Redis cluster creation, capacity expansion and capacity reduction

Pull the mirror image

```bash
docker pull redis:6.0.8
```

establish redis Cluster container

perform docker command

```bash
docker run -d --name redis-node-1 --net host --privileged=true -v /data/redis/share/redis-node-1:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6381

docker run -d --name redis-node-2 --net host --privileged=true -v /data/redis/share/redis-node-2:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6382

docker run -d --name redis-node-3 --net host --privileged=true -v /data/redis/share/redis-node-3:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6383

docker run -d --name redis-node-4 --net host --privileged=true -v /data/redis/share/redis-node-4:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6384

docker run -d --name redis-node-5 --net host --privileged=true -v /data/redis/share/redis-node-5:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6385

docker run -d --name redis-node-6 --net host --privileged=true -v /data/redis/share/redis-node-6:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6386
```

Into the container

```bash
docker exec -ti redis-node-1 /bin/bash
```

Execute the following command

redis-cli --cluster create 10.255.237.120:6381 10.255.237.120:6382 10.255.237.120:6383 10.255.237.120:6384 10.255.237.120:6385 10.255.237.120:6386 --cluster-replicas 1

Input yes after

5. At this time, the representative has been successfully created

View the cluster

stay redis-node-1 Execute the following commands in the container

	redis-cli -p 6381 -c 

Check it with the following command redis Cluster situation

```bash
	 cluster info
	 cluster nodes
```

redis Cluster expansion cases 【 Expansion from three masters and three slaves to four masters and four slaves 】

The implementation is as follows docker command

```bash
docker run -d --name redis-node-7 --net host --privileged=true -v /data/redis/share/redis-node-7:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6387
docker run -d --name redis-node-8 --net host --privileged=true -v /data/redis/share/redis-node-8:/data redis:6.0.8 --cluster-enabled yes --appendonly yes --port 6388
```

Get into 6387 Instance internal

Will add 6387 node （ Empty slot number ） As master The node joins the original cluster

```bash
redis-cli --cluster add-node 10.255.237.120:6387 10.255.237.120:6381
```

Use the following command to check 6387 The node has joined , However, you can see that no slots are allocated

redis-cli --cluster check 10.255.237.120:6381

Reassign slot numbers

redis-cli --cluster  reshard 10.255.237.120:6381

0-16383 Number selection of interval 
16383/master Number of nodes , This selection is 4096
 choice all

redis-cli --cluster check 10.255.237.120:6381

Perform discovery , The newly added master node is to evenly slot each node of the previous master node to the new master node , Instead of reallocating them all

Master node 6387 Assign slave nodes 6388

cluster-master-id by 6387 The number of

redis-cli --cluster add-node 10.255.237.120:6388  10.255.237.120:6387 --cluster-slave --cluster-master-id 135f091ecb2b7eade2d472c2589413fda8c6926b

thus , Expansion completed

Shrinkage capacity 【 Delete 6387-6388】

When you shrink , You should delete the slave first , Then delete the host

perform redis-cli --cluster check 10.255.237.120:6381 command , obtain 6388 node id, Here's the picture

The command to delete a node is as follows

redis-cli --cluster del-node 10.255.237.120:6388 50acca20c6240f83e81c1a5de2a0c17e3dbda523

Reassign the slot number to the cluster

redis-cli --cluster reshard 10.255.237.120:6381

take 6387 All slot numbers of are assigned to other nodes , Assigned here to 6382 了

As shown in the figure below 6387 The slot of is 0 了

Delete node

6387 The slots of have been allocated , Now you can delete 6387 The node

redis-cli --cluster del-node 10.255.237.120:6387 135f091ecb2b7eade2d472c2589413fda8c6926b

Check the cluster

redis-cli --cluster check 10.255.237.120:6381

thus ,redis Cluster creation , Capacity expansion , The volume reduction operation is finished