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HashRangeAutoSplitStickyKeyConsumerSelector.java
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HashRangeAutoSplitStickyKeyConsumerSelector.java
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/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
* KIND, either express or implied. See the License for the
* specific language governing permissions and limitations
* under the License.
*/
package org.apache.pulsar.broker.service;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Map.Entry;
import java.util.concurrent.ConcurrentSkipListMap;
import org.apache.pulsar.broker.service.BrokerServiceException.ConsumerAssignException;
/**
* This is a consumer selector based fixed hash range.
*
* 1.Each consumer serves a fixed range of hash value
* 2.The whole range of hash value could be covered by all the consumers.
* 3.Once a consumer is removed, the left consumers could still serve the whole range.
*
* Initializing with a fixed hash range, by default 2 << 5.
* First consumer added, hash range looks like:
*
* 0 -> 65536(consumer-1)
*
* Second consumer added, will find a biggest range to split:
*
* 0 -> 32768(consumer-2) -> 65536(consumer-1)
*
* While a consumer removed, The range for this consumer will be taken over
* by other consumer, consumer-2 removed:
*
* 0 -> 65536(consumer-1)
*
* In this approach use skip list map to maintain the hash range and consumers.
*
* Select consumer will return the ceiling key of message key hashcode % range size.
*
*/
public class HashRangeAutoSplitStickyKeyConsumerSelector implements StickyKeyConsumerSelector {
private final int rangeSize;
private final ConcurrentSkipListMap<Integer, Consumer> rangeMap;
private final Map<Consumer, Integer> consumerRange;
public HashRangeAutoSplitStickyKeyConsumerSelector() {
this(DEFAULT_RANGE_SIZE);
}
public HashRangeAutoSplitStickyKeyConsumerSelector(int rangeSize) {
if (rangeSize < 2) {
throw new IllegalArgumentException("range size must greater than 2");
}
if (!is2Power(rangeSize)) {
throw new IllegalArgumentException("range size must be nth power with 2");
}
this.rangeMap = new ConcurrentSkipListMap<>();
this.consumerRange = new HashMap<>();
this.rangeSize = rangeSize;
}
@Override
public synchronized void addConsumer(Consumer consumer) throws ConsumerAssignException {
if (rangeMap.size() == 0) {
rangeMap.put(rangeSize, consumer);
consumerRange.put(consumer, rangeSize);
} else {
splitRange(findBiggestRange(), consumer);
}
}
@Override
public synchronized void removeConsumer(Consumer consumer) {
Integer removeRange = consumerRange.remove(consumer);
if (removeRange != null) {
if (removeRange == rangeSize && rangeMap.size() > 1) {
Map.Entry<Integer, Consumer> lowerEntry = rangeMap.lowerEntry(removeRange);
rangeMap.put(removeRange, lowerEntry.getValue());
rangeMap.remove(lowerEntry.getKey());
consumerRange.put(lowerEntry.getValue(), removeRange);
} else {
rangeMap.remove(removeRange);
}
}
}
@Override
public Consumer select(int hash) {
if (rangeMap.size() > 0) {
int slot = hash % rangeSize;
return rangeMap.ceilingEntry(slot).getValue();
} else {
return null;
}
}
@Override
public Map<String, List<String>> getConsumerKeyHashRanges() {
Map<String, List<String>> result = new HashMap<>();
int start = 0;
for (Map.Entry<Integer, Consumer> entry: rangeMap.entrySet()) {
result.computeIfAbsent(entry.getValue().consumerName(), key -> new ArrayList<>())
.add("[" + start + ", " + entry.getKey() + "]");
start = entry.getKey() + 1;
}
return result;
}
private int findBiggestRange() {
int slots = 0;
int busiestRange = rangeSize;
for (Entry<Integer, Consumer> entry : rangeMap.entrySet()) {
Integer lowerKey = rangeMap.lowerKey(entry.getKey());
if (lowerKey == null) {
lowerKey = 0;
}
if (entry.getKey() - lowerKey > slots) {
slots = entry.getKey() - lowerKey;
busiestRange = entry.getKey();
}
}
return busiestRange;
}
private void splitRange(int range, Consumer targetConsumer) throws ConsumerAssignException {
Integer lowerKey = rangeMap.lowerKey(range);
if (lowerKey == null) {
lowerKey = 0;
}
if (range - lowerKey <= 1) {
throw new ConsumerAssignException("No more range can assigned to new consumer, assigned consumers "
+ rangeMap.size());
}
int splitRange = range - ((range - lowerKey) >> 1);
rangeMap.put(splitRange, targetConsumer);
consumerRange.put(targetConsumer, splitRange);
}
private boolean is2Power(int num) {
if (num < 2) {
return false;
}
return (num & num - 1) == 0;
}
Map<Integer, Consumer> getRangeConsumer() {
return Collections.unmodifiableMap(rangeMap);
}
}