Pub/sub limitations (no persistence) in Redis - Mini Project: Build & Apply

Understanding Redis Pub/Sub Limitations: No Persistence

📖 Scenario: You are building a simple chat application using Redis Pub/Sub. You want to understand how messages are delivered and what happens if a user is offline.

🎯 Goal: Create a Redis Pub/Sub setup that demonstrates message publishing and subscribing, and observe the limitation that messages are not stored if the subscriber is offline.

📋 What You'll Learn

Create a Redis channel named chatroom

Subscribe to the chatroom channel

Publish messages to the chatroom channel

Demonstrate that messages sent while subscriber is offline are not received

💡 Why This Matters

🌍 Real World

Many chat apps and real-time systems use Redis Pub/Sub for instant messaging but must handle the limitation that messages are not saved if users are offline.

💼 Career

Understanding Redis Pub/Sub limitations is important for backend developers and system architects designing real-time communication systems.

1

Create a Redis channel named chatroom

Write the Redis command to create a channel named chatroom by subscribing to it using the command SUBSCRIBE chatroom.

Redis

# Use the command to subscribe to the chatroom channel
# Your code here

Need a hint?

Use the SUBSCRIBE command followed by the channel name chatroom.

2

Publish a message to the chatroom channel

Write the Redis command to publish the message Hello everyone! to the chatroom channel using PUBLISH chatroom "Hello everyone!".

Redis

SUBSCRIBE chatroom
# Publish a message to the chatroom channel
# Your code here

Need a hint?

Use the PUBLISH command with the channel name and the message in quotes.

3

Simulate subscriber offline and publish a message

Write the Redis command to publish the message Are you there? to the chatroom channel while no subscriber is connected, using PUBLISH chatroom "Are you there?".

Redis

SUBSCRIBE chatroom
PUBLISH chatroom "Hello everyone!"
# Publish a message while subscriber is offline
# Your code here

Need a hint?

Use the PUBLISH command again with the new message.

4

Explain the limitation of Redis Pub/Sub with no persistence

Add a comment explaining that Redis Pub/Sub does not store messages, so if a subscriber is offline, it will miss messages published during that time.

Redis

SUBSCRIBE chatroom
PUBLISH chatroom "Hello everyone!"
PUBLISH chatroom "Are you there?"
# Your explanation here

Need a hint?

Write a comment starting with # explaining the no persistence limitation.