一、实战死循环导致CPU飙高
top -p pid -H
jstack pid
printf "%s" 十进制的线程id
二、创建CUP100%实例（死循环）
1、创建CpuController
@RestController
public class CpuController { @RequestMapping("/loop")
public List<Long> loop(){
String data = "{\"data\":[{\"partnerid\":]}";
return getPartneridsFromJson(data);
} public static List<Long> getPartneridsFromJson(String data){
//{\"data\":[{\"partnerid\":982,\"count\":\"10000\",\"cityid\":\"11\"},{\"partnerid\":983,\"count\":\"10000\",\"cityid\":\"11\"},{\"partnerid\":984,\"count\":\"10000\",\"cityid\":\"11\"}]}
//上面是正常的数据
List<Long> list = new ArrayList<Long>(2);
if(data == null || data.length() <= 0){
return list;
}
int datapos = data.indexOf("data");
if(datapos < 0){
return list;
}
int leftBracket = data.indexOf("[",datapos);
int rightBracket= data.indexOf("]",datapos);
if(leftBracket < 0 || rightBracket < 0){
return list;
}
String partners = data.substring(leftBracket+1,rightBracket);
if(partners == null || partners.length() <= 0){
return list;
}
while(partners!=null && partners.length() > 0){
int idpos = partners.indexOf("partnerid");
if(idpos < 0){
break;
}
int colonpos = partners.indexOf(":",idpos);
int commapos = partners.indexOf(",",idpos);
if(colonpos < 0 || commapos < 0){
//partners = partners.substring(idpos+"partnerid".length());//
continue;
}
String pid = partners.substring(colonpos+1,commapos);
if(pid == null || pid.length() <= 0){
//partners = partners.substring(idpos+"partnerid".length());//
continue;
}
try{
list.add(Long.parseLong(pid));
}catch(Exception e){
//do nothing
}
partners = partners.substring(commapos);
}
return list;
} }
getPartneridsFromJson发生死循环 2.打包
D:\workspace\monitor_tuning>mvn clean package -Dmaven.test.skip pom.xml的配置如下
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion> <groupId>com.example</groupId>
<artifactId>monitor_tuning</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging> <name>monitor_tuning</name>
<description>Demo project for Spring Boot</description> <parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>2.1.1.RELEASE</version>
<relativePath/> <!-- lookup parent from repository -->
</parent> <properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties> <dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency> <dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency> <dependency>
<groupId>asm</groupId>
<artifactId>asm</artifactId>
<version>3.3.1</version>
</dependency>
</dependencies> <build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<version>3.1</version>
<!-- compile for Java 1.8 -->
<configuration>
<source>1.8</source>
<target>1.8</target>
<encoding>UTF-8</encoding>
<compilerArgs>
<!-- 过期的方法的警告-->
<arg>-Xlint:deprecation</arg>
</compilerArgs>
<compilerArguments>
<!-- 是否输出所有的编译信息（包括类的加载等）-->
<!--<verbose />-->
<!-- 解决maven命令编译报错，因为rt.jar 和jce.jar在jre的lib下面，不在jdk的lib下面，
导致maven找不到（java7以后会出现这个问题），将这2个jar包拷贝到jdk的lib下面估计也好使-->
<bootclasspath>${java.home}\lib\rt.jar;${java.home}\lib\jce.jar</bootclasspath>
</compilerArguments>
</configuration>
</plugin>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins>
</build> </project>
端口设置为9080
3、生成jar完成后，将它放在测试服务器
nohup java -jar monitor_tuning-0.0.1-SNAPSHOT.jar
四、我这里是将 monitor_tuning以war包的的形式部署到我的测试服务器
1）打开多个页面调用loop方法
http://*.*.*.*:7080/monitor_tuning/loop 2）使用top命令查看cpu的使用
3、jstack 20738 > 20738.txt
sz 20738.txt 下载文件 4、 打印所有的线程
top -p 20738 -H
打印946为10进制，结果为3b2
打开刚才的20738.txt文件
查找3b2
这样就定位到了getPartneridsFromJson这个方法。
三、创建CUP100%实例（死锁）
创建两个线程，线程1先获得锁1，然后获得锁2； 线程二先获得锁2，然后获得锁1. 然后两个线程造成死锁。
private Object lock1 = new Object();
private Object lock2 = new Object(); /**
* 死锁
*/
@RequestMapping("/deadlock")
public String deadlock(){
new Thread(()->{
synchronized (lock1){
try {
Thread.sleep(1000);
synchronized (lock2){
System.out.println("Thread1 over");
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start(); new Thread(()->{
synchronized (lock2){
try {
Thread.sleep(1000);
synchronized (lock1){
System.out.println("Thread2 over");
}
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}).start(); return "deadlock";
}
jstack 8704 > 8704.txt 8704为tomcat的进程
将8704.txt拉到底部，可以看到死锁的信息。
Found one Java-level deadlock:
=============================
"Thread-9":
waiting to lock monitor 0x0000000000eaeb08 (object 0x00000000f6d7abf8, a java.lang.Object),
which is held by "Thread-8"
"Thread-8":
waiting to lock monitor 0x00007f82ac0062c8 (object 0x00000000f6d7ac08, a java.lang.Object),
which is held by "Thread-9" Java stack information for the threads listed above:
===================================================
"Thread-9":
at com.example.monitor_tuning.chapter2.CpuController.lambda$deadlock$1(CpuController.java:52)
- waiting to lock <0x00000000f6d7abf8> (a java.lang.Object)
- locked <0x00000000f6d7ac08> (a java.lang.Object)
at com.example.monitor_tuning.chapter2.CpuController$$Lambda$389/1326472202.run(Unknown Source)
at java.lang.Thread.run(Thread.java:748)
"Thread-8":
at com.example.monitor_tuning.chapter2.CpuController.lambda$deadlock$0(CpuController.java:39)
- waiting to lock <0x00000000f6d7ac08> (a java.lang.Object)
- locked <0x00000000f6d7abf8> (a java.lang.Object)
at com.example.monitor_tuning.chapter2.CpuController$$Lambda$388/1104652864.run(Unknown Source)
at java.lang.Thread.run(Thread.java:748) Found 1 deadlock.