Redis Series (i): 10 minutes to play the Redis

1. about Redis

Redis is an open source, memory-based Key-value database written using the ANSI C language.

It supports storing more value types, including string (string), list (linked list), set (set), Zset (sorted set-ordered set), and hash (hash type).

Redis supports master-slave synchronization, where data can be synchronized from the primary server to any number of slave servers, and because of the full implementation of the publish/subscribe mechanism, you can subscribe to a channel and receive a complete message release record from the primary server when the tree is synchronized anywhere from the database.

The following advantages are compared to Memcached,rdeis:

1. Redis native supports more data types.
2. Redis has a persistence mechanism that can periodically persist the in-memory data to the hard disk.
3. Redis supports Master-slave mode of data backup.

4. Performance. The Redis authors say that the performance is average to a single core, and Redis is better in the case of small pieces of data.

Why do you say that, the reason is that Redis is a single-threaded operation. Because it is single-threaded, the overall performance will certainly be low compared to memcached multithreading. Because it is single-threaded, IO is serialized, network IO, and memory Io, so performance is affected when the single data is too large to be followed up by waiting for all of the IO of a command to complete for subsequent commands.

2. installation Redis2.1 Redis is easy to install and can be installed directly with Yum or Apt-get

12	# yum install epel-release （centos 7可以直接安装epel源）# yum install redis

2.2 Start/Stop Redis

1234	# redis-server /etc/redis.conf# systemctl start redis# systemctl stop redis

3. Use Redis3.1 REDIS-CLI Command line operation KV

Connect to Redis

12	# redis-cli -p port# redis-cli

Ping

1	127.0.0.1:6379> ping<br>PONG

Set the key value

12	127.0.0.1:6379> settestkey "hello"OK

Query key

12	127.0.0.1:6379> get testkey"hello"

Delete key

12	127.0.0.1:6379> del testkey(integer) 1

Set Validity period

12	127.0.0.1:6379> setex test10 111OK

Use Expire key s to set the expiration time in milliseconds with Pexpire

12	127.0.0.1:6379> EXPIRE test11 300(integer) 1

Use TTL key to view expiration time in milliseconds with Pttl

12	127.0.0.1:6379> TTL test11(integer) 288

Cancel the expiration time with persist key

12	127.0.0.1:6379> PERSIST test11(integer) 1

3.2 Advanced features 3.2.1 Self-increment, self-reduction, INCR, DECR, Incrby, SORT

12345678

127.0.0.1:6379> setcounter 100OK127.0.0.1:6379> incr counter(integer) 101127.0.0.1:6379> incr counter(integer) 102127.0.0.1:6379> decr counter(integer) 101

3.2.2 Transactions

123456789101112

127.0.0.1:6379> MULTIOK127.0.0.1:6379> settest11 111111QUEUED127.0.0.1:6379> settest12 121212QUEUED127.0.0.1:6379> incr counterQUEUED127.0.0.1:6379> EXEC1) OK2) OK3) (integer) 102

3.2.3 Hyperloglogs

Redis added the Hyperloglog algorithm in version 2.8.9.

3.2.4 Publish/Subscribe feature

A Redis Publish Subscription (PUB/SUB) is a message communication pattern: the Sender (pub) sends a message and the Subscriber (sub) receives the message. Redis clients can subscribe to any number of channels.

Subscribe to a channel on a client redischat

12345

127.0.0.1:6379> SUBSCRIBE redisChatReading messages... (press Ctrl-C to quit)1) "subscribe"2) "redisChat"3) (integer) 1

On another client, sending a message to the channel Redischat, the Subscriber can receive the message

Publishing side:

12	127.0.0.1:6379> PUBLISH redisChat "redis haha"(integer) 1

Subscribers:

12345678

127.0.0.1:6379> SUBSCRIBE redisChatReading messages... (press Ctrl-C to quit)1) "subscribe"2) "redisChat"3) (integer) 11) "message"2) "redisChat"3) "redis haha"

3. 3 View Redis Status

1	127.0.0.1:6379> info

Info output is a lot of information, you can specify the part of the output

1	127.0.0.1:6379> info stats

1	127.0.0.1:6379> info memory

Used_memory: The total amount of memory allocated by the Redis allocator, in bytes (byte).

