Arthas系列(一)-Arthas整体架构

谁践踏了优雅 2023-09-23 21:14 136阅读 0赞

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### 一、开篇 ###

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Arthas是Alibaba开源的Java诊断工具，日常用这个工具排查很多问题，例如：类冲突问题、接口耗时很长问题、线程池阻塞问题等等，arthas还支持获取堆中对象、执行对象方法、修改对象属性值，真的是有了Arthas便可为所欲为！

当前对它的命令还算比较熟练了，想再进一步了解一下这个神器，学习它的原理和设计。

Arthas用到了JVM Attach API、Java agent、JVMTI、ClassLoader类隔离等技术，后面我们将跟着Arthas源码去探索一下神器是如何巧妙地使用这些手段。

第一篇，将从了解Arthas项目整体结构开始。

### 二、初探Arthas项目结构 ###

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#### 源码工程结构 ####

先从github上clone最新的Arthas源码，地址：[github.com/alibaba/art…][github.com_alibaba_art]

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从github上看到Arthas源码约74%是Java写的，看到这就放心了，源码理解起来应该不会很费劲。

再将源码导入IDEA，项目结构如下：

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模块比较多，我们挑重点讲解一下：

<table style="table-layout:fixed;width:28px;"> 
 <tbody> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">模块</td> 
 <td style="width:369px;vertical-align:top;height:52px;">功能</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">agent</td> 
 <td style="width:369px;vertical-align:top;height:52px;">Java agent的模块</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">arthas-vmtool</td> 
 <td style="width:369px;vertical-align:top;height:52px;">vmtool命令由这个模块实现</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">async-profiler</td> 
 <td style="width:369px;vertical-align:top;height:52px;">火焰图相关</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">boot</td> 
 <td style="width:369px;vertical-align:top;height:52px;">启动入口</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">core</td> 
 <td style="width:369px;vertical-align:top;height:52px;">核心功能模块，包括：1.attach宿主应用进程，load arthas-agent 2.核心命令的实现 3.和arthas-client通信</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">math-game</td> 
 <td style="width:369px;vertical-align:top;height:52px;">一个测试用的demo</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">memorycompiler</td> 
 <td style="width:369px;vertical-align:top;height:52px;">字节码编译。主要是从<a style="color:#0A6CFF;" href="https://link.juejin.cn/?target=https%3A%2F%2Fgithub.com%2Fskalogs%2FSkaETL%2Ftree%2Fmaster%2Fcompiler%25E9%25A1%25B9%25E7%259B%25AEfork%25E4%25B8%258B%25E6%259D%25A5%25E7%259A%2584%25E5%25B7%25A5%25E5%2585%25B7%25EF%25BC%258Cmc%25E7%25BC%2596%25E8%25AF%2591%2560.java%2560%25E6%2596%2587%25E4%25BB%25B6%25E7%2594%259F%25E6%2588%2590%2560.class%2560%25E5%25B0%25B1%25E7%2594%25A8%25E5%2588%25B0%25E4%25BA%2586%25E8%25BF%2599%25E4%25B8%25AA%25E6%25A8%25A1%25E5%259D%2597" rel="nofollow">github.com/skalogs/Ska…</a></td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">packaging</td> 
 <td style="width:369px;vertical-align:top;height:52px;">定义项目打包的规则</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">spy</td> 
 <td style="width:369px;vertical-align:top;height:52px;">只包含Spy类，简单理解为实现类似spring aop的Advice，有前置方法，后置方法等</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">tunnel-client、tunnel-common、tunnel-server</td> 
 <td style="width:369px;vertical-align:top;height:52px;">tunnel-server/tunnel-client 实现远程管理/连接多个 Agent</td> 
 </tr> 
 <tr> 
 <td style="width:369px;vertical-align:top;height:52px;">web-ui</td> 
 <td style="width:369px;vertical-align:top;height:52px;">Web Console用到的前端资源</td> 
 </tr> 
 </tbody> 
</table>

#### 打包后工程结构 ####

在github上下载RELEASE包，地址: [github.com/alibaba/art…][github.com_alibaba_art 1]

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其中，重点关注其中的jar包。

### 三、核心模块 ###

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#### arthas-boot、as.sh、as.bat ####

arthas-boot、as.sh、as.bat功能类似，arthas-boot是java的方式，可以通过jar -jar arthar-boot.jar启动arthas服务端，而as.sh是通过脚本的方式启动arthas服务端。我们用java -jar arthas-boot.jar启动或者as.sh启动，会加载出下面的界面：

