Redis: redis configuration file related configuration and redis persistence

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Catalog ：

（1）Redis Configuration file for

（2） General configuration

（3） Security configuration

（4）Redis Persistence strategy of RDB

（5）Redis Persistence strategy of AOF 

（6）Redis The persistence of

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（1）Redis Configuration file for

1. redis.conf Storage location ：

Redis Under the installation root directory of (/opt/redis-5.0.2),Redis This configuration file will be loaded at startup , Work according to the configuration at run time . Sometimes we take out this document , Store in a separate location , When it starts Must be clearly specified Which profile to use , This document will take effect .

After modifying the configuration file , Start up Redis When you need , Add the name of the configuration file

  2.Redis Network related configuration

    （1）bind： binding IP Address , Other machines can use this IP visit Redis, The default binding 127.0.0.1, It can also be modified to the local IP Address .

   （2）port： To configure Redis Ports occupied , The default is 6379.

  （3）tcp-keepalive：TCP Connect the survival strategy , Can pass tcp-keepalive Configuration item to set , The unit is in seconds , If set to 60 second , be server End meeting every 60 Second to connect idle clients once ACK request , To check if the client has hung up , For unresponsive clients, the connection is closed . If set to 0, No life preservation test will be carried out .

  When connecting the client, you must follow the port number specified by him 、 and IP Address connection ： You can no longer use the default connection method

 

The port number should also be added when closing the client ：

 

（2） General configuration

 

 

Redis The general configuration of

1、loglevel： The level of logging , The development phase can be set to debug, The production phase is usually set to notice perhaps warning.

2、logfile： Specify the log file name , If you don't specify ,Redis Only standard output . To ensure that the directory where the log file is located must exist , The file can not exist . Still in redis Specify the configuration file to use at startup , Otherwise configuration doesn't work .

3、databases： To configure Redis Number of databases , The default is 16 individual .

for example ： In the configuration file , Change log information

  Set the log information , Not displayed on the console , Write to log file

 

  Restart Redis： It is found that the console has no output , Printed to log file

 （3） Security configuration

Redis Security configuration

1、requirepass： To configure Redis Access code for . No password is configured by default , That is, access does not require password authentication . This configuration item needs to be in protected-mode=yes It works . Log in to the client with a password ：

redis-cli -h ip -p 6379 -a pwd

 

（4）Redis Persistence strategy of RDB

 

 Redis Of RDB To configure

1、save <seconds> <changes>： Configure composite snapshot trigger conditions , namely Redis stay seconds Seconds key change changes Time ,Redis Save the data in the snapshot to disk once . The default policy is ：

1 It changed in minutes 1 Ten thousand times

perhaps 5 It changed in minutes 10 Time

perhaps 15 It changed in minutes 1 Time

If you want to disable Redis Persistence of , Then put all the save The configuration is commented out .

2、stop-writes-on-bgsave-error： When bgsave Stop writing data to disk when snapshot operation fails , This ensures the consistency of memory data and disk data , But if you don't care about this consistency , To be in bgsave Continue to write when there is an error in the snapshot operation , It needs to be configured as no.

3、rdbcompression： Set whether snapshots stored on disk are compressed , Set to yes when ,Redis Will be used LZF Algorithm for compression ; If you don't want to consume CPU If you compress , It can be set to no, Turn off this function .

4、rdbchecksum： After storing snapshots , Can also let Redis Use CRC64 Algorithm to check data , But this will consume some performance , If the system pays more attention to the improvement of performance , It can be set to no, Turn off this function .

5、dbfilename：Redis File name generated by persistent data , The default is dump.rdb, You can also configure it yourself .

6、dir：Redis Directory where persistent data generation files are saved , The default is ./ namely redis Start directory for , You can also configure it yourself .

（5）Redis Persistence strategy of AOF 

To make up for the above RDB The defects of , If you just write a piece of data , Trigger conditions are not met , The plane crashed ,  Therefore, the following AOF Strategy , But this efficiency ratio RDB low ,Redis By default RDB Strategy

Redis AOF To configure

1、appendonly： Configure whether to turn on AOF,yes Open for indication ,no Means closing . The default is no.

2、appendfilename：AOF Save filename

3、appendfsync：AOF Asynchronous persistence strategy

always： Synchronous persistence , Every time a data change occurs, it is immediately written to disk . Poor performance but good data integrity （ slow , Security ）
everysec： Factory default recommendation , Record asynchronously once per second （ The default value is ）
no： No instant synchronization , It's up to the operating system to decide when to synchronize .

4、no-appendfsync-on-rewrite： Can I use appendsync, Default no, It can guarantee the security of data .

5、auto-aof-rewrite-percentage： Set the base percentage of rewrite

6、auto-aof-rewrite-min-size： Set the overridden benchmark

 

（6）Redis The persistence of

redis Is a memory database , It stores data in memory , This not only speeds up the reading speed, but also brings new problems to the data security , When redis After the server goes down ,redis All data in the database will be lost . To solve this problem ,redis Provides persistence ——RDB and AOF（Append Only File）.

