ddt的用法：根据数据来生成测试用例

Posted 2020-12-19 xj-excellent

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前言

前文学习了redis的主从复制，通过配置实现了一主多从，既读写分离又互为备份。但是如果出于不可抗力，主服务器下线了，那么redis集群将失去写功能，如果可以实现主服务器掉线后，自动选举从服务器升级为主服务器，那上述问题自然迎刃而解。事实上从redis2.6版本开始，便有了这么一种解决方案——Sentinel。（PS：实验Redis版本为5.0.5）

Sentinel哨兵

? 哨兵是由一个或多个Sentinel实例组成哨兵集群，监控任意多个主服务器和从服务器。当主服务器下线后，将自动从在线的从服务器中选一台升级为主服务器。并将原主服务器标记为从服务器。实现了主从服务器的自主切换，提高了redis的可用性。

准备

前文使用三台虚拟机搭建了一主二从，今天使用另外一种方法，通过复制三份redis.conf文件，修改端口实现单机主从复制。

准备三个配置文件，分别使用端口6379、6380、6381

# redis-6379.conf
...
bind 127.0.0.1
protected-mode yes
port 6379
daemonize yes
...

# redis-6380.conf
...
bind 127.0.0.1
protected-mode yes
port 6380
daemonize yes

# redis-6381.conf
...
bind 127.0.0.1
protected-mode yes
port 6381
daemonize yes

为从库配置追加主从复制

# 6379 和 6381中追加以下配置
slaveof 127.0.0.1 6380

启动主从服务器

redis-server redis-6379.conf
redis-server redis-6380.conf
redis-server redis-6381.conf
---------------------------------------------------------------------------------------------
[root@VM-0-4-centos etc]# ps -ef|grep redis
root      6321     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6379
root      6342     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6380
root      6372     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6381
root      6418 31466  0 21:36 pts/3    00:00:00 grep --color=auto redis

配置哨兵

修改sentinel-6379.conf配置文件指定master的IP和port，quorum,其中quorum的值用于设定最少需要几个Sentinel实例对master失去连接时判定为主机下线。
```
// 修改默认启动方式为后台启动，这里为方便查看日志，未做修改
daemonize yes
// 监听主机ip port rum
sentinel monitor mymaster 192.168.204.121 6380 1
```

启动

[root@VM-0-4-centos etc]# redis-sentinel sentinel-6379.conf 
6903:X 10 Aug 2020 21:39:08.389 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
6903:X 10 Aug 2020 21:39:08.389 # Redis version=5.0.5, bits=64, commit=00000000, modified=0, pid=6903, just started
6903:X 10 Aug 2020 21:39:08.389 # Configuration loaded
                _._                                                  
           _.-``__ ‘‘-._                                             
      _.-``    `.  `_.  ‘‘-._           Redis 5.0.5 (00000000/0) 64 bit
  .-`` .-```.  ```/    _.,_ ‘‘-._                                   
 (    ‘      ,       .-`  | `,    )     Running in sentinel mode
 |`-._`-...-` __...-.``-._|‘` _.-‘|     Port: 26379
 |    `-._   `._    /     _.-‘    |     PID: 6903
  `-._    `-._  `-./  _.-‘    _.-‘                                   
 |`-._`-._    `-.__.-‘    _.-‘_.-‘|                                  
 |    `-._`-._        _.-‘_.-‘    |           http://redis.io        
  `-._    `-._`-.__.-‘_.-‘    _.-‘                                   
 |`-._`-._    `-.__.-‘    _.-‘_.-‘|                                  
 |    `-._`-._        _.-‘_.-‘    |                                  
  `-._    `-._`-.__.-‘_.-‘    _.-‘                                   
      `-._    `-.__.-‘    _.-‘                                       
          `-._        _.-‘                                           
              `-.__.-‘                                               

