Adding and removing nodes in Redis - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the command to add a new node to a Redis cluster.

Redis

redis-cli --cluster add-node [1] 127.0.0.1:7001 127.0.0.1:7000

Drag options to blanks, or click blank then click option'

A127.0.0.1:7005

B127.0.0.1:7003

C127.0.0.1:7004

D127.0.0.1:7002

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same address as an existing node.

Mixing up the order of node addresses.

The add-node command requires the address of the new node to add. Here, 127.0.0.1:7002 is the new node being added to the cluster.

2fill in blank

medium

Complete the command to remove a node from a Redis cluster by its node ID.

Redis

redis-cli --cluster del-node 127.0.0.1:7000 [1]

Drag options to blanks, or click blank then click option'

A1234567890abcdef1234567890abcdef12345678

Babcdef1234567890abcdef1234567890abcdef12

Cfedcba0987654321fedcba0987654321fedcba09

D0987654321fedcba0987654321fedcba09876543

Attempts:

3 left

💡 Hint

Common Mistakes

Using the IP address instead of the node ID.

Using an incorrect or partial node ID.

The del-node command requires the node ID to remove. The correct node ID here is 1234567890abcdef1234567890abcdef12345678.

3fill in blank

hard

Fix the error in the command to add a node to the cluster by filling the blank.

Redis

redis-cli --cluster add-node 127.0.0.1:7000 [1]

Drag options to blanks, or click blank then click option'

A127.0.0.1

B127.0.0.1:7001

C7001

Dlocalhost:7001

Attempts:

3 left

💡 Hint

Common Mistakes

Providing only the port number.

Using hostname instead of IP address.

The add-node command requires the full address (IP and port) of the new node. Only 127.0.0.1:7001 is valid here.

4fill in blank

hard

Fill both blanks to create a command that removes a node by ID from the cluster.

Redis

redis-cli --cluster del-node [1] [2]

Drag options to blanks, or click blank then click option'

A127.0.0.1:7000

Babcdefabcdefabcdefabcdefabcdefabcdefabcd

C1234567890abcdef1234567890abcdef12345678

D127.0.0.1:7001

Attempts:

3 left

💡 Hint

Common Mistakes

Swapping the node address and node ID.

Using an invalid node ID.

The first blank is the cluster node address to connect to, and the second blank is the node ID to remove.

5fill in blank

hard

Fill all three blanks to create a command that adds a node and assigns slots to it.

Redis

redis-cli --cluster add-node [1] [2] --cluster-slots [3]

Drag options to blanks, or click blank then click option'

A127.0.0.1:7002

B127.0.0.1:7000

C0-5460

D127.0.0.1:7001

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up the order of node addresses.

Using invalid slot ranges.

The first blank is the new node address, the second is the existing cluster node address, and the third is the slot range assigned to the new node.

Practice

1. What is the primary purpose of adding nodes to a Redis cluster?

easy

A. To increase the cluster's capacity and distribute data

B. To delete all data from the cluster

C. To backup the cluster data

D. To change the Redis version on all nodes

Solution

1. Step 1: Understand what adding nodes means

   Adding nodes means increasing the number of servers in the cluster to share the data load.

2. Step 2: Identify the effect of adding nodes

   More nodes mean more capacity and better data distribution across the cluster.

3. Final Answer:

   To increase the cluster's capacity and distribute data -> Option A

4. Quick Check:

   Adding nodes = More capacity and distribution [OK]

Hint: Adding nodes grows cluster capacity and data spread [OK]

Common Mistakes:

• Thinking adding nodes deletes data
• Confusing adding nodes with backup
• Assuming adding nodes upgrades Redis version

2. Which of the following is the correct syntax to add a node to a Redis cluster using redis-cli?

easy

A. redis-cli --cluster add-node :<port> :<port>

B. redis-cli --cluster remove-node :<port>

C. redis-cli --cluster create-node :<port>

D. redis-cli --cluster add :<port>

Solution

1. Step 1: Recall the command to add a node

   The correct command uses --cluster add-node followed by the new node and an existing node in the cluster.

2. Step 2: Match the syntax

   redis-cli --cluster add-node :<port> :<port> matches the correct syntax: redis-cli --cluster add-node new-node existing-node.

3. Final Answer:

   redis-cli --cluster add-node <new-node-ip>:<port> <existing-node-ip>:<port> -> Option A

4. Quick Check:

   Correct add-node syntax = redis-cli --cluster add-node :<port> :<port> [OK]

Hint: Add node command uses --cluster add-node with new and existing nodes [OK]

Common Mistakes:

• Using remove-node instead of add-node
• Using create-node which does not exist
• Omitting existing node IP in command

3. Given the command redis-cli --cluster del-node 192.168.1.5:7000 07c37dfeb2352e03a5a1e1f3a2f8b9a1f2e3d4c5, what will happen?

medium

A. A new node will be added at 192.168.1.5:7000

B. The node at 192.168.1.5:7000 will be removed from the cluster

C. The cluster will be created with the given node ID

D. The command will fail due to wrong syntax

Solution

1. Step 1: Understand the del-node command

   The command redis-cli --cluster del-node removes a node from the cluster using its IP and node ID.

2. Step 2: Analyze the given command

   The command specifies the node IP and the node ID, so it will remove that node from the cluster.

3. Final Answer:

   The node at 192.168.1.5:7000 will be removed from the cluster -> Option B

4. Quick Check:

   del-node removes specified node [OK]

Hint: del-node removes node by IP and node ID [OK]

Common Mistakes:

• Confusing del-node with add-node
• Thinking it adds a node
• Assuming command syntax is incorrect

4. You run redis-cli --cluster add-node 192.168.1.10:7003 192.168.1.11:7000 but get an error. What is the most likely cause?

medium

A. The new node is already part of the cluster

B. The existing node IP is incorrect

C. The command should be --cluster del-node instead

D. Redis server is not running on the new node

Solution

1. Step 1: Check prerequisites for adding a node

   The new node must be running Redis and reachable for the add-node command to succeed.

2. Step 2: Identify common causes of add-node failure

   If Redis is not running on the new node, the command will fail because it cannot connect.

3. Final Answer:

   Redis server is not running on the new node -> Option D

4. Quick Check:

   New node must run Redis to add [OK]

Hint: New node must be running Redis before adding [OK]

Common Mistakes:

• Assuming IP typo without checking server status
• Confusing add-node with del-node command
• Ignoring that Redis must run on new node

5. You want to remove a node from a Redis cluster but keep its data safe. Which sequence of commands should you use?

hard

A. Use redis-cli --cluster del-node then backup data manually

B. Directly stop the Redis server on the node and remove it

C. Use redis-cli --cluster reshard to move slots, then redis-cli --cluster del-node

D. Use redis-cli --cluster add-node to replace the node

Solution

1. Step 1: Understand data safety when removing nodes

   Removing a node without moving its data causes data loss.

2. Step 2: Use reshard to move data slots

   Resharding moves the data slots from the node to be removed to other nodes safely.

3. Step 3: Remove the node after resharding

   After data is moved, del-node safely removes the node without data loss.

4. Final Answer:

   Use redis-cli --cluster reshard to move slots, then redis-cli --cluster del-node -> Option C

5. Quick Check:

   Reshard then del-node = safe removal [OK]

Hint: Reshard slots before removing node to keep data safe [OK]

Common Mistakes:

• Removing node without moving data first
• Stopping server directly causing data loss
• Confusing add-node with removal process