Redis learning journey -- getting to know redis for the first time

** Ben Xiaobai is based on B Station crazy God video learning , If you have any questions, you can leave a comment , Or go B Stand and watch the video to understand ！！！** Finally, I would like to thank crazy God Da ！

summary

Redis What is it? ？

Redis（Remote Dictionary Server） Remote Dictionary Service ！ Is an open source use ANSIC Language To write 、 Support network 、 Log type that can be memory based or persistent 、key-value database , And provide multilingual API. It's free and open source ！ It's the hottest thing right now NoSQL One of the technologies ！ Also known as structured database ！Redis Periodically, updated data is written to disk or changes are written to an appended log file , And on this basis to achieve master-slave（ Master-slave ） Sync .

Redis What can I do? ？

• Memory storage 、 Persistence （ In memory, power is lost 、 So persistence is important （ people rdb、aof））
• Efficient 、 Can be used to tell the cache
• Publish subscribe system （ Message queue ）
• Map information analysis
• timer 、 Counter （ Browse volume ）
• …

Redis Characteristics

• A variety of data types
• Persistence
• colony
• Business
• …

expand

• Redis Official website ：https://redis.io/
• Redis Chinese official website ：http://www.redis.cn/

Be careful ：Wdinow stay Github Upload and download （ It's been a long time ！）
Redis The recommendations are all in Linux Built on the server , be based on Linux Study ！

download

Windows download

1. Online disk download link https://pan.baidu.com/s/1VHiNbmrupYU2yN9D_nybYQ
2. Unzip it to your computer environment ！Redis A very small , Only 5M

3. Turn on Redis, Double click to run the service

4, Open the client for link test

Linux install

• Download installation package ！ Network disk link https://pan.baidu.com/s/1B7VQauxUXbuspqXpQTMcXQ

• decompression Redis Installation package ！ programmatic /opt Under the table of contents

• Enter the extracted file , You can see us Redis Configuration file for
  
• Basic environment installation

yum install gcc-c++
make
make install

• Default installation path /usr/local/bin

• Copy the default profile

• Redis It is not started in the background by default , The configuration file needs to be modified

• start-up Redis service

• Use redis-cli Test connection

• see Redis Is the process on ps -ef|grep redis
  
• close Redis service
  
• Check to see if the process exists
  

redis-benchmark( Performance tested ）

 test ：100 Two concurrent connections ,100000 A request 
redis-benchmark -h localhost -p 6379 -c 100 -n 100000

View analysis

Redis Memory retirement strategy

Redis Is to constantly delete some expired data , But there must be more and more data without expiration time , that Redis How to deal with when the memory is not enough ？ The answer is the elimination strategy （ When Redis After the memory exceeds the maximum allowed memory ,Redis Will trigger the memory obsolescence policy , Delete some unusual data , In order to make sure Redis The normal operation of the server ）

• 1、noeviction: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Just go back to error, Then do nothing
• 2、allkeys-lru: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Will scan all key, Eliminate some that have not been used recently key
• 3、volatile-lru: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Scan the expiration time in the settings key, Eliminate some that have not been used recently key
• 4、allkeys-random: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Will scan all key, Randomly eliminate some key
• 5、volatile-random: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Scan the expiration time in the settings key, Randomly eliminate some key
• 6、volatile-ttl: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Scan the expiration time in the settings key, Eliminate some that are about to expire key
• 7、volatile-lfu: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Will eliminate some set expiration time , And the least used recently key
• 8、allkeys-lfu: When adding data , If redis Judge that this operation will cause the occupied memory size to exceed the memory limit , Will scan all key, Eliminate some of the least recently used key

Redis Basic knowledge of

Relevant concepts

Redis Yes 16 A database , By default, the number... Is used 0 individual , It can be used select Command to switch

Different databases store different values , Do not interfere with each other

• keys * See all the keywords
• flushdb Clear current database
• flushall Clear all database contents

Redis It's single threaded ！

We need to understand Redis It's very fast , Official expression ,Redis It's based on memory operations ,CPU No Redis Performance bottlenecks ,Redis The bottleneck is related to the memory and network bandwidth of the machine , Since you can use single threads , It is realized by single thread ！
Redis Yes, it is c Written language , The official data is 1000000+ Of QPS, It's no better than using the same key-value Of Memecache Bad ！

Redis Why is single thread so fast ？

myth 1： Does a high-performance server have to be multi-threaded ？
myth 2： Multithreading （CPU Context switching will be performed ） It must be more efficient than a single thread ？

The core ： efficiency ：CPU > Memory > Hard disk Redis Is to put all the data in memory , It is said that using a single thread to operate is the most efficient （ Multithreading CPU The context switches , It takes time ） For memory systems , If there is no context switching, the efficiency is the highest ！