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Redis tutorial

2022-07-25 01:45:00 【51CTO】

redis course ：

summary

redis It's a kind of nosql database , His data is stored in memory , meanwhile redis Can regularly synchronize memory data to disk , That is, data can be persisted , And he's better than memcached Support more data structures (string,list list [ Queues and stacks ],set[ aggregate ],sorted set[ Ordered set ],hash(hash surface )). Relevant reference documents ： http://redisdoc.com/index.html

redis Use scenarios ：

Login session store ： Stored in redis in , And memcached comparison , Data will not be lost .
Ranking version / Counter ： For example, some show projects , There are often some top anchor rankings . There are also some techniques for reading articles , Or the number of likes on Sina Weibo .
As message queue ： such as celery Is the use of redis As a middleman .
The current number of people online ： Or the previous show example , It will show how many people are online in the current system .
Some commonly used data caching ： Like our BBS Forum , Plates don't change often , But every time you visit the home page, you have to start from mysql In order to get , Can be in redis In the cache , You don't have to request the database every time .
The former 200 Article cache or comment cache ： General users browse websites , I will only browse the previous articles or comments , Then you can put the front 200 Article and corresponding comments are cached . User access exceeds , Just access the database , And later articles exceed 200 piece , Delete the previous article .
Friend relationship ： Microblogging friends use redis Realization .
Publish and subscribe ： Can be used to make chat software .

`redis` and `memcached` Comparison ：

	memcached	redis
type	Pure memory database	Memory disk synchronization database
data type	In defining value We need to fix the data type	Unwanted
Virtual memory	I won't support it	Support
Expiration strategy	Support	Support
Storage data security	I won't support it	You can synchronize data to dump.db in
disaster recovery	I won't support it	You can restore the data in the disk to memory
Distributed	Support	Master slave synchronization
Subscribe and publish	I won't support it	Support

`redis` stay `ubuntu` Installation and startup in the system

install ：

       
        sudo apt-get install redis-server
      
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uninstall ：

       
        sudo apt-get purge --auto-remove redis-server
      
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start-up ：redis After installation , It will start automatically by default , You can view... With the following command ：

       
        ps aux|grep redis
      
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If you want to start it manually , You can start with the following command ：

       
        sudo service redis-server start
      
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stop it ：

       
        sudo service redis-server stop
      
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Yes `redis` The operation of

Yes redis There are two ways to do this , The first way is to use redis-cli, The second way is programming language , such as Python、PHP and JAVA etc. .

Use redis-cli Yes redis String operation ：
start-up redis：

       
         sudo service redis-server start
      
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Connected to the redis-server：

       
         redis-cli -h [ip] -p [ port ]
      
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add to ：

       
         set key value
       
   Such as ：
       
  set username xiaotuo
      
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String value value Related to key. If key Has held other values ,set The order overwrites the old value , Regardless of the type . And the default expiration time is permanent , That is, it will never expire .

Delete ：

       
         del key
       
   Such as ：
       
  del username
      
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Set expiration time ：

       
         expire key timeout( The unit is in seconds )
      
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You can also set the value when , Specify expiration time together ：

       
         set key value EX timeout
       
   or ：
       
  setex key timeout value
      
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View expiration time ：

       
         ttl key
       
   Such as ：
       
  ttl username
      
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View the current redis All in key：

The list of operations ：

Add an element to the left of the list ：

       
         lpush key value
      
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Will value value Insert into list key The header . If key non-existent , An empty list is created and executed lpush operation . When key When there is but not a list type , An error will be returned .

Add an element to the right of the list ：

       
         rpush key value
      
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Will value value Insert into list key At the end of the watch . If key non-existent , An empty list is created and executed RPUSH operation . When key When there is but not a list type , Return an error .

View the elements in the list ：

       
         lrange key start stop
      
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Returns a list of key The elements in the specified interval , The interval is offset by start and stop Appoint , If you want the first to the last on the left lrange key 0 -1.

Remove the elements from the list ：

Remove and return to list key The head element of ：

       
         lpop key
      
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Remove and return the last element of the list ：

       
       rpop key
      
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Remove and return to list key The intermediate element of ：

       
         lrem key count value
      
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Will delete key In this list ,count The values are value The elements of .

Specifies the number of elements to return ：

       
         lindex key index
      
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Will return key In this list , The index for index This element of .