 

RDB

RDB（Redis DataBase） yes Redis Default persistence scheme . Within a specified time interval , Perform the specified number of writes , Data in memory is written to disk . That is to generate a dump.rdb file .Redis Restart will be done by loading dump.rdb File to recover data .

RDB principle ：

Redis Will copy a process that is the same as the current process . All the data for the new process （ Variable 、 environment variable 、 Program counter, etc ） The values are consistent with the original process , But it's a whole new process , And as a child of the original process , To persist .

The whole process , The main process is not going to do anything IO Operation of the , This ensures extremely high performance .

If large-scale data recovery is needed , And it's not very sensitive to the integrity of data recovery , that RDB The way is better than AOF It's more efficient .RDB The disadvantage is that the data may be lost after the last persistence .

1.RDB Saved files ：

RDB The saved file is dump.rdb file , The location is saved in Redis Start directory for .Redis Each time the data is synchronized to the disk, a dump.rdb file , new dump.rdb Will overwrite the old dump.rdb file .

2. To configure RDB Persistence strategy

stay redis.conf In the snapshot configuration of , To configure RDB Saved policy .

Execute... On the client side FLUSHDB perhaps FLUSHALL perhaps SHUTDOWN when , The data in the snapshot will also be saved to dump.rdb, But this operation has cleared the data , The saved file is also empty , It makes no sense .

3. Save manually RDB snapshot

save Command to perform a synchronous save operation , Will the current Redis All data snapshots of the instance (snapshot) With RDB The file is saved to the hard disk .

because save Instructions will block all clients , So the task of saving the database is usually done by  BGSAVE  Commands are executed asynchronously , and save As a last resort to save data , When the backend process responsible for saving data unfortunately has problems .

4.RDB Data recovery

The script will Redis Produced dump.rdb File backup (cp dump.rdb dump_bak.rdb), Each start Redis front , Put the backup dump.rdb File Replace to Redis The corresponding table of contents ( stay redis.conf Medium matching dir Catalog ) Next ,Redis It will load on startup dump.rdb file , And read the data into memory .

5.RDB Summary ​​​​​​​ 

Redis Default on RDB Persistence mode , It is suitable for large-scale data recovery, but its data consistency and integrity are poor .

AOF

AOF(Append Only File),Redis Not on by default . It appears to make up for RDB Deficiency （ Data inconsistency ）, So it takes the form of a log to record every Write operations , and Additional To a file .Redis Restart will execute the write instruction from front to back according to the contents of the log file to complete the data recovery .

​​​​​​​AOF principle

Redis Log every write operation in the form of a log , take Redis All written instructions executed are recorded ( Reading operation does not record ),

Only files can be added but not rewritten ,redis At the beginning of startup, it will read the file and rebuild the data , In other words ,redis In case of restart, execute the write instruction from the front to the back according to the contents of the log file to complete the data recovery .

1.AOF Saved files

AOF The saved file is appendonly.aof file , The location is saved in Redis Start directory for . If it's on AOF,Redis Every record writing operation will go appendonly.aof Add new log contents to the file .

2. To configure AOF Persistence strategy

stay redis.conf Of “APPEND ONLY MODE” In the configuration module , To configure AOF Save strategy .

3.AOF Data recovery

The script will Redis Produced appendonly.aof File backup (cp appendonly.aofappendonly_bak.aof), Each start Redis front , Put the backup appendonly.aof File Replace to Redis The corresponding table of contents ( stay redis.conf Medium matching dir Catalog ) Next , Just turn on AOF The function of ,Redis Each start , The write instruction will be executed from front to back according to the contents of the log file to complete the data recovery .

But in real development , It may be for some reason that appendonly.aof Abnormal file format , This leads to data restore failure , By command redis-check-aof --fix appendonly.aof Make repairs . All write operation logs in the future will be removed from the abnormal part .

4.AOF Rewriting of

AOF By means of document addition , The documents will become larger and larger to avoid this , New rewrite mechanism , When AOF When the file size exceeds the set threshold ,Redis Will start AOF The content of the file is compressed , Keep only the smallest instruction set that can recover data .

       AOF When files continue to grow and become too large , Meeting fork A new process to rewrite the file ( Also write temporary documents first and then rename), Traverse the data in memory of the new process , Each record has one Set sentence . rewrite aof Operation of file , Not reading the old aof file , Instead, the database contents in the whole memory are rewritten with a new command aof file , It's a bit like a snapshot .

Redis It will record the last time it was rewritten AOF size , The default configuration is when AOF The file size is last rewrite Double the size and the file is larger than 64M Trigger when . Of course , It can also be configured in the configuration file .

​​​​​​​AOF Summary ：

Redis Manual opening required AOF Persistence mode ,AOF Data integrity ratio of RDB high , But there's more to the record , It will affect the efficiency of data recovery .

About Redis The use of persistence ： If you only intend to use Redis Do the cache , You can turn off persistence . If you plan to use Redis The persistence of , Suggest RDB and AOF All on . Actually RDB More suitable for data backup , Keep a back hand .AOF Something is wrong. , also RDB.

AOF And RDB Mode can be enabled at the same time , It's not a conflict . If AOF Is available , that Redis Will load automatically at startup AOF, This file can provide better persistence guarantee .