6903:X 10 Aug 2020 21:39:08.390 # WARNING: The TCP backlog setting of 511 cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of 128.
6903:X 10 Aug 2020 21:39:08.390 # Sentinel ID is de4d4a52a39c8e4532dca5a91679749aeffbfccd
6903:X 10 Aug 2020 21:39:08.390 # +monitor master mymaster 127.0.0.1 6380 quorum 1
6903:X 10 Aug 2020 21:39:08.392 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:39:08.401 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380

如上所示，单哨兵启动，监控主(127.0.0.1 6380)从（127.0.0.1 6379、127.0.0.1 6381）工作状态。

验证主从切换

# 关闭主数据库
[root@VM-0-4-centos etc]# ps -ef|grep redis
root      6321     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6379
root      6342     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6380
root      6372     1  0 21:36 ?        00:00:00 redis-server 127.0.0.1:6381
root      6903 31466  0 21:39 pts/3    00:00:00 redis-sentinel *:26379 [sentinel]
root      7425 26828  0 21:42 pts/0    00:00:00 grep --color=auto redis
[root@VM-0-4-centos etc]# kill -9 6342

---↓↓↓哨兵日志↓↓↓-----------------------------------------------------------------------
6903:X 10 Aug 2020 21:42:41.759 # +sdown master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.759 # +odown master mymaster 127.0.0.1 6380 #quorum 1/1
6903:X 10 Aug 2020 21:42:41.759 # +new-epoch 2
6903:X 10 Aug 2020 21:42:41.759 # +try-failover master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.764 # +vote-for-leader de4d4a52a39c8e4532dca5a91679749aeffbfccd 2
6903:X 10 Aug 2020 21:42:41.764 # +elected-leader master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.764 # +failover-state-select-slave master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.835 # +selected-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.835 * +failover-state-send-slaveof-noone slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:41.890 * +failover-state-wait-promotion slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:42.434 # +promoted-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:42.434 # +failover-state-reconf-slaves master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:42.519 * +slave-reconf-sent slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:43.457 * +slave-reconf-inprog slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:43.457 * +slave-reconf-done slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:43.512 # +failover-end master mymaster 127.0.0.1 6380
6903:X 10 Aug 2020 21:42:43.512 # +switch-master mymaster 127.0.0.1 6380 127.0.0.1 6381
6903:X 10 Aug 2020 21:42:43.512 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
6903:X 10 Aug 2020 21:42:43.512 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
6903:X 10 Aug 2020 21:42:46.550 # +sdown slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381

如上所示，主从切换经过以下几个步骤：

哨兵检测到master下线
哨兵通知所有哨兵进行测试（这里是单机，所以结果为1/1）
哨兵（集群）超过半数认定master已离线，发起纪元更新
哨兵选举执行者执行主从切换
哨兵选举的leader将当前master标记为slave
哨兵从当前slave中选取一个标记为master
标记结束，新的master（6381）连接仍存活的slave-6379以及降级为slave的6380

重新连接

原master（6380）断线重连后，自动以slave的身份继续工作

[root@VM-0-4-centos etc]# redis-server redis-6380.conf 
10338:C 10 Aug 2020 22:03:17.687 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
10338:C 10 Aug 2020 22:03:17.687 # Redis version=5.0.5, bits=64, commit=00000000, modified=0, pid=10338, just started
10338:C 10 Aug 2020 22:03:17.687 # Configuration loaded
---↓↓↓哨兵日志↓↓↓-----------------------------------------------------------------------
6903:X 10 Aug 2020 22:03:18.262 # -sdown slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
6903:X 10 Aug 2020 22:03:28.230 * +convert-to-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381

如上所示，6380重连后，哨兵将6380离线的状态解除，并将6380转为slave of 6381

哨兵集群

复制哨兵配置

sentinel-6379.conf
sentinel-6380.conf
sentinel-6381.conf

修改哨兵port及myid

这里部署3台哨兵，quorum取（n/2）+1 = 2

# sentinel-6379.conf
port 26379
sentinel myid de4d4a52a39c8e4532dca5a91679749aeffbfccd
sentinel monitor mymaster 127.0.0.1 6381 2

