Implementation:Apache Dolphinscheduler MasterClusters And WorkerClusters

Knowledge Sources	Apache DolphinScheduler
Domains	Distributed_Systems, Cluster_Management
Last Updated	2026-02-10 00:00 GMT

Overview

Concrete tool for tracking master and worker node health using MasterClusters, WorkerClusters, MasterSlotManager, and ClusterManager with registry-based heartbeat subscriptions.

Description

MasterClusters extends AbstractClusterSubscribeListener<MasterServerMetadata> and implements IClusters<MasterServerMetadata>. It maintains a map of active master nodes and provides getServers(), getNormalServers(), and listener registration. WorkerClusters extends AbstractClusterSubscribeListener<WorkerServerMetadata> and additionally tracks worker groups via getNormalWorkerServerAddressByGroup(String) and containsWorkerGroup(String). MasterSlotManager implements IMasterSlotReBalancer providing getCurrentMasterSlot(), getTotalMasterSlots(), and doReBalance(). ClusterManager initializes both cluster objects via start().

Usage

Automatically managed by the master server's Spring context. ClusterManager.start() is called during bootstrap.

Code Reference

Source Location

Repository: dolphinscheduler
File: dolphinscheduler-master/src/main/java/org/apache/dolphinscheduler/server/master/cluster/MasterClusters.java (L37-98)
File: dolphinscheduler-master/src/main/java/org/apache/dolphinscheduler/server/master/cluster/WorkerClusters.java (L38-182)
File: dolphinscheduler-master/src/main/java/org/apache/dolphinscheduler/server/master/cluster/MasterSlotManager.java (L31-62)
File: dolphinscheduler-master/src/main/java/org/apache/dolphinscheduler/server/master/cluster/ClusterManager.java (L34-87)

Signature

public class MasterClusters extends AbstractClusterSubscribeListener<MasterServerMetadata>
        implements IClusters<MasterServerMetadata> {
    public List<MasterServerMetadata> getServers();
    public List<MasterServerMetadata> getNormalServers();
    public void registerListener(IClustersChangeListener<MasterServerMetadata> listener);
    @Override protected void onServerAdded(MasterServerMetadata server);
    @Override protected void onServerRemove(MasterServerMetadata server);
    @Override protected void onServerUpdate(MasterServerMetadata server);
}

public class WorkerClusters extends AbstractClusterSubscribeListener<WorkerServerMetadata>
        implements IClusters<WorkerServerMetadata> {
    public List<String> getNormalWorkerServerAddressByGroup(String workerGroup);
    public boolean containsWorkerGroup(String workerGroup);
    public void registerListener(IClustersChangeListener<WorkerServerMetadata> listener);
}

public class MasterSlotManager implements IMasterSlotReBalancer {
    public int getCurrentMasterSlot();
    public int getTotalMasterSlots();
    public boolean checkSlotValid();
    public void doReBalance(List<MasterServerMetadata> masters);
}

@Component
public class ClusterManager {
    public void start();
}

Import

import org.apache.dolphinscheduler.server.master.cluster.MasterClusters;
import org.apache.dolphinscheduler.server.master.cluster.WorkerClusters;
import org.apache.dolphinscheduler.server.master.cluster.MasterSlotManager;
import org.apache.dolphinscheduler.server.master.cluster.ClusterManager;

I/O Contract

Inputs

Name	Type	Required	Description
Registry heartbeats	JSON events	Yes	ADD/REMOVE/UPDATE events from service registry

Outputs

Name	Type	Description
Master topology	List<MasterServerMetadata>	Live list of active master nodes
Worker topology	Map<String, List<String>>	Worker group to address mapping
Slot assignment	int/int	Current slot and total slots for work distribution

Usage Examples

Querying Worker Availability

// Check if a worker group has available workers
boolean available = workerClusters.containsWorkerGroup("data-team");

// Get worker addresses for a group
List<String> workers = workerClusters.getNormalWorkerServerAddressByGroup("data-team");

Checking Slot Assignment

// Check if this master should process a given workflow
int slot = masterSlotManager.getCurrentMasterSlot();
int total = masterSlotManager.getTotalMasterSlots();
boolean shouldProcess = (workflowCode % total == slot);

Related Pages

Implements Principle

Principle:Apache_Dolphinscheduler_Cluster_Health_Monitoring

Requires Environment

Page Connections

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Principle

Implementation

Heuristic

Environment