Get the number of elements in the list ：

       
         llen key
       
   Such as ：
       
  llen languages
      
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Delete the specified element ：

       
         lrem key count value
       
   Such as ：
       
  lrem languages 0 php
      
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According to the parameters count Value , Remove the list and parameters value Equal elements .count The values of can be the following ：

count > 0： Search from header to footer , Remove and value Equal elements , The number of count.
count < 0： Search from the end of the table to the header , Remove and value Equal elements , The number of count The absolute value of .
count = 0： Remove all and from the table value Equal value .

set Operations on collections ：

Additive elements ：

       
         sadd set value1 value2....
       
   Such as ：
       
  sadd team xiaotuo datuo
      
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Check out the elements ：

       
         smembeers set
       
   Such as ：
       
  smembers team
      
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Remove elements ：

       
         srem set member...
       
   Such as ：
       
  srem team xiaotuo datuo
      
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View the number of elements in the collection ：

       
         scard set
       
   Such as ：
       
  scard team1
      
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Get the intersection of multiple sets ：

       
         sinter set1 set2
       
   Such as ：
       
  sinter team1 team2
      
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Get union of multiple sets ：

       
         sunion set1 set2
       
   Such as ：
       
  sunion team1 team2
      
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Get the difference set of multiple sets ：

       
       sdiff set1 set2
       
 Such as ：
       
sdiff team1 team2
      
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hash The hash operation ：

Add a new value ：

       
         hset key field value
       
   Such as ：
       
  hset website baidu baidu.com
      
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Hash table key In the domain field The value of the set value.
If key non-existent , A new hash table is created and executed HSET operation . If the domain field It already exists in the hash table , The old value will be overwritten .

Gets the in the hash field Corresponding value ：

       
         hget key field
       
   Such as ：
       
  hget website baidu
      
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Delete field One of the field：

       
         hdel key field
       
   Such as ：
       
  hdel website baidu
      
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Get all in a hash field and value：

       
         hgetall key
       
   Such as ：
       
  hgetall website
      
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Get all in a hash field：

       
         hkeys key
       
   Such as ：
       
  hkeys website
      
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Get all the values in a hash ：

       
       hvals key
       
 Such as ：
       
hvals website
      
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Determine if there is a... In the hash field：

       
       hexists key field
       
 Such as ：
       
hexists website baidu
      
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Get the total key value pairs in the hash ：

       
       hlen field
       
 Such as ：
       
hlen website
      
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The transaction operations ：Redis Transactions can execute more than one command at a time , Transactions have the following characteristics ：

Isolation operation ： All commands in the transaction are serialized 、 To execute in order , Will not be disturbed by other orders .
Atomic manipulation ： The commands in the transaction are either all executed , Or none of it .
Start a transaction ：

All future commands , Are executed in this transaction .

Perform transactions ：

Will be in multi and exec Submit together with the operations in .

Cancel the business ：

       
         discard
      
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Will multi All subsequent commands are cancelled .

Monitor one or more key：

       
         watch key...
      
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Watch one ( Or more )key, If before the transaction is executed ( Or these ) key Altered by other orders , Then the business will be interrupted .

Cancel all key Surveillance ：

       
         unwatch
      
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Release / Subscription operation ：

Post a message to a channel ：

       
         publish channel message
      
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Subscribe to messages on a channel ：

       
         subscribe channel
      
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Persistence ：redis Two data backup methods are provided , One is RDB, The other is AOF, These two backup strategies are described in detail below ：
| | RDB | AOF | | --- | --- | --- | | On off | Turn on ： Default on . close ： Put all in the configuration file save All notes , It's just shut down . | Turn on ： In the configuration file appendonly yes It turns on aof, by no close . | | Synchronization mechanism | You can specify how many commands occur in a certain time to synchronize . such as 1 Within minutes 2 subcommand , Just synchronize once . | Synchronize every second or after every command | | Store content | What's stored is redis The specific value inside | What is stored is the operation command of updating data executed | | The path where the file is stored | according to dir as well as dbfilename To specify the path and specific file name | according to dir as well as appendfilename To specify the specific path and file name | | advantage | （1） Storing data in a file is compressed , File volume ratio aof Small .（2） Because it stores redis Specific value , And it will be compressed , Therefore, the recovery speed is faster than AOF fast .（3） Ideal for backup . | （1）AOF Our strategy is to synchronize every second or every time a write occurs , So even if the server fails , At most, it will only be lost 1 Second data . （2）AOF What's stored is Redis command , And it is directly added to aof Behind file , So every time you back up, just add new data .（3） If AOF The file is quite large , that Redis Will be rewritten , Keep only the smallest set of commands . | | shortcoming | （1）RDB The synchronization mechanism will start when how many write operations occur in how long , Because of the compression mechanism ,RDB When synchronizing, save the whole again Redis Data in , So you usually set it at least 5 The data is saved only once per minute . under these circumstances , Once the server fails , Can cause 5 Minutes of data lost .（2） Save the data in RDB When ,Redis Meeting fork A child process is used to synchronize , When the amount of data is large , It can be very time consuming . | （1）AOF The file is not compressed , So the volume ratio RDB Big . （2）AOF Backup every second or every write operation , Therefore, if the concurrency is large , Efficiency may be a little slow .（3）AOF File because it stores commands , So in disaster recovery Redis It will run again AOF The command , Not as fast as RDB. | | more | http://redisdoc.com/topic/persistence.html#redis | |
Security ： In the configuration file , Set up requirepass password, When the client connects , Need to use password ：

