Redis Introduction and Configuration

• What is Redis?

We all know that MySQL and Oracle are relational databases, and they are characterized by an Excel table and are all SQL statements. But you may see a thing called NoSQL. NoSQL refers to a non-relational database, his storage structure and relational database is not the same, usually stored data are in KV format. and relational databases generally support transactions, and non-relational databases generally do not support transactions.

NoSQL has no unified language, and each NoSQL database has its own syntax. Redis is a NoSQL database.

In addition to Redis, there are other:

Mongodb

Hbase Hadoop

Cassandra Hadoop

But for now, the most used is redis.

• Redis Benefits

• Redis supports data persistence, which saves data in memory on disk and can be loaded again for use when restarting.
• Redis supports backup of data, that is, Master-slave mode of data backup.
• The performance is very high –redis can read the speed is 110,000 times/s, the write speed is 81,000 times/s.
• Rich data types –redis support binary case Strings, Lists, hashes, sets and Ordered sets data type operations.
• Rich features –redis also supports publish/subscribe, notifications, key expiration, and more.

• Redis Application Scenarios

• All the data used to do the cache (ehcache/memcached)--redis is in memory (in-memory database)
• Can be used to replace traditional databases in certain scenarios-such as social applications
• In some large systems, the ingenious implementation of some specific functions: Session sharing, Shopping cart

• Redis Installation

wget http://download.redis.io/releases/redis-4.0.9.tar.gz

Tar xzvf redis-4.0.9.tar.gz

sudo mv./redis-4.0.9/usr/local/redis/

cd/usr/local/redis/

sudo make

sudo make install

sudo mv/usr/local/redis/redis.conf/etc/redis/ # Put the configuration file in/etc for easy search

• Redis's Open

Redis contains the server and the client. Before opening the client, of course, you must first open the server.

Open the service side:

redis-server/etc/redis/redis.conf # Redis-server followed by the Redis configuration file, which means to open it with this configuration.

Redis is basically run in the background in a daemon way

In the corresponding configuration file:

Daemonize Yes

Open the client:

REDIS-CLI # If you modify the port, remember to P [port]. If you do not modify the direct input this command is OK. The default port of 6379 opens. -H [Host] similarly

In the corresponding configuration file:

Port xxx

Bind xxx

To exit the service side:

Exit

Select database:

SELECT [0-15] # default is 16 databases, 0 to 15. Of course, the number of databases can be changed in the configuration file.

In the corresponding configuration file:

Databases 16

• Common configuration for Redis (go: https://www.cnblogs.com/qq78292959/archive/2013/09/21/3331032.html)

1. Redis is not running as a daemon by default and can be modified by this configuration item, enabling the daemon with Yes

daemonize No

2. When Redis is running as a daemon, Redis writes the PID to the/var/run/redis.pid file by default and can be specified by pidfile

pidfile/var/run/redis.pid

3. Specify the Redis listening port, the default port is 6379, the author in his own article blog post explains why 6379 as the default port, because 6379 Merz the corresponding number on the phone keypad, and Merz from Italy showgirl Alessia Merz name

Port 6379

4. The host address of the binding

bind 127.0.0.1

5. If the client closes the connection after a long period of inactivity, if it is specified as 0, the function is turned off

Timeout

6. Specify logging level, Redis supports four levels in total: Debug, verbose, notice, warning, default is verbose

loglevel verbose

7. Logging mode, default to standard output, if Redis is configured to run as daemon, and this is configured as logging mode as standard output, the log will be sent to/dev/null

logfile stdout

8. Set the number of databases, the default database is 0, you can use the Select <dbid> command to specify the database ID on the connection

Databases

9. Specify how many times the update operation will synchronize the data to the data file and can be combined with multiple conditions

Save <seconds> <changes>

There are three conditions available in the Redis default configuration file:

Save 1

Save

Save 10000

Represents 1 changes in 900 seconds (15 minutes), 5 changes in 300 seconds (10 minutes), and 60 changes in 10,000 seconds.

