Package io.hekate.messaging.loadbalance

Class DefaultLoadBalancer<T>

java.lang.Object

io.hekate.messaging.loadbalance.DefaultLoadBalancer<T>

Type Parameters:

T - Base type of messages that can be handled by this load balancer.

All Implemented Interfaces:

LoadBalancer<T>

Direct Known Subclasses:

DefaultRpcLoadBalancer

public class DefaultLoadBalancer<T>
extends Object
implements LoadBalancer<T>

Default implementation of the LoadBalancer interface.

This load balancer uses nonAffinityRoute(Object, LoadBalancerContext) and affinityRoute(Object, LoadBalancerContext) methods to perform actual load balancing. Which of those methods will be used depends on whether the load balanced operation has an affinity key or not. Please see the documentation of those methods for more details about their logic.

Constructor Summary

Constructors

Constructor	Description
DefaultLoadBalancer()

Method Summary

Modifier and Type	Method	Description
protected ClusterNode	affinityRoute(T msg, LoadBalancerContext ctx)	Selects a node based on the partition mapping of the operation's affinity key.
protected ClusterNode	nonAffinityRoute(T msg, LoadBalancerContext ctx)	Selects a random node from the load balancer context.
ClusterNodeId	route(T msg, LoadBalancerContext ctx)	Selects one of the cluster nodes from the load balancer context.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

DefaultLoadBalancer

public DefaultLoadBalancer()

Method Detail

route

public ClusterNodeId route(T msg,
                           LoadBalancerContext ctx)
                    throws LoadBalancerException

Description copied from interface: LoadBalancer

Selects one of the cluster nodes from the load balancer context. Note that the provided context contains only those nodes that are capable of receiving messages of this channel (i.e. have MessageReceiver) and match the channel's topology filtering rules.

Returning null from this method (if target node can't be selected for some reason) will cause message sending operation to fail with LoadBalancerException.

Specified by:

route in interface LoadBalancer<T>

Parameters:

msg - Message.

ctx - Load balancer context.

Returns:

Node that should be used for the messaging operation.

Throws:

LoadBalancerException - if failed to perform load balancing.

nonAffinityRoute

protected ClusterNode nonAffinityRoute(T msg,
                                       LoadBalancerContext ctx)
                                throws LoadBalancerException

Selects a random node from the load balancer context. If the selected node is known to be failed then another random non-failed node will be selected. If all nodes are known to be failed then this method will fallback to the initially selected node.

Parameters:

msg - Message.

ctx - Load balancer context.

Returns:

Selected node.

Throws:

LoadBalancerException - if failed to perform load balancing.

affinityRoute

protected ClusterNode affinityRoute(T msg,
                                    LoadBalancerContext ctx)
                             throws LoadBalancerException

Selects a node based on the partition mapping of the operation's affinity key.

This method tries to use the primary node of the selected Partition. If the selected node is known to be failed then a backup node will be selected. If partition doesn't have any backup nodes or if it is known that all backup nodes failed then this method will fallback to the initially selected node.

Parameters:

msg - Message.

ctx - Load balancer context.

Returns:

Selected node.

Throws:

LoadBalancerException - if failed to perform load balancing.

toString

public String toString()

Overrides:

toString in class Object