Status

Current state:  "Under Discussion" Accepted

Discussion thread: here [Change the link from the KIP proposal email archive to your own email thread] 

JIRA: here

Please keep the discussion on the mailing list rather than commenting on the wiki (wiki discussions get unwieldy fast).

Motivation

 CurrentlyCurrently, Kafka Streams does not support ProcessingExceptionHandler for GlobalKTable processors. When a processing exception occurs during GlobalKTable record processing, the GlobalStreamThread fails and terminates, causing the entire Kafka  Kafka Streams application to shut - down. This behavior behaviour is inconsistent with regular KStream/KTable processing, where ProcessingExceptionHandler allows applications to handle exceptions gracefully and continue processing.

Public Interfaces

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New property:

Name	Type	Default	Importance	Deprecated	Removed	Description
processing.exception.handler.global.enabled	Boolean	False	HIGH	4.3	5.0	When false (default), maintains backwards-compatible behaviour where global exceptions terminate or gracefully shut down the application. When true, enables the ProcessingExceptionHandler for GlobalKTable exceptions. This config will be removed in Kafka Streams 5.0, where global exception handling will be enabled by default

Proposed Changes

This KIP extends the applicability of the existing ProcessingExceptionHandler to GlobalKTable processors. Currently, this exception handler only applies to regular stream regular stream processing (KStream/KTable). After this KIP, the same handler will also
handle processing exceptions in GlobalKTable. The feature is gated behind a configuration flag to prevent unexpected behaviour in existing handler implementations that may not be designed to handle GlobalKTable exceptions, which could cause crashes or undesired side effects. This provides a safe migration path for users to test and adapt their exception handling logic.

Exception Handling Scope

After this KIP, the ProcessingExceptionHandler configured via `default.processing.exception.handler` will be invoked for:

  - KStream processing exceptions (existing)
  - KTable processing exceptions (existing)
  - GlobalKTable processing exceptions (new capability added by this KIP)

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Current State

 DeserializationExceptionHandler is configured via StreamsConfig, instantiated via TopologyConfig, passed to GlobalStateUpdateTask, and used during GlobalKTable deserialization. No Global Processor exception is being handled. We will be replicating the same framework of initialization for ProcessingExceptionHandler in GlobalKTables.

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Currently, while DeserializationExceptionHandler is passed to both regular stream tasks and global state update tasks, ProcessingExceptionHandler is only passed to regular stream tasks, resulting in unhandled processing exceptions for GlobalKTable processors.

Proposed Extension

The infrastructure for configuration and instantiation of the ProcessingExceptionHandler already exists. However, it is currently only passed to regular stream tasks, not to global state update tasks. This KIP extends the existing pattern to pass ProcessingExceptionHandler to GlobalStateUpdateTask, mirroring how DeserializationExceptionHandler is already passed to both regular and global tasks. This enables exception handling during GlobalKTable during GlobalKTable processor execution.

Implementation

  Add ProcessingExceptionHandler as a constructor parameter to GlobalStateUpdateTask and pass it to processor initializationinitialisation, mirroring the existing DeserializationExceptionHandler implementation. When invoked, the ProcessingExceptionHandler instance will call the handleError() method (not handle()). This provides automatic backward compatibility through the implementation defined in KIP-1034.

Limitation

In this KIP, DLQ records returned by the handler will be logged with full metadata but NOT sent to Kafka for GlobalKTable processors. This is because GlobalKTable processing does not currently have producer infrastructure. We will cover DLQ in a separate KIP. 

Compatibility, Deprecation, and Migration Plan

This change is fully backward compatible:
  - Applications without a configured handler experience no behavior change
  - Applications with a configured handler automatically get GlobalKTable support
  - The handler interface is not modified - The handleError() method (introduced in KIP-1034) will be called for GlobalKTable exceptions. 
  - No new configuration properties are introduced- Fully backwards compatible by default - existing behaviour is preserved unless config is explicitly enabled
  - New configuration `processing.exception.handler.global.enabled` defaults to `false`
  - Config is deprecated immediately upon introduction
  - In Kafka Streams 5.0, this config will be removed, and the handler will always be invoked for GlobalKTable exceptions
  - Migration path: Users should test with the config enabled before upgrading to 5.0

Test Plan

Since this is a fairly small change, unit tests and integration test tests should be sufficient.

Rejected Alternatives

Create a new

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ProcessExceptionalHandler interface for the global thread, which

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requires introducing new configuration at the stream config level. This would create unnecessary

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operational overload for the end users as it require to implement multiple interfaces.