Accessing headers

This page describes a tutorial for access headers via SQL Studio.

Since version 0.11, Apache Kafka supports message headers. Headers are a typical concept in messaging systems like JMS and transport systems like TCP or HTTP.

They can be used for routing, filtering, and annotation. The header can contain pairs of key=value, where the key is always a string(text), and the value is an array of bytes.

Given that the actual value is an array of bytes, the developer who produces the messages knows whether this array of bytes represents a string, an int, a long, or a double. Lenses can visualize and use the record headers via SQL queries.

By default, Lenses fetches the headers of messages and displays them on the UI.

To view the value of a specific header you can run:

SELECT HEADERASSTRING("User") as user
FROM trips
LIMIT 100