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Smooth Round Robin selection
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@jasonjoo2010 @jason-joo
jasonjoo2010 authored and jason-joo committed Oct 16, 2018
1 parent 2e826a6 commit 437b4eb
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Showing 3 changed files with 296 additions and 110 deletions.
177 changes: 119 additions & 58 deletions ...luster/src/main/java/com/alibaba/dubbo/rpc/cluster/loadbalance/RoundRobinLoadBalance.java
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Original file line number Diff line number Diff line change
Expand Up @@ -17,13 +17,15 @@
package com.alibaba.dubbo.rpc.cluster.loadbalance;

import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.common.utils.AtomicPositiveInteger;
import com.alibaba.dubbo.rpc.Invocation;
import com.alibaba.dubbo.rpc.Invoker;

import java.util.LinkedHashMap;
import java.util.Collection;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

Expand All @@ -32,72 +34,131 @@
*
*/
public class RoundRobinLoadBalance extends AbstractLoadBalance {

public static final String NAME = "roundrobin";

private static int RECYCLE_PERIOD = 60000;

protected static class WeightedRoundRobin {
private int weight;
private int current;
private long lastRecycle;
private long lastUpdate;
public int getWeight() {
return weight;
}
public void setWeight(int weight) {
this.weight = weight;
}
public void setCurrent(int current) {
this.current = current;
}
public int increaseWeight() {
current += weight;
return current;
}
public void sel(int total) {
current -= total;
}
public long getLastRecycle() {
return lastRecycle;
}
public void setLastRecycle(long lastRecycle) {
this.lastRecycle = lastRecycle;
}
public long getLastUpdate() {
return lastUpdate;
}
public void setLastUpdate(long lastUpdate) {
this.lastUpdate = lastUpdate;
}
}

private final ConcurrentMap<String, AtomicPositiveInteger> sequences = new ConcurrentHashMap<String, AtomicPositiveInteger>();

private ConcurrentMap<String, Map<String, WeightedRoundRobin>> methodWeightMap = new ConcurrentHashMap<String, Map<String, WeightedRoundRobin>>();

/**
* get invoker addr list cached for specified invocation
* <p>
* <b>for unit test only</b>
*
* @param invokers
* @param invocation
* @return
*/
protected <T> Collection<String> getInvokerAddrList(List<Invoker<T>> invokers, Invocation invocation) {
String key = invokers.get(0).getUrl().getServiceKey() + "." + invocation.getMethodName();
Map<String, WeightedRoundRobin> map = methodWeightMap.get(key);
if (map != null) {
return map.keySet();
}
return null;
}

@Override
protected <T> Invoker<T> doSelect(List<Invoker<T>> invokers, URL url, Invocation invocation) {
String key = invokers.get(0).getUrl().getServiceKey() + "." + invocation.getMethodName();
int length = invokers.size(); // Number of invokers
int maxWeight = 0; // The maximum weight
int minWeight = Integer.MAX_VALUE; // The minimum weight
final LinkedHashMap<Invoker<T>, IntegerWrapper> invokerToWeightMap = new LinkedHashMap<Invoker<T>, IntegerWrapper>();
int weightSum = 0;
for (int i = 0; i < length; i++) {
int weight = getWeight(invokers.get(i), invocation);
maxWeight = Math.max(maxWeight, weight); // Choose the maximum weight
minWeight = Math.min(minWeight, weight); // Choose the minimum weight
if (weight > 0) {
invokerToWeightMap.put(invokers.get(i), new IntegerWrapper(weight));
weightSum += weight;
}
Map<String, WeightedRoundRobin> map = methodWeightMap.get(key);
if (map == null) {
methodWeightMap.putIfAbsent(key, new HashMap<String, WeightedRoundRobin>());
map = methodWeightMap.get(key);
}
AtomicPositiveInteger sequence = sequences.get(key);
if (sequence == null) {
sequences.putIfAbsent(key, new AtomicPositiveInteger());
sequence = sequences.get(key);
}
int currentSequence = sequence.getAndIncrement();
if (maxWeight > 0 && minWeight < maxWeight) {
int mod = currentSequence % weightSum;
for (int i = 0; i < maxWeight; i++) {
for (Map.Entry<Invoker<T>, IntegerWrapper> each : invokerToWeightMap.entrySet()) {
final Invoker<T> k = each.getKey();
final IntegerWrapper v = each.getValue();
if (mod == 0 && v.getValue() > 0) {
return k;
}
if (v.getValue() > 0) {
v.decrement();
mod--;
synchronized (map) {
int totalWeight = 0;
int maxCurrent = Integer.MIN_VALUE;
long now = System.currentTimeMillis();
boolean needRecycle = false;
Invoker<T> selectedInvoker = null;
WeightedRoundRobin selectedWRR = null;
for (Invoker<T> invoker : invokers) {
String identifyString = invoker.getUrl().toIdentityString();
WeightedRoundRobin weightedRoundRobin = map.get(identifyString);
int weight = getWeight(invoker, invocation);
if (weight < 0) {
weight = 0;
}
if (weightedRoundRobin == null) {
weightedRoundRobin = new WeightedRoundRobin();
weightedRoundRobin.setCurrent(0);
weightedRoundRobin.setWeight(weight);
weightedRoundRobin.setLastRecycle(now);
map.put(identifyString, weightedRoundRobin);
}
if (weight != weightedRoundRobin.getWeight()) {
//weight changed
weightedRoundRobin.setCurrent(0);
weightedRoundRobin.setWeight(weight);
}
int cur = weightedRoundRobin.increaseWeight();
weightedRoundRobin.setLastUpdate(now);
if (!needRecycle && now - weightedRoundRobin.getLastRecycle() > RECYCLE_PERIOD) {
//try to recycle useless item every 60s if there is one outdated
needRecycle = true;
}
if (cur > maxCurrent) {
maxCurrent = cur;
selectedInvoker = invoker;
selectedWRR = weightedRoundRobin;
}
totalWeight += weight;
}
//recycle
if (needRecycle) {
Iterator<Entry<String, WeightedRoundRobin>> it = map.entrySet().iterator();
while (it.hasNext()) {
Entry<String, WeightedRoundRobin> item = it.next();
if (now - item.getValue().getLastUpdate() > RECYCLE_PERIOD) {
it.remove();
} else {
//pass
item.getValue().setLastRecycle(now);
}
}
}
if (selectedInvoker != null) {
selectedWRR.sel(totalWeight);
return selectedInvoker;
}
}
// Round robin
return invokers.get(currentSequence % length);
}

private static final class IntegerWrapper {
private int value;

public IntegerWrapper(int value) {
this.value = value;
}

public int getValue() {
return value;
}

public void setValue(int value) {
this.value = value;
}

public void decrement() {
this.value--;
}
return null;
}

}
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