Redis 使用 hotkeys 查看热点数据

前置要求

Redis 4.0.3中新增查看热点数据命令行，使用热点数据必须将内存策略修改为LFU算法。

查看内存策略

config get maxmemory-policy

输出：

127.0.0.1:6379> config get maxmemory-policy
1) "maxmemory-policy"
2) "noeviction"

查看 key 使用频率

object freq myKey

输出异常信息，需修改内存淘汰策略为LFU算法。

127.0.0.1:6379> object freq myKey
(error) ERR An LFU maxmemory policy is not selected, access frequency not tracked. Please note that when switching between policies at runtime LRU and LFU data will take some time to adjust.

LFU

Least Frequently Used：最不经常使用。

Redis有两种LFU算法：

• volatile-lfu：设置了过期时间的key中，进行LFU淘汰。
• allkeys-lfu：所有key参与LFU淘汰。

更改内存策略

config set maxmemory-policy allkeys-lfu

查看热点数据

统计时间隔0.1秒，防止阻塞其他线程。

redis-cli --hotkeys -i 0.1

输出：

root@root:~# redis-cli --hotkeys -i 0.1

# Scanning the entire keyspace to find hot keys as well as
# average sizes per key type.  You can use -i 0.1 to sleep 0.1 sec
# per 100 SCAN commands (not usually needed).

[00.00%] Hot key 'aaa' found so far with counter 1

-------- summary -------

Sampled 4 keys in the keyspace!
hot key found with counter: 1    keyname: aaa