add classloader command scenario #847 (#1375)

alibaba · Aug 14, 2020 · 3d99c44 · 3d99c44
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diff --git a/site/src/site/sphinx/classloader.md b/site/src/site/sphinx/classloader.md
@@ -1,6 +1,8 @@
 classloader
 ===
 
+[`classloader`在线教程](https://arthas.aliyun.com/doc/arthas-tutorials?language=cn&id=command-classloader)
+
 > 查看classloader的继承树，urls，类加载信息
 
 `classloader` 命令将 JVM 中所有的classloader的信息统计出来，并可以展示继承树，urls等。

diff --git a/site/src/site/sphinx/en/classloader.md b/site/src/site/sphinx/en/classloader.md
@@ -1,6 +1,8 @@
 classloader
 ===========
 
+[`classloader` online tutorial](https://arthas.aliyun.com/doc/arthas-tutorials?language=en&id=command-classloader)
+
 View hierarchy, urls and classes-loading info for the class-loaders.
 
 `classloader` can search and print out the URLs for a specified resource from one particular classloader. It is quite handy when analyzing `ResourceNotFoundException`.

diff --git a/tutorials/katacoda/command-classloader-cn/arthas-boot.md b/tutorials/katacoda/command-classloader-cn/arthas-boot.md
@@ -0,0 +1,16 @@
+
+
+
+
+在新的`Terminal 2`里，下载`arthas-boot.jar`，再用`java -jar`命令启动：
+
+`wget https://arthas.aliyun.com/arthas-boot.jar
+java -jar arthas-boot.jar`{{execute T2}}
+
+`arthas-boot`是`Arthas`的启动程序，它启动后，会列出所有的Java进程，用户可以选择需要诊断的目标进程。
+
+选择第一个进程，输入 `1`{{execute T2}} ，再`Enter/回车`：
+
+Attach成功之后，会打印Arthas LOGO。输入 `help`{{execute T2}} 可以获取到更多的帮助信息。
+
+![Arthas Boot](/arthas/scenarios/common-resources/assets/arthas-boot.png)
diff --git a/tutorials/katacoda/command-classloader-cn/classloader.md b/tutorials/katacoda/command-classloader-cn/classloader.md
@@ -0,0 +1,183 @@
+
+> 查看classloader的继承树，urls，类加载信息
+
+`classloader` 命令将 JVM 中所有的classloader的信息统计出来，并可以展示继承树，urls等。
+
+可以让指定的classloader去getResources，打印出所有查找到的resources的url。对于`ResourceNotFoundException`比较有用。
+
+
+### 参数说明
+
+|参数名称|参数说明|
+|---:|:---|
+|[l]|按类加载实例进行统计|
+|[t]|打印所有ClassLoader的继承树|
+|[a]|列出所有ClassLoader加载的类，请谨慎使用|
+|`[c:]`|ClassLoader的hashcode|
+|`[classLoaderClass:]`|指定执行表达式的 ClassLoader 的 class name|
+|`[c: r:]`|用ClassLoader去查找resource|
+|`[c: load:]`|用ClassLoader去加载指定的类|
+
+### 使用参考
+
+先访问一个jsp网页，触发jsp的加载： https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/hello
+
+### 列出所有ClassLoader
+
+`classloader -l`{{execute T2}}
+
+```bash
+$ classloader -l
+ name                                                             loadedCount  hash      parent
+ BootstrapClassLoader                                             2724         null      null
+ com.taobao.arthas.agent.ArthasClassloader@411ce1ab               2009         411ce1ab  sun.misc.Launcher$ExtClassLoader@7494e528
+ com.taobao.arthas.agent.ArthasClassloader@22ae1234               1253         22ae1234  sun.misc.Launcher$ExtClassLoader@7494e528
+ org.apache.jasper.servlet.JasperLoader@65361d9a                  1            65361d9a  TomcatEmbeddedWebappClassLoader
+                                                                                           context: ROOT
+                                                                                           delegate: true
+                                                                                         ----------> Parent Classloader:
+                                                                                         org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
+
+ TomcatEmbeddedWebappClassLoader                                  0            8546cd5   org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
+   context: ROOT
+   delegate: true
+ ----------> Parent Classloader:
+ org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
