Redis 6

Catalog

Redis 6

One ．Redis Introduce

Two ． Download and install

2.1Redis Common command

2.2redis Boot interface

2.3 Redis It's single threaded

2.4 Redis Why is single thread so fast ？

2.5 Redis-key Basic commands

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This article is my previous notes , If I saw it on the Nuggets, it's right , Or myself Cheng Cheng My personal homepage - dynamic - Nuggets This is the only one . If there is anything wrong, you are welcome to point out the problem , I am a little white .

The last article is ：CSDN , This is Redis.

If it is springboot If so, please see springboot Create project _ Cheng Cheng is Xiaobai's blog -CSDN Blog , This is from scratch, not finished springboot, Study together ！！！！

One ．Redis Introduce

      Redis（Remote Dictionary Server ), Remote dictionary service , Is an open source use ANSI C Language writing 、 Support network 、 Log type that can be memory based or persistent 、Key-Value database , And provide multilingual API.

redis It's a key-value The storage system . and Memcached similar , It supports storage value There are more types , Include string( character string )、list（ Linked list ）、set( aggregate )、zset(sorted set -- Ordered set ) and hash（ Hash type ）. these data type All support push/pop、add/remove And take intersection, union and difference sets and more abundant operations , And these operations are atomic . On this basis ,redis Support various sorts of sorting . And memcached equally , To ensure efficiency , The data is cached in memory . The difference is 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 Is a high-performance key-value database . redis Appearance , A lot of compensation memcached This kind of key/value Insufficient storage , In the department The situation can be a good complement to the relational database . It provides Java,C/C++,C#,PHP,JavaScript,Perl,Object-C,Python,Ruby,Erlang Such as the client , Easy to use . 

Redis Support master-slave synchronization . Data can be synchronized from the master server to any number of slaves , A slave server can be the master server associated with other slaves . This makes Redis Single-layer tree replication can be performed . The disk can write to the data intentionally or unintentionally . Because it's fully realized Release / subscribe Mechanism , Enables trees to be synchronized anywhere from the database , Subscribe to a channel and receive a complete record of message publication from the master server . Synchronization helps with scalability and data redundancy for read operations .

redis Official website , Very easy to remember , yes redis.io.（ The domain name suffix io It's a country domain , yes british Indian Ocean territory, The British Indian Ocean territory ）,Vmware In the fund redis Project development and maintenance .

from 2010 year 3 month 15 The date of ,Redis Development work by VMware host . from 2013 year 5 Month begins ,Redis The development of the Pivotal sponsorship .

Two ． Download and install

 download epel Warehouse yum install epel-release -y
 download redis database yum install redis -y
 start-up redis service systemctl start redis

2.1Redis Common command

systemctl status redis View service status

systemctl stop redis Out of Service

systemctl restart redis Restart the service

ps -ef | grep redis see reids Service information

systemctl enable redis redis Boot up

2.2redis Boot interface

Set up redis Remote connection and password

vim /etc/redis.conf   without vim First yum install -y vim

notes #bind 127.0.0.1

modify protected-mode no

modify daemonize yes

modify requirepass Dd123=123

Turn off firewall or open 6379 port ( Please Baidu )

1,yum install redis      -- install redis database （-- yum How to install redsi Configuration file in /etc/redis.conf）

2,systemctl start redis.service -- Turn on redis service

3,ps -ef | grep redis -- see redis Open or not

4, Repair configuration file - Change Password

# requirepass foobared Remove the comment , It is amended as follows requirepass 123456 // Change Password

1. systemctl restart redis.service -- restart

/usr/local/bin/redis-cli Enter operation

Redis Basic knowledge of

Redis The default is 16 A database , The default is number 0 individual .

have access to select Switch the database ,

DBSIZE see DB size ,

keys * View all key,

Clear current database flushdb,

Clear all database contents flushall

2.3 Redis It's single threaded

understand Redis It's very fast , Official expression ,Redis It's based on memory operations ,CPU No Redis Performance bottleneck ,Redis The bottleneck is based on the memory and network bandwidth of the machine , It can be realized by using one-way process , Just use a single thread ！ All used

Redis yes C Written language , The official data is 100000+QPS, It's no better than using the same key-vale Of Memecache

2.4 Redis Why is single thread so fast ？

The official interpretation seems to be ：

CPU It's not you who use Redis Bottleneck , Because usually Redis Or limited by memory , Or it's limited by the Internet . for example , Used in general Linux The pipeline running on the system Redis One million requests per second , therefore , If your application primarily uses O（N） or O（log（N）） command , It's almost impossible to use too much CPU .

however , In order to make the most of CPU, You can start multiple on the same server Redis example , And treat them as different servers . At some point , A single instance may not be enough , therefore , If you want to use multiple CPU, You can start to consider some method of dividing earlier .

however , stay Redis 4.0 in , We began to make Redis Have more threads . at present , This is limited to deleting objects in the background , And stop passing Redis Commands implemented by the module . For future versions , The plan is to make Redis More and more threaded .

since redis The bottleneck is not cpu, So when a single thread can be implemented , Naturally, single threads are used .

My own interpretation

got it redis It's memory based .

Multithreading is the use of multiple cpu Simulate multiple threads , Yes redis To operate . This will cause a huge problem , Namely cpu The context switching problem of .cpu The efficiency of context switching is much lower than reading directly in memory .redis Using a single cpu Bind a memory , Memory processing is single threaded , This avoids context switching , So it's very fast .

that redis Adopting single thread also avoids many problems . If redis Use multithreading to , Then we must consider the data security problems brought by multithreading , When operating redis Of list,hash Wait for the data structure . Multithreading may lead to data insecurity , This is to lock . Once locked, the execution speed of the program will be affected .

1. myth 1： High performance servers must be multithreaded ？

2. myth 2： Multithreading （CPU The context switches ） It must be more efficient than a single thread ！

Go first CPU> Memory > To understand the speed of the hard disk :

The core ：Redis Is to prevent all data from being stored in the memory system , So the efficiency of using single thread operation is the highest , Multithreading （CPU The context switches ： The long-running ！！）, For memory systems , If there is no context switching, the efficiency is the highest ！ Read and write many times in the same CPU Upper , In the case of memory, this is the best solution ！

2.5 Redis-key Basic commands

EXISTS name Judge the present key Whether there is

Keys * View all

Clear Clear the screen

Del/unlink name Delete specified data

Move name 1 Remove current key

EXPIRE name 10 Set up key The expiration time of , Unit second

TTL name View the current key The rest of the time

Type name View the current key A type of