目录

redis-py和Redis

redis-py和Redis 哨兵

主机改变和哨兵故障转移

python连接redis的工具类 python连接redis哨兵_redis-py

关于Redis复制和Redis哨兵的主题仍然是——使用Python的redis-py库的几个例子。

以前的系列帖子：

  1. Redis：复制，第1部分——概述 复制与分片、哨兵与集群、Redis拓扑
  2. Redis：复制，第2部分——主从复制和Redis哨兵

可以在此处找到Python的所有Redis客户端——redis.io/clients。

首先，我们将使用没有哨兵的redis-py，只是为了检查它是如何工作的。

然后——我们将启动哨兵并检查主机和从机的发现。

在上一篇文章中已经配置了一个名为Redis复制和Redis 哨兵的工作环境——这里只是Python示例。

redis-py和Redis

redis-py在Debian上安装：

root@redis-0:/home/admin# apt install python-redis

此外，pip可以使用，但我更喜欢使用普通的存储库。

检查：

root@redis-0:/home/admin# python
Python 2.7.13 (default, Sep 26 2018, 18:42:22)
[GCC 6.3.0 20170516] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import redis
>>> r = redis.Redis(host='localhost', port=6379, db=0)
>>> r.get('test')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 880, in get
return self.execute_command('GET', name)
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 573, in execute_command
return self.parse_response(connection, command_name, **options)
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 585, in parse_response
response = connection.read_response()
File "/usr/lib/python2.7/dist-packages/redis/connection.py", line 582, in read_response
raise response
redis.exceptions.ResponseError: NOAUTH Authentication required.

好的，有效。

在文档中查找授权：

>>> help(redis.Redis)

添加password：

>>> r = redis.Redis(host='localhost', password='foobared', port=6379, db=0)
>>> r.get('test')
'test'

好了。

redis-py和Redis 哨兵

现在运行哨兵实例（如果它们尚未启动），让我们通过Redis 哨兵集群客户端尝试Redis。

sentinel monitor redis-test 52.58.69.184 6379 2
sentinel down-after-milliseconds redis-test 6001
sentinel failover-timeout redis-test 60000
bind 0.0.0.0
sentinel auth-pass redis-test foobared

哨兵实例启动后——它将更新配置，所以现在redis-1（这是第一个从机），配置看起来像：

admin@redis-1:~$ cat /etc/redis/sentinel.conf
sentinel myid e3e62e6577aa975f93346dad3d4f8e25833fd8f1
sentinel monitor redis-test 52.29.101.118 6379 2
sentinel down-after-milliseconds redis-test 6001
bind 0.0.0.0
sentinel failover-timeout redis-test 60000
Generated by CONFIG REWRITE
port 26379
dir "/home/admin"
sentinel auth-pass redis-test foobared
sentinel config-epoch redis-test 1
sentinel leader-epoch redis-test 1
sentinel known-slave redis-test 52.58.69.184 6379
sentinel known-slave redis-test 35.159.18.26 6379
sentinel known-sentinel redis-test 172.31.46.202 26379 e0fe655c59aa3cc32eab1c0858c52418700abe79
sentinel known-sentinel redis-test 172.31.41.39 26379 07a450af0d2f178410b78ee0f5ae99ce1cd0ac62
sentinel current-epoch 1

检查哨兵群集状态：

root@redis-0:/home/admin# redis-cli -p 26379 info 哨兵

root@redis-0:/home/admin# redis-cli -p 26379 info sentinel
Sentinel
sentinel_masters:1
sentinel_tilt:0
sentinel_running_scripts:0
sentinel_scripts_queue_length:0
sentinel_simulate_failure_flags:0
master0:name=redis-test,status=ok,address=52.58.69.184:6379,slaves=2,sentinels=3

并使用redis-py：

>>> from redis.sentinel import Sentinel
>>> sentinel = Sentinel([('localhost', 26379)], socket_timeout=0.1)

您可以使用以下discover_master()方法获取主机IP ：

>>> sentinel.discover_master('redis-test')
('52.58.69.184', 6379)

和从机IP：

>>> sentinel.discover_slaves('redis-test')
[('52.29.101.118', 6379), ('35.159.18.26', 6379)]

要使用master，请使用master_for()方法：

| master_for(self, service_name, redis_class=<class ‘redis.client.StrictRedis’>, 
connection_pool_class=<class ‘redis.sentinel.SentinelConnectionPool’>, **kwargs)
| Returns a redis client instance for the "service_name" master.
>>> master = sentinel.master_for('redis-test', socket_timeout=0.1)

但是如果现在调用master——它会告诉我们我们没有被授权：

>>> master.set('test-key', 'test-value')
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 1072, in set
return self.execute_command('SET', *pieces)
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 573, in execute_command
return self.parse_response(connection, command_name, **options)
File "/usr/lib/python2.7/dist-packages/redis/client.py", line 585, in parse_response
response = connection.read_response()
File "/usr/lib/python2.7/dist-packages/redis/sentinel.py", line 55, in read_response
return super(SentinelManagedConnection, self).read_response()
File "/usr/lib/python2.7/dist-packages/redis/connection.py", line 582, in read_response
raise response
redis.exceptions.ResponseError: NOAUTH Authentication required.

