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[fix][broker] Fix out-of-order issues with ConsistentHashingStickyKey…
…ConsumerSelector (apache#23327)
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pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ConsumerIdentityWrapper.java
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| @@ -0,0 +1,70 @@ | ||
| /* | ||
| * 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; | ||
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| /** | ||
| * A wrapper class for a Consumer instance that provides custom implementations | ||
| * of equals and hashCode methods. The equals method returns true if and only if | ||
| * the compared instance is the same instance. | ||
| * | ||
| * <p>The reason for this class is the custom implementation of {@link Consumer#equals(Object)}. | ||
| * Using this wrapper class will be useful in use cases where it's necessary to match a key | ||
| * in a map by instance or a value in a set by instance.</p> | ||
| */ | ||
| class ConsumerIdentityWrapper { | ||
| final Consumer consumer; | ||
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| public ConsumerIdentityWrapper(Consumer consumer) { | ||
| this.consumer = consumer; | ||
| } | ||
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| /** | ||
| * Compares this wrapper to the specified object. The result is true if and only if | ||
| * the argument is not null and is a ConsumerIdentityWrapper object that wraps | ||
| * the same Consumer instance. | ||
| * | ||
| * @param obj the object to compare this ConsumerIdentityWrapper against | ||
| * @return true if the given object represents a ConsumerIdentityWrapper | ||
| * equivalent to this wrapper, false otherwise | ||
| */ | ||
| @Override | ||
| public boolean equals(Object obj) { | ||
| if (obj instanceof ConsumerIdentityWrapper) { | ||
| ConsumerIdentityWrapper other = (ConsumerIdentityWrapper) obj; | ||
| return consumer == other.consumer; | ||
| } | ||
| return false; | ||
| } | ||
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| /** | ||
| * Returns a hash code for this wrapper. The hash code is computed based on | ||
| * the wrapped Consumer instance. | ||
| * | ||
| * @return a hash code value for this object | ||
| */ | ||
| @Override | ||
| public int hashCode() { | ||
| return consumer.hashCode(); | ||
| } | ||
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| @Override | ||
| public String toString() { | ||
| return consumer.toString(); | ||
| } | ||
| } |
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pulsar-broker/src/main/java/org/apache/pulsar/broker/service/ConsumerNameIndexTracker.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; | ||
|
|
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| import java.util.HashMap; | ||
| import java.util.Map; | ||
| import javax.annotation.concurrent.NotThreadSafe; | ||
| import org.apache.commons.lang3.mutable.MutableInt; | ||
| import org.roaringbitmap.RoaringBitmap; | ||
|
|
||
| /** | ||
| * Tracks the used consumer name indexes for each consumer name. | ||
| * This is used by {@link ConsistentHashingStickyKeyConsumerSelector} to get a unique "consumer name index" | ||
| * for each consumer name. It is useful when there are multiple consumers with the same name, but they are | ||
| * different consumers. The purpose of the index is to prevent collisions in the hash ring. | ||
| * | ||
| * The consumer name index serves as an additional key for the hash ring assignment. The logic keeps track of | ||
| * used "index slots" for each consumer name and assigns the first unused index when a new consumer is added. | ||
| * This approach minimizes hash collisions due to using the same consumer name. | ||
| * | ||
| * An added benefit of this tracking approach is that a consumer that leaves and then rejoins immediately will get the | ||
| * same index and therefore the same assignments in the hash ring. This improves stability since the hash assignment | ||
| * changes are minimized over time, although a better solution would be to avoid reusing the same consumer name | ||
| * in the first place. | ||
| * | ||
| * When a consumer is removed, the index is deallocated. RoaringBitmap is used to keep track of the used indexes. | ||
| * The data structure to track a consumer name is removed when the reference count of the consumer name is zero. | ||
