Redis
What is Redis
- Redis is an open source software based on the BSD protocol. It can be used as a database, cache, and message queue.
- Redis's processing data is all stored in memory, which greatly improves performance. In order to make data persistent, it provides two ways to write data to disk
- Redis supports many data structures, such as: list, set, hashes, string, etc.
- Redis has built-in master-slave replication and redis cluster to ensure the high availability of Redis
- The transactional nature of Redis ensures that all its commands are executed in order. When a Redis transaction occurs, a request from another client will never occur, ensuring that the commands are individually isolated. Another characteristic of the atom is that either everything succeeds or none succeeds.
Install Redis
The epel source of centos7 contains the Redis package. Can be installed directly using yum
yum install -y redis
Files after Redis installation
/etc/redis.conf #Redis的配置文件
/usr/lib/systemd/system/redis.service #Redis的服务
/usr/bin/redis-cli #Redis的客户端
/var/lib/redis #Redis默认存放的路径
Use Redis
Redis is a database based on KEY-VALUE. It supports many data structures, let’s talk about the commonly used
string
The data type supported by Redis, String. It can store up to 512M.
We use redis-cli to enter interactive mode
127.0.0.1:6379> help @string
#查询string的用法
SET
Syntax: SET key value [EX seconds] [PX milliseconds] [NX|XX]
the key used to set the string
EX seconds: expiration time
127.0.0.1:6379> SET name tangseng EX 20
OK
# 设置name键，值为tangseng ， 20s后过期
GET
Syntax: GET key
Display the value of the key
127.0.0.1:6379> GET name
"tangseng"
INCR
Syntax: INCR KEY
Increase the value of a key by 1, which must be an integer
DECR
Syntax: DECR KEY
Decrease the value of a key by 1, which must be an integer
SETNX
Syntax: SETNX key value
if the created key does not exist, create it, if it exists, do not create it
127.0.0.1:6379> SETNX name ydong
(integer) 0
# 因为name存在，创建失败
127.0.0.1:6379> SETNX students xiaowang
(integer) 1
SETEX
grammar:SETEX key seconds value
Set key value and expiration time
SETEX name 20 ydong
OK
INCRBYFLOAT
grammar:INCRBYFLOAT key increment
Increment the floating point value of the key by the given amount
127.0.0.1:6379> INCRBYFLOAT number 0.2
"7.2"
127.0.0.1:6379> INCRBYFLOAT number 0.2
"7.4"
MGET
Syntax: MGET key [key ...]
Get all the values of a given key
127.0.0.1:6379> MGET number students
1) "7.8"
2) "xiaowang"
MSET
Syntax: MSET key value [key value ...]
set the given key and key value
127.0.0.1:6379> MSET number 2 students dasheng
OK
127.0.0.1:6379> MGET number students
1) "2"
2) "dasheng"
list
listIt is a list function, like all the data is placed in a box, filled with data, then when we want to insert data, we can insert it from the left or from the right. Insert one at either end and squeeze out the data at the other end. This is what we call a message queue.
LPUSH
grammar:LPUSH key value [value ...]
Set one or more values of the key, insert from the left
127.0.0.1:6379> LPUSH colors green red yellow
(integer) 4
127.0.0.1:6379> LRANGE colors 0 2
1) "yellow"
2) "red"
3) "green"
RPUSH
grammar:RPUSH key value [value ...]