10. Specify whether to compress the data when storing to the local database, the default is Yes,redis with LZF compression, if you want to save CPU time, you can turn off this option, but it will cause the database file to become huge

rdbcompression Yes

11. Specify the local database file name, the default value is Dump.rdb

dbfilename Dump.rdb

12. Specify the local database to hold the directory

dir./

13. Set the IP address and port of the master service when this machine is a Slav service, and it will automatically synchronize data from master when Redis boots

slaveof <masterip> <masterport>

14. When the master service is password protected, the Slav service connects the password of master

masterauth <master-password>

15. Set up the Redis connection password, if the connection password is configured, the client will need to provide the password via auth <password> command when connecting to Redis, turn off by default

requirepass foobared

16. Set the maximum number of client connections at the same time, the default is unlimited, Redis can open the number of client connections for the Redis process can open the maximum number of file descriptors, if set maxclients 0, indicating no restrictions. When the number of client connections reaches the limit, Redis closes the new connection and returns the max number of clients reached error message to the client

maxclients

17. Specify the maximum Redis memory limit, Redis will load data into memory when it is started, Redis will try to clear expired or expiring key first, when this method processing, still reach the maximum memory setting, will no longer write operation, but still can read operation. Redis new VM mechanism will store key memory, value will be stored in swap area

maxmemory <bytes>

18. Specifies whether logging occurs after each update operation, which, by default, writes data to disk asynchronously and, if not turned on, may result in data loss over a period of time when power is lost. Because the Redis itself synchronizes data files in sync with the save conditions above, some data will only exist in memory for a period of time. Default is No

appendonly No

19. Specify the update log file name, default to Appendonly.aof

appendfilename appendonly.aof

20. Specify the update log condition, a total of 3 optional values:
No: Indicates that the data cache of the operating system is synchronized to disk (fast)
always: Represents a manual call to Fsync () to write data to disk (slow, secure) after each update operation
everysec: Indicates synchronization once per second (trade-offs, default values)

appendfsync everysec

21. Specify whether to enable the virtual memory mechanism, the default value is no, a simple introduction, the VM mechanism to store data paging, by Redis will be less accessible pages, such as cold data swap to disk, Access to multiple pages is automatically swapped out into memory by the disk (in a later article I will carefully analyze the Redis VM mechanism)

vm-enabled No

22. Virtual memory file path, default value is/tmp/redis.swap, cannot be shared by multiple Redis instances

Vm-swap-file/tmp/redis.swap

23. Store all data greater than vm-max-memory in virtual memory, regardless of the vm-max-memory settings, all index data is memory stored (REDIS index data is keys), that is, when the vm-max-memory is set to 0, In fact, all value is present on disk. The default value is 0

vm-max-memory 0

The Redis swap file is divided into a number of page, an object can be saved on more than one page, but a page can not be shared by multiple objects, Vm-page-size is based on the size of the stored data to set, the author suggests that if you store many small objects, The page size is best set to 32 or 64bytes, and if you store large objects, you can use a larger page, and if you are unsure, use the default values

vm-page-size

25. Set the number of pages in the swap file, since the page table (a bitmap that indicates that the page is idle or used) is in memory and consumes 1byte of memory per 8 pages on disk.

vm-pages 134217728

26. Set the number of threads to access swap files, preferably do not exceed the machine's core number, if set to 0, then all the swap file operation is serial, may cause a relatively long delay. The default value is 4

vm-max-threads 4

27. Set when replying to the client, whether to merge the smaller package into one package send, the default is to turn on

glueoutputbuf Yes

28. Specifies that a special hashing algorithm is used when more than a certain number or maximum element exceeds a critical value

hash-max-zipmap-entries

Hash-max-zipmap-value

29. Specify whether to activate the reset hash, which is on by default (described later in the introduction of the Redis hashing algorithm)

activerehashing Yes

30. Specify other profiles that can use the same configuration file across multiple Redis instances on the same host, while each instance has its own specific configuration file

include/path/to/local.conf

Redis Introduction and Configuration