JAVA堆溢出OOM场景模拟及排除过程

模拟过程

• 加参数定义最大堆空间和最小堆空间

	-Xms20m -Xmx20m 

• 加参数在堆溢出dump出当前的堆快照

-XX:+HeapDumpOnOutOfMemoryError

上代码

import java.util.ArrayList;
import java.util.List;

/**
 * @author yangyuanliang
 * @version 1.9
 * @date 2022/4/24 21:49
 */
public class HeapOOM {
	static class OOMObject{
	}

	public static void main(String[] args) {
		List<HeapOOM> ooms = new ArrayList<>();
		while(true) {
			ooms.add(new HeapOOM());
		}
	}
}

运行结果

/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/bin/java -Xms20m -Xmx20m -XX:+HeapDumpOnOutOfMemoryError -javaagent:/Applications/IntelliJ IDEA.app/Contents/lib/idea_rt.jar=53845:/Applications/IntelliJ IDEA.app/Contents/bin -Dfile.encoding=UTF-8 -classpath /Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/charsets.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/deploy.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/cldrdata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/dnsns.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/jaccess.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/jfxrt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/localedata.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/nashorn.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/sunec.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/sunjce_provider.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/sunpkcs11.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/ext/zipfs.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/javaws.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/jce.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/jfr.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/jfxswt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/jsse.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/management-agent.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/plugin.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/resources.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/jre/lib/rt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/ant-javafx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/dt.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/javafx-mx.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/jconsole.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/packager.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/sa-jdi.jar:/Library/Java/JavaVirtualMachines/jdk1.8.0_191.jdk/Contents/Home/lib/tools.jar:/Users/liang/ruijie/jvm-test/out/production/jvm-test HeapOOM
java.lang.OutOfMemoryError: Java heap space
Dumping heap to java_pid76264.hprof ...
Heap dump file created [27766960 bytes in 0.100 secs]
Exception in thread "main" java.lang.OutOfMemoryError: Java heap space
	at java.util.Arrays.copyOf(Arrays.java:3210)
	at java.util.Arrays.copyOf(Arrays.java:3181)
	at java.util.ArrayList.grow(ArrayList.java:265)
	at java.util.ArrayList.ensureExplicitCapacity(ArrayList.java:239)
	at java.util.ArrayList.ensureCapacityInternal(ArrayList.java:231)
	at java.util.ArrayList.add(ArrayList.java:462)
	at HeapOOM.main(HeapOOM.java:17)

Process finished with exit code 1

分析过程

Java堆内存的OutOfMemoryError异常是实际应用中最常见的内存溢出异常情况。常规的处理方法，通过内存映像分析工具对Dump出来的堆快照进行分析。确认是内存泄露还是内存溢出（这个是基于导致OOM的对象是否是必要的来决定的）。

内存泄露

如果是内存泄漏，可进一步借助攻击分析查看对象到GC Roots的引用链，找到泄漏对象通过怎样的引用路径，与那些GC Roots相关联，才导致垃圾收集器无法回收他们，根据对象的类型信息以及他到GCRoots引用链的信息，一般可以准确的定位到这些对象创建的位置，进而找出内存泄漏代码的位置

内存溢出

内存溢出的话，那就应该检查Java虚拟机的堆参数，通过- Xmx与-Xms设置，与机器内存对比，看看是否还有空间可调整。在从代码简称是否存在某些对象生命周期过长，持有状态时间过长，存储结构设计不合理的情况，尽量减少程序运行期的内存消耗。