com.taosdata.jdbc.ws.loadbalance

Class RebalanceManager

java.lang.Object

com.taosdata.jdbc.ws.loadbalance.RebalanceManager

public class RebalanceManager
extends Object

Rebalance Manager for TDengine cluster endpoints Manages endpoint connection count, health status, and automatic load rebalancing logic Implements singleton pattern with static inner class (lazy loading + thread-safe initialization) This class is responsible for cluster registration, endpoint state maintenance, and rebalancing trigger

Version:

1.0

Method Summary

Modifier and Type	Method and Description
void	addBgHealthCheckInstance()
void	clearAllForTest()
void	connected(List<Endpoint> endpoints, int index) Mark the specified endpoint as online when connection is successful
void	decrementConnectionCount(Endpoint endpoint) Decrement the connection count of the specified endpoint Called when a connection is closed to the endpoint
void	disconnected(ConnectionParam original, int index, InFlightRequest inFlightRequest) Handle endpoint disconnection event 1.
void	disconnectedBySelf(ConnectionParam original, int index) Handle self-initiated disconnection (only decrement connection count)
void	endpointUp(ConnectionParam param, Endpoint endpoint) Mark endpoint as online and trigger rebalancing if conditions are met
int	getBgHealthCheckInstanceCount()
int[]	getConnectCountsAsc(List<Endpoint> endpoints) Get endpoint indexes sorted by connection count in ascending order Used for load balancing to select the least loaded endpoint
EndpointInfo	getEndpointInfo(Endpoint endpoint) Get the metadata (connection count + health status) of the specified endpoint
static RebalanceManager	getInstance() Get the singleton instance of RebalanceManager This is the only way to access the manager's functionality
int	getMinConnectionEndpointIndex(ConnectionParam param) Get the index of the endpoint with the minimum connection count Used to select the least loaded endpoint for rebalancing
boolean	handleRebalancing(ConnectionParam param, Endpoint currentEndpoint) Handle rebalancing logic for the current connection 1.
void	incrementConnectionCount(Endpoint endpoint) Increment the connection count of the specified endpoint Called when a new connection is established to the endpoint
boolean	isRebalancing() Check if there is any cluster in global rebalancing state
boolean	isRebalancing(Endpoint endpoint) Check if the cluster of the specified endpoint is in rebalancing state
void	newCluster(List<Endpoint> endpoints) Register a new cluster and initialize endpoint metadata Idempotent operation: no effect if the cluster is already registered
void	removeBgHealthCheck(BgHealthCheck bgHealthCheck)
void	removeBgHealthCheckInstance()
void	startBackgroundHealthCheck(ConnectionParam original, int index, InFlightRequest inFlightRequest) Start background health check for offline endpoints Monitors endpoint recovery status and updates state when online

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

getInstance

public static RebalanceManager getInstance()

Get the singleton instance of RebalanceManager This is the only way to access the manager's functionality

Returns:

Singleton instance of RebalanceManager

isRebalancing

public boolean isRebalancing(Endpoint endpoint)

Check if the cluster of the specified endpoint is in rebalancing state

Parameters:

endpoint - Target endpoint to check

Returns:

true if the cluster is rebalancing, false otherwise

isRebalancing

public boolean isRebalancing()

Check if there is any cluster in global rebalancing state

Returns:

true if global rebalancing is ongoing, false otherwise

incrementConnectionCount

public void incrementConnectionCount(Endpoint endpoint)

Increment the connection count of the specified endpoint Called when a new connection is established to the endpoint

Parameters:

endpoint - Target endpoint

decrementConnectionCount

public void decrementConnectionCount(Endpoint endpoint)

Decrement the connection count of the specified endpoint Called when a connection is closed to the endpoint

Parameters:

endpoint - Target endpoint

connected

public void connected(List<Endpoint> endpoints,
                      int index)

Mark the specified endpoint as online when connection is successful

Parameters:

endpoints - List of cluster endpoints

index - Index of the connected endpoint in the list

disconnected

public void disconnected(ConnectionParam original,
                         int index,
                         InFlightRequest inFlightRequest)

Handle endpoint disconnection event 1. Decrement connection count via disconnectedBySelf 2. Start background health check if auto-connect is enabled and endpoint is first marked as offline

Parameters:

original - Original connection parameters

index - Index of the disconnected endpoint in the list

inFlightRequest - In-flight request container for health check response handling

disconnectedBySelf

public void disconnectedBySelf(ConnectionParam original,
                               int index)

Handle self-initiated disconnection (only decrement connection count)

Parameters:

original - Original connection parameters

index - Index of the disconnected endpoint in the list

newCluster

public void newCluster(List<Endpoint> endpoints)

Register a new cluster and initialize endpoint metadata Idempotent operation: no effect if the cluster is already registered

Parameters:

endpoints - List of endpoints in the new cluster

endpointUp

public void endpointUp(ConnectionParam param,
                       Endpoint endpoint)

Mark endpoint as online and trigger rebalancing if conditions are met

Parameters:

param - Connection parameters (contains rebalance thresholds)

endpoint - The endpoint that recovered to online state

getEndpointInfo

public EndpointInfo getEndpointInfo(Endpoint endpoint)

Get the metadata (connection count + health status) of the specified endpoint

Parameters:

endpoint - Target endpoint

Returns:

EndpointInfo object containing endpoint metadata

getConnectCountsAsc

public int[] getConnectCountsAsc(List<Endpoint> endpoints)

Get endpoint indexes sorted by connection count in ascending order Used for load balancing to select the least loaded endpoint

Parameters:

endpoints - List of cluster endpoints

Returns:

Sorted array of endpoint indexes (ascending by connection count)

startBackgroundHealthCheck

public void startBackgroundHealthCheck(ConnectionParam original,
                                       int index,
                                       InFlightRequest inFlightRequest)

Start background health check for offline endpoints Monitors endpoint recovery status and updates state when online

Parameters:

original - Original connection parameters

index - Index of the offline endpoint in the list

inFlightRequest - In-flight request container for health check responses

handleRebalancing

public boolean handleRebalancing(ConnectionParam param,
                                 Endpoint currentEndpoint)

Handle rebalancing logic for the current connection 1. Update cluster/global rebalancing state if conditions are no longer met 2. Determine if the current connection needs to be rebalanced to a less loaded endpoint

Parameters:

param - Connection parameters with rebalance thresholds

currentEndpoint - The endpoint currently connected to

Returns:

true if rebalancing is required for this connection, false otherwise

getMinConnectionEndpointIndex

public int getMinConnectionEndpointIndex(ConnectionParam param)

Get the index of the endpoint with the minimum connection count Used to select the least loaded endpoint for rebalancing

Parameters:

param - Connection parameters with endpoint list

Returns:

Index of the endpoint with the least connections (-1 if endpoint list is empty)

addBgHealthCheckInstance

public void addBgHealthCheckInstance()

removeBgHealthCheckInstance

public void removeBgHealthCheckInstance()

getBgHealthCheckInstanceCount

public int getBgHealthCheckInstanceCount()

removeBgHealthCheck

public void removeBgHealthCheck(BgHealthCheck bgHealthCheck)

clearAllForTest

public void clearAllForTest()