Redis has three methods for checking big keys, which are necessary for optimization

In daily life Redis In use , Inevitably encountered because key Too much data is stored, causing requests to be slow or even blocked , This is the time to check Redis The big key To optimize the business , The following provides a summary of some troubleshooting schemes , For reference only .

One 、 What size key It's big ？

Redis practice （ For reference only ）：

reasonable Key in Value Byte size of , Less than recommended 10 KB.

Too much Value Will cause data skew 、 hotspot Key、 Instance traffic or CPU Problems such as full performance , The performance impact of such problems should be avoided from the design source .

that value Bytes > 10 kb Can be used as a judgment Big key A reference value of .

Two 、 Troubleshooting key Methods

1、 Use command --bigkeys

--bigkeys yes redis The order that comes with you , To the whole Key scan , Statistics string,list,set,zset,hash The largest of these common data types key.

string The type of statistics is value Bytes of ; in addition 4 Types of complex structures count the number of elements , Can not be seen intuitively value Bytes occupied , therefore --bigkeys For analysis string Large of type key It is useful to , The type of complex structure also needs some third-party tools .

notes ： Fewer elements , not always value not big ; There are many elements , Not necessarily. value Big

redis-cli -h 127.0.0.1 -p 6379 -a "password" --bigkeys

--bigkeys In order to scan Scan all by delaying calculation key, Therefore, there will be no blocking during execution redis, But there are a large number of instances keys when , The command takes a long time to execute , In this case, it is suggested that slave Scan up .

–-bigkeys In fact, it is to find the largest of the types key, maximal key It doesn't have to be big key, maximal key Not more than 10kb Words , It means that there is no big key.

But if a certain type has more big key (>10kb), Statistics only top1 the key, If you want to count all greater than 10kb Of key, Need to scan with third-party tools rdb Persistent files .

2、 Use memory Command view key Size （ Support only Redis 4.0 Later versions ）

redis-cli -h 127.0.0.1 -p 6379 -a password

MEMORY USAGE keyname1
(integer) 157481

MEMORY USAGE keyname2
(integer) 312583

3、 Use Rdbtools tool kit

Rdbtools yes python Written A third-party open source tool , Used to resolve Redis Snapshot file . In addition to parsing rdb file , It also provides statistics of individual key Tools of size .

1、 install

git clone https://github.com/sripathikrishnan/redis-rdb-tools
cd redis-rdb-tools sudo && python setup.py install

2、 Use

from dump.rdb Snapshot file statistics , Will all > 10kb Of key Output to a csv file

rdb dump.rdb -c memory --bytes 10240 -f live_redis.csv