所以在创建master对象时——添加password：

>>> master = sentinel.master_for('redis-test', socket_timeout=0.1, password='foobared')

现在检查：

>>> master.set('test-key', 'test-value')
True

此外，您可以获得整个主机的配置：

>>> master.config_get()
{'appendonly': 'no', ... 'slave-announce-port': '0'}

或者以更易读的视图：

>>> for i in master.config_get():
...   print(i)
...
appendonly
requirepass
daemonize
protected-mode
zset-max-ziplist-entries
zset-max-ziplist-value
dir
slave-serve-stale-data
cluster-require-full-coverage
slowlog-log-slower-than
masterauth
rdbchecksum
...

在从机上——检查我们之前添加的密钥：

admin@redis-1:~$ redis-cli -a foobared get test-key
"test-value"

使用从机与主机方式类似：

>>> slave = sentinel.slave_for('redis-test', socket_timeout=0.1, password='foobared')
>>> slave.get('test-key')
'test-value'

主机改变和哨兵故障转移

我们现在来看看主机：

>>> sentinel.discover_master('redis-test')
('52.58.69.184', 6379)

最后，让我们尝试在主机上停止Redis主机redis-0：

root@redis-0:/home/admin# systemctl stop redis-server

或者通过：

root@redis-0:/home/admin# redis-cli -a foobared DEBUG sleep 600

（如果你只是用kill来杀死redis-server进程——哨兵将重新启动它）。

检查哨兵的日志：

10633:X 01 Apr 13:46:10.430 # +sdown master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.486 # +odown master redis-test 52.58.69.184 6379 #quorum 2/2
10633:X 01 Apr 13:46:10.486 # +new-epoch 1
10633:X 01 Apr 13:46:10.486 # +try-failover master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.488 # +vote-for-leader e3e62e6577aa975f93346dad3d4f8e25833fd8f1 1
10633:X 01 Apr 13:46:10.492 # 07a450af0d2f178410b78ee0f5ae99ce1cd0ac62 voted for e3e62e6577aa975f93346dad3d4f8e25833fd8f1 1
10633:X 01 Apr 13:46:10.492 # e0fe655c59aa3cc32eab1c0858c52418700abe79 voted for e3e62e6577aa975f93346dad3d4f8e25833fd8f1 1
10633:X 01 Apr 13:46:10.559 # +elected-leader master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.559 # +failover-state-select-slave master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.611 # +selected-slave slave 52.29.101.118:6379 52.29.101.118 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.612 * +failover-state-send-slaveof-noone slave 52.29.101.118:6379 52.29.101.118 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:10.664 * +failover-state-wait-promotion slave 52.29.101.118:6379 52.29.101.118 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:11.498 # +promoted-slave slave 52.29.101.118:6379 52.29.101.118 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:11.498 # +failover-state-reconf-slaves master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:11.557 * +slave-reconf-sent slave 35.159.18.26:6379 35.159.18.26 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:12.550 * +slave-reconf-inprog slave 35.159.18.26:6379 35.159.18.26 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:12.550 * +slave-reconf-done slave 35.159.18.26:6379 35.159.18.26 6379 @ redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:12.632 # -odown master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:12.632 # +failover-end master redis-test 52.58.69.184 6379
10633:X 01 Apr 13:46:12.632 # +switch-master redis-test 52.58.69.184 6379 52.29.101.118 6379
10633:X 01 Apr 13:46:12.632 * +slave slave 35.159.18.26:6379 35.159.18.26 6379 @ redis-test 52.29.101.118 6379
10633:X 01 Apr 13:46:12.632 * +slave slave 52.58.69.184:6379 52.58.69.184 6379 @ redis-test 52.29.101.118 6379
10633:X 01 Apr 13:46:18.647 # +sdown slave 52.58.69.184:6379 52.58.69.184 6379 @ redis-test 52.29.101.118 6379

从Python检查：

>>> sentinel.discover_master('redis-test')
('52.29.101.118', 6379)

主机改变了——52.29.101.118——这是redis-1主几。

检查redis-1状态：

admin@redis-1:~$ redis-cli -a foobared info replication

复制角色：master connected_slaves：1 slave0：ip = 35.159.18.26，port = 6379，state = online，offset = 76847，lag = 0 ...

检查redis-0主机上的Redis节点状态——它现在必须成为从机：

root@redis-0:/home/admin# redis-cli -a foobared info replication
Replication
role:slave
...

并尝试使用我们之前创建的相同master对象在redis-0主机上添加Python的新密钥：

>>> master.set('test-key2', 'test-value2')
True

校验：

admin@redis-2:~$ redis-cli -a foobared get test-key2
"test-value2"

完成。