XTRIM for stream capping in Redis - Mini Project: Build & Apply

Using XTRIM to Cap Redis Streams

📖 Scenario: You are managing a Redis stream that collects temperature sensor readings from a smart home system. To keep the stream size manageable and avoid using too much memory, you want to limit the stream to only the latest 5 readings.

🎯 Goal: Build a Redis stream capped at 5 entries using the XTRIM command to automatically remove older entries when new ones are added.

📋 What You'll Learn

Create a Redis stream called sensor:temperature with initial entries.

Set a maximum length variable max_len to 5.

Use the XADD command with the MAXLEN option to add new entries while trimming the stream.

Verify that the stream never exceeds 5 entries after adding new data.

💡 Why This Matters

🌍 Real World

IoT devices and real-time data systems often use Redis streams to collect sensor data. Capping streams prevents memory overflow and keeps data manageable.

💼 Career

Understanding how to cap Redis streams is useful for backend developers and system administrators managing real-time data pipelines and ensuring efficient resource use.

1

Create the initial Redis stream with 3 temperature readings

Use the XADD command to create a Redis stream called sensor:temperature and add these exact entries: {"temp": "22.5"}, {"temp": "23.0"}, and {"temp": "22.8"}. Use the * ID to let Redis generate IDs automatically.

Redis

# Use XADD to add three entries to sensor:temperature stream
# Your code here

Need a hint?

Use XADD with * for automatic IDs and specify the field temp with the given values.

2

Set a maximum length variable for the stream

Create a variable called max_len and set it to 5 to represent the maximum number of entries allowed in the stream.

Redis

XADD sensor:temperature * temp 22.5
XADD sensor:temperature * temp 23.0
XADD sensor:temperature * temp 22.8

# Set max_len variable to 5
# Your code here

Need a hint?

Just assign the number 5 to a variable named max_len.

3

Add new entries using XADD with MAXLEN to cap the stream

Use the XADD command with the MAXLEN option set to ~ and the variable max_len to add two new temperature readings: 23.2 and 23.5. Use the * ID for automatic IDs.

Redis

XADD sensor:temperature * temp 22.5
XADD sensor:temperature * temp 23.0
XADD sensor:temperature * temp 22.8

max_len = 5

# Add two new entries with XADD using MAXLEN ~ max_len
# Your code here

Need a hint?

Use XADD sensor:temperature MAXLEN ~ 5 * followed by the field and value to add entries while trimming.

4

Verify the stream is capped at 5 entries

Use the XLEN command on the sensor:temperature stream to check that it contains exactly 5 entries after adding the new data.

Redis

XADD sensor:temperature * temp 22.5
XADD sensor:temperature * temp 23.0
XADD sensor:temperature * temp 22.8

max_len = 5

XADD sensor:temperature MAXLEN ~ 5 * temp 23.2
XADD sensor:temperature MAXLEN ~ 5 * temp 23.5

# Use XLEN to check the stream length
# Your code here

Need a hint?

Use XLEN sensor:temperature to get the number of entries in the stream.