c | 3.0.0   | 45 kB   | false     |         4 |      16726 |

+------------------+------------------+---------+---------+-----------+-----------+------------+

etcdctl --endpoints=$ENDPOINTS endpoint health

10.240.0.17:2379 is healthy: successfully committed proposal: took = 3.345431ms

10.240.0.19:2379 is healthy: successfully committed proposal: took = 3.767967ms

10.240.0.18:2379 is healthy: successfully committed proposal: took = 4.025451ms

Member

添加，删除，更新成员。

巴特西

ETCD 简介及基本用法