本文主要参考慕课网若鱼老师课程Java生产环境下性能监控与调优详解
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本章关键词：BTrace、拦截、注意事项
一、入门
1.做什么的？
- 可以在应用程序不重启，不修改的情况下，正在运行的情况下，动态的修改字节码，达到监控调试的目的
- 可以动态的向目标应用程序的字节码注入追踪代码
- 用到的技术
JavaComplierApi、JVMTI、Agent、Instrumentation+ASM
2.安装
- 到官网中下载相应版本
- 新建环境变量BTRACE_HOME，添加Path:%BTRACE_HOME%\bin
环境变量的添加请自行百度
- 两种运行脚本方式
- JVisualVM中添加Btrace插件（参见上一章），添加classpath
2.使用命令行btrace <pid> <trace_script>
3.使用详解
-
代码示例
btrace需要引入三个jar，就是下载的btrace程序中，build目录下的三个
jar包.png
引入jar包
<!--btrace -->
<dependency>
<groupId>com.sun.btrace</groupId>
<artifactId>btrace-boot</artifactId>
<version>1.3.11</version>
<type>jar</type>
<scope>system</scope>
<systemPath>D:\btrace-bin-1.3.11\build\btrace-boot.jar</systemPath>
</dependency>
<dependency>
<groupId>com.sun.btrace</groupId>
<artifactId>btrace-agent</artifactId>
<version>1.3.11</version>
<type>jar</type>
<scope>system</scope>
<systemPath>D:\btrace-bin-1.3.11\build\btrace-agent.jar</systemPath>
</dependency>
<dependency>
<groupId>com.sun.btrace</groupId>
<artifactId>btrace-client</artifactId>
<version>1.3.11</version>
<type>jar</type>
<scope>system</scope>
<systemPath>D:\btrace-bin-1.3.11\build\btrace-client.jar</systemPath>
</dependency>
将要被拦截的代码
package com.qinxianyun.monitor_tuning.chapter4;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;
/**
* @author Qinxianyun
* @version V1.0
* @time 2018/7/21.12:50
* @description 演示btrace
*/
@RestController
@RequestMapping("ch4")
public class Ch4Controller {
@RequestMapping("/arg1")
public String arg1(@RequestParam("name")String name){
return "hello," + name;
}
}
btrace脚本（脚本和代码没有必要关联性，脚本可以随便写在哪里，没有必要写在方法的一个项目里面）
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
@BTrace
public class PrintArgSimple {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
method = "arg1",
location = @Location(Kind.ENTRY)
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, AnyType[] args){
BTraceUtils.printArray(args);
BTraceUtils.println(pcn + "," + pmn);
BTraceUtils.println();
}
}
@OnMethod表示我们要拦截哪个类的哪个方法，在什么时候进行拦截
Kind.ENTRY表示在入口的时候拦截（也就是一进入方法的时候）
@param pcn 拦截方法类的类名
@param pmn 拦截方法的方法名
@param args 参数
-
进入到btrace脚本的目录下
进入目录.png -
查看进程id
查看进程id.png -
运行脚本文件
运行中.png -
浏览器中输入http://localhost:8080/ch4/arg1?name=qinxianyun
出现如下处理结果
处理结果.png -
Java VisualVM打开btrace（需要已经安装了插件，详情见上一章）
vm打开btrace.png
界面详解.png
输出.png
二、拦截构造函数、同名函数
1.拦截方法（普通方法、构造方法、同名方法）
- 普通方法 @OnMethod(clazz=" ",method=" ")
参考上面的例子
- 构造函数@OnMethod(clazz=" ",method="<init>")
因为构造函数在字节码层面是叫init，所以用<init>
@RequestMapping("/constructor")
public User arg1(User user){
return user;
}
package com.qinxianyun.monitor_tuning.chapter2;
/**
* @author Qinxianyun
* @version V1.0
* @time 2018/7/15.14:52
* @description 用户实体
*/
public class User {
private int id;
private String name;
public User(int id, String name) {
this.id = id;
this.name = name;
}
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
}
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.ProbeClassName;
import com.sun.btrace.annotations.ProbeMethodName;
@BTrace
public class PrintConstructor {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter2.User",
method = "<init>"
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, AnyType[] args){
BTraceUtils.println(pcn + "," + pmn);
BTraceUtils.printArray(args);
BTraceUtils.println();
}
}
运行结果.png
- 同名方法（用参数区分）
@RequestMapping("/same1")
public String same(@RequestParam("name")String name){
return "hello," + name;
}
@RequestMapping("/same2")
public String same(@RequestParam("name")String name,@RequestParam("id")int id){
return "hello," + name + "," +id;
}
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;
import com.sun.btrace.annotations.OnMethod;
import com.sun.btrace.annotations.ProbeClassName;
import com.sun.btrace.annotations.ProbeMethodName;
@BTrace
public class PrintSame {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
method = "same"
