问题描述

当一个Key的Value过大或List、Hash等类型的数据中存储了大量的元素时，读取、删除这些数据的操作可能会耗费较长时间，阻塞单线程的Redis服务。此时您需要对内存结构进行优化，找出大Key并进行调整。

获取大Key

查找大Key的方法多种多样，以下介绍使用redis-cli工具查找大Key的方法。

前提条件

• 具备可以与Redis实例互通的云服务器。
• 云服务器中已经安装原生Redis。

操作步骤

执行以下命令：

redis-cli -h 服务IP -a 密码 --bigkeys

说明：

• -h指定Redis的内网连接地址。
• -a指定Redis的认证密码。
• --bigkeys查找大Key。

显示结果如下：

redis-cli  -h 10.XX.XX.3 -a XXXX --bigkeys 
# Scanning the entire keyspace to find biggest 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%] Biggest zset   found so far 'testzset' with 129 members  
[00.00%] Biggest hash   found so far 'h2' with 513 fields
[00.00%] Biggest set    found so far 'si1' with 5 members
[00.00%] Biggest hash   found so far 'h4' with 514 fields
[00.00%] Biggest string found so far 'key' with 9 bytes
-------- summary -------
Sampled 9 keys in the keyspace!
Total key length in bytes is 27 (avg len 3.00)
Biggest string found 'key' has 9 bytes
Biggest    set found 'si1' has 5 members
Biggest   hash found 'h4' has 514 fields
Biggest   zset found 'testzset' has 129 members
1 strings with 9 bytes (11.11% of keys, avg size 9.00)
0 lists with 0 items (00.00% of keys, avg size 0.00)
2 sets with 8 members (22.22% of keys, avg size 4.00)
4 hashs with 1541 fields (44.44% of keys, avg size 385.25)
2 zsets with 132 members (22.22% of keys, avg size 66.00)
0 streams with 0 entries (00.00% of keys, avg size 0.00)

优化大Key

对于大Key，如果是一个Key的Value过大，您可以将对象拆分成多个 key-value，将操作压力平摊到多个 Redis 实例。如果是 Key 过多，您可以参考 hash 结构存储，将多个 Key 存储在一个 hash 结构中。