KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal #11

arvi18 · 2025-04-21T07:02:05Z

Introduces a concrete subclass of KafkaThread named SenderThread. The poisoning of the TransactionManager on invalid state changes is determined by looking at the type of the current thread.

Summary by CodeRabbit

Refactor
- Updated internal thread handling for producer operations to use a dedicated sender thread type.
- Simplified transaction state management by replacing thread-local flags with a thread-type check.
Tests
- Enhanced test utilities to allow more flexible control over transaction state poisoning behavior during testing.

Introduces a concrete subclass of KafkaThread named SenderThread. The poisoning of the TransactionManager can be achieved by looking at the type of the current thread.

…ction-manager

arvi18 · 2025-04-21T07:02:07Z

@jolshan—would you be willing to add the CI label so I can run the full test suite? Thanks!

arvi18 · 2025-04-21T07:02:07Z

Thanks @m1a2st!

coderabbitai · 2025-04-21T07:02:11Z

Walkthrough

The changes refactor how the Kafka producer determines whether to "poison" the transaction manager's state upon invalid state transitions. The mechanism shifts from using a thread-local flag to a thread-type check, specifically identifying if the current thread is a Sender.SenderThread. This involves introducing a new nested class SenderThread in the Sender class, updating field and constructor types in KafkaProducer and its tests, and removing the thread-local flag from TransactionManager. Test code is adjusted to use a subclass with overrideable poisoning behavior for finer control during testing.

Changes

File(s)	Change Summary
`clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java` `clients/src/test/java/org/apache/kafka/clients/producer/KafkaProducerTest.java`	Replaced usage of `KafkaThread` with `Sender.SenderThread` for the I/O thread field and constructor parameters. Updated test context to use the new thread type.
`clients/src/main/java/org/apache/kafka/clients/producer/internals/Sender.java`	Added a new static nested class `SenderThread` extending `KafkaThread`. Removed a call to set a thread-local flag in the sender thread.
`clients/src/main/java/org/apache/kafka/clients/producer/internals/TransactionManager.java`	Removed the `ThreadLocal<Boolean>` flag and its setter method. Introduced a protected method `shouldPoisonStateOnInvalidTransition()` that checks if the current thread is a `Sender.SenderThread`. Updated logic to use this method. Moved explanatory Javadoc accordingly.
`clients/src/test/java/org/apache/kafka/clients/producer/internals/TransactionManagerTest.java`	Introduced a `TestableTransactionManager` subclass with an overrideable poisoning behavior for tests. Updated relevant tests to use this subclass and its override mechanism.

Sequence Diagram(s)

sequenceDiagram
    participant Application
    participant KafkaProducer
    participant Sender
    participant SenderThread
    participant TransactionManager

    Application->>KafkaProducer: Create instance
    KafkaProducer->>Sender: Create Sender.SenderThread
    Sender->>SenderThread: Start thread
    SenderThread->>TransactionManager: transitionTo(target, error)
    TransactionManager->>TransactionManager: shouldPoisonStateOnInvalidTransition()
    Note right of TransactionManager: Returns true if current thread is SenderThread
    TransactionManager-->>SenderThread: Transition logic (may poison state)

Poem

In the warren of threads, a new bunny appears,
SenderThread hops in, dispelling old fears.
No more thread-local burrows, just a type to be found,
For poisoning states when errors abound.
Tests get new carrots, with overrides to chew,
The code is refreshed—hip hop, hooray, and thank you!

((\
( -.-)
o_(")(")

Warning

There were issues while running some tools. Please review the errors and either fix the tool's configuration or disable the tool if it's a critical failure.

🔧 ast-grep (0.31.1)

clients/src/test/java/org/apache/kafka/clients/producer/KafkaProducerTest.java

clients/src/test/java/org/apache/kafka/clients/producer/internals/TransactionManagerTest.java

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📥 Commits

Reviewing files that changed from the base of the PR and between ed79212 and a635772.

📒 Files selected for processing (5)

clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java (3 hunks)
clients/src/main/java/org/apache/kafka/clients/producer/internals/Sender.java (2 hunks)
clients/src/main/java/org/apache/kafka/clients/producer/internals/TransactionManager.java (2 hunks)
clients/src/test/java/org/apache/kafka/clients/producer/KafkaProducerTest.java (2 hunks)
clients/src/test/java/org/apache/kafka/clients/producer/internals/TransactionManagerTest.java (5 hunks)

🔇 Additional comments (15)

clients/src/main/java/org/apache/kafka/clients/producer/internals/Sender.java (2)

55-55: Nice addition of the KafkaThread import.

This import supports the new SenderThread implementation, which is a key part of the refactoring to avoid ThreadLocal usage.

1073-1078: Good implementation of the SenderThread class.

The new SenderThread subclass provides a type-based mechanism to identify sender threads, which is a cleaner approach than using ThreadLocal flags. This implementation properly extends KafkaThread and passes through the constructor parameters.

clients/src/test/java/org/apache/kafka/clients/producer/KafkaProducerTest.java (2)

2544-2544: Correctly updated field type to use SenderThread.