# sentinel-6380.conf
port 26380
sentinel myid de4d4a52a39c8e4532dca5a91679749aeffbfccc
sentinel monitor mymaster 127.0.0.1 6381 2
# sentinel-6381.conf
port 26381
sentinel myid de4d4a52a39c8e4532dca5a91679749aeffbfcce
sentinel monitor mymaster 127.0.0.1 6381 2

启动三个哨兵

[root@VM-0-4-centos etc]# redis-sentinel sentinel-6379.conf 
...
11749:X 10 Aug 2020 22:13:51.528 # Sentinel ID is de4d4a52a39c8e4532dca5a91679749aeffbfccd
11749:X 10 Aug 2020 22:13:51.528 # +monitor master mymaster 127.0.0.1 6381 quorum 1

[root@VM-0-4-centos etc]# redis-sentinel sentinel-6380.conf 
...
11916:X 10 Aug 2020 22:14:57.418 # Sentinel ID is de4d4a52a39c8e4532dca5a91679749aeffbfccc
11916:X 10 Aug 2020 22:14:57.418 # +monitor master mymaster 127.0.0.1 6381 quorum 2
11916:X 10 Aug 2020 22:14:57.419 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
11916:X 10 Aug 2020 22:14:57.429 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
11916:X 10 Aug 2020 22:14:58.832 * +sentinel sentinel de4d4a52a39c8e4532dca5a91679749aeffbfccd 127.0.0.1 26379 @ mymaster 127.0.0.1 6381
11916:X 10 Aug 2020 22:14:58.841 # +new-epoch 2

[root@VM-0-4-centos ~]# cd /usr/local/redis/etc/
[root@VM-0-4-centos etc]# redis-sentinel sentinel-6381.conf 
...
12131:X 10 Aug 2020 22:16:08.834 # Sentinel ID is de4d4a52a39c8e4532dca5a91679749aeffbfcce
12131:X 10 Aug 2020 22:16:08.834 # +monitor master mymaster 127.0.0.1 6381 quorum 2
12131:X 10 Aug 2020 22:16:08.836 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
12131:X 10 Aug 2020 22:16:08.840 * +slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
12131:X 10 Aug 2020 22:16:10.244 * +sentinel sentinel de4d4a52a39c8e4532dca5a91679749aeffbfccd 127.0.0.1 26379 @ mymaster 127.0.0.1 6381
12131:X 10 Aug 2020 22:16:10.252 # +new-epoch 2
12131:X 10 Aug 2020 22:16:10.769 * +sentinel sentinel de4d4a52a39c8e4532dca5a91679749aeffbfccc 127.0.0.1 26380 @ mymaster 127.0.0.1 6381