Set one or more values of the key, insert from the right end
127.0.0.1:6379> RPUSH colors blue
(integer) 4
127.0.0.1:6379> LRANGE colors 0 3
1) "yellow"
2) "red"
3) "green"
4) "blue"
LPOP
Syntax: LPOP key
delete and get the first element in the list, starting from the left
127.0.0.1:6379> LPOP colors
"yellow"
127.0.0.1:6379> LRANGE colors 0 3
1) "red"
2) "green"
3) "blue"
RPOP
Syntax: RPOP key
delete and get the first element in the list, starting from the right end
127.0.0.1:6379> RPOP colors
"blue"
127.0.0.1:6379> LRANGE colors 0 3
1) "red"
2) "green"
LPUSHX
Syntax: LPUSHX key value
Only when the list exists, add a value before the list
127.0.0.1:6379> LPUSHX name ydong
(integer) 0
127.0.0.1:6379> LPUSHX colors yellow
(integer) 3
127.0.0.1:6379> LRANGE colors 0 3
1) "yellow"
2) "red"
3) "green"
LRANGE
Syntax: LRANGE key start stop
remove the range of elements from the list
LINDEX
Syntax: LINDEX key index
Get elements by index
127.0.0.1:6379> LINDEX colors 0
"yellow"
LSET
Syntax: LSET key index value
Set the value of the index through the specified index
127.0.0.1:6379> LSET colors 0 blue
OK
127.0.0.1:6379> LRANGE colors 0 3
1) "blue"
2) "red"
3) "green"
SET
There is no sorted character set, and the members must be unique. The maximum number of members in the set is 232-1 (4294967295, each set can store more than 4 billion members). The collection of set is implemented by hash, so the performance is extremely high
SADD
grammar:SADD key member [member ...]
Add 1 or more members to the collection
127.0.0.1:6379> SADD name1 dasheng zhubajie tangseng bailongma
(integer) 4
SMEMBERS
Syntax: SMEMBERS key
Display all members in the collection
127.0.0.1:6379> SMEMBERS name1
1) "dasheng"
2) "bailongma"
3) "tangseng"
4) "zhubajie"
SPOP
Syntax: SPOP key [count]
randomly delete members and return one or more members, count can be set to delete several members
127.0.0.1:6379> SMEMBERS name1
1) "dasheng"
2) "bailongma"
3) "tangseng"
4) "zhubajie"
127.0.0.1:6379> SPOP name1 2
1) "dasheng"
2) "tangseng"
SREM
Syntax: SREM key member [member ...]
delete 1 or more members
127.0.0.1:6379> SMEMBERS name1
1) "dasheng"
2) "bailongma"
3) "tangseng"
4) "zhubajie"
127.0.0.1:6379> SREM name1 dasheng bailongma
(integer) 2
127.0.0.1:6379> SMEMBERS name1
1) "tangseng"
2) "zhubajie"
SRANDMEMBER
Syntax: SRANDMEMBER key [count]
get one or more members randomly
127.0.0.1:6379> SRANDMEMBER name1 1
1) "tangseng"
127.0.0.1:6379> SRANDMEMBER name1 1
1) "zhubajie"
SINTER
Syntax: SINTER key [key ...]
Take a collection of one or more keys
127.0.0.1:6379> SMEMBERS name1
1) "zhubajie"
2) "tangseng"
127.0.0.1:6379> SMEMBERS name2
1) "dasheng"
2) "shawujing"
3) "tangseng"
127.0.0.1:6379> SINTER name1 name2
1) "tangseng"
SUNION
Syntax: SUNION key [key ...]
Take a key or a collection of multiple keys
127.0.0.1:6379> SUNION name1 name2
1) "dasheng"
2) "shawujing"
3) "tangseng"
4) "zhubajie"
SDIFF
Syntax: SDIFF key [key ...]
the difference between the two keys, the first key removes the same members as the second key, and returns the result of the first key
127.0.0.1:6379> SDIFF name1 name2
1) "zhubajie"
SISMEMBER
Syntax: SISMEMBER key member
Determine whether the given value is in the key
127.0.0.1:6379> SISMEMBER name1 shawujing
(integer) 0
127.0.0.1:6379> SISMEMBER name1 zhubajie
(integer) 1
sorted_set
Ordered collection, no duplicate values, sorted according to the given score.
ZADD
Syntax: ZADD key [NX|XX] [CH] [INCR] score member [score member ...]
