Advanced redis applications [password protection, data persistence, master-slave synchronization, sentinel mode, transactions] [not completed yet (semi-finished products)]

1、 Password protection

to redis Server set password

Can pass redis The configuration file set password parameters , So the client connects to redis The service needs password verification , This will make your redis The service is safer .
Check whether password authentication is set ：

127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) ""

Modify this parameter with the following command

127.0.0.1:6379> CONFIG SET requirepass "123"
OK
127.0.0.1:6379> CONFIG GET requirepass
(error) NOAUTH Authentication required.

After setting password verification, you must verify it before you can perform other operations ：

127.0.0.1:6379> AUTH 123
OK
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) "123"

Be careful ： The command settings are only valid at this time , Failure after restarting the service .

127.0.0.1:6379> quit
[[email protected] ~]# systemctl restart redis
[[email protected] ~]# redis-cli 
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) ""

To be permanent , You need to modify the configuration file and restart the service .

vim /etc/redis.conf

requirepass 123456 
[[email protected] ~]# systemctl restart redis

3、 Client login

[[email protected] ~]# redis-cli -a 123456
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) "123456" 

 or 
 Use in interactive mode 【auth  password 】  command  

[[email protected] ~]# redis-cli
127.0.0.1:6379> AUTH 123456
OK
127.0.0.1:6379> CONFIG GET requirepass
1) "requirepass"
2) "123456"
127.0.0.1:6379> quit

2、 Data persistence

1、 brief introduction
redis For the integrity and security of its own data ,redis The data in memory needs to be synchronized to disk frequently , This process is called a persistence operation . Start again next time redis The service , The data saved on the disk will be reloaded into memory .

     Common persistence methods ：
    a、 Snapshot based approach ：redis Synchronize the data in the memory to the disk file according to a certain period 
    b、 Append based on file ：redis Will put right redis The command causing the change of data is recorded in the log file , Then restart again , In the execution log file redis The operation of writing , Achieve data restore .

2、 Snapshot based persistence
Modify the configuration file , Turn on the snapshot based option
save 900 1 #900 If it exceeds in seconds 1 individual key Be modified , Then initiate snapshot saving
save 300 10 #300 Second content if more than 10 individual key Be modified , Then initiate snapshot saving
save 60 10000 #60 Second content if more than 10000 individual key Be modified , Then initiate snapshot saving
# The above is the default configuration of the system

Files kept on disk

[[email protected] ~]# egrep "^(dbfilename|dir)" /etc/redis.conf
dbfilename dump.rdb  #  Keep the file name 
dir /var/lib/redis #  Keep your path 
[[email protected] ~]# cd /var/lib/redis/
[[email protected] redis]# ls
dump.rdb

Simulate deleting files , Save manually , Check... After restart

[[email protected] redis]# systemctl stop redis
[[email protected] redis]# rm -f dump.rdb 
[[email protected] redis]# systemctl start redis
[[email protected] redis]# ls
[[email protected] redis]# redis-cli -a 123456
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> set names tom
OK
127.0.0.1:6379> get names
"tom"
127.0.0.1:6379> bgsave
Background saving started
127.0.0.1:6379> quit
[[email protected] redis]# ls
dump.rdb

[[email protected] redis]# systemctl restart redis
[[email protected] redis]# redis-cli -a 123456
Warning: Using a password with '-a' or '-u' option on the command line interface may not be safe.
127.0.0.1:6379> get names
"tom"
127.0.0.1:6379> quit

3、 Persistent based on file append
Be careful ： Default not on

#appendonly #  Enable Persistence Based on log file append 
appendonly yes 

appendfilename "appendonly.aof" #  Log files 

Backup file cycle

# appendfsync always
appendfsync everysec
# appendfsync no

appendfsync always // Force write to disk every time write command is received , The slowest , But make sure it's completely persistent , It is not recommended to use

appendfsync everysec // Force write to disk every second , A good compromise between performance and persistence , recommend

appendfsync no // Completely dependent on os, Best performance , Persistence is not guaranteed

Restart test

[[email protected] ~]# systemctl restart redis
[[email protected] ~]# ls /var/lib/redis/
appendonly.aof  dump.rdb

