Introduction to redis II: RedHat 6.5 installation and use

Redis The server

Redis There will be one in the directory redis.conf The configuration file , It's inside Redis Default configuration , Generally speaking, we will start multiple... On one machine Redis, And centrally manage the configuration in the specified directory , Handwritten configuration... And not completely handwritten , It's going to be redis.conf Modify as a template .

Use the configuration file to start ：redis-server redis.conf The path of /redis.confRedis Command line client

C/C++ operation Redis Use hiredis

Log in and copy

      
      

       
         1 #include <hiredis/hiredis.h>
       
       
  2 #include <iostream>
       
       
  3 #include <string>
       
       
  4 #include "time.h"
       
       
  5 int main(int argc, char**argv)
       
       
  6 {
       
       
  7         struct timeval timeout = {2, 0}; //2s Timeout time 
       
       
  8         //redisContext yes Redis Action object 
       
       
  9         redisContext *pRedisContext = (redisContext*)redisConnectWithTimeout("127.0.0.1",6379,timeout);
       
       
 10         if((NULL == pRedisContext)||(pRedisContext->err))
       
       
 11         {
       
       
 12                 if(pRedisContext)
       
       
 13                 {
       
       
 14                         std::cout << "connect error:" << pRedisContext->errstr << std::endl;
       
       
 15                 }else{
       
       
 16                         std::cout << "connect error: can't allocate redis context" << std::endl;
       
       
 17                 }
       
       
 18                 return -1;
       
       
 19         }
       
       
 20         //redisReply yes Redis Command reply object  redis The returned information is saved in redisReply object 
       
       
 21         redisReply *pRedisReply = (redisReply*)redisCommand(pRedisContext, "INFO");
       
       
 22         std::cout << pRedisReply->str << std::endl;
       
       
 23         // After each execution Redis You need to clear after the command redisReply In order to avoid the next Redis Impact of operation 
       
       
 24         freeReplyObject(pRedisReply);
       
       
 25         return 0;
       
       
 26 }
      
      
      
      

       
       
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Redis There are two advantages to this design ： First of all , Internal coding can be improved , And the external data structure and command have no influence , So once you develop better internal code , There is no need to change the external data structure and commands , for example Redis3.2 Provides quicklist, Combined with the ziplist and linkedlist Advantages of both , Provides a better internal coding implementation for list types , For external users, it is almost imperceptible . second , A variety of internal coding implementations can play their own advantages in different scenarios , for example ziplist More memory saving , But when there are more list elements , There will be a drop in performance , Now Redis The internal implementation of the list type is converted to linkedlist.

The internal encoding of a string type is 3 Kind of ：int(8 A long integer of bytes )、embstr( Less than or equal to 39 A byte string )、raw( Greater than 39 A byte string ).

The internal codes of list types are 2 Kind of ：
ziplist（ Compressed list ） When the number of elements in the list is less than list-max-ziplist-entries To configure （ Default 512 individual ）、 At the same time, the value of each element in the list is less than list-max-ziplist-value To configure （ Default 64 byte ） when ,Redis Will use ziplist As an internal implementation of hash to reduce memory usage .
linkedlist（ Linked list ） When the list type cannot satisfy ziplist The condition of ,Redis Will use linkedlist As an internal implementation of the list .
Redis 3.2 Version provides quicklist Internal encoding , To put it simply, it takes a ziplist For node linkedlist, It is a combination of ziplist and linkedlist Advantages of both .

The internal encoding of hash type is 2 Kind of ：
ziplist（ Compressed list ） When the number of hash type elements is less than hash-max-ziplist-entries To configure （ Default 512 individual ）、 At the same time, all values are less than hash-max-ziplist-value To configure （ Default 64 byte ） when ,Redis Will use ziplist As an internal implementation of hash ,ziplist Use a more compact structure to achieve continuous storage of multiple elements , So in terms of saving memory hashtable Better .
hashtable（ Hashtable ） When the hash type cannot be satisfied ziplist The condition of ,Redis Will use hashtable As an internal implementation of hash , So now ziplist The efficiency of reading and writing will decrease , and hashtable The time complexity of reading and writing is O(1).

There are two types of internal encoding for collection types ：
intset（ Set of integers ） When all the elements in the set are integers and the number of elements is less than set-max-intset-entries To configure （ Default 512 individual ） when ,Redis Will choose intset As an internal implementation of a collection , Thus reducing the use of memory .
hashtable（ Hashtable ） When the set type cannot satisfy intset The condition of ,Redis Will use hashtable As an internal implementation of a collection .

There are two kinds of internal codes for ordered set types ：
ziplist（ Compressed list ） When the number of elements in an ordered set is less than zset-max-ziplist-entries To configure （ Default 128 individual ）, At the same time, the value of each element is less than zset-max-ziplist-value To configure （ Default 64 byte ） when ,Redis Will use ziplist As an internal implementation of an ordered set ,ziplist Can effectively reduce the use of memory .
skiplist（ Skip list ） When ziplist When the conditions are not met , Ordered sets will use skiplist As an internal implementation , So now ziplist The efficiency of reading and writing will decrease .

Use scenarios for lists ：

lpush+brpop The command combination can block the queue , The producer client uses lpush Insert elements from the left side of the list , Multiple consumer clients use brpop Command blocking grabs the elements at the end of the list .

data structure	Whether duplicate elements are allowed	Is it orderly	Orderly implementation	Storage	Application scenarios
list	yes	yes	Index the following table	value	time axis 、 Message queuing, etc
Hash	no	no	nothing	Key value
aggregate	no	no	nothing	value	label 、 Social, etc
Ordered set	no	yes	fraction	Key value	Ranking system 、 Social, etc

Redis It is a single thread to process commands , A command from the client to the server will not be executed immediately , All commands go into a queue , And then it's executed one by one . The execution order of multiple client commands is uncertain , But no two commands will be executed at the same time .Redis Use epoll As I/O The realization of multiplexing technology , Plus Redis Its own event handling model will epoll Connection in 、 Reading and writing 、 Close all converted to events , Not in the network I/O Waste too much time on .

The communication protocol between client and server is TCP Built on top of the agreement .Redis Formulated the RESP(Redis Serialization Protocol,Redis Serialization protocol ) Realize the normal interaction between the client and the server .

​ ​http://zeromq.org/​​

Redis 3.0 Chinese annotation
​​ ​ https://github.com/huangz1990/redis-3.0-annotated​​