Hash slot of rediscluster cluster cluster implementation principle

Redis Clusters use data fragmentation , Instead of consistent hashing , One Redis The cluster contains 16384 Hash slot （hash slot）, Use set The stored data belongs to 16384 One of the hash slots , Cluster use crc16(key) % 16384 To calculate key Which slot does it belong to .

Illustrate with examples , Now we need to build Cluster colony 6 Nodes ,redis Of Port number In turn 7000,7001,7002,7003,7004,7005,6 Nodes are divided into 3 Group , A master (master) A congruent form

Here's the picture

Calculate the hash slot sorting for each group , Each group =16384/3=5461

that ：

First set of ports 7000 The hash slot of is 0-5460

First set of ports 7001 The hash slot of is 5461-10922

First set of ports 7002 The hash slot of is 10923-16383

notes ： The figure below is a bit wrong , I'm too lazy to redraw

Let's prepare for practical operation ：

One , Cluster Cluster building

1, The first step is to be ready 8 individual redis.conf file

linux In the environment ,redis Deployed in /application Under the table of contents , First create a good 8 Directories execute the following commands ：

cd /application
mkdir rediscluster
cd rediscluster/
mkdir redis7000
mkdir redis7001
mkdir redis7002
mkdir redis7003
mkdir redis7004
mkdir redis7005

# Then dynamically add to the hash slot 
mkdir redis7006
mkdir redis7007

A copy of redis.conf, Modify the following ：

dbfilename 7000dump.rdb
daemonize yes # Background start 
protected-mode no ; ##  Allow external access 
port 7000 # Modify port number , from 7000 To 7007
cluster-enabled yes # Turn on cluster, Remove annotations 
cluster-config-file 7000nodes.conf # Automatic generation 
cluster-node-timeout 15000 # Node communication time 
logfile  /application/rediscluster/redis7000/redis.log"/application/rediscluster/redis7000/redis.log"

Then the file is copied 8 Share , Modify the above contents in turn , Change it and put it in the corresponding folder .

Pay attention to the upper band 7000-7007 It's the port number , Each folder corresponds to the corresponding port number , for example ：redis7005 In a folder redis.conf The content corresponds to  

dbfilename 7005dump.rdb
port 7005 # Modify port number , from 7000 To 7007
cluster-config-file 7005nodes.conf # Automatic generation 
logfile  /application/rediscluster/redis7005/redis.log"/application/rediscluster/redis7005/redis.log"

give the result as follows ：

 2, The second step , start-up 6 individual redis

/application/redis/bin/redis-server /application/rediscluster/redis7000/redis.conf
/application/redis/bin/redis-server /application/rediscluster/redis7001/redis.conf
/application/redis/bin/redis-server /application/rediscluster/redis7002/redis.conf
/application/redis/bin/redis-server /application/rediscluster/redis7003/redis.conf
/application/redis/bin/redis-server /application/rediscluster/redis7004/redis.conf
/application/redis/bin/redis-server /application/rediscluster/redis7005/redis.conf

Check the process ：ps -ef|grep redis

notes ： No hash slot is allocated set operation , Because the data is stored in the hash slot , I haven't been assigned how to write ？

  3, The third step , Assign hashico

/application/redis/bin/redis-cli --cluster create  172.16.166.122:7000  172.16.166.122:7001  172.16.166.122:7002  172.16.166.122:7003  172.16.166.122:7004  172.16.166.122:7005  --cluster-replicas 1

The following figure will pop up after execution , Ask whether to set the above configuration ？ Input yes

This completes the allocation of hash slots

  4, Step four , View the assigned Hashi slots

First connect to 7000 Port node

#172.16.166.122  It's the intranet IP
/application/redis/bin/redis-cli -h 172.16.166.122 -p 7000 -c

Enter the command ： cluster nodes

You can see that there is 3 Group master, Only master To allocate Hashi slots , The cluster will automatically conduct the election , Here's the picture 7000,7001,7002 yes master node ,7000 The slave node of is 7004, Maybe some friends built it according to the above figure 7000 The children of are 7003, It's all possible , The result of the election shall prevail

 7000 and 7004 How nodes are associated ？ Look at the picture below to see the answer

Test cluster ：

Test write operation ：

# Connect to cluster 
/application/redis/bin/redis-cli -h 172.16.166.122 -p 7000 -c

test set aaa 1 Data stored in [10439] Hash slot , Belong to 7001 node

test set bbb 2 Data stored in [5287] Hash slot , Belong to 7000 node

 

Test read operation ：

test get aaa from 7001 Hashi slot of node [10439] To find the key The result is 1