3、 Master slave synchronization

The role of master-slave replication

1.  data redundancy ： Master-slave replication realizes hot backup of data , It's a way of data redundancy beyond persistence .
2.  Fault recovery ： When there is a problem with the master node , Can be served by a slave node , Fast fault recovery ; It's actually a redundancy of services .
3.  Load balancing ： On the basis of master-slave replication , Cooperate with the separation of reading and writing , Write service can be provided by the master node , Read service provided by slave node （ The write Redis Connect master node when data is applied , read Redis Apply connection from node when data ）, Share server load ; Especially in the situation of less writing and more reading , Sharing read load through multiple slave nodes , Can be greatly improved Redis Concurrency of servers .
4.  Read / write separation ： Can be used to achieve read-write separation , Main library write 、 Read from library , Read write separation can not only improve the load capacity of the server , At the same time, according to the change of demand , Change the number of slave Libraries ;
5.  High availability cornerstone ： In addition to the above functions , Master slave replication is also the foundation for sentinels and clusters to implement , So master-slave replication is Redis High availability Foundation .

Redis Master slave replication process ：
* Slave And master Establishing a connection , send out sync Synchronization command
* Master A background process will be started , Save the database snapshot to a file , meanwhile master The main process will start collecting new write commands and caching .
* After the background is saved , Send this file to slave
* Slave Save this file to your hard disk

• One master You can have multiple slave, One slave You can have more than one slave, Go on like this , Formed a powerful multi-level server cluster architecture
• such as , take ip by 192.168.1.10 Your machine acts as the master server , take ip by 192.168.1.11 The machine acts as a slave server
• Set the configuration of the master server

bind 192.168.1.10

• Set the configuration of the slave server
• Be careful ： stay slaveof Write the host later ip, Then write the port , And the port must write

bind 192.168.1.11
slaveof 192.168.1.10 6379

• stay master and slave Separately info command , View the output ：info replication
• stay master Write the data on

set hello world

• stay slave Up reading data

get hello

4、 Sentinel mode

High availability solution ：

1、cluster colony

2、sentinel sentry

High availability Sentinel sentry

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​ Sentinel The sentry is redis Official high availability solution , It can be used to monitor multiple Redis The operation of the service instance .Redis Sentinel Is a program that runs in a special mode Redis The server .Redis Sentinel It's in multiple Sentinel Working together in a process environment .

Sentinel The system has three main tasks ：
1. monitor ：Sentinel Constantly check whether the master service and slave server work as expected .
2. remind ： Monitored Redis When something goes wrong ,Sentinel The administrator or other applications will be notified .
3. Automatic failover ： The master of monitoring Redis Not working properly ,Sentinel The failover operation will begin . Upgrade a slave server to a new master server . Let other slave servers hang to the new master server . At the same time, provide the client with a new master server address

High availability Sentinel Sentinel configuration
Sentry as a pair of redis Monitoring of instances , The robustness and high availability of sentinels are guaranteed by election algorithm , So sentinels should at least deploy 3 platform , Meet the half rule , need 5 perhaps 7, More than half , Not half of the time , To elect leader, To switch between master and slave .
redis service , At least one needs to survive , To ensure the normal operation of the service sentinel , Select new master The principle is that the most recently available and the latest data, the highest priority and the longest active
Sentinel high availability test ： Connect the corresponding... Respectively redis Server side , Manually stop the sentry , Stop the master reids service , See whether the master-slave switch is successful .
Three sentinels ：redis Hang up two instances , The remaining one can be the master , Automatic switch

The process of building the sentry system , There are several points to pay attention to ：
（1） The master and slave nodes in the sentinel system , It is no different from the normal master-slave node , Fault detection and transfer are controlled and completed by sentinels .
（2） Sentinel nodes are essentially redis node .
（3） Every sentinel node , Just configure the monitoring master , You can automatically find other sentinel nodes and slave nodes .
（4） In the sentinel node startup and failover phase , The configuration file of each node will be rewritten (config rewrite).
（5） A sentinel can monitor only one master node ; actually , A sentinel can monitor multiple master nodes , By configuring multiple sentinel monitor That is to say .