       
        > redis-cli -p 127.0.0.1 -p 6379
       
 redis> set username xxx
       
 (error) NOAUTH Authentication required.
       
 redis> auth password
       
 redis> set username xxx
       
 OK
      
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Python operation redis

install python-redis：

       
        pip install redis
      
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Create a new file, such as redis_test.py, Then initialize a redis Instance variables , And in ubuntu Open in virtual machine redis. For example, virtual machine ip The address is 192.168.174.130. The sample code is as follows ：

       
        #  from redis Import Redis class 
       
 from redis import Redis
       
 #  initialization redis Instance variables 
       
 xtredis = Redis(host='192.168.174.130',port=6379)
      
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Operations on strings ： operation redis Method name of , Same as before redis-cli equally , Now let's make a brief introduction to some commonly used , The sample code is as follows ( Undertake the above code )：

       
        #  Add a value in , And set the expiration time to 60 second , If not set , Will never expire 
       
 xtredis.set('username','xiaotuo',ex=60)
       
 #  Get a value 
       
 xtredis.get('username')
       
 #  Delete a value 
       
 xtredis.delete('username')
       
 #  Give a value self increment 1
       
 xtredis.set('read_count',1)
       
 xtredis.incr('read_count')  #  Now read_count Turn into 2
       
 #  Decrease a value 1
       
 xtredis.decr('read_count') #  Now read_count Turn into 1
      
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Operations on lists ： Same string operation , Name and use of all methods redis-cli The operation is the same ：

       
        #  to languages Add one to the left of this list python
       
 xtredis.lpush('languages','python')
       
 #  to languages Add one to the left of this list php
       
 xtredis.lpush('languages','php')
       
 #  to languages Add one to the left of this list javascript
       
 xtredis.lpush('languages','javascript')
       
 #  obtain languages All values in this list 
       
 print xtredis.lrange('languages',0,-1)
       
 > ['javascript','php','python']
      
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Operations on sets ：

       
        #  To assemble team Add an element xiaotuo
       
 xtredis.sadd('team','xiaotuo')
       
 #  To assemble team Add an element datuo
       
 xtredis.sadd('team','datuo')
       
 #  To assemble team Add an element slice
       
 xtredis.sadd('team','slice')
       
 #  Get all the elements in the collection 
       
 xtredis.smembers('team')
       
 > ['datuo','xiaotuo','slice'] #  A disorderly 
      
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Pair hash (hash) The operation of ：

       
        #  to website Add to this hash baidu
       
 xtredis.hset('website','baidu','baidu.com')
       
 #  to website Add to this hash google
       
 xtredis.hset('website','google','google.com')
       
 #  obtain website All values in this hash 
       
 print xtredis.hgetall('website')
       
 > {"baidu":"baidu.com","google":"google.com"}
      
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Business ( The Conduit ) operation ：redis Support transaction operations , That is, some operations can only be completed uniformly , It's done . Otherwise, the execution fails , use python operation redis It's also very simple , The sample code is as follows ：

       
        #  Define a pipe instance 
       
 pip = xtredis.pipeline()
       
 #  Do the first step , to BankA Self growth 1
       
 pip.incr('BankA')
       
 #  Do the second step , to BankB Self reduction 1
       
 pip.desc('BankB')
       
 #  Perform transactions 
       
 pip.execute()
      
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The above shows python-redis Some common methods of , If you want to know more about other methods , You can refer to python-redis Source code （ View the source code pycharm Shortcut key prompt ： Place the mouse cursor on import Redis Of Redis On , Then press ctrl+b You can enter ）.

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