常见 OOM 异常场景

1. 堆内存溢出java.lang.OutOfMemoryError: Java heap space
2. 栈溢出-java.lang.StackOverFlowError、java.lang.OutOfMemorryError
3. 元空间溢出java.lang.OutOfMemoryError: Metaspace
4. 直接内存溢出java.lang.OutOfMemoryError: Direct buffer memory
5. GC超限java.lang.OutOfMemoryError: GC overhead limit exceeded

查看本地 JVM 垃圾回收器

java -XX:+PrintFlagsFinal-version 

前置条件

1. jdk 版本为 1.8 。jdk 版本垃圾回收机制均不太一样，同样内存结构也有变化，尤其是 1.6、1.7、1.8 三个版本表现出比较明显，目前大部分企业用的是 jdk1.8 版本，本最佳实践也采用 jdk1.8 版本作为基础，如果是其他版本的jdk，可以借鉴。
2. 接入ARMS 。

栈溢出 java.lang.StackOverFlowError

启动参数

-javaagent:C:\Users\Administrator\Downloads\ctyunArmsAgent\ctyunArmsAgent.jar -Dotel.resource.attributes=service.name=arms_example -Darms.licenseKey=${licenseKey}-Dotel.exporter.otlp.endpoint=${endpoint}

APM监控

堆溢出 java.lang.OutOfMemoryError: Java heap space

启动参数

-Xmx100m  -javaagent:C:\Users\Administrator\Downloads\ctyunArmsAgent\ctyunArmsAgent.jar -Dotel.resource.attributes=service.name=arms_example -Darms.licenseKey=${licenseKey} -Dotel.exporter.otlp.endpoint=${endpoint}

APM监控

直接内存溢出 java.lang.OutOfMemoryError: Direct buffer memory

参数：

-Xmx100m-XX:MaxMetaspaceSize=100M  -javaagent:C:\Users\Administrator\Downloads\ctyunArmsAgent\ctyunArmsAgent.jar -Dotel.resource.attributes=service.name=arms_example -Darms.licenseKey=${licenseKey}-Dotel.exporter.otlp.endpoint=${endpoint}

APM监控

代码：

package com.arms.example.controller;

import jdk.internal.org.objectweb.asm.ClassWriter;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;

import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.TimeUnit;

@RequestMapping("/exec")
@RestController
public class ExceptionController {

    @GetMapping("/heapOOM")
    public void heapOOM() {
        List<LargeObject> list = new ArrayList<>();
        while (true) {
            try {
                Thread.sleep(1000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            list.add(new LargeObject());
        }
    }

    @GetMapping("/stackOOM")
    public void stackOOM() {
        while (true) {
            Thread thread = new Thread(() -> {
                while (true) {
                    try {
                        TimeUnit.HOURS.sleep(1);
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }

            });
            thread.start();
        }
    }

    @GetMapping("/directBufferOOM")
    public void directBufferOOM() throws InterruptedException {
        final int _1M = 1024 * 1024 * 1;
        List<ByteBuffer> buffers = new ArrayList<>();
        int count = 1;
        while (true) {
            ByteBuffer byteBuffer = ByteBuffer.allocateDirect(_1M);
            buffers.add(byteBuffer);
            System.out.println(count++);
            Thread.sleep(1000);

        }
    }

    @GetMapping("/stackOverflow")
    public void StackOFE() {
        stackOverFlowErrorMethod();
     }

    public static void stackOverFlowErrorMethod() {
        stackOverFlowErrorMethod();
    }

    @GetMapping("/metaspaceOOM")
    public void metaspaceOOM() {
        try {
            List<Class<?>> generatedClasses = new ArrayList<>();
            MyClassLoader classLoader = new MyClassLoader();

            while (true) {
                String className = "com.arms.example.controller.GeneratedClass"+System.nanoTime();
                byte[] classData = generateClassData(className);

                Class<?> generatedClass = classLoader.defineClass(className, classData);
                generatedClasses.add(generatedClass);
            }
        } catch (OutOfMemoryError e) {
            System.out.println("Metaspace OOM occurred!");
            e.printStackTrace();
        }
    }

    private static byte[] generateClassData(String className) {
        ClassWriter cw = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
        cw.visit(Opcodes.V1_8, Opcodes.ACC_PUBLIC, className.replace('.','/'), null, "java/lang/Object", null);

        MethodVisitor constructor = cw.visitMethod(Opcodes.ACC_PUBLIC, "<init>", "()V", null, null);
        constructor.visitCode();
        constructor.visitVarInsn(Opcodes.ALOAD, 0);
        constructor.visitMethodInsn(Opcodes.INVOKESPECIAL, "java/lang/Object", "<init>", "()V", false);
        constructor.visitInsn(Opcodes.RETURN);
        constructor.visitMaxs(1, 1);
        constructor.visitEnd();

        // 生成一个方法，输出 "Hello, World!"
        MethodVisitor mv = cw.visitMethod(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, "sayHello", "()V", null, null);
        mv.visitCode();
        mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
        mv.visitLdcInsn("Hello, World!");
        mv.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "java/io/PrintStream", "println", "(Ljava/lang/String;)V", false);
        mv.visitInsn(Opcodes.RETURN);
        mv.visitMaxs(2, 0);
        mv.visitEnd();

        cw.visitEnd();
        return cw.toByteArray();
    }

    static class MyClassLoader extends ClassLoader {
        public Class<?> loadClass(String name) throws ClassNotFoundException {
            if (name.startsWith("com.example.generated")) {
                return super.findClass(name);
            }
            return super.loadClass(name);
        }

        public Class<?> defineClass(String name, byte[] b) {
            return defineClass(name, b, 0, b.length);
        }
    }

    public class LargeObject {
        private byte[] data;

        public LargeObject(){
            this(256);
        }

        public LargeObject(int sizeInKB) {
            int sizeInBytes = sizeInKB * 1024;
            data = new byte[sizeInBytes];
        }
    }
}