前言

除了程序计数器外，虚拟机内存的其他几个运行时区域都有发生OutOfMemoryError(OOM)异常的可能。以下代码测试环境为JDK 1.8。

Java Heap 溢出

Java heap space

// -Xmx8m
public class TestOomTooManyObject {public static void main(String[] args) {String name = "hello";for (int i = 0; i < 10000000; i++) {name += name;}System.out.println(name);}
}

输出结果：

Exception in thread "main" java.lang.OutOfMemoryError: Java heap spaceat java.util.Arrays.copyOfRange(Arrays.java:3664)at java.lang.String.<init>(String.java:207)at java.lang.StringBuilder.toString(StringBuilder.java:407)at com.fast.summary.jvm.oom.TestOomTooManyObject.main(TestOomTooManyObject.java:12)

Metaspace

// -XX:MetaspaceSize=8m -XX:MaxMetaspaceSize=10m
// 模拟不断生成类, 但类无法卸载的情况
public class TestOomTooManyClass {static String base = "string";public static void main(String[] args) {testDynamicCreateClass();}private static void testDynamicCreateClass() {AtomicInteger c = new AtomicInteger();while (true) {try (FileReader reader = new FileReader("script")) {GroovyShell shell = new GroovyShell();shell.evaluate(reader);System.out.println(c.incrementAndGet());} catch (IOException e) {e.printStackTrace();}}}
}

输出结果：

Exception in thread "main" java.lang.OutOfMemoryError: Metaspaceat java.lang.ClassLoader.defineClass1(Native Method)at java.lang.ClassLoader.defineClass(ClassLoader.java:763)at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)at java.net.URLClassLoader.defineClass(URLClassLoader.java:468)at java.net.URLClassLoader.access$100(URLClassLoader.java:74)at java.net.URLClassLoader$1.run(URLClassLoader.java:369)at java.net.URLClassLoader$1.run(URLClassLoader.java:363)at java.security.AccessController.doPrivileged(Native Method)at java.net.URLClassLoader.findClass(URLClassLoader.java:362)at java.lang.ClassLoader.loadClass(ClassLoader.java:424)at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)at java.lang.ClassLoader.loadClass(ClassLoader.java:357)at org.codehaus.groovy.util.SingleKeyHashMap.getOrPut(SingleKeyHashMap.java:67)at org.codehaus.groovy.runtime.metaclass.MetaMethodIndex.<init>(MetaMethodIndex.java:85)at groovy.lang.MetaClassImpl.<init>(MetaClassImpl.java:193)at groovy.lang.MetaClassImpl.<init>(MetaClassImpl.java:221)at groovy.lang.MetaClassImpl.<init>(MetaClassImpl.java:233)at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createNormalMetaClass(MetaClassRegistry.java:166)at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.createWithCustomLookup(MetaClassRegistry.java:156)at groovy.lang.MetaClassRegistry$MetaClassCreationHandle.create(MetaClassRegistry.java:139)at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.<init>(MetaClassRegistryImpl.java:133)at org.codehaus.groovy.runtime.metaclass.MetaClassRegistryImpl.<init>(MetaClassRegistryImpl.java:86)at groovy.lang.GroovySystem.<clinit>(GroovySystem.java:37)at org.codehaus.groovy.runtime.InvokerHelper.<clinit>(InvokerHelper.java:88)at groovy.lang.GroovyObjectSupport.getDefaultMetaClass(GroovyObjectSupport.java:46)at groovy.lang.GroovyObjectSupport.<init>(GroovyObjectSupport.java:32)at groovy.lang.Binding.<init>(Binding.java:33)at groovy.lang.GroovyShell.<init>(GroovyShell.java:63)at com.fast.summary.jvm.oom.TestOomTooManyClass.testDynamicCreateClass(TestOomTooManyClass.java:21)at com.fast.summary.jvm.oom.TestOomTooManyClass.main(TestOomTooManyClass.java:14)

Direct buffer memory

// -Xms10m -Xmx10m -XX:+PrintGCDetails -XX:MaxDirectMemorySize=5m
public class TestOomDirectBufferMemory {public static void main(String[] args) {System.out.println("查看配置的本地内存maxDirectMemory:" + (sun.misc.VM.maxDirectMemory() / (double) 1024 / 1024) + "MB");//停顿一下方便看效果try {Thread.sleep(3000);} catch (InterruptedException e) {e.printStackTrace();}//-XX:MaxDirectMemorySize=5m 本地内存配置的是5MB,这里实际使用的是6MBByteBuffer bb = ByteBuffer.allocateDirect(6 * 1024 * 1024);}
}