Add one or more members to the sorted set. If it already exists, update its score. After the addition is completed, it will be automatically sorted according to the score
127.0.0.1:6379> ZADD score 60 xiaotian 80 xiaoming 70 xiaohong
(integer) 3
ZCARD
Syntax: ZCARD key
get the number of members in the key
127.0.0.1:6379> ZCARD score
(integer) 3
ZCOUNT
Grammar: How ZCOUNT key min max
many members are between the largest and smallest
127.0.0.1:6379> ZCOUNT score 70 90
(integer) 2
ZRANK
Syntax: ZRANK key member
return the index of a given member value
127.0.0.1:6379> ZRANK score xiaotian
(integer) 0
ZRANGE
Syntax: ZRANGE key start stop [WITHSCORES]
Return all members within the given index range
127.0.0.1:6379> ZRANGE score 0 2
1) "xiaotian"
2) "xiaohong"
3) "xiaoming"
hash
Equivalent to an associative array, storing data with key[field] value
HSET
Syntax: HSET key field value
Set the field and value of a key
127.0.0.1:6379> HSET class xiaoming 1
(integer) 1
HMSET
Syntax: HMSET key field value [field value ...]
Set the fields and values of multiple keys
127.0.0.1:6379> HMSET class xiaohong 2 xiaotian 3 xiaoma 1
OK
HGET
Syntax: HGET key field
According to a given field, return value
127.0.0.1:6379> HGET class xiaoming
"1"
HMGET
Syntax: HMGET key field [field ...]
According to the given field, return all values
127.0.0.1:6379> HMGET class xiaoming xiaohong xiaotian
1) "1"
2) "2"
3) "3"
HKEYS
Syntax: HKEYS key
return all fields in the key
127.0.0.1:6379> HKEYS class
1) "xiaoming"
2) "xiaohong"
3) "xiaotian"
4) "xiaoma"
HVALS
Syntax: HVALS key
return all values in the key
127.0.0.1:6379> HVALS class
1) "1"
2) "2"
3) "3"
4) "1"
HDEL
Syntax: HDEL key field [field ...]
delete one or more fields
127.0.0.1:6379> HDEL class xiaoming xiaohong
(integer) 2
HGETALL
Syntax: HGETALL key
Return all fields and values in the key
127.0.0.1:6379> HGETALL class
1) "xiaotian"
2) "3"
3) "xiaoma"
4) "2"
pub/sub
Publish, subscribe. The news published by the publisher can be sent to specific subscribers through the channel. On the contrary, if the subscriber is interested in multiple channels, it can follow more publishers.
If the message published by the publisher is sent to a large number of subscribers, a 1-to-N effect can be achieved.
PSUBSCRIBE
Syntax: PSUBSCRIBE pattern [pattern ...]
listen to messages posted to channels in pattern mode.
127.0.0.1:6379> PSUBSCRIBE football
Reading messages... (press Ctrl-C to quit)
1) "psubscribe"
2) "football"
3) (integer) 1
#监听之后，。会阻塞在这里，等发布者发布消息到对应的频道
PUBLISH
Syntax: PUBLISH channel message
publish a message to the specified channel
127.0.0.1:6379> PUBLISH football hello
(integer) 1
Subscribers will receive the message
127.0.0.1:6379> PSUBSCRIBE football
Reading messages... (press Ctrl-C to quit)
1) "psubscribe"
2) "football"
3) (integer) 1
1) "pmessage"
2) "football"
3) "football"
4) "hello"
UNSUBSCRIBE
Syntax: UNSUBSCRIBE [channel [channel ...]]