Used_memory_rss: Returns the total amount of memory allocated by Redis (commonly known as the resident set size) from the operating system's perspective. This value is consistent with the output of commands such as top and PS.

rss > used, and the difference between the two values, indicates the existence (internal or external) memory fragmentation.

The rate of memory fragmentation can be seen through the Mem_fragmentation_ratio value.

Used > rss, it means that part of Redis's memory is swapped out to swap space, in which case the operation can have a noticeable delay.

Used_memory_peak: Peak, set maximum memory greater than peak

3. 4 other Commands

View the number of records

1	127.0.0.1:6379> dbsize

View all Keys

1	127.0.0.1:6379> KEYS *

List all client connections

1	127.0.0.1:6379> CLIENT LIST

Close the Ip:port client

1	127.0.0.1:6379> CLIENT KILL 127.0.0.1:11902

Clear all keys for all databases

1	127.0.0.1:6379> FLUSHALL

Empties all keys in the current database

1	127.0.0.1:6379> FLUSHDB

Returns the last time the data was successfully saved to disk, expressed in the UNIX timestamp format

1	127.0.0.1:6379> LASTSAVE

Returns the current server time, expressed in UNIX timestamp format

1	127.0.0.1:6379> TIME

Connect to a different database (default database is 0)

12	127.0.0.1:6379> SELECT 1OK

Moves the key of the current database to the specified database

12	127.0.0.1:6379> MOVE test2 1(integer) 1

4. settings File4.1/etc/redis.conf

12345678910111213

daemonize no      是否以后台daemon方式运行timeout 0         请求超时时间maxclients 10000  最大连接数maxmemory <bytes>              最大内存maxmemory-policy volatile-lru  达到最大内存时的LRU驱逐策略maxmemory-samples 3            随机抽取n个key执行LRUhash-max-ziplist-entries 512   Map内部不超过多少个成员时会采用线性紧凑格式存储hash-max-ziplist-value 64      Map内成员值长度不超过多少字节会采用线性紧凑格式存储类似的还有，list-max-ziplist-entries 512，list-max-ziplist-value 64等等 slowlog-log-slower-than 10000  slow log计入时间，microseconds（1000000）slowlog-max-len 128            slow log计入条数

4.2 Viewing the maximum number of connections

123	127.0.0.1:6379> config get maxclients1) "maxclients"2) "10000"

Adjusting parameters during Operation

1	127.0.0.1:6379> config setmaxclients 10001

4.3 View Slow Log

123456

127.0.0.1:6379> SLOWLOG get127.0.0.1:6379> SLOWLOG get 101) 1) (integer) 0   2) (integer) 1448413479   3) (integer) 124211   4) 1) "FLUSHALL"

Confirm Slow log Bar number setting

1	127.0.0.1:6379> SLOWLOG len

Empty slow Log

1	127.0.0.1:6379> SLOWLOG reset

5. Data Persistence 5.1 Snapshot ( Snapshot )5.1.1 Setting a snapshot in the settings file

1234	save <seconds> <changes>      开启快照，并设定保存快照到硬盘的频率rdbcompression yes/no保存快照的时候，是否压缩dbfilename dump.rdb           指定快照的文件名（Append Only File也保存在此）dir /var/lib/redis/指定快照存放的场所

5.1.2 Creating a snapshot manually

To execute the Save or bgsave command at the command line

12	127.0.0.1:6379> SAVEOK

5.2 Log Backups ( Append only File )

Similar to the MySQL Binlog, the operation is recorded in log. When snapshots do not reach the required precision, they are used in conjunction with snapshots and are not recommended for use alone. The default interval is 1 seconds and can be modified.

5.2.1 setting aof in the settings file

1234	appendonly yes开启Append Only Fileappendfilename "appendonly.aof" 指定日志文件名appendfsync always/everysec/no指定写日志的频率no-appendfsync-on-rewrite no       当有bgsave等其他进程执行fsync()时，AOF和appendfsync none动作一样

5.3 Restore

To recover Redis data simply move the Redis backup file (dump.rdb,appendonly.aof) to the Redis directory and start the server.

To get your Redis directory, use the command as shown below:

123	127.0.0.1:6379> config get dir1) "dir"2) "/var/lib/redis"

6. PostScript

This paper briefly introduces the installation and use of Redis, then introduces the master-slave synchronization, load dispersion.

Redis Series (i): 10-minute redis (turn)