StackOverflowError

/*** StackOverflowError ：栈溢出* 什么时候会让 Java Method Stack 栈溢出啊？* 栈的基本特点就是 FILO（First In Last Out），* 如果 in 的太多而 out 的太少，就好 overflow 了。* 而 Java Method Stack 的功能就是保存每一次函数调用时的“现场”，* 即为入栈，函数返回就对应着出栈，所以函数调用的深度越大，栈就变得越大，足够大的时候就会溢出。* 所以模拟 Java Method Stack 溢出，只要不断递归调用某一函数就可以。* @author qinfuxiang*/
public class TestStackOverflowError {private static int stackLength = 0;public void stackOverflow() {++stackLength;stackOverflow();}public static void main(String[] args) {TestStackOverflowError test = new TestStackOverflowError();try {test.stackOverflow();} catch (Throwable e) {System.out.println("stack length: " + test.stackLength);throw e;}}
}

运行结果：

Exception in thread "main" java.lang.StackOverflowErrorat com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)at com.fast.summary.jvm.oom.TestStackOverflowError.stackOverflow(TestStackOverflowError.java:18)

Executors 默认的几种会出现OOM

newFixedThreadPool

• LinkedBlockingQueue为无界队列

// -Xmx8m
private static void fixedThreadPool() {ExecutorService executor = Executors.newFixedThreadPool(2);LoggerUtils.get().debug("begin...");while (true) {executor.submit(() -> {try {LoggerUtils.get().debug("send sms...");TimeUnit.SECONDS.sleep(30);} catch (InterruptedException e) {e.printStackTrace();}});}}

运行结果：

Exception in thread "main" java.lang.OutOfMemoryError: GC overhead limit exceededat java.util.concurrent.Executors.callable(Executors.java:407)at java.util.concurrent.FutureTask.<init>(FutureTask.java:152)at java.util.concurrent.AbstractExecutorService.newTaskFor(AbstractExecutorService.java:87)at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:111)at com.fast.summary.jvm.oom.TestOomThreadPool.fixedThreadPool(TestOomThreadPool.java:32)

newSingleThreadExecutor

• LinkedBlockingQueue为无界队列

// -Xmx8m -XX:-UseGCOverheadLimit
private static void singleThreadExecutor() {ExecutorService executor = Executors.newSingleThreadExecutor();LoggerUtils.get().debug("begin...");while (true) {executor.submit(() -> {try {LoggerUtils.get().debug("send sms...");TimeUnit.SECONDS.sleep(30);} catch (InterruptedException e) {e.printStackTrace();}});}}

运行结果：

Exception in thread "main" java.lang.OutOfMemoryError: Java heap spaceat java.util.concurrent.Executors.callable(Executors.java:407)at java.util.concurrent.FutureTask.<init>(FutureTask.java:152)at java.util.concurrent.AbstractExecutorService.newTaskFor(AbstractExecutorService.java:87)at java.util.concurrent.AbstractExecutorService.submit(AbstractExecutorService.java:111)at java.util.concurrent.Executors$DelegatedExecutorService.submit(Executors.java:678)at com.fast.summary.jvm.oom.TestOomThreadPool.singleThreadExecutor(TestOomThreadPool.java:47)at com.fast.summary.jvm.oom.TestOomThreadPool.main(TestOomThreadPool.java:22)

newCachedThreadPool

• 会不断创建线程

static ExecutorService executorService = Executors.newCachedThreadPool();static class Task implements Runnable {@Overridepublic void run() {try {TimeUnit.SECONDS.sleep(1000000);} catch (InterruptedException e) {e.printStackTrace();}}}private static void scheduledThreadPool() {ExecutorService executor = Executors.newScheduledThreadPool(2);LoggerUtils.get().debug("begin...");while (true) {executor.submit(() -> {try {LoggerUtils.get().debug("send sms...");TimeUnit.SECONDS.sleep(30);} catch (InterruptedException e) {e.printStackTrace();}});}}

运行结果：

Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native threadat java.lang.Thread.start0(Native Method)at java.lang.Thread.start(Thread.java:717)at java.util.concurrent.ThreadPoolExecutor.addWorker(ThreadPoolExecutor.java:957)at java.util.concurrent.ThreadPoolExecutor.execute(ThreadPoolExecutor.java:1378)at com.fast.summary.jvm.oom.TestOomThreadPool.cachedThreadPool(TestOomThreadPool.java:60)at com.fast.summary.jvm.oom.TestOomThreadPool.main(TestOomThreadPool.java:23)
Java HotSpot(TM) 64-Bit Server VM warning: Exception java.lang.OutOfMemoryError occurred dispatching signal SIGINT to handler- the VM may need to be forcibly terminated

newScheduledThreadPool

• DelayedWorkQueue 是无界队列

运行结果：

java.lang.OutOfMemoryError: Java heap spacejava.util.concurrent.ScheduledThreadPoolExecutor.schedule(ScheduledThreadPoolExecutor.java:530)at java.util.concurrent.ScheduledThreadPoolExecutor.submit(ScheduledThreadPoolExecutor.java:632)at com.fast.summary.jvm.oom.TestOomThreadPool.scheduledThreadPool(TestOomThreadPool.java:81)at com.fast.summary.jvm.oom.TestOomThreadPool.main(TestOomThreadPool.java:24)

github代码： https://github.com/fafeidou/fast-summary/tree/master/fast-summary-jvm/src/main/java/com/fast/summary/jvm/oom