2024-07-12
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A relational database is a structured database, built on a relational model database, and is record-oriented.
Common relational databases: Oracle, MySQL, SQL Server, Microsoft Access, DB2.
NOSQL=Not Only SQL is a general term for non-relational databases. Depending on the storage method, storage structure and usage scenario, it is called a non-relational database. Databases other than mainstream relational databases can be called non-relational databases.
Common non-relational databases: Redis, MongoDB, Hbase, CouhDB.
Redis is an open source NoSQL database written in C language. It runs based on memory and supports persistence. It uses key-value storage. Its port number is 6379.
1. Install Redis
[root@localhost ~]# systemctl stop firewalld
[root@localhost ~]# setenforce 0
[root@localhost ~]# yum -y install gcc* zlib-devel
[root@localhost ~]# tar xvzf redis-4.0.9.tar.gz
[root@localhost ~]# cd redis-4.0.9/
[root@localhost redis-4.0.9]# make
Notice:
After make, an error message will be generated.
solution:
Solution 1: Use make MALLOC=libc to specify the memory allocator as libc for compilation
Solution 2: make clean && make distclean
[root@localhost redis-4.0.9]# make PREFIX=/usr/local/redis install
[root@localhost utils]# ln -s /usr/local/redis/bin/* /usr/local/bin/
[root@localhost redis-4.0.9]# cd utils/
Among them: install_server.sh is the initialization script
[root@localhost utils]# ./install_server.sh
Please select the redis executable path [] /usr/local/redis/bin/redis-server (Give the executable path)
View process and service control
[root@localhost utils]# netstat -anpt | grep redis
tcp 0 0 127.0.0.1:6379 0.0.0.0:* LISTEN 5360/redis-server 1
[root@localhost utils]# /etc/init.d/redis_6379 stop (redis is closed)
[root@localhost utils]# /etc/init.d/redis_6379 start (Open)
[root@localhost utils]# /etc/init.d/redis_6379 status (state)
Modification of configuration parameters
[root@localhost ~]#vim /etc/redis/6379.conf
bind 127.0.0.1 192.168.10.101 //Host address to listen to
port 6379 //port
daemonize yes // Enable the daemon process
pidfile /var/run/redis_6379.pid //Specify PID file
loglevel notice //Log level
logfile /var/log/redis_6379.log //Specify the log file
[root@localhost~]#/etc/init.d/redis_6379 restart
2. redis command tool
[root@localhost utils]# redis-cli (Local login)
[root@localhost utils]# redis-cli -h 192.168.10.101 -p 6379 (Remote login)
192.168.10.101:6379> ping (Test service is running normally)
PONG
3: redis-benchmark test tool
redis-benchmark is the official Redis performance testing tool that can effectively test the performance of the Redis service.
(1) Test request performance
[root@localhost ~]#redis-benchmark -h 192.168.10.101 -p 6379 -c 100 -n 100000
Remark:
-h: specifies the server host name;
-p: specifies the server port;
-c: specifies the number of concurrent connections;
-n: specifies the number of requests;
(2) Test access performance
[root@localhost ~]#redis-benchmark -h 192.168.10.101 -p 6379 -q -d 100
Remark:
-h: specifies the server host name;
-p: specifies the server port;
-d: specifies the data size of the SET/GET value in bytes;
-q: Force exit redis. Only query/sec value is displayed;
set stores data Command format set key value
get Get data Command format get key
1. Add key-value pairs
127.0.0.1:6379> set 1 1
OK
127.0.0.1:6379> set 2 2
OK
127.0.0.1:6379> set 3 3
OK
2. View all values in the database
127.0.0.1:6379> keys *
1) "3"
2) "1"
3) "2"
3. View the data starting with v in the database
127.0.0.1:6379>KEYS v*
4. View any data starting with v in the database
127.0.0.1:6379>KEYS v?
5.View the current database v At the beginningContains any two digits of data
127.0.0.1:6379>KEYS v??
Determine whether the value exists.
127.0.0.1:6379>exists f5 Determine whether f5 exists
(integer) 1 The result is 1, indicating that the F5 key exists
like
(integer) 0 The result is 0, indicating that the F5 key does not exist.
del The command can delete the specified key
127.0.0.1:6379> del v5 Delete v5 in the database
(integer) 1
127.0.0.1:6379>get v5
(nil)
use type The command can be obtained key corresponding value Value Types
127.0.0.1:6379>type k1
string
Remark:
Data types supported by redis
rename The command is to key Rename
In actual use, it is recommended to use exists Command to view target key Whether it exists, and then decide whether to execute rename command to avoid overwriting important data.
127.0.0.1:6379>rename v22 v2 Rename v22 to v2
OK
renamenx The command is used to key Rename and check if the new name exists.
userenamenx When the command is rename, if the target key If it exists, it will not be renamed.
dbsize The command is used to view the current database key Number of.
