Redis data persistence

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1. What is data persistence

Redis All data is saved in memory , If you do not do any persistence operation, when Redis Data loss on shutdown , Data persistence is to prevent data loss ,Redis Will asynchronously save data on the hard disk .

2. Data persistence

• RDB( Snapshot mode )

• AOF( How to log )

3.Redis Data persistence -RDB

Redis Save data to disk in binary form , The saved file is suffixed with rdb, Load the next time you start rdb File recovery data , To achieve persistence .

(1) Trigger RDB The way

• Automatic mode

Through the relevant configuration in the configuration file ,Redis Automatic persistence according to the configuration .

RDB Configuration item information for :

Enter the directory where the configuration file is located , And pass Vim Command to edit

RDB The configuration information is as follows :

Configuration details :

save 60 1
dbfilename dbdump.rdb
dir /usr/local/redis-6.0.6/
stop-writes-on-bgsave-error yes
rdbcompression yes
rdbchecksum yes

remarks :save 60 1 Express 60s There is a key Save changes , It's a strategy , Multiple policies can be set at the same time , as follows :

start-up Redis Server side :

adopt RDM In the db2 Add a message to the database key = Java value=best! The data of

We will find that Redis There is one more... In the catalog dbdump.rdb The file of

adopt Vim see dbdump.rdb file , There will be data in it , But it's a mess , Understandable because Redis Save in binary

.

take Redis Server shutdown , Then start again to see if the data still exists :

We will find that the data still exists , Data persistence succeeded !

• Manual mode

When it comes to persistence , Input save or bgsave Command persistence ( Are single thread blocking , This means that no other commands can be executed while saving ),save and bgsave Orders are essentially the same , One runs synchronously and the other runs asynchronously , But they are all single thread blocking .

(2) RDB The shortcomings of

4.Redis Data persistence -AOF

Use the log method to add and save the command of each step of our operation to the disk , The format actually saved here is not the command format , It's a specific format , The file suffix is AOF, Data recovery will AOF File loading .

(1) Log an additional - AOF

(2) Log recovery

(3) AOF The addition of (fsync) Strategy

appendfsync Append strategy ( Such as :appendfsync everysec)

(4) AOF Three ways to compare

(5) AOF rewrite

Only care about the final state , Save the command executed in the current latest state , For example, in the following table set hello world ,set hello java and set hello hehe The last status of the command is set hello hehe The state in which the command is executed , So these three commands only save set hello hehe command , The same is true of other orders , So finally AOF The command saved after rewriting is set hello hehe ,set counter 2 and rpush mylist a b c These three orders .

(6) AOF How to implement

• Automatic mode ( Use AOF Override configuration mode )

AOF Rewrite the configuration options as follows :

Shut down first Redis Server side :

And then through vim Command to edit Redis Configuration file for , newly added Aof Configuration of :

Configuration details :

appendonly yes
appendfilename aof-6666.aof
appendfsync everysec
no-appendfsync-on-rewrite yes
auto-aof-rewrite-percentage 100
auto-aof-rewrite-min-size 64mb

Start again Redis Server side :

adopt RDM Add to database 2 Add a piece of data key=PHP value=Java

We will find that Redis There is one more... In the catalog aof-6666.aof The file of

We go through vim Command to view the file :

About rewrite explain

• Manual mode ( Use bgrewriteaof Command mode )

5.RDB And AOF The choice of

( AOF The load priority of is compared to RDB Higher )