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arthas 运维监控

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alibaba 开源的一个jvm监控软件，能够

  • 反编译运行中的java程序的代码，
  • 查看java程序的内存、
  • 查看java程序的线程
  • 查看类的静态变量值
  • 查看classloader的继承树，urls，类加载信息
  • 等等

https://alibaba.github.io/arthas/sysenv.html

下面为精简的常用接口

查看类的静态属性

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$ getstatic demo.MathGame random
field: random
@Random[
    serialVersionUID=@Long[3905348978240129619],
    seed=@AtomicLong[120955813885284],
    multiplier=@Long[25214903917],
    addend=@Long[11],
    mask=@Long[281474976710655],
    DOUBLE_UNIT=@Double[1.1102230246251565E-16],
    BadBound=@String[bound must be positive],
    BadRange=@String[bound must be greater than origin],
    BadSize=@String[size must be non-negative],
    seedUniquifier=@AtomicLong[-3282039941672302964],
    nextNextGaussian=@Double[0.0],
    haveNextNextGaussian=@Boolean[false],
    serialPersistentFields=@ObjectStreamField[][isEmpty=false;size=3],
    unsafe=@Unsafe[sun.misc.Unsafe@2eaa1027],
    seedOffset=@Long[24],
]

打印出类的Field信息

该方法只能获取 类信息，无法获取实例信息

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$ sc -d -f demo.MathGame
class-info        demo.MathGame
code-source       /private/tmp/arthas-demo.jar
name              demo.MathGame
isInterface       false
isAnnotation      false
isEnum            false
isAnonymousClass  false
isArray           false
isLocalClass      false
isMemberClass     false
isPrimitive       false
isSynthetic       false
simple-name       MathGame
modifier          public
annotation
interfaces
super-class       +-java.lang.Object
class-loader      +-sun.misc.Launcher$AppClassLoader@3d4eac69
                    +-sun.misc.Launcher$ExtClassLoader@66350f69
classLoaderHash   3d4eac69
fields            modifierprivate,static
                  type    java.util.Random
                  name    random
                  value   java.util.Random@522b4
                          08a
 
                  modifierprivate
                  type    int
                  name    illegalArgumentCount
 
Affect(row-cnt:1) cost in 19 ms.

反编译指定已加载类的源码

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jad demo.MathGame

查看ClassLoader的继承树

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$ classloader -t
+-BootstrapClassLoader
+-sun.misc.Launcher$ExtClassLoader@66350f69
  +-com.taobao.arthas.agent.ArthasClassloader@68b31f0a
  +-sun.misc.Launcher$AppClassLoader@3d4eac69
Affect(row-cnt:4) cost in 3 ms.

使用ClassLoader去查找resource

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$ classloader -c 3d4eac69  -r META-INF/MANIFEST.MF
 jar:file:/System/Library/Java/Extensions/MRJToolkit.jar!/META-INF/MANIFEST.MF
 jar:file:/private/tmp/arthas-demo.jar!/META-INF/MANIFEST.MF
 jar:file:/Users/hengyunabc/.arthas/lib/3.0.5/arthas/arthas-agent.jar!/META-INF/MANIFEST.MF

观察方法调用前和方法返回后

watch 命令 具体 https://alibaba.github.io/arthas/watch.html

输出当前方法被调用的调用路径

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$ stack demo.MathGame primeFactors 'params[0]<0' -n 2
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 30 ms.
ts=2018-12-04 01:34:27;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
    @demo.MathGame.run()
        at demo.MathGame.main(MathGame.java:16)
 
ts=2018-12-04 01:34:30;thread_name=main;id=1;is_daemon=false;priority=5;TCCL=sun.misc.Launcher$AppClassLoader@3d4eac69
    @demo.MathGame.run()
        at demo.MathGame.main(MathGame.java:16)
 
Command execution times exceed limit: 2, so command will exit. You can set it with -n option.

排查 method not found

先通过sc获取当前类的来源，执行以下命令后 查看 code-source 信息

sc -d 类名

使用 jad 反编译 代码，确认方法是否存在。

jad 类名

使用maven排查依赖

其他实践

watch com.example.demo.arthas.user.UserController * ‘{params, throwExp} –e

trace javax.servlet.Servlet * > servlet.txt # 结果在 ~/logs/arthas-cache/

trace javax.servlet.Filter *

  • 动态修复代码/测试

redefine –p UserController.class

  • UserController的logger是什么实现？

ognl ‘@com.example.demo.arthas.user.UserController@logger’

  • 动态修改logger级别

ognl ‘@org.slf4j.LoggerFactory@getLogger(“root”).setLevel(@ch.qos.logback.classic.Level@DEBUG)’

  • 查找冲突的logback.xml/log4j.properties

classloader -c 18b4aac2 -r logback.xml

  • Spring Boot应用的Classloader结构

classloader –t
classloader -a -c 758f7d25

  • jad反编绎jsp的实现

jad org.apache.jsp.jsp.hello_jsp

  • tt 获取Spring Context

tt -t org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter invokeHandlerMethod

tt -i 1000 -w ‘target.getApplicationContext().getBean(“helloWorldService”).getHelloMessage()’

http://hengyunabc.github.io/spring-boot-inside/