XREAD for reading entries in Redis - Mini Project: Build & Apply

Reading Stream Entries with XREAD in Redis

📖 Scenario: You are managing a chat application where messages are stored in a Redis stream. You want to read new messages as they arrive.

🎯 Goal: Build a Redis command sequence to read entries from a stream using XREAD.

📋 What You'll Learn

Create a Redis stream key called chat_stream with initial messages

Set a variable last_id to track the last read message ID

Use XREAD to read new messages from chat_stream starting from last_id

Update last_id to the ID of the last message read

💡 Why This Matters

🌍 Real World

Reading messages from a Redis stream is common in chat apps, event processing, and real-time data pipelines.

💼 Career

Understanding XREAD helps in building scalable, real-time applications that process streaming data efficiently.

1

Create the Redis stream with initial messages

Use the Redis command XADD to create a stream called chat_stream and add two messages with fields user and message. Add the first message with user as Alice and message as Hello. Add the second message with user as Bob and message as Hi.

Redis

# Use XADD to add messages to chat_stream
# Your code here

Need a hint?

Use XADD with * to auto-generate IDs.

2

Set the last read message ID variable

Create a variable called last_id and set it to 0-0 to indicate reading from the start of the stream.

Redis

XADD chat_stream * user Alice message Hello
XADD chat_stream * user Bob message Hi
# Set last_id to '0-0'
# Your code here

Need a hint?

Use a string variable last_id with value '0-0'.

3

Read new messages from the stream using XREAD

Use the Redis command XREAD with COUNT 10 to read up to 10 new entries from the stream chat_stream starting from the ID stored in last_id. Use the syntax: XREAD COUNT 10 STREAMS chat_stream last_id.

Redis

XADD chat_stream * user Alice message Hello
XADD chat_stream * user Bob message Hi
last_id = '0-0'
# Use XREAD to read new messages from chat_stream starting from last_id
# Your code here

Need a hint?

Use XREAD COUNT 10 STREAMS chat_stream last_id to read messages.

4

Update last_id to the ID of the last message read

After reading messages, update the variable last_id to the ID of the last message read from the stream. For this exercise, set last_id to "1609459200000-0" as an example of a message ID.

Redis

XADD chat_stream * user Alice message Hello
XADD chat_stream * user Bob message Hi
last_id = '0-0'
XREAD COUNT 10 STREAMS chat_stream last_id
# Update last_id to the last message ID read
# Your code here

Need a hint?

Assign last_id the string value "1609459200000-0".