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Sub-pages:

• Using Kafka Streams:
  
  • Usage Patterns
  • Application Reset Tool

  • Join Semantics

  • Streams FAQs
  • Data (Re)Processing Scenarios
• Development:
  • KIP overview by release
  • Development Plan
  • Discussions
  • Data (Re)Processing Scenarios
  • Kafka Streams DSL Grammar
  • Streams Runtime Architecture with New Threading
• Internals:
  
  • Data Management
  • Architecture
  • DSL Optimizer

Find more links about Kafka Streams at Kafka Ecosystem page.

Kafka Streams related KIPs:

Adopted

• future release Kafka 2.5:
  • KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner (partially implemented in v1.1)
  • KIP-150 - Kafka-Streams Cogroup
  • KIP-221: Enhance DSL with Connecting Topic Creation and Repartition Hint (partially implemented in v2.3)
  • KIP-258: Allow to Store Record Timestamps in RocksDB (partially implemented in v2.3)
  • KIP-300: Add Windowed KTable API in StreamsBuilder
  • KIP-328: Ability to suppress updates for KTables (partially implemented in v2.1)
• upcoming release Kafka 2.4:
  • KIP-213 Support non-key joining in KTable
  • KIP-221: Enhance DSL with Connecting Topic Creation and Repartition Hint (partially implemented in v2.3)
  • KIP-307: Allow to define custom processor names with KStreams DSL (partially implemented in v2.3)
  • KIP-401: TransformerSupplier/ProcessorSupplier StateStore connecting
  • KIP-444: Augment metrics for Kafka Streams (partially implemented in v2.3)
  • KIP-446: Add changelog topic configuration to KTable suppress
  • KIP-466: Add support for List<T> serialization and deserialization
  • KIP-470: TopologyTestDriver test input and output usability improvements
  • KIP-471: Expose RocksDB Metrics in Kafka Streams (partially implemented in v2.3)
  • KIP-474: To deprecate WindowStore#put(key, value)
  • KIP-479: Add Materialized to Join
• Kafka 2.3: 
  • KIP-258: Allow to Store Record Timestamps in RocksDB (partially implemented in v2.3)
  • KIP-307: Allow to define custom processor names with KStreams DSL (partially implemented in v2.3)
  • KIP-313: Add KStream.flatTransform and KStream.flatTransformValues (finished in v2.3; partially implemented in v2.2)
  • KIP-331 Add default implementation to close() and configure() for Serializer, Deserializer and Serde
  • KIP-428: Add in-memory window store
  • KIP-442: Return to default max poll interval in Streams
  • KIP-443: Return to default segment.ms and segment.index.bytes in Streams repartition topics
  • KIP-445: In-memory Session Store
  • KIP-453: Add close() method to RocksDBConfigSetter
  • KIP-462: Use local thread id for KStreams
• Kafka 2.2:
  

  • KIP-313: Add KStream.flatTransform and KStream.flatTransformValues (partially implemented in v2.2)

  • KIP-376: Implement AutoClosable on appropriate classes that want to be used in a try-with-resource statement

  • KIP-386: Standardize on Min/Avg/Max metrics' default value

  • KIP-393: Time windowed serde to properly deserialize changelog input topic

  • KIP-414: Expose Embedded ClientIds in Kafka Streams

  • KIP-420: Add Single Value Fetch in Session Stores

Below is a list of KIPs that are not release yet. Go to Kafka Streams KIP Overview for KIPs by release (including discarded KIPs).

