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Handle hash collision in KeyShared subscription mode #8396

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Merged
codelipenghui merged 1 commit into from
Oct 31, 2020
Merged

Handle hash collision in KeyShared subscription mode #8396

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46 changes: 36 additions & 10 deletions ...ain/java/org/apache/pulsar/broker/service/ConsistentHashingStickyKeyConsumerSelector.java
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Original file line number Diff line number Diff line change
Expand Up @@ -18,16 +18,19 @@
*/
package org.apache.pulsar.broker.service;

import com.google.common.collect.Lists;
import org.apache.pulsar.broker.service.BrokerServiceException.ConsumerAssignException;
import org.apache.pulsar.common.util.Murmur3_32Hash;

import java.util.Collections;
import java.util.Comparator;
import java.util.List;
import java.util.Map;
import java.util.NavigableMap;
import java.util.TreeMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;

import org.apache.pulsar.broker.service.BrokerServiceException.ConsumerAssignException;
import org.apache.pulsar.common.util.Murmur3_32Hash;

/**
* This is a consumer selector based fixed hash range.
*
Expand All @@ -39,7 +42,7 @@ public class ConsistentHashingStickyKeyConsumerSelector implements StickyKeyCons
private final ReadWriteLock rwLock = new ReentrantReadWriteLock();

// Consistent-Hash ring
private final NavigableMap<Integer, Consumer> hashRing;
private final NavigableMap<Integer, List<Consumer>> hashRing;

private final int numberOfPoints;

Expand All @@ -57,7 +60,17 @@ public void addConsumer(Consumer consumer) throws ConsumerAssignException {
for (int i = 0; i < numberOfPoints; i++) {
String key = consumer.consumerName() + i;
int hash = Murmur3_32Hash.getInstance().makeHash(key.getBytes());
hashRing.put(hash, consumer);
hashRing.compute(hash, (k, v) -> {
if (v == null) {
return Lists.newArrayList(consumer);
} else {
if (!v.contains(consumer)) {
v.add(consumer);
v.sort(Comparator.comparing(Consumer::consumerName, String::compareTo));
}
return v;
}
});
}
} finally {
rwLock.writeLock().unlock();
Expand All @@ -72,7 +85,17 @@ public void removeConsumer(Consumer consumer) {
for (int i = 0; i < numberOfPoints; i++) {
String key = consumer.consumerName() + i;
int hash = Murmur3_32Hash.getInstance().makeHash(key.getBytes());
hashRing.remove(hash, consumer);
hashRing.compute(hash, (k, v) -> {
if (v == null) {
return null;
} else {
v.removeIf(c -> c.consumerName().equals(consumer.consumerName()));
if (v.isEmpty()) {
v = null;
}
return v;
}
});
}
} finally {
rwLock.writeLock().unlock();
Expand All @@ -89,18 +112,21 @@ public Consumer select(byte[] stickyKey) {
return null;
}

Map.Entry<Integer, Consumer> ceilingEntry = hashRing.ceilingEntry(hash);
List<Consumer> consumerList;
Map.Entry<Integer, List<Consumer>> ceilingEntry = hashRing.ceilingEntry(hash);
if (ceilingEntry != null) {
return ceilingEntry.getValue();
consumerList = ceilingEntry.getValue();
} else {
return hashRing.firstEntry().getValue();
consumerList = hashRing.firstEntry().getValue();
}

return consumerList.get(hash % consumerList.size());

@lhotari lhotari Sep 20, 2024

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@ltamber I have a question about this line of code in #23315 (comment) . Are you available to answer that question? Thanks /cc @codelipenghui

@lhotari lhotari Sep 20, 2024

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I made a change already, #23327

} finally {
rwLock.readLock().unlock();
}
}

Map<Integer, Consumer> getRangeConsumer() {
Map<Integer, List<Consumer>> getRangeConsumer() {
return Collections.unmodifiableMap(hashRing);
}
}