Redis usage scenario

1、 cache
        Redis Today's most familiar use scenarios . It's very effective in improving server performance ; Some frequently accessed data , If the frequently accessed data is placed in a relational database , Every query costs a lot , And put it in redis in , because redis It's in memory and can be accessed very efficiently .

for example ： Hot data cache （ For example, report 、 Star cheating ）, Object caching 、 Full page caching 、 Can improve access to hotspot data .

2、 Data sharing distributed

String type , because Redis It's a distributed, stand-alone service , It can be shared among multiple applications

for example ： Distributed Session

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<dependency>  <groupId>org.springframework.session</groupId>  <artifactId>spring-session-data-redis</artifactId> </dependency>

Default Session It's stored in a file on the server , If it's a cluster service , The same user may fall on different machines , This will cause users to log in frequently ; use Redis preservation Session after , No matter which machine the user falls on, they can get the corresponding Session Letter Rest .

3、 Ranking List
        Using traditional relational databases （mysql oracle etc. ） To do this , Very troublesome , And the use of Redis Of SortSet( Ordered set ) Data structure can be done easily ;

 

 4. Luck draw

With a random value

1	spop myset

5、 The shopping cart

String or hash. all String What can be done hash You can do it.

• key： user id;field： goods id;value： The number .
• +1：hincr.-1：hdecr. Delete ：hdel. Future generations ：hgetall. Number of goods ：hlen.

6、 Calculator / Speed governor

int type ,incr Method
        Redis Self increasing operation of middle atomicity , We can count the likes of similar users 、 Number of user visits, etc , If this kind of operation is used MySQL, Frequent reading Writing can bring considerable pressure ; The typical use scenario of speed limiter is to restrict a user's access to a certain API The frequency of , Commonly used when there is a rush to buy , prevent Stop unnecessary pressure caused by users' crazy clicks ;

7、 Simple message queuing
except Redis Own release / A subscription model , We can also use it List To implement a queuing mechanism , such as ： Notice of arrival 、 E-mail sending and so on demand , No need for high reliability , But it will bring very big DB pressure , It can be used completely List To achieve asynchronous decoupling ;

List Two blocked pop-up operations are provided ：blpop/brpop, Timeout can be set

• blpop：blpop key1 timeout Remove and get the first element of the list , If there are no elements in the list, it will block the list until the wait timeout or pop-up elements are found .
• brpop：brpop key1 timeout Remove and get the last element of the list , If there are no elements in the list, it will block the list until the wait timeout or pop-up elements are found .

Operation above . In fact, that is java Blocking queue . The more you learn . The lower the cost of learning

• queue ： First in, first out ：rpush blpop, Left head right tail , Right into the queue , Queue left
• Stack ： First in, then out ：rpush brpop

8、 Distributed lock
        In the distributed environment , You cannot use locks in a stand-alone environment to synchronize processes on multiple nodes . have access to Redis Self contained SETNX command Implement distributed locks , besides , You can also use the official RedLock Distributed lock implementation .

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publicstaticboolean getLock(String key) {     Long flag = jedis.setnx(key, "1");     if(flag == 1) {         jedis.expire(key, 10);     }     returnflag == 1; } publicstaticvoidreleaseLock(String key) {     jedis.del(key); }

String type setnx Method , Only when it doesn't exist can it be added successfully , return true