| * | ||
| * This class is not thread-safe and should be used in a synchronized context in the caller. | ||
| */ | ||
| @NotThreadSafe | ||
| class ConsumerNameIndexTracker { | ||
| // tracks the used index slots for each consumer name | ||
| private final Map<String, ConsumerNameIndexSlots> consumerNameIndexSlotsMap = new HashMap<>(); | ||
| // tracks the active consumer entries | ||
| private final Map<ConsumerIdentityWrapper, ConsumerEntry> consumerEntries = new HashMap<>(); | ||
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| // Represents a consumer entry in the tracker, including the consumer name, index, and reference count. | ||
| record ConsumerEntry(String consumerName, int nameIndex, MutableInt refCount) { | ||
| } | ||
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| /* | ||
| * Tracks the used indexes for a consumer name using a RoaringBitmap. | ||
| * A specific index slot is used when the bit is set. | ||
| * When all bits are cleared, the customer name can be removed from tracking. | ||
| */ | ||
| static class ConsumerNameIndexSlots { | ||
| private RoaringBitmap indexSlots = new RoaringBitmap(); | ||
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| public int allocateIndexSlot() { | ||
| // find the first index that is not set, if there is no such index, add a new one | ||
| int index = (int) indexSlots.nextAbsentValue(0); | ||
| if (index == -1) { | ||
| index = indexSlots.getCardinality(); | ||
| } | ||
| indexSlots.add(index); | ||
| return index; | ||
| } | ||
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| public boolean deallocateIndexSlot(int index) { | ||
| indexSlots.remove(index); | ||
| return indexSlots.isEmpty(); | ||
| } | ||
| } | ||
|
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| /* | ||
| * Adds a reference to the consumer and returns the index assigned to this consumer. | ||
| */ | ||
| public int increaseConsumerRefCountAndReturnIndex(ConsumerIdentityWrapper wrapper) { | ||
| ConsumerEntry entry = consumerEntries.computeIfAbsent(wrapper, k -> { | ||
| String consumerName = wrapper.consumer.consumerName(); | ||
| return new ConsumerEntry(consumerName, allocateConsumerNameIndex(consumerName), new MutableInt(0)); | ||
| }); | ||
| entry.refCount.increment(); | ||
| return entry.nameIndex; | ||
| } | ||
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| private int allocateConsumerNameIndex(String consumerName) { | ||
| return getConsumerNameIndexBitmap(consumerName).allocateIndexSlot(); | ||
| } | ||
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| private ConsumerNameIndexSlots getConsumerNameIndexBitmap(String consumerName) { | ||
| return consumerNameIndexSlotsMap.computeIfAbsent(consumerName, k -> new ConsumerNameIndexSlots()); | ||
| } | ||
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| /* | ||
| * Decreases the reference count of the consumer and removes the consumer name from tracking if the ref count is | ||
| * zero. | ||
| */ | ||
| public void decreaseConsumerRefCount(ConsumerIdentityWrapper removed) { | ||
| ConsumerEntry consumerEntry = consumerEntries.get(removed); | ||
| int refCount = consumerEntry.refCount.decrementAndGet(); | ||
| if (refCount == 0) { | ||
| deallocateConsumerNameIndex(consumerEntry.consumerName, consumerEntry.nameIndex); | ||
| consumerEntries.remove(removed, consumerEntry); | ||
| } | ||
| } | ||
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| private void deallocateConsumerNameIndex(String consumerName, int index) { | ||
| if (getConsumerNameIndexBitmap(consumerName).deallocateIndexSlot(index)) { | ||
| consumerNameIndexSlotsMap.remove(consumerName); | ||
| } | ||
| } | ||
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| /* | ||
| * Returns the currently tracked index for the consumer. | ||
| */ | ||
| public int getTrackedIndex(ConsumerIdentityWrapper wrapper) { | ||
| ConsumerEntry consumerEntry = consumerEntries.get(wrapper); | ||
| return consumerEntry != null ? consumerEntry.nameIndex : -1; | ||
| } | ||
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| int getTrackedConsumerNamesCount() { | ||
| return consumerNameIndexSlotsMap.size(); | ||
| } | ||
|
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| int getTrackedConsumersCount() { | ||
| return consumerEntries.size(); | ||
| } | ||
| } |
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