如上所示，哨兵只需要配置master即可自动识别slave和其他的哨兵。

验证主从切换

[root@VM-0-4-centos ~]# ps -ef|grep redis
root      6321     1  0 21:36 ?        00:00:02 redis-server 127.0.0.1:6379
root      6372     1  0 21:36 ?        00:00:02 redis-server 127.0.0.1:6381
root     10339     1  0 22:03 ?        00:00:01 redis-server 127.0.0.1:6380
root     11749 31466  0 22:13 pts/3    00:00:00 redis-sentinel *:26379 [sentinel]
root     11916 26828  0 22:14 pts/0    00:00:00 redis-sentinel *:26380 [sentinel]
root     12131 12033  0 22:16 pts/1    00:00:00 redis-sentinel *:26381 [sentinel]
root     12468 12407  0 22:18 pts/2    00:00:00 grep --color=auto redis
[root@VM-0-4-centos ~]# kill -9 6372
---↓↓↓哨兵日志选取其中一台↓↓↓-----------------------------------------------------------------------
11749:X 10 Aug 2020 22:18:41.165 # +sdown master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.165 # +odown master mymaster 127.0.0.1 6381 #quorum 1/1
11749:X 10 Aug 2020 22:18:41.165 # +new-epoch 3
11749:X 10 Aug 2020 22:18:41.165 # +try-failover master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.170 # +vote-for-leader de4d4a52a39c8e4532dca5a91679749aeffbfccd 3
11749:X 10 Aug 2020 22:18:41.185 # de4d4a52a39c8e4532dca5a91679749aeffbfcce voted for de4d4a52a39c8e4532dca5a91679749aeffbfccd 3
11749:X 10 Aug 2020 22:18:41.185 # de4d4a52a39c8e4532dca5a91679749aeffbfccc voted for de4d4a52a39c8e4532dca5a91679749aeffbfccd 3
11749:X 10 Aug 2020 22:18:41.246 # +elected-leader master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.246 # +failover-state-select-slave master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.329 # +selected-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.330 * +failover-state-send-slaveof-noone slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:41.406 * +failover-state-wait-promotion slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:42.204 # +promoted-slave slave 127.0.0.1:6380 127.0.0.1 6380 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:42.204 # +failover-state-reconf-slaves master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:42.265 * +slave-reconf-sent slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:43.250 * +slave-reconf-inprog slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:43.250 * +slave-reconf-done slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:43.305 # +failover-end master mymaster 127.0.0.1 6381
11749:X 10 Aug 2020 22:18:43.305 # +switch-master mymaster 127.0.0.1 6381 127.0.0.1 6380
11749:X 10 Aug 2020 22:18:43.305 * +slave slave 127.0.0.1:6379 127.0.0.1 6379 @ mymaster 127.0.0.1 6380
11749:X 10 Aug 2020 22:18:43.305 * +slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
11749:X 10 Aug 2020 22:18:46.339 # +sdown slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380

如上所示，其中一台发现master失联后，发起全员测试 -> 投票选举 -> 标记下线 -> slave升级为master -> 新master重连其余实例，同单机哨兵模式一致，只在于多了几台哨兵共同测定master是否离线。

PS：哨兵集群最好为单数台，便于计算出中间值。

PS：quorum值设定具有一定参考意义，但是无论设定为多少，哨兵集群只会在超过半数哨兵认定master离线时发起主从切换。

重新连接

[root@VM-0-4-centos etc]# redis-server redis-6381.conf 
13449:C 10 Aug 2020 22:25:48.758 # oO0OoO0OoO0Oo Redis is starting oO0OoO0OoO0Oo
13449:C 10 Aug 2020 22:25:48.758 # Redis version=5.0.5, bits=64, commit=00000000, modified=0, pid=13449, just started
13449:C 10 Aug 2020 22:25:48.758 # Configuration loaded
-------------哨兵打印6381重连并且转化为slave的日志-----------------------------
11749:X 10 Aug 2020 22:25:49.418 # -sdown slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380
11749:X 10 Aug 2020 22:25:59.352 * +convert-to-slave slave 127.0.0.1:6381 127.0.0.1 6381 @ mymaster 127.0.0.1 6380

END

查看到原redis.conf中配置发生改变

slaveof 127.0.0.1 6380
变为：
replicaof 127.0.0.1 6380

sentinel.conf文件末尾追加了一部分内容，用于标记当前集群内的master、slave、sentinel信息。

sentinel leader-epoch mymaster 3
sentinel known-replica mymaster 127.0.0.1 6379
sentinel known-replica mymaster 127.0.0.1 6381
sentinel known-sentinel mymaster 127.0.0.1 26381 de4d4a52a39c8e4532dca5a91679749aeffbfcce
sentinel known-sentinel mymaster 127.0.0.1 26380 de4d4a52a39c8e4532dca5a91679749aeffbfccc
sentinel current-epoch 3

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