Implementation:Apache Shardingsphere SessionConnectionReconnectListener Handle

Knowledge Sources	Apache_Shardingsphere
Domains	Cluster, ZooKeeper
Last Updated	2026-02-10 00:00 GMT

Overview

SessionConnectionReconnectListener handles ZooKeeper session reconnection by regenerating worker IDs and re-registering the compute node after connection loss.

Description

SessionConnectionReconnectListener implements Curator's ConnectionStateListener interface. When a ConnectionState.LOST event is received, it enters a retry loop calling reconnect until successful. The reconnect method blocks until the ZooKeeper client reconnects or times out. Upon successful reconnection, if the instance previously had a worker ID (not -1), it regenerates the worker ID via ComputeNodeInstanceContext.generateWorkerId. It then re-registers the instance as online using ClusterComputeNodePersistService.registerOnline. If the connection attempt fails, it sleeps for 5 seconds (configurable via RECONNECT_INTERVAL_SECONDS) before retrying. InterruptedException is handled by restoring the interrupt flag and exiting the retry loop.

Usage

This listener is registered with the Curator framework when initializing the ZooKeeper cluster repository. It ensures that after a ZooKeeper session loss (which causes ephemeral node deletion), the compute node re-establishes its presence in the cluster registry, maintaining proper worker ID assignment and online status.

Code Reference

Source Location

• Repository: Apache_Shardingsphere
• File: SessionConnectionReconnectListener.java
• Lines: 1-85

Signature

@Slf4j
public final class SessionConnectionReconnectListener implements ConnectionStateListener {

    public SessionConnectionReconnectListener(final ComputeNodeInstanceContext computeNodeInstanceContext,
                                               final ClusterPersistRepository repository)

    public void stateChanged(final CuratorFramework client, final ConnectionState connectionState)
}

Import

import org.apache.shardingsphere.mode.repository.cluster.zookeeper.listener.SessionConnectionReconnectListener;

I/O Contract

Inputs

Name	Type	Required	Description
computeNodeInstanceContext	ComputeNodeInstanceContext	Yes	Context for the local compute node instance
repository	ClusterPersistRepository	Yes	Repository for creating ClusterComputeNodePersistService
client	CuratorFramework	Yes	Curator client passed in the stateChanged callback
connectionState	ConnectionState	Yes	Current connection state (only LOST triggers reconnection)

Outputs

Name	Type	Description
void	void	Side effects: regenerates worker ID and re-registers instance online upon reconnection

Usage Examples

// Register the listener during ZooKeeper repository initialization
SessionConnectionReconnectListener listener = new SessionConnectionReconnectListener(
    computeNodeInstanceContext, clusterPersistRepository);
curatorClient.getConnectionStateListenable().addListener(listener);
// On connection loss, the listener will automatically retry reconnection,
// regenerate worker ID if needed, and re-register the instance.

Related Pages

• Principle:Apache_Shardingsphere_Cluster_Repository_Initialization