Refer to the configuration file

# Whether it is a daemon 
daemonize yes

pidfile "/var/run/redis/redis-sentinel.pid"
logfile "/var/log/redis/redis-sentinel.log"
bind 127.0.0.1
port 26379

# working directory 
dir "/var/lib/redis"

# Declare that the Sentinel's main library is mymaster, The main library ip And ports are 127.0.0.1 and 6379
# the last one 2 The meaning is , At the sentinel leadership election , The sentry needs to get 2 Tickets can become leader
sentinel monitor mymaster 127.0.0.1 6379 2

# stay mymaster Downtime 30 Subjective offline in seconds 
sentinel down-after-milliseconds mymaster 30000
# Specify when failover There can be at most 1 individual slave Simultaneously on the new master To synchronize 
sentinel parallel-syncs mymaster 1

# Set the failover timeout to 180 second 
# The meaning of this parameter is complex , For details, please refer to the official notes 
sentinel failover-timeout mymaster 180000

# Found two slave nodes 
sentinel known-slave mymaster 127.0.0.1 6380
sentinel known-slave mymaster 127.0.0.1 6381

#epoch Realize functions similar to version number 
sentinel current-epoch 0	

5、 Publish subscribe

-  The publisher is not planning to send a message to a specific recipient （ subscriber ）, It's about sending messages to different channels , There's no need to know what kind of subscriber to subscribe to 
-  Subscribers are interested in one or more channels , Just receive messages of interest , You don't need to know what kind of publisher 
-  The decoupling of publishers and subscribers can bring greater scalability and more dynamic network topology 
-  The message sent by the client to the channel , Will be pushed to all clients who subscribe to this channel 
-  The client does not need to take the initiative to get the message , Just subscribe to the channel , The content of this channel will be pushed 

Format of message

-  The format of push message consists of three parts 
- part1: Message type , There are three types 
  - subscribe, Indicates the subscription is successful 
  - unsubscribe, Indicates that unsubscribe succeeded 
  - message, Indicates that other terminals publish messages 
-  If the value of the first part is subscribe, Then the second part is the channel , The third part is the number of channels subscribed now 
-  If the value of the first part is unsubscribe, Then the second part is the channel , The third part is the number of channels subscribed now , If 0 It means that no channel is subscribed to at present , When in Pub/Sub Outside state , The client can send any message redis command 
-  If the value of the first part is message, The second part is the name of the source channel , The third part is the content of the message 

command

• subscribe

SUBSCRIBE  Channel name  [ Channel name  ...]

• Unsubscribe
• If you don't write parameters , Means to cancel all subscriptions

UNSUBSCRIBE  Channel name  [ Channel name  ...]

• Release

PUBLISH  channel   news 

Example ：

127.0.0.1:6379> PUBLISH chan1 "hello redis"
(integer) 1
127.0.0.1:6379> SUBSCRIBE chan1
Reading messages... (press Ctrl-C to quit)
1) "subscribe"
2) "chan1"
3) (integer) 1
1) "message"
2) "chan1"
3) "hello redis"

6、 Business

Redis Transactions can execute more than one command at a time , And with the following two important guarantees ：
A transaction is a separate isolation operation ： All commands in the transaction are serialized 、 To execute in order . Transaction is in the process of execution , Will not be interrupted by command requests from other clients .
A transaction is an atomic operation ： The commands in the transaction are either all executed , Or none of it .

A transaction goes through the following three stages from the beginning to the execution ：

​ Start business .multi

​ Order to join the team .

​ Perform transactions .

Serial number	Command and description
1	DISCARD Cancel the business , Give up executing all commands within the transaction block .
2	EXEC Execute commands within all transaction blocks .
3	MULTI Mark the beginning of a transaction block .
4	UNWATCH Cancel WATCH Command to all key Surveillance .
5	WATCH key [key …] Watch one ( Or more ) key , If before the transaction is executed ( Or these ) key Altered by other orders , Then the business will be interrupted .

7、 Many database

​ redis There is also a database , The default has been created , Altogether 16 individual , Respectively 0,1,2,…15
​ redis The default data operation is in 0 No. database .
​ Key value pairs cannot be shared between databases .

 Switch database  
 select 1    // Switch to 1 The database 
 
 Move the key value to the specified database 
 move address 0 // Assume that the current is 1 The database , take 1 The database address Move to 0 The database 
 
 Clear the current database ：flushdb
 Empty all databases on the server ：flushall

 Be careful ： Empty the database and use it with caution ！！！