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#### arthas-core ####

arthas-boot里启动类com.taobao.arthas.boot.Bootstrap用到了通过java -jar arthas-core.jar启动子进程，

这个子进程只会短暂存在。该进程的信息示例：

MacBook-Pro:arthas-github terry$ ps -ef|grep arthas-core
      503 43456 43321   0 10:35PM ??         0:00.23 /Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home/jre/../bin/java -Xbootclasspath/a:/Library/Java/JavaVirtualMachines/zulu-8.jdk/Contents/Home/jre/../lib/tools.jar -jar /Users/terry/software_developmet_1/arthas/arthas-bin-3.6.7/arthas-core.jar -pid 43120 -core /Users/terry/software_developmet_1/arthas/arthas-bin-3.6.7/arthas-core.jar -agent /Users/terry/software_developmet_1/arthas/arthas-bin-3.6.7/arthas-agent.jar
    复制代码

java -jar arthas-core.jar运行时，会执行com.taobao.arthas.core.Arthas\#main，然后解析参数，attach到目标进程，目标进程挂载arthas-agent.jar，arthas-agent的premain方法com.taobao.arthas.agent334.AgentBootstrap\#premain会执行，然后加载arthas-core.jar【多次出现arthar-core.jar，感觉设计不是很好，应该分离多个模块】，此时会调用com.taobao.arthas.core.server.ArthasBootstrap，com.taobao.arthas.core.server.ArthasBootstrap会加载spy.jar

#### arthas-client ####

arthas-client是arthas客户端，支持通过telnet的方式连接到arthas服务端。

#### arthas-agent ####

一个Java agent的jar，支持Attach API方式被动态加载，也支持\-javaagent:方式被静态加载。arthas-agent的premain或者agentmain方法会执行com.taobao.arthas.agent334.AgentBootstrap\#main会执行，然后加载arthas-core.jar

#### arthas-spy ####

arthas-core.jar被挂载到宿主应用的进程后，arthas-core会让BootstrapClassLoader去加载arthas-spy.jar。该模块只包含Spy类，简单理解为实现类似spring aop的Advice，有前置方法，后置方法等。

### 四、小结 ###

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上文简述了arthas的项目结构和核心模块，下一篇将梳理一下arthas启动流程。

[format_png]: https://img-blog.csdnimg.cn/img_convert/c13159a6b0290f8b51b2f959a97a19e9.webp?x-oss-process=image/format,png
[Link 1]: https://juejin.cn/post/7167294154827890702
[format_png 1]: https://img-blog.csdnimg.cn/img_convert/2699ac8bb64719fd5f5341b4e1a0eaf5.webp?x-oss-process=image/format,png
[github.com_alibaba_art]: https://link.juejin.cn/?target=https%3A%2F%2Fgithub.com%2Falibaba%2Farthas.git%25E3%2580%2582
[format_png 2]: https://img-blog.csdnimg.cn/img_convert/86cd5958001ce2f222a2eb62da5e0250.webp?x-oss-process=image/format,png
[format_png 3]: https://img-blog.csdnimg.cn/img_convert/33362f4c5bf91bdf31335d44d403667a.webp?x-oss-process=image/format,png
[github.com_alibaba_art 1]: https://link.juejin.cn/?target=https%3A%2F%2Fgithub.com%2Falibaba%2Farthas%2Freleases%25EF%25BC%258C%25E4%25B8%258B%25E8%25BD%25BD**arthas-bin.zip**%25E6%2596%2587%25E4%25BB%25B6%25E3%2580%2582%25E8%25A7%25A3%25E5%258E%258B%25E6%2596%2587%25E4%25BB%25B6%25EF%25BC%258C%25E5%258F%25AF%25E4%25BB%25A5%25E7%259C%258B%25E5%2588%25B0%25E6%2589%2593%25E5%258C%2585%25E5%2590%258E%25E7%259A%2584%25E9%25A1%25B9%25E7%259B%25AE%25E7%25BB%2593%25E6%259E%2584%25EF%25BC%259A
[format_png 4]: https://img-blog.csdnimg.cn/img_convert/ce833dd8024a1257f12df393367b0635.webp?x-oss-process=image/format,png
[format_png 5]: https://img-blog.csdnimg.cn/img_convert/e1c1864734184dfc229c89bd203e7a21.webp?x-oss-process=image/format,png