Implementation:Apache Kafka CoordinatorRuntime ScheduleWriteOperation

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

Overview

Concrete tool for scheduling coordinator state mutations provided by the CoordinatorRuntime framework.

Description

The scheduleWriteOperation method creates a CoordinatorWriteEvent and enqueues it for processing. The event executes the write operation lambda, serializes the generated records, appends them to the partition via PartitionWriter, and completes the returned future when the records are committed.

Usage

Called by coordinator service implementations (e.g., GroupCoordinatorService, ShareCoordinatorService) to enqueue state mutations.

Code Reference

Source Location

Repository: Apache Kafka
File: coordinator-common/src/main/java/org/apache/kafka/coordinator/common/runtime/CoordinatorRuntime.java
Lines: L2070-2080

Signature

public <T> CompletableFuture<T> scheduleWriteOperation(
    String name,
    TopicPartition tp,
    CoordinatorWriteOperation<S, T, U> op
)

Import

import org.apache.kafka.coordinator.common.runtime.CoordinatorRuntime;
import org.apache.kafka.common.TopicPartition;
import java.util.concurrent.CompletableFuture;

I/O Contract

Inputs

Name	Type	Required	Description
name	String	Yes	Operation name for logging
tp	TopicPartition	Yes	The coordinator's topic-partition
op	CoordinatorWriteOperation<S, T, U>	Yes	Lambda that generates records from coordinator state

Outputs

Name	Type	Description
CompletableFuture<T>	future	Completes with operation result when records are committed

Usage Examples

CompletableFuture<Void> future = coordinatorRuntime.scheduleWriteOperation(
    "JoinGroup",
    new TopicPartition("__consumer_offsets", 0),
    (coordinator) -> {
        // Generate records for group join
        List<CoordinatorRecord> records = coordinator.handleJoinGroup(request);
        return new CoordinatorResult<>(records, null);
    }
);

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