Under discussion

• KIP-406: GlobalStreamThread should honor custom reset policy
• KIP-424: Allow suppression of intermediate events based on wall clock time
• KIP-439: Cleanup built-in Store interfaces
• KIP-448: Add State Stores Unit Test Support to Kafka Streams Test Utils
• KIP-508: Make Suppression State Queriable
• KIP-513: Distinguish between Key and Value serdes in scala wrapper library for kafka streams
• KIP-540: Implement per key stream time tracking
• KIP-560: Auto infer external topic partitions in stream reset tool
• KIP-598: Augment TopologyDescription with store and source / sink serde information
• KIP-634: Complementary support for headers and record metadata in Kafka Streams DSL
• KIP-647: Add ability to handle late messages in streams-aggregation
• KIP-655: Windowed Distinct Operation for Kafka Streams API
• KIP-669: Preserve Source Partition in Kafka Streams from context
• KIP-674: Metric Reporter to Aggregate Metrics in Kafka Streams
• KIP-675: Convert KTable to a KStream using the previous value
• KIP-677: Migrating Topology methods to the Builder pattern
• KIP-718: Make KTable Join on Foreign key unopinionated
• KIP-747 Add support for basic aggregation APIs
• KIP-807: Refactor KafkaStreams exposed metadata hierarchy
• KIP-816: Topology changes without local state reset
• KIP-819: Merge multiple KStreams in one operation
• KIP-839: Provide builders for KafkaProducer/KafkaConsumer and KafkaStreams
• KIP-857: Streaming recursion in Kafka Streams
• KIP-948: Allow custom prefix for internal topic names in Kafka Streams
• KIP-955: Add stream-table join on foreign key
• KIP-969: Support range Interactive Queries (IQv2) for Versioned State Stores 
• KIP-989: RocksDB Iterator Metrics
• KIP-990: Capability to PAUSE Tasks on DeserializationException
• KIP-997: update WindowRangeQuery and unify WindowKeyQuery and WindowRangeQuery

Adopted

• inactive, not (fully) implemented (feel free to pick up):
• Kafka 2.1:
  
  • KIP-206: Add support for UUID serialization and deserialization
  • KIP-312: Add Overloaded StreamsBuilder Build Method to Accept java.util.Properties

  • KIP-319: Replace segments with segmentInterval in WindowBytesStoreSupplier

  • KIP-321: Update TopologyDescription to better represent Source and Sink Nodes

  • KIP-324: Add method to get metrics() in AdminClient

  • KIP-328: Ability to suppress updates for KTables (partially implemented in v2.1)

  • KIP-330: Add retentionPeriod in SessionBytesStoreSupplier

  • KIP-353: Improve Kafka Streams Timestamp Synchronization

  • KIP-356: Add withCachingDisabled() to StoreBuilder

  • KIP-358: Migrate Streams API to Duration instead of long ms times

  • KIP-365: Materialized, Serialized, Joined, Consumed and Produced with implicit Serde

  • KIP-366: Make FunctionConversions deprecated

  • KIP-372: Naming Repartition Topics for Joins and Grouping

• Kafka 2.0:
  • KIP-244: Add Record Header support to Kafka Streams Processor API
  • KIP-245: Use Properties instead of StreamsConfig in KafkaStreams constructor
  • KIP-251: Allow timestamp manipulation in Processor API
  • KIP-261: Add Single Value Fetch in Window Stores
  • KIP-265: Make Windowed Serde to public APIs
  • KIP-267: Add Processor Unit Test Support to Kafka Streams Test Utils
  • KIP-268: Simplify Kafka Streams Rebalance Metadata Upgrade
  • KIP-270 - A Scala Wrapper Library for Kafka Streams
  • KIP-274: Kafka Streams Skipped Records Metrics
  • KIP-276 Add StreamsConfig prefix for different consumers
  • KIP-284: Set default retention ms for Streams repartition topics to Long.MAX_VALUE
  • KIP-292: Add transformValues() method to KTable
  • KIP-295 Add Streams Configuration Allowing for Optional Topology Optimization
  • KIP-303: Add Dynamic Routing in Streams Sink
• Kafka 1.1:
  