+
+ org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3  5416         1be6f5c3  sun.misc.Launcher$AppClassLoader@3d4eac69
+ sun.misc.Launcher$AppClassLoader@3d4eac69                        45           3d4eac69  sun.misc.Launcher$ExtClassLoader@7494e528
+ sun.misc.Launcher$ExtClassLoader@7494e528                        4            7494e528  null
+```
+
+* TomcatEmbeddedWebappClassLoader 加载的class数量是0，所以在spring boot embedded tomcat里，它只是一个空壳，所有的类加载都是`LaunchedURLClassLoader`完成的
+
+注意hashcode是变化的，需要先查看当前的ClassLoader信息，提取对应ClassLoader的hashcode。
+
+如果你使用`-c`，你需要手动输入hashcode：`-c <hashcode>`
+
+```bash
+$ classloader -c 65361d9a
+```
+
+对于只有唯一实例的ClassLoader可以通过`--classLoaderClass`指定class name，使用起来更加方便：
+
+```bash
+$ classloader --classLoaderClass org.apache.jasper.servlet.JasperLoader
+```
+`--classLoaderClass` 的值是ClassLoader的类名，只有匹配到唯一的ClassLoader实例时才能工作，目的是方便输入通用命令，而`-c <hashcode>`是动态变化的。
+
+### 列出ClassLoader里加载的所有类
+
+列出上面的`org.apache.jasper.servlet.JasperLoader`加载的类：
+
+`classloader -a --classLoaderClass org.apache.jasper.servlet.JasperLoader`{{execute T2}}
+
+```bash
+$ classloader -a --classLoaderClass org.apache.jasper.servlet.JasperLoader
+ hash:1698045338, org.apache.jasper.servlet.JasperLoader@65361d9a
+ org.apache.jsp.jsp.hello_jsp
+```
+
+### 查看类的classloader层次
+
+`sc -d org.apache.jsp.jsp.hello_jsp`{{execute T2}}
+
+### 查看ClassLoader树
+
+
+`classloader -t`{{execute T2}}
+
+```
+$ classloader -t
++-BootstrapClassLoader
++-sun.misc.Launcher$ExtClassLoader@28cbbddd
+  +-com.taobao.arthas.agent.ArthasClassloader@8c25e55
+  +-sun.misc.Launcher$AppClassLoader@55f96302
+    +-org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
+      +-TomcatEmbeddedWebappClassLoader
+          context: ROOT
+          delegate: true
+        ----------> Parent Classloader:
+        org.springframework.boot.loader.LaunchedURLClassLoader@1be6f5c3
+
+        +-org.apache.jasper.servlet.JasperLoader@21ae0fe2
+```
+
+### 查看URLClassLoader实际的urls
+
+比如上面查看到的spring LaunchedURLClassLoader的 hashcode是`1be6f5c3`，可以通过`-c`参数来指定classloader，或者直接使用`--classLoaderClass`，从而查看URLClassLoader实际的urls：
+
+`classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader`{{execute T2}}
+
+```
+$ classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader
+jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/classes!/
+jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/lib/spring-boot-starter-aop-1.5
+.13.RELEASE.jar!/
+...
+```
+
+### 加载指定ClassLoader里的资源文件
+
+查找指定的资源文件： `classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r logback-spring.xml`{{execute T2}}
+
+```
+$ classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r logback-spring.xml
+ jar:file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/classes!/logback-spring.xml
+```
+也可以尝试查找类的class文件：
+
+`classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r java/lang/String.class`{{execute T2}}
+
+```bash
+$ classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader -r java/lang/String.class
+ jar:file:/Library/Java/JavaVirtualMachines/jdk1.8.0_60.jdk/Contents/Home/jre/lib/rt.jar!/java/lang/String.class
+```
+
+### 尝试加载指定的类
+
+比如用上面的spring LaunchedURLClassLoader 尝试加载 `ch.qos.logback.classic.spi.StackTraceElementProxy` ：
+
+首先使用`sc ch.qos.logback.classic.spi.StackTraceElementProxy`{{execute T2}}查看，可发现未加载：
+
+```bash
+Affect(row-cnt:0) cost in 18 ms.
+```
+
+因而使用spring LaunchedURLClassLoader 尝试加载：
+
+`classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader --load ch.qos.logback.classic.spi.StackTraceElementProxy`{{execute T2}}
+
+```bash
+$ classloader --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader --load ch.qos.logback.classic.spi.StackTraceElementProxy
