View Kafka message headersΒΆ

Apache Kafka (since version 0.11) supports message headers. Headers are a typical concept on 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 the actual value is an array of bytes, the developer who produces the messages knows whether this array of bytes represents a string, int, long, double. Lenses can visualize and use the record headers via SQL queries.

To view the headers of messages in Kafka, run:

SELECT HEADERKEYS() as headers
FROM trips
LIMIT 100

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

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

See all available SQL functions here