Stream entry IDs in Redis - Mini Project: Build & Apply

Working with Redis Stream Entry IDs

📖 Scenario: You are building a simple message queue using Redis streams to track user notifications in a web app.

🎯 Goal: Create a Redis stream called notifications and add entries with specific IDs. Then, retrieve entries using their IDs.

📋 What You'll Learn

Create a Redis stream named notifications with initial entries and exact IDs

Define a variable last_id to hold the last entry ID

Add a new entry to the notifications stream using the last_id

Retrieve entries from the notifications stream by their IDs

💡 Why This Matters

🌍 Real World

Redis streams are used in real-time messaging, event sourcing, and logging systems to handle ordered data efficiently.

💼 Career

Understanding Redis streams and entry IDs is valuable for backend developers working with real-time data pipelines and scalable messaging systems.

1

Create the Redis stream with initial entries

Use the Redis command XADD to create a stream called notifications with two entries. Add the first entry with ID 1609459200000-0 and field message set to Welcome. Add the second entry with ID 1609459260000-0 and field message set to New message received.

Redis

# Use XADD commands to create the stream and add two entries with exact IDs

Need a hint?

Use XADD with the stream name, exact ID, and field-value pairs.

2

Define the last entry ID variable

Create a variable called last_id and set it to the string 1609459260000-0, which is the ID of the last entry added to the notifications stream.

Redis

XADD notifications 1609459200000-0 message Welcome
XADD notifications 1609459260000-0 message "New message received"
# Define last_id variable with the last entry ID

Need a hint?

Assign the string ID to the variable last_id.

3

Add a new entry using the last ID

Use the Redis command XADD to add a new entry to the notifications stream. Use the special ID (last_id to add the entry with an ID greater than last_id. Set the field message to System update.

Redis

XADD notifications 1609459200000-0 message Welcome
XADD notifications 1609459260000-0 message "New message received"
last_id = "1609459260000-0"
# Add a new entry with ID greater than last_id

Need a hint?

Use XADD with (last_id to add an entry with a higher ID.

4

Retrieve entries by their IDs

Use the Redis command XRANGE to retrieve entries from the notifications stream between the IDs 1609459200000-0 and 1609459300000-0. This will return all entries including the new one you added.

Redis

XADD notifications 1609459200000-0 message Welcome
XADD notifications 1609459260000-0 message "New message received"
last_id = "1609459260000-0"
XADD notifications (1609459260000-0 message "System update"
# Retrieve entries between two IDs

Need a hint?

Use XRANGE with the stream name and the start and end IDs.