  • KIP-149: Enabling key access in ValueTransformer, ValueMapper, and ValueJoiner (partially implemented in v1.1)
  • KIP-171 - Extend Consumer Group Reset Offset for Stream Application216: IQ should throw different exceptions for different errors
  • KIP-205: Add all() and range() API to ReadOnlyWindowStore
  • KIP-210 - Provide for custom error handling when Kafka Streams fails to produce
  • KIP-220: Add AdminClient into Kafka Streams' ClientSupplier
  • KIP-224: Add configuration parameter `retries` to Streams AP
  • KIP-233: Simplify StreamsBuilder#addGlobalStore
  • KIP-239 Add queryableStoreName() to GlobalKTable
  • KIP-247: Add public test utils for Kafka Streams
  • Kafka 1.0:
    • KIP-120: Cleanup Kafka Streams builder API
    • KIP 130: Expose states of active tasks to KafkaStreams public API
    • KIP-138: Change punctuate semantics
    • KIP 157 - Add consumer config options to streams reset tool
    • KIP-160: Augment KStream.print(), KStream.writeAsText() to allow users pass in extra parameters in the printed string
    • KIP-161: streams deserialization exception handlers
    • KIP-167: Add interface for the state store restoration process
    • KIP-173: Add prefix to StreamsConfig to enable setting default internal topic configs
    • KIP-182: Reduce Streams DSL overloads and allow easier use of custom storage engines
    • KIP-198: Remove ZK dependency from Streams Reset Tool
    • KIP-202 Move merge() from StreamsBuilder to KStream
  • Kafka 0.11.0:
    • KIP-114: KTable state stores and improved semantics
    • KIP-123: Allow per stream/table timestamp extractor
    • KIP-121: Add KStream peek method
    • KIP-129: Streams Exactly-Once Semantics
    • KIP-134: Delay initial consumer group rebalance
    • KIP 155 - Add range scan for windowed state stores
    • KIP 156 Add option "dry run" to Streams application reset tool
  • Kafka 0.10.2:
    • KIP-77: Improve Kafka Streams Join Semantics
    • KIP-90: Remove zkClient dependency from Streams
    • KIP-93: Improve invalid timestamp handling in Kafka Streams
    • KIP-94: Session Windows
    • KIP-97: Improved Kafka Client RPC Compatibility Policy 
    • KIP-99: Add Global Tables to Kafka Streams
    • KIP-100: Relax Type constraints in Kafka Streams API
    • KIP-104: Granular Sensors for Streams

  • Kafka 0.10.1:

    • KIP-62: Allow consumer to send heartbeats from a background thread
    • KIP-63: Unify store and downstream caching in streams
    • KIP-67: Queryable state for Kafka Streams
    • KIP-71: Enable log compaction and deletion to co-exist

  • Kafka 0.10.0:

    • KIP-28: Add a processor client
    • KIP-32: Add timestamps to Kafka message

  ...

  • • 258: Allow to Store Record Timestamps in RocksDB (partially implemented in v2.3)
    • KIP-300: Add Windowed KTable API in StreamsBuilder (accepted but postponed because current code base does not allow to implement it as proposed) 
    • KIP-328: Ability to suppress updates for KTables (partially implemented in v2.1)
    • KIP-557: Add emit on change support for Kafka Streams (partially implemented in v2.6 reverted again in 2.8.0, 2.7.1, and 2.6.2 due to potential data loss)
    • KIP-698: Add Explicit User Initialization of Broker-side State to Kafka Streams
    • KIP-796: Interactive Query v2 (split up into multiple sub KIPs)
    • KIP-844: Transactional State Stores (cf KIP-892: Transactional Semantics for StateStores)
    • KIP-878: Internal Topic Autoscaling for Kafka Streams
  • WIP (open PR / in review):
    
    • KIP-759: Unneeded repartition canceling
    • KIP-770: Replace "buffered.records.per.partition" & "cache.max.bytes.buffering" with "{statestore.cache}/{input.buffer}.max.bytes" (partially implemented in 3.4)
    • KIP-813: Shareable State Stores
    • KIP-892: Transactional Semantics for StateStores
    • KIP-869: Improve Streams State Restoration Visibility (partially implemented in 3.5)
  • next release Kafka 3.7 (merged):
    • KIP-714: Client metrics and observability (includes some minor Kafka Streams changes)
    • KIP-925: Rack aware task assignment in Kafka Streams (completed; partially implemented in 3.6)
    • KIP-954: expand default DSL store configuration to custom types
    • KIP-960: Support single-key_single-timestamp interactive queries for versioned state stores
    • KIP-962: Relax non-null key requirement in Kafka Streams
    • KIP-968: Support single-key_multi-timestamp Interactive Queries (IQv2) for Versioned State Stores 
    • KIP-985: Add reverseRange and reverseAll query over kv-store in IQv2
    • KIP-988: Streams Standby Update Listener
    • KIP-992: Proposal to introduce IQv2 Query Types: TimestampedKeyQuery and TimestampedRangeQuery