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, String name ,int id){
BTraceUtils.println(pcn + "," + pmn + "," + name + "," + id);
BTraceUtils.println();
}
}
拦截重载的方法，是根据参数的类型区分的，脚本中的名字可以和代码中参数名不一致
运行结果：
运行结果1.png
三、拦截返回值、异常行号
1.拦截时机
- Kind.ENTRY : 入口，默认值
参考第一个例子
- Kind.RETURN ： 返回
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.AnyType;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
@BTrace
public class PrintReturn {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
method = "arg1",
location = @Location(Kind.RETURN)
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, @Return AnyType result){
BTraceUtils.println(pcn + "," + pmn + "," + result);
BTraceUtils.println();
}
}
- Kind.THROW ： 异常
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
@BTrace
public class PrintOnThrow {
@TLS
static Throwable currentException;
@OnMethod(
clazz = "java.lang.Throwable",
method = "<init>"
)
public static void onthrow(@Self Throwable self){//new Throwable()
currentException = self;
}
@OnMethod(
clazz = "java.lang.Throwable",
method = "<init>"
)
public static void onthrow1(@Self Throwable self,String s){//new Throwable(String msg)
currentException = self;
}
@OnMethod(
clazz = "java.lang.Throwable",
method = "<init>"
)
public static void onthrow1(@Self Throwable self,String s,Throwable cause){//new Throwable(String msg,Throwable cause)
currentException = self;
}
@OnMethod(
clazz = "java.lang.Throwable",
method = "<init>"
)
public static void onthrow2(@Self Throwable self,Throwable cause){//new Throwable(Throwable cause)
currentException = self;
}
@OnMethod(
clazz = "java.lang.Throwable",
method = "<init>",
location = @Location(Kind.RETURN)
)
public static void onthrowreturn(){
if (currentException != null){
BTraceUtils.Threads.jstack(currentException);
BTraceUtils.println("========================");
currentException = null;
}
}
}
- Kind.Line ：行
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
@BTrace
public class PrintLine {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
location = @Location(value = Kind.LINE,line = 41)
)
public static void anyRead(@ProbeClassName String pcn,@ProbeMethodName String pmn,int line){
BTraceUtils.println(pcn + "," + pmn + "," + line);
BTraceUtils.println();
}
}
四、拦截复杂参数、环境变量、正则匹配拦截
1.拦截this、入参、返回
- this：@Self
- 入参：可以用AnyType，也可以用真实类型，同名的用真实的
- 返回：@Return
2.获取对象的值
- 简单类型：直接获取
- 复杂类型：反射，类名+属性名
package com.qinxianyun.monitor_tuning.chapter4;
import com.qinxianyun.monitor_tuning.chapter2.User;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
import java.lang.reflect.Field;
@BTrace
public class PrintArgComplex {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
method = "arg2",
location = @Location(Kind.ENTRY)
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn, User user){
BTraceUtils.printFields(user);
Field field2 = BTraceUtils.field("com.qinxianyun.monitor_tuning.chapter2.User","name");
BTraceUtils.println(BTraceUtils.get(field2,user));
BTraceUtils.println(pcn + "," + pmn);
BTraceUtils.println();
}
}
注意：复杂类型.png
引用的需要加上-cp
3.正则表达式
- 拦截任意方法
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.*;
@BTrace
public class PrintRegex {
@OnMethod(
clazz = "com.qinxianyun.monitor_tuning.chapter4.Ch4Controller",
method = "/.*/"
)
public static void anyRead(@ProbeClassName String pcn, @ProbeMethodName String pmn){
BTraceUtils.println(pcn + "," + pmn);
BTraceUtils.println();
}
}
4.打印环境变量
- 打印(输出类似Jinfo命令)
package com.qinxianyun.monitor_tuning.chapter4;
import com.sun.btrace.BTraceUtils;
import com.sun.btrace.annotations.BTrace;
@BTrace
public class PrintJinfo {
static {
BTraceUtils.println("System Properties:");
BTraceUtils.printProperties();
BTraceUtils.println("VM Flags:");
BTraceUtils.printVmArguments();
BTraceUtils.println("OS Enviroment:");
BTraceUtils.printEnv();
BTraceUtils.exit();
}
}
-
输出结果
输出.png
注意事项：
1.默认只能本地运行
2.生产环境下可以使用，但是被修改的字节码不会被还原（即使btrace退出）
因此，脚本中不要有太耗系统资源的东西，否则会影响服务器。