127.0.0.1:6379> dbsize
(integer) 5
Redis Included by default without any changes 16 databases, the database names are numbers 0-15 To be named in sequence
（1）Switch to the sequence number 10 Database
127.0.0.1:6379>select 10
OK
（2）Switch to the sequence number 15 Database
127.0.0.1:6379[10]>select 15
OK
（3）Switch to the sequence number 0 Database
127.0.0.1:6379[15]>select 0
127.0.0.1:6379>set k1 100 Create k1 in database 0
OK
127.0.0.1:6379>get k1
"100"
127.0.0.1:6379>move k1 1 // Move k1 from database 0 to database 1
(integer) 1
127.0.0.1:6379>select 1 //Switch to target database 1
OK
127.0.0.1:6379[1]>get k1 //View the moved data
"100"
127.0.0.1:6379[1]> select 0
OK
127.0.0.1:6379> get k1 //The value of k1 cannot be found in database 0
(nil)
Clear the current database data, use FLUSHDB
Command implementation; clear all database data, use FLUSHALL Command implementation.
Redis All data is stored in memory and then saved to disk asynchronously from time to time.(This is called“Semi-persistent mode”); You can also write every data change to a append only file(aof)in(This is called“Full persistence mode”)。
because Redis The data is stored in memory. If no persistence is configured,Redis After restarting, all data will be lost. Therefore, you need to turn on Redis The persistence function saves the data to disk. Redis After reboot, the data can be restored from the disk.Redis Provides two ways to persist, one is RDB（Redis DataBase） Persistence (the principle is to ReidsIn-memory database records are dumped regularly (dump） to disk RDB persistence), the other is AOF（append only file）Persistence (the principle is to Reids The operation log is written to the file in append mode).
The difference between RDB and AOF
ROB writes data snapshots to disk within a specified time interval. It is a child process of fork. It first writes data to a temporary folder. After success, it replaces the previous file and stores it in binary compression.
AOF records every write and delete operation of the server in the form of logs. Query operations are not recorded but recorded in text form.
Advantages and disadvantages of RDB and AOF
RDB advantages:
RDB is a compact and compressed binary file that represents a snapshot of Redis data at a certain point in time. It is very suitable for backup, full replication and other scenarios. For example, perform bgsave backup every 6 hours and copy the RDB file to a remote machine or file system for disaster recovery.
Fast data recovery speed.
Maximize performance
High startup efficiency
RDBshortcoming:
Any data not saved before the crash will be lost.
RDB is completed through the fork child process, consuming resources
AOF advantages:
High data durability
In append mode, a crash will not destroy the log file contents.
The rewrite mechanism can be enabled to protect data security.
AOF Disadvantages:
AOF data recovery speed is slow
AOF operation efficiency is low
The criteria for choosing between the two:
Sacrifice some performance in exchange for higher cache consistency (AOF），
When write operations are frequent, do not enable backup to obtain higher performance. save When you have time, make a backup (RDB）
Remark:
If redies restarts, a persistent file needs to be loaded.priorityThe AOF file will be selected.
If RDB is enabled first and then AOF is enabled, and RDB is persisted first, the content in the RDB file will be overwritten by AOF.
[root@localhost ~]# vim /etc/redis/6379.conf
Open 6379.conf After the file, search save, you can see the configuration information as shown below.
exist Redis There are three synchronization modes in the configuration file, they are:
always: Synchronous persistence, every data change will be written to disk immediately ##702 lines
everysec: Default recommendation, asynchronous recording once per second (default value)
no: no synchronization, let the operating system decide how to synchronize
Ignore the last potentially problematic instruction
[root@localhost ~]#/etc/init.d/redis_6379 restart
192.168.9.236:7001> info memory
used_memory:1210776 The size of the memory used, in bytes
used_memory_human:1.15M Displayed with units, in M
used_memory_rss:7802880 How much memory does redis take up from the operating system perspective
used_memory_rss_human:7.44M With unit display
maxmemory:1073741824 Maximum memory size
maxmemory_human:1.00G With unit display
maxmemory-policy: Recycling strategy
volatile-lru: It allows Redis Pick the least recently used key To delete
volatile-ttl：Eliminate according to the expiration time of the key
volatile-random: Randomly select data from the data set with set expiration time and eliminate it;
allkeys-lru:use LRU The algorithm eliminates data from all data sets;
allkeys-random: Randomly select data from the data set and eliminate them;
noeviction: Disable data elimination (default value)
Set the expiration time of the key
127.0.0.1:6379> expire v1 10 The expiration time of v1 is 10 seconds
Remark:
when Redis Due to memory pressure, a key hour,Redis The first consideration is not to recycle the oldest data, but the least recently used data. key or about to expire key Randomly select one key, removed from the dataset
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