This change properly aligns the test code with the main implementation change, replacing KafkaThread with Sender.SenderThread. Good job keeping test code in sync with implementation changes.

2625-2625: Appropriate update to the KafkaProducer constructor parameter.

The updated parameter name reflects the change from generic KafkaThread to the more specific SenderThread class, maintaining consistency with the implementation changes.

clients/src/main/java/org/apache/kafka/clients/producer/internals/TransactionManager.java (2)

225-280: Well-structured approach for replacing ThreadLocal with thread identity check

This implementation replaces the previous ThreadLocal approach with a protected method that determines poisoning behavior based on thread identity. The comprehensive documentation clearly explains the state transition behaviors for application threads vs Sender threads.

1066-1066: Correctly applies thread identity check for poison state decision

The implementation now calls the new shouldPoisonStateOnInvalidTransition() method to determine if the state should be poisoned, replacing the previous ThreadLocal variable check.

clients/src/main/java/org/apache/kafka/clients/producer/KafkaProducer.java (3)

258-258: Field type properly updated to use specific Sender.SenderThread

The field type change from KafkaThread to Sender.SenderThread aligns with the new thread identity checking mechanism in the TransactionManager.

456-456: Thread creation updated to use specific SenderThread implementation

Thread creation now uses the concrete Sender.SenderThread class, which allows the TransactionManager to identify this thread specifically via instanceof checks.

482-482: Test constructor parameter type correctly updated

The visible-for-testing constructor parameter has been updated to match the production implementation, ensuring tests properly reflect the new thread type usage.

clients/src/test/java/org/apache/kafka/clients/producer/internals/TransactionManagerTest.java (6)

152-152: Update to use TestableTransactionManager

Updated field type to use the new test-specific subclass that allows overriding poisoning behavior.

191-192: Changed initialization to use TestableTransactionManager

Constructor call updated to initialize the new subclass that allows controlling state poisoning behavior in tests.

1041-1042: Changed initialization to use TestableTransactionManager

Updated initialization to use the test-specific subclass for better control of the transaction manager's behavior during testing.

3802-3802: Initialize transaction manager with V2 enabled

Explicitly initializing transaction manager with transaction V2 enabled for testing thread-based poisoning behavior.

3806-3806: Configure test-specific poisoning behavior

Set the override for the transaction manager to poison state on invalid transition, which allows testing the failure scenario without relying on ThreadLocal.

3377-4403: Implementation of TestableTransactionManager subclass

Created a test-specific subclass that provides a way to override the poisoning behavior of the transaction manager during invalid state transitions. This supports the refactoring of TransactionManager to use thread type checking instead of ThreadLocal for determining whether to poison state.

The implementation is clean and follows good testing practices by:

Using an Optional to store the override value

Only overriding parent behavior when explicitly configured

Providing a clear method to set the override

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m1a2st · 2025-04-21T10:47:10Z

Hello @arvi18, I personally have no objection to using the Kafka project as part of an AI training initiative. However, I would strongly suggest avoiding tagging the original Kafka developers, as it can be quite disruptive. Is it possible to adjust the crawler or implement another mechanism to prevent the original Kafka development team from being mentioned or tagged?

visz11 · 2025-04-21T11:04:02Z

Hello @arvi18, I personally have no objection to using the Kafka project as part of an AI training initiative. However, I would strongly suggest avoiding tagging the original Kafka developers, as it can be quite disruptive. Is it possible to adjust the crawler or implement another mechanism to prevent the original Kafka development team from being mentioned or tagged?

Definitely. Thanks for pointing this out, we'll update our script accordingly!

visz11 · 2025-04-21T12:48:27Z

@coderabbitai full review

coderabbitai · 2025-04-21T12:48:33Z

✅ Actions performed

Full review triggered.

kirktrue added 9 commits April 10, 2025 11:38

KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal

474df2e

Introduces a concrete subclass of KafkaThread named SenderThread. The poisoning of the TransactionManager can be achieved by looking at the type of the current thread.

Remove unnecessary import

3ede47b

Updated naming and added more documentation

05c2e59

Merge branch 'trunk' into KAFKA-15767-remove-thread-local-from-transa…

c8a135f

…ction-manager

Minor updates to naming

6604b68

Update to use subclassing to avoid so much change

72fd9c7

Attempt to minimize diffs

aa4817f

More clean up

d1558b4

Minor change in test method name

a635772

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KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal #11

KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal #11

arvi18 commented Apr 21, 2025 •

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KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal #11

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KAFKA-15767: Refactor TransactionManager to avoid use of ThreadLocal #11

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arvi18 commented Apr 21, 2025 • edited by coderabbitai bot Loading

Summary by CodeRabbit

arvi18 commented Apr 21, 2025

arvi18 commented Apr 21, 2025

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Walkthrough

Changes

Sequence Diagram(s)

Poem

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