Implementation:Apache Kafka CoordinatorRuntime OnMetadataUpdate

Knowledge Sources	Apache Kafka
Domains	Distributed_Systems, Metadata_Management
Last Updated	2026-02-09 12:00 GMT

Overview

Concrete tool for propagating cluster metadata updates to coordinators provided by the CoordinatorRuntime.

Description

The onMetadataUpdate method updates the global metadataImage and schedules an internal event for each registered coordinator partition. Each event checks the coordinator's state and, if ACTIVE, calls coordinator.onMetadataUpdate(delta, newImage) to deliver the metadata change.

Usage

Called by the Kafka broker's metadata listener when it receives new metadata from the KRaft controller.

Code Reference

Source Location

Repository: Apache Kafka
File: coordinator-common/src/main/java/org/apache/kafka/coordinator/common/runtime/CoordinatorRuntime.java
Lines: L2368-2410

Signature

public void onMetadataUpdate(
    CoordinatorMetadataDelta delta,
    CoordinatorMetadataImage newImage
)

Import

import org.apache.kafka.coordinator.common.runtime.CoordinatorRuntime;
import org.apache.kafka.coordinator.common.runtime.CoordinatorMetadataDelta;
import org.apache.kafka.coordinator.common.runtime.CoordinatorMetadataImage;

I/O Contract

Inputs

Name	Type	Required	Description
delta	CoordinatorMetadataDelta	Yes	The metadata changes
newImage	CoordinatorMetadataImage	Yes	The new complete metadata image

Outputs

Name	Type	Description
void		Global metadataImage updated; each ACTIVE coordinator notified

Usage Examples

// Called by broker metadata listener
coordinatorRuntime.onMetadataUpdate(metadataDelta, newMetadataImage);

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