unsubscribe
Redis configuration file
NETWORK
bind: Bind address, which is bound to 127.0.0.1 by default. If you want to bind to all addresses, write:bind 0.0.0.0protected-mode: Whether to enable security authentication. When the user does not display the specified bind or password, this option will only be accessed locally. The user has set a password and bind address and can be opened. The default is yesport 6379: Redis porttcp-backlog 511: The length of the queue for tcp to complete the three-way handshake. In the case of high concurrency, it is generally necessary to increase this item. Alleviate the slow down of user connections. You can refer to the definition of tcp-backlogunixsocket /tmp/redis.sock: Set the file path of the socket, it can be opened if it is only accessed by the local machine.timeout 0: The client is automatically disconnected if it does not connect to the server within the specified idle time, 0 means no disconnectiontcp-keepalive 300: If the setting is not 0, the so_keepalive value of tcp is used. This detection has two advantages. It can detect the status of the peer device, and it can also detect whether the network device connection in the middle is alive. Linux internally set how long it takes to send an ack message to the Redis socket, and it takes twice as long to close the connection of the peer. This time has been tested and 300s is a reasonable value
GENERAL
daemonize no: Whether to run as a daemonpidfile /var/run/redis_6379.pid: Process fileloglevel notice: Logging levellogfile /var/log/redis/redis.log: Log pathsyslog-enabled no: Whether to use syslog to record logs, just choose onedatabases 16: Redis as a database, how many libraries can be supported at most. 16 by default
Redis persistence
SNAPSHOTTING
The default persistent storage function of Redis is to periodically synchronize the data in the memory to the disk according to the command displayed by the client. The data is stored in /var/lib/redis/dump.db by default
The persistent storage method is defined in the configuration file:
save <seconds> <change>
save 900 1: If there is a key change in 900 seconds, take a snapshotsave 300 10: If there are 10 key changes in 300 seconds, take a snapshotsave 60 10000: There are 1w key changes in 60 seconds, just take a snapshot
Other related configuration
stop-writes-on-bgsave-error yes: If the dump file fails to write, whether to prohibit new operation requests from coming inrdbcompression yes: Whether the snapshot is compressed when copying to the diskrdbchecksum yes: Check the consistency of the datadbfilename dump.rdb: Store the file namedir /var/lib/redis: Dump storage path
In addition to the automatic storage method in the configuration file above, you can also explicitly use commands to store it in the interactive line. savewithbgsave
save: When using save, the redis client will be blocked until the RDB execution ends, and the new RDB file will replace the old filebgsave: Redis forks the parent process and the child process, and all the persistent storage is completed by the child process. This blocking only occurs in the fork process, and this process will be very short.
The use of RDB persistent storage has the following characteristics:
- Since RDB is a snapshot at a certain moment, it can be used as a full backup
- RDB is a single file, which can be restored much faster than AOF, and RDB files can be sent to another host for disaster recovery backup
- Since RDB is a snapshot, when the host fails, data will be lost at a certain moment, resulting in incomplete data
APPEND ONLY MODE
AOF is different from RDB. AOF appends each record to a file on the disk in seconds. When redis is shut down and restarted, it will automatically read the record into the memory.
Since the AOF file will be written larger and larger, redis provides the BGREWRITEAOF command, which reads the data in the existing memory and writes it in the temporary file by command, and replaces the existing AOF file after completion.
Related configuration:
appendonly no: Whether to enable AOF, default NOappendfilename "appendonly.aof": The name of the stored file, the default path /var/lib/redisappendfsync everysec: AOF synchronizes once per second, and AOF also provides two ways.always：Every sentence once, as long as the sentence is written, it is immediately saved in the fileno: Redis does not automatically perform synchronization operations, but the kernel determines when to perform synchronization operations
no-appendfsync-on-rewrite no: Whether to mobilize fsync during AOF rewriting in the background. no means callauto-aof-rewrite-percentage 100: Compare the new part with the original one, and rewrite it when it reaches 100%auto-aof-rewrite-min-size 64mb：Compare the new part with the original one, the minimum difference is 64M- The above two differences must be met at the same time to enable automatic rewriting
aof-load-truncated yes: There is a problem with the sentence during the recovery process, whether to automatically clear it
LUA SCRIPTING
requirepass centos:safety certificate.
Need to use in interactive modeAUTH password
127.0.0.1:6379> GET name
(error) NOAUTH Authentication required.
127.0.0.1:6379> AUTH centos
OK
127.0.0.1:6379> GET name
(nil)
Or use the -a option in the command line
[root@localhost ~]# redis-cli -a centos
127.0.0.1:6379> keys *
1) "num"
2) "colors"
3) "students"
4) "number"
LIMITS
maxclients 10000: Maximum number of concurrent connectionsmaxmemory <bytes>: Set the maximum memory occupied by redis. When the occupied memory reaches the upper limit, themaxmemory-policypreviously set key will be eliminated according to it.maxmemory-policy noeviction: Redis default strategy, no value is eliminated, redis provides the following elimination strategiesvolatile-lru: Use the LRU algorithm to eliminate the keys that set the expiration timeallkeys-lru: LRU algorithm for all keysvolatile-random: Randomly eliminate keys with expiration timeallkeys-random: Random eliminationvolatile-ttl：Compared with the key that sets the expiration time, the smaller the key