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任务堆积导致 OOM（内存溢出）

问题描述

使用无界队列（如 LinkedBlockingQueue）的线程池，在任务提交速率远高于处理速率时，队列无限堆积，最终导致内存溢出（OOM）。

错误实现

public class QueueOOMDemo {// 静态集合防止GC回收内存（加速OOM）private static final List<byte[]> memoryHolder = new ArrayList<>();public static void main(String[] args) {// 使用无界队列（快速堆积大对象）ThreadPoolExecutor executor = new ThreadPoolExecutor(2, 4, 60, TimeUnit.SECONDS,new LinkedBlockingQueue<>());// 提交大量任务，每个任务分配2MB内存（加速内存消耗）for (int i = 0; i < 20000; i++) {executor.execute(() -> {// 分配2MB内存，并存入静态集合防止GC回收byte[] chunk = new byte[2 * 1024 * 1024];synchronized (memoryHolder) {memoryHolder.add(chunk);}// 模拟任务耗时try {Thread.sleep(10);} catch (InterruptedException e) {e.printStackTrace();}});}}
}

运行结果

Exception in thread "pool-1-thread-2" Exception in thread "pool-1-thread-3" Exception in thread "pool-1-thread-1" Exception in thread "pool-1-thread-4" Exception in thread "pool-1-thread-6" Exception in thread "pool-1-thread-5" Exception in thread "pool-1-thread-7" Exception in thread "pool-1-thread-8" java.lang.OutOfMemoryError: Java heap spaceat com.szkingdom.example.thread01.QueueOOMDemo.lambda$main$0(QueueOOMDemo.java:30)at com.szkingdom.example.thread01.QueueOOMDemo$$Lambda$1/897913732.run(Unknown Source)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)at java.lang.Thread.run(Thread.java:748)
Exception in thread "pool-1-thread-12" java.lang.OutOfMemoryError: Java heap space
Exception in thread "pool-1-thread-13" java.lang.OutOfMemoryError: Java heap space

问题分析

- 无界队列风险：默认队列容量为 `Integer.MAX_VALUE`，任务无限堆积，直至内存耗尽。
- OOM类型：通常为 `GC overhead limit exceeded` 或 `Java heap space`。

正确实现

• 限制队列容量：使用有界队列，防止任务无限堆积。
• 合理拒绝策略：任务满时触发拒绝策略，避免内存溢出。

public class QueueOOMFixedDemo {public static void main(String[] args) {// 使用有界队列（容量1000）和拒绝策略ThreadPoolExecutor executor = new ThreadPoolExecutor(2, 4, 60, TimeUnit.SECONDS,new ArrayBlockingQueue<>(1000), // 队列容量1000new ThreadPoolExecutor.AbortPolicy());try {for (int i = 0; i < 20000; i++) {executor.execute(() -> {try {Thread.sleep(10);} catch (InterruptedException e) {e.printStackTrace();}});}} catch (RejectedExecutionException e) {System.err.println("任务被拒绝，已提交任务数：" + executor.getTaskCount());}executor.shutdown();}
}

运行结果

任务被拒绝，已提交任务数：1004