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[fix][broker] Fix thread unsafe access on the bundle range cache for …
…load managers
### Background Knowledge
A concurrent hash map (no matter the `ConcurrentOpenHashMap` in Pulsar
or the official `ConcurrentHashMap`) is not a synchronized hash map.
For example, given a `ConcurrentHashMap<Integer, Integer>` object `m`,
```java
synchronized (m) {
m.computeIfAbsent(1, __ -> 100); // [1]
m.computeIfAbsent(2, __ -> 200); // [2]
}
```
```java
m.computeIfAbsent(1, __ -> 300); // [3]
```
If these two code blocks are called in two threads, `[1]->[3]->[2]` is a
possible case.
### Motivation
`SimpleLoadManagerImpl` and `ModularLoadManagerImpl` both maintain the
bundle range cache:
```java
// The 1st key is broker, the 2nd key is namespace
private final ConcurrentOpenHashMap<String, ConcurrentOpenHashMap<String, ConcurrentOpenHashSet<String>>>
brokerToNamespaceToBundleRange;
```
However, when accessing the `namespace -> bundle` map, it still needs a
synchronized code block:
https://github.com/apache/pulsar/blob/1c495e190b3c569e9dfd44acef2a697c93a1f771/pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/ModularLoadManagerImpl.java#L591-L595
The code above is a composite operation of `clear()` and multiple
`computeIfAbsent` operations on the `ConcurrentOpenHashMap<String, ConcurrentOpenHashSet<String>>` object.
So the other place that access this map also requires the same lock even
if the operation itself is thread safe:
https://github.com/apache/pulsar/blob/1c495e190b3c569e9dfd44acef2a697c93a1f771/pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/ModularLoadManagerImpl.java#L882-L886
P.S. `SimpleLoadManagerImpl` does not apply the synchronized block.
However, when accessing `brokerToNamespaceToBundleRange` in the static
methods of `LoadManagerShared`, they are not synchronized. So the access
on the `Map<String, Set<String>>` value is not thread safe.
### Modifications
Add a `BundleRangeCache` abstraction to provide some methods to support
required operations on the bundle range cache.- Loading branch information
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pulsar-broker/src/main/java/org/apache/pulsar/broker/loadbalance/impl/BundleRangeCache.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -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.loadbalance.impl; | ||
|
|
||
| import java.util.List; | ||
| import java.util.Map; | ||
| import java.util.Set; | ||
| import java.util.concurrent.CompletableFuture; | ||
| import java.util.concurrent.ConcurrentHashMap; | ||
| import java.util.function.BiFunction; | ||
| import java.util.stream.Stream; | ||
|
|
||
| public class BundleRangeCache { | ||
|
|
||
| // Map from brokers to namespaces to the bundle ranges in that namespace assigned to that broker. | ||
| // Used to distribute bundles within a namespace evenly across brokers. | ||
| private final Map<String, Map<String, Set<String>>> data = new ConcurrentHashMap<>(); | ||
|
|
||
| public void reloadFromBundles(String broker, Stream<String> bundles) { | ||
| final var namespaceToBundleRange = new ConcurrentHashMap<String, Set<String>>(); | ||
| bundles.forEach(bundleName -> { | ||
| final String namespace = LoadManagerShared.getNamespaceNameFromBundleName(bundleName); | ||
| final String bundleRange = LoadManagerShared.getBundleRangeFromBundleName(bundleName); | ||
| initConcurrentHashSet(namespaceToBundleRange, namespace).add(bundleRange); | ||
| }); | ||
| data.put(broker, namespaceToBundleRange); | ||
| } | ||
|
|
||
| public void addBundleRange(String broker, String namespace, String bundleRange) { | ||
| getBundleRangeSet(broker, namespace).add(bundleRange); | ||
| } | ||
|
|
||
| public int getBundles(String broker, String namespace) { | ||
| return getBundleRangeSet(broker, namespace).size(); | ||
| } | ||
|
|
||
| public List<CompletableFuture<Void>> runTasks( | ||
| BiFunction<String/* broker */, String/* namespace */, CompletableFuture<Void>> task) { | ||
| return data.entrySet().stream().flatMap(e -> { | ||
| final var broker = e.getKey(); | ||
| return e.getValue().entrySet().stream().filter(__ -> !__.getValue().isEmpty()).map(Map.Entry::getKey) | ||
| .map(namespace -> task.apply(broker, namespace)); | ||
| }).toList(); | ||
| } | ||
|
|
||
| private Set<String> getBundleRangeSet(String broker, String namespace) { | ||
| return initConcurrentHashSet(data.computeIfAbsent(broker, __ -> new ConcurrentHashMap<>()), namespace); | ||
| } | ||
|
|
||
| private static Set<String> initConcurrentHashSet(Map<String, Set<String>> namespaceToBundleRangeSet, | ||
| String namespace) { | ||
| return namespaceToBundleRangeSet.computeIfAbsent(namespace, __ -> ConcurrentHashMap.newKeySet()); | ||
| } | ||
| } |
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