Kafka Streams

Kafka Streams is a client library for building applications and microservices, where the input and output data are stored in a Kafka cluster. It combines the simplicity of writing and deploying standard Java and Scala applications on the client side with the benefits of Kafka’s server-side cluster technology.

Quick Start Guide

The Kafka Streams Quick Start demonstrates how to run your first Java application that uses the Kafka Streams library by showcasing a simple end-to-end data pipeline powered by Kafka.

Streams API Screencasts

Watch the Intro to Streams API on YouTube.

Table of Contents

• Introduction
  • The Kafka Streams API in a Nutshell
  • Use Case Examples
  • A Closer Look
• Requirements
  • Apache Kafka
  • Confluent
• Kafka Streams Quick Start
  • Purpose
  • Start the Kafka cluster
  • Prepare the topics and the input data
  • Process the input data with Kafka Streams
  • Inspect the output data
  • Stop the Kafka cluster
  • Next steps
• Kafka Streams Demo Application
  • Requirements
  • Running the Kafka Music demo application
  • Running further Confluent demo applications for the Kafka Streams API
  • Appendix
    • Inspecting the input topics of the Kafka Music application
    • Creating new topics
    • Listing available topics
• Concepts
  • Kafka 101
  • Stream
  • Stream Processing Application
  • Processor Topology
  • Stream Processor
  • Stateful Stream Processing
  • Duality of Streams and Tables
  • KStream
  • KTable
  • GlobalKTable
  • Time
  • Aggregations
  • Joins
  • Windowing
  • Interactive Queries
• Architecture
  • Processor Topology
  • Parallelism Model
    • Stream Partitions and Tasks
    • Threading Model
    • Example
  • State
  • Memory management
    • Record caches
  • Fault Tolerance
  • Processing Guarantees
  • Flow Control with Timestamps
  • Backpressure
• Code Examples
  • Getting started examples
    • Java
    • Scala
  • Security examples
    • Java programming language
  • Interactive queries examples
    • Java
  • End-to-end application examples
    • Java
    • Scala
• Developer Guide
  • Writing a Streams Application
    • Libraries and Maven artifacts
    • Using Kafka Streams within your application code
  • Configuring a Streams Application
    • Configuration parameter reference
  • Streams DSL
    • Overview
    • Creating source streams from Kafka
    • Transform a stream
    • Writing streams back to Kafka
  • Processor API
    • Overview
    • Defining a Stream Processor
    • State Stores
    • Connecting Processors and State Stores
  • Data Types and Serialization
    • Configuring SerDes
    • Overriding default SerDes
    • Available SerDes
    • Implementing custom SerDes
  • Interactive Queries
    • Querying local state stores for an app instance
    • Querying remote state stores for the entire app
    • Demo applications
  • Memory Management
    • Record caches in the DSL
    • Record caches in the Processor API
    • Other memory usage
  • Running Streams Applications
    • Starting a Kafka Streams application
    • Elastic scaling of your application
  • Managing Streams Application Topics
    • User topics
    • Internal topics
  • Streams Security
    • Required ACL setting for secure Kafka clusters
    • Security example
  • Application Reset Tool
    • Step 1: Run the application reset tool
    • Step 2: Reset the local environments of your application instances
• Operations
  • Capacity planning and sizing
    • Background and context
    • Stateless vs. stateful
    • Examples
    • Troubleshooting
  • Monitoring your application
    • Metrics
    • Run-time Status Information
    • Integration with Confluent Control Center
• Upgrade Guide
  • Upgrading from CP 3.3.x (Kafka 0.11.0.x-cp1) to CP 4.0.0 (Kafka 1.0.0-cp1)
    • Compatibility
    • Upgrading your Kafka Streams applications to CP 4.0.0
    • API changes
    • Full upgrade workflow
  • Upgrading older Kafka Streams applications to CP 4.0.0
    • API changes (from CP 3.2 to CP 3.3)
    • API changes (from CP 3.1 to CP 3.2)
    • API changes (from CP 3.0 to CP 3.1)
• FAQ
  • General
    • Is Kafka Streams a project separate from Apache Kafka?
    • Is Kafka Streams a proprietary library of Confluent?
    • Do Kafka Streams applications run inside the Kafka brokers?
    • Why Does My Kafka Streams Application Use So Much Memory?
    • What are the system dependencies of Kafka Streams?
    • How do I migrate my older Kafka Streams applications to the latest Confluent Platform version?
    • Which versions of Kafka clusters are supported by Kafka Streams?
    • What programming languages are supported?
    • Why is my application re-processing data from the beginning?
  • Scalability
    • Maximum parallelism of my application? Maximum number of app instances I can run?
  • Processing
    • Accessing record metadata such as topic, partition, and offset information?
    • Difference between map, peek, foreach in the DSL?
    • How to avoid data repartitioning if you know it’s not required?
    • How can I replace RocksDB with a different store?
  • Failure and exception handling
    • Handling corrupted records and deserialization errors (“poison pill records”)?
    • Sending corrupt records to a quarantine topic or dead letter queue?
  • Interactive Queries
    • Handling InvalidStateStoreException: “the state store may have migrated to another instance”?
  • Security
    • Application fails when running against a secured Kafka cluster?
  • Troubleshooting and debugging
    • Easier to interpret Java stacktraces?
    • Visualizing topologies?
    • Inspecting streams and tables?
    • Invalid Timestamp Exception
    • Why do I get an IllegalStateException when accessing record metadata?
    • Why is punctuate() not called?
    • Scala: compile error “no type parameter”, “Java-defined trait is invariant in type T”
    • How can I convert a KStream to a KTable without an aggregation step?
    • RocksDB behavior in 1-core environments
• Javadocs