XACK for acknowledging messages in Redis - Mini Project: Build & Apply

Acknowledging Messages with Redis XACK

📖 Scenario: You are building a simple message queue system using Redis streams. Messages are added to a stream and consumers read them. After processing a message, the consumer must acknowledge it to tell Redis the message was handled successfully.

🎯 Goal: Learn how to acknowledge messages in a Redis stream using the XACK command to remove them from the pending entries list.

📋 What You'll Learn

Create a Redis stream called mystream with some messages

Create a consumer group called mygroup for mystream

Read messages from the stream as a consumer

Acknowledge a specific message ID using XACK

💡 Why This Matters

🌍 Real World

Redis streams are used in real-time messaging systems, task queues, and event sourcing where reliable message processing is critical.

💼 Career

Understanding how to acknowledge messages ensures you can build robust consumer applications that handle messages exactly once, a key skill for backend developers and system engineers.

1

Create the Redis stream with messages

Use the XADD command to add two messages to a Redis stream called mystream. Add one message with field task and value clean, and another message with field task and value cook.

Redis

# Your code here to add messages to mystream

Need a hint?

Use XADD mystream * task clean to add the first message.

2

Create a consumer group for the stream

Use the XGROUP CREATE command to create a consumer group called mygroup for the stream mystream. Use $ as the ID to start reading new messages.

Redis

XADD mystream * task clean
XADD mystream * task cook
# Your code here to create consumer group mygroup

Need a hint?

Use XGROUP CREATE mystream mygroup $ MKSTREAM to create the group.

3

Read messages as a consumer

Use the XREADGROUP command to read messages from mystream as consumer consumer1 in group mygroup. Read up to 2 messages starting from > to get new messages.

Redis

XADD mystream * task clean
XADD mystream * task cook
XGROUP CREATE mystream mygroup $ MKSTREAM
# Your code here to read messages as consumer1

Need a hint?

Use XREADGROUP GROUP mygroup consumer1 COUNT 2 STREAMS mystream > to read messages.

4

Acknowledge a message with XACK

Use the XACK command to acknowledge a message with ID 1526985058136-0 from the stream mystream in the consumer group mygroup. This tells Redis the message was processed.

Redis

XADD mystream * task clean
XADD mystream * task cook
XGROUP CREATE mystream mygroup $ MKSTREAM
XREADGROUP GROUP mygroup consumer1 COUNT 2 STREAMS mystream >
# Your code here to acknowledge message 1526985058136-0

Need a hint?

Use XACK mystream mygroup 1526985058136-0 to acknowledge the message.