  Inactive (feel free to pick up and resume the discussion):

  • KIP-95: Incremental Batch Processing for Kafka Streams
  • KIP-159: Introducing Rich functions to Streams
  • KIP-216: IQ should throw different exceptions for different errors260: add primary join operation for Stream-Stream join (WIP) (draft)
  • KIP-311: Async processing with dynamic scheduling in Kafka StreamsKIP-228 Negative record timestamp support
  • KIP-314: KTable to GlobalKTable Bi-directional Join
  • KIP-326: Schedulable KTable as Graph source
  • KIP-335: Consider configurations for KafkaStreams
  • KIP-362: Support dynamic gap session windowKIP-378: Enable Dependency Injection for Kafka Streams handlers
  • KIP-406: GlobalStreamThread should honor custom reset policyKIP-408: Add Asynchronous Processing To Kafka Streams
  • KIP-418: A method-chaining way to branch KStream
  • KIP-422: [Streams] Support multiple topic resolution in TopicNameExtractor
  • KIP-424: Allow suppression of intermediate events based on wall clock time
  • KIP-429: Kafka Consumer Incremental Rebalance Protocol
  • KIP-439: Cleanup built-in Store interfaces
  • KIP-448: Add State Stores Unit Test Support to Kafka Streams Test Utils
  • 457: Add DISCONNECTED status to Kafka Streams
  • KIP-459: Improve KafkaStreams#closeKIP-450: Sliding Window Aggregations in the DSL
  • KIP-463: Auto-configure non-default Serdes passed alongside the TopologyBuilder
  • KIP-472: Add header to RecordContext/KafkaProducer
  • KIP-478 - Strongly typed Processor API
  • KIP-508: Make Suppression State Queriable
  • KIP-523: Add KStream#toTable to the Streams DSL
  • KIP-527: Add VoidSerde to Serdes
  • KIP-528: Deprecate PartitionGrouper configuration and interface

  Inactive (feel free to pick up):

  • KIP-95: Incremental Batch Processing for Kafka Streams
  • KIP-311: Async processing with dynamic scheduling in Kafka Streams
  • KIP-399: Extend ProductionExceptionHandler to cover serialization exceptions

  Discarded:

  • 645: Replace Windows with a proper interface
  • KIP-667: Remove deprecated methods from ReadOnlyWindowStore (no KIP needed)
  • KIP-XXX: [Streams] Support multiple topic resolution in TopicNameExtractor (draft
  • KIP-116: Add State Store Checkpoint Interval Configuration
  • KIP-132: Augment KStream.print to allow extra parameters in the printed string (duplicated by KIP-160)
  • KIP-147: Add missing type parameters to StateStoreSupplier factories and KGroupedStream/Table methods (covered via KIP-182)
  • KIP-165: Extend Interactive Queries for return latest update timestamp per key (covered via KIP-258)
  • KIP 230: Name Windowing Joins (covered via KIP-372: Naming Repartition Topics for Joins and Grouping)
  • KIP-262: Metadata should include number of state stores for task
    
  • KIP-364: Remove implicit Materialized, Consumed and Produced (covered via KIP-365: Materialized, Serialized, Joined, Consumed and Produced with implicit Serde)
    
  • KIP-451: Make TopologyTestDriver output iterable (subsumed by KIP-456)
  • KIP-456: Helper classes to make it simpler to write test logic with TopologyTestDriver (subsumed by KIP-470)
  • KIP-485: Make topic optional when using through() operations in DSL (subsumed by KIP-221)