KSQL - Streaming SQL for Apache Kafka

Important: This release is a developer preview and is free and open-source from Confluent under the Apache 2.0 license. We do not yet recommend its use for production purposes. The planned GA release date for KSQL is March 2018.

KSQL is an open source streaming SQL engine for Apache Kafka. It provides a simple and completely interactive SQL interface for stream processing on Kafka; no need to write code in a programming language such as Java or Python. KSQL is open-source (Apache 2.0 licensed), distributed, scalable, reliable, and real-time. It supports a wide range of powerful stream processing operations including aggregations, joins, windowing, sessionization, and much more.

Click here to watch a screencast of the KSQL demo on YouTube.

Quick Start

If you are ready to see the power of KSQL, try out these:

• KSQL Quick Start: Demonstrates a simple workflow using KSQL to write streaming queries against data in Kafka.
• Clickstream Analysis Demo: Shows how to build an application that performs real-time user analytics.

Use Cases and Examples

Streaming ETL

Apache Kafka is a popular choice for powering data pipelines. KSQL makes it simple to transform data within the pipeline, readying messages to cleanly land in another system.

CREATE STREAM vip_actions AS
  SELECT userid, page, action
  FROM clickstream c
  LEFT JOIN users u ON c.userid = u.user_id
  WHERE u.level = 'Platinum';

Anomaly Detection

KSQL is a good fit for identifying patterns or anomalies on real-time data. By processing the stream as data arrives you can identify and properly surface out of the ordinary events with millisecond latency.

CREATE TABLE possible_fraud AS
  SELECT card_number, count(*)
  FROM authorization_attempts
  WINDOW TUMBLING (SIZE 5 SECONDS)
  GROUP BY card_number
  HAVING count(*) > 3;

Monitoring

Kafka's ability to provide scalable ordered messages with stream processing make it a common solution for log data monitoring and alerting. KSQL lends a familiar syntax for tracking, understanding, and managing alerts.

CREATE TABLE error_counts AS
  SELECT error_code, count(*)
  FROM monitoring_stream
  WINDOW TUMBLING (SIZE 1 MINUTE)
  WHERE  type = 'ERROR'
  GROUP BY error_code;

Latest news

• KSQL Feb 2018 release available -- introduced the KSQL Experimental UI -- further bug fixes, performance and stability improvements
• KSQL Jan 2018 release available -- improved data exploration with PRINT TOPIC, SHOW TOPICS; improved analytics with TOPK, TOPKDISTINCT aggregations; operational improvements (command line tooling for metrics); distributed failure testing in place
• KSQL Dec 2017 release available -- support for Avro and Confluent Schema Registry; easy data conversion between Avro, JSON, Delimited data; joining streams and tables across different data formats; operational improvements (DESCRIBE EXTENDED, EXPLAIN, and new metrics); optimizations (faster server startup and recovery times, better resource utilization)
• KSQL Nov 2017 release available -- focus on community-raised issues and requests (369 pull requests, 50 closed issues)

Documentation

You can find the KSQL documentation here

Join the Community

Whether you need help, want to contribute, or are just looking for the latest news, you can find out how to connect with your fellow Confluent community members here.

• Ask a question in the #ksql channel in our public Confluent Community Slack. Account registration is free and self-service.
• Join the Confluent Google group.

Contributing

Contributions to the code, examples, documentation, etc, are very much appreciated. For more information, see the contribution guidelines.

• Report issues and bugs directly in this GitHub project.

License

The project is licensed under the Apache License, version 2.0.

Apache, Apache Kafka, Kafka, and associated open source project names are trademarks of the Apache Software Foundation.