com.netflix.loadbalancer
Class WeightedResponseTimeRule

java.lang.Object
  com.netflix.loadbalancer.AbstractLoadBalancerRule
      com.netflix.loadbalancer.RoundRobinRule
          com.netflix.loadbalancer.WeightedResponseTimeRule

All Implemented Interfaces:

com.netflix.client.IClientConfigAware, IRule

public class WeightedResponseTimeRule
extends RoundRobinRule

Rule that use the average/percentile response times to assign dynamic "weights" per Server which is then used in the "Weighted Round Robin" fashion.

The basic idea for weighted round robin has been obtained from JCS The implementation for choosing the endpoint from the list of endpoints is as follows:Let's assume 4 endpoints:A(wt=10), B(wt=30), C(wt=40), D(wt=20).

Using the Random API, generate a random number between 1 and10+30+40+20. Let's assume that the above list is randomized. Based on the weights, we have intervals as follows:

1-----10 (A's weight)
11----40 (A's weight + B's weight)
41----80 (A's weight + B's weight + C's weight)
81----100(A's weight + B's weight + C's weight + C's weight)

Here's the psuedo code for deciding where to send the request:

if (random_number between 1 & 10) {send request to A;}
else if (random_number between 11 & 40) {send request to B;}
else if (random_number between 41 & 80) {send request to C;}
else if (random_number between 81 & 100) {send request to D;}

When there is not enough statistics gathered for the servers, this rule will fall back to use RoundRobinRule.

Field Summary

static int	DEFAULT_TIMER_INTERVAL
protected java.util.concurrent.atomic.AtomicBoolean	serverWeightAssignmentInProgress
protected java.util.Timer	serverWeightTimer
static com.netflix.client.config.IClientConfigKey<java.lang.Integer>	WEIGHT_TASK_TIMER_INTERVAL_CONFIG_KEY

Constructor Summary

WeightedResponseTimeRule()

WeightedResponseTimeRule(ILoadBalancer lb)

Method Summary

Server	choose(ILoadBalancer lb, java.lang.Object key)
void	initWithNiwsConfig(com.netflix.client.config.IClientConfig clientConfig)
void	setLoadBalancer(ILoadBalancer lb)
void	shutdown()

Methods inherited from class com.netflix.loadbalancer.RoundRobinRule

choose

Methods inherited from class com.netflix.loadbalancer.AbstractLoadBalancerRule

getLoadBalancer

Methods inherited from class java.lang.Object

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

Field Detail

WEIGHT_TASK_TIMER_INTERVAL_CONFIG_KEY

public static final com.netflix.client.config.IClientConfigKey<java.lang.Integer> WEIGHT_TASK_TIMER_INTERVAL_CONFIG_KEY

DEFAULT_TIMER_INTERVAL

public static final int DEFAULT_TIMER_INTERVAL

See Also:

Constant Field Values

serverWeightTimer

protected java.util.Timer serverWeightTimer

serverWeightAssignmentInProgress

protected java.util.concurrent.atomic.AtomicBoolean serverWeightAssignmentInProgress

Constructor Detail

WeightedResponseTimeRule

public WeightedResponseTimeRule()

WeightedResponseTimeRule

public WeightedResponseTimeRule(ILoadBalancer lb)

Method Detail

setLoadBalancer

public void setLoadBalancer(ILoadBalancer lb)

Specified by:

setLoadBalancer in interface IRule

Overrides:

setLoadBalancer in class AbstractLoadBalancerRule

shutdown

public void shutdown()

choose

public Server choose(ILoadBalancer lb,
                     java.lang.Object key)

Overrides:

choose in class RoundRobinRule

initWithNiwsConfig

public void initWithNiwsConfig(com.netflix.client.config.IClientConfig clientConfig)

Specified by:

initWithNiwsConfig in interface com.netflix.client.IClientConfigAware

Overrides:

initWithNiwsConfig in class RoundRobinRule