Cluster creation in Redis - Step-by-Step Execution

Concept Flow - Cluster creation

Start Redis nodes

↓

Assign node IDs

↓

Configure cluster slots

↓

Connect nodes

↓

Replicate nodes assigned

↓

Cluster ready

The flow shows starting Redis nodes, assigning IDs, configuring slots, connecting nodes, assigning replicas, and completing cluster setup.

Execution Sample

Redis

redis-cli --cluster create \
  127.0.0.1:7000 127.0.0.1:7001 \
  127.0.0.1:7002 127.0.0.1:7003 \
  --cluster-replicas 1

This command creates a Redis cluster with 4 nodes and assigns 1 replica per master.

Execution Table

Step	Action	Details	Result
1	Start nodes	Nodes at ports 7000,7001,7002,7003 started	Nodes running
2	Assign node IDs	Each node gets unique ID	Node IDs assigned
3	Configure slots	Slots 0-16383 divided among masters	Slots assigned to nodes
4	Connect nodes	Nodes exchange info and connect	Cluster nodes linked
5	Assign replicas	Each master assigned 1 replica	Replication set
6	Cluster ready	Cluster state is OK	Cluster operational
7	Exit	All steps done	Cluster creation complete

💡 All nodes configured and connected, cluster is operational

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 5	Final
nodes	Not running	Running with IDs	Slots assigned	Replicas assigned	Cluster operational
slots	None	None	Distributed among masters	Distributed	Distributed
replicas	None	None	None	Assigned to masters	Assigned

Key Moments - 3 Insights

Why do we assign slots to nodes during cluster creation?

Slots determine which node holds which part of the data. See execution_table row 3 where slots are divided among masters.

What does '--cluster-replicas 1' mean in the command?

It means each master node will have one replica node for data redundancy, as shown in execution_table row 5.

Why must all nodes be running before creating the cluster?

Because the cluster command connects nodes and assigns roles; if nodes are not running, connection fails. See execution_table row 1.

Visual Quiz - 3 Questions

Look at the execution_table, at which step are slots assigned to nodes?

A Step 3

B Step 4

C Step 2

D Step 5

💡 Hint

Check the 'Configure slots' action in execution_table row 3

According to variable_tracker, what is the state of 'replicas' after Step 3?

A Distributed among masters

B Assigned to masters

C None

D Cluster operational

💡 Hint

Look at the 'replicas' row under 'After Step 3' column in variable_tracker

If a node is not running at Step 1, what will happen to cluster creation?

A Cluster creation proceeds normally

B Cluster creation fails due to connection issues

C Node IDs assigned anyway

D Slots assigned to offline nodes

💡 Hint

Refer to key_moments question about nodes running and execution_table row 1

Concept Snapshot

Redis Cluster Creation:
- Start multiple Redis nodes
- Assign unique node IDs
- Divide hash slots among master nodes
- Connect nodes to form cluster
- Assign replicas per master (--cluster-replicas)
- Cluster becomes operational after setup

Full Transcript

To create a Redis cluster, first start all Redis nodes on different ports. Each node receives a unique ID. Then, the cluster slots (0 to 16383) are divided among the master nodes to distribute data. Nodes connect to each other exchanging cluster info. Replicas are assigned to masters for redundancy based on the --cluster-replicas option. When all steps complete, the cluster is operational and ready to use.