+load class success.
+ class-info        ch.qos.logback.classic.spi.StackTraceElementProxy
+ code-source       file:/home/scrapbook/tutorial/demo-arthas-spring-boot.jar!/BOOT-INF/lib/logback-classic-1.
+                   1.11.jar!/
+ name              ch.qos.logback.classic.spi.StackTraceElementProxy
+ isInterface       false
+ isAnnotation      false
+ isEnum            false
+ isAnonymousClass  false
+ isArray           false
+ isLocalClass      false
+ isMemberClass     false
+ isPrimitive       false
+ isSynthetic       false
+ simple-name       StackTraceElementProxy
+ modifier          public
+ annotation
+ interfaces        java.io.Serializable
+ super-class       +-java.lang.Object
+ class-loader      +-org.springframework.boot.loader.LaunchedURLClassLoader@5674cd4d
+                     +-sun.misc.Launcher$AppClassLoader@70dea4e
+                       +-sun.misc.Launcher$ExtClassLoader@56a96482
+ classLoaderHash   5674cd4d
+```
+
+再次使用`sc ch.qos.logback.classic.spi.StackTraceElementProxy`{{execute T2}}查看，发现已经加载：
+
+```bash
+ch.qos.logback.classic.spi.StackTraceElementProxy
+Affect(row-cnt:1) cost in 19 ms.
+```
diff --git a/tutorials/katacoda/command-classloader-cn/finish.md b/tutorials/katacoda/command-classloader-cn/finish.md
@@ -0,0 +1,12 @@
+
+在“classloader”中，我们演示了了Arthas的classloader命令。如果有更多的技巧或者使用疑问，欢迎在Issue里提出。
+
+* Issues: https://github.com/alibaba/arthas/issues
+* 文档： https://arthas.aliyun.com/doc
+
+
+如果您在使用Arthas，请让我们知道，您的使用对我们非常重要：[查看](https://github.com/alibaba/arthas/issues/111)
+
+欢迎关注公众号，获取Arthas项目的信息，源码分析，案例实践。
+
+![Arthas公众号](/arthas/scenarios/common-resources/assets/qrcode_gongzhonghao.jpg)
diff --git a/tutorials/katacoda/command-classloader-cn/index.json b/tutorials/katacoda/command-classloader-cn/index.json
@@ -0,0 +1,45 @@
+{
+  "title": "Arthas classloader命令",
+  "description": "Arthas classloader命令",
+  "difficulty": "精通者",
+  "time": "10-20 分钟",
+  "details": {
+    "steps": [
+      {
+        "title": "启动demo",
+        "text": "start-demo.md"
+      },
+      {
+        "title": "启动arthas-boot",
+        "text": "arthas-boot.md"
+      },
+      {
+        "title": "classloader命令",
+        "text": "classloader.md"
+      }
+    ],
+    "intro": {
+      "text": "intro.md"
+    },
+    "finish": {
+      "text": "finish.md"
+    },
+    "assets": {
+      "host01": []
+    }
+  },
+  "environment": {
+    "uilayout": "terminal",
+    "showdashboard": true,
+    "dashboards": [
+      {
+        "name": "Web Port 80",
+        "port": 80
+      }
+    ]
+  },
+  "backend": {
+    "imageid": "java",
+    "environmentsprotocol": "http"
+  }
+}
diff --git a/tutorials/katacoda/command-classloader-cn/intro.md b/tutorials/katacoda/command-classloader-cn/intro.md
@@ -0,0 +1,23 @@
+
+
+
+![Arthas](https://arthas.aliyun.com/doc/_images/arthas.png)
+
+`Arthas` 是Alibaba开源的Java诊断工具，深受开发者喜爱。在线排查问题，无需重启；动态跟踪Java代码；实时监控JVM状态。
+
+`Arthas` 支持JDK 6+，支持Linux/Mac/Windows，采用命令行交互模式，同时提供丰富的 `Tab` 自动补全功能，进一步方便进行问题的定位和诊断。
+
+当你遇到以下类似问题而束手无策时，Arthas可以帮助你解决：
+
+- 这个类从哪个 jar 包加载的？为什么会报各种类相关的 Exception？
+- 我改的代码为什么没有执行到？难道是我没 commit？分支搞错了？
+- 遇到问题无法在线上 debug，难道只能通过加日志再重新发布吗？
+- 线上遇到某个用户的数据处理有问题，但线上同样无法 debug，线下无法重现！
+- 是否有一个全局视角来查看系统的运行状况？
+- 有什么办法可以监控到JVM的实时运行状态？
+- 怎么快速定位应用的热点，生成火焰图？
+
+本教程会以一个普通的Spring Boot应用为例，演示classloader命令。
+
+* Github: https://github.com/alibaba/arthas
+* 文档: https://arthas.aliyun.com/doc/
diff --git a/tutorials/katacoda/command-classloader-cn/start-demo.md b/tutorials/katacoda/command-classloader-cn/start-demo.md
@@ -0,0 +1,14 @@
+
+
+
+
+下载`demo-arthas-spring-boot.jar`，再用`java -jar`命令启动：
+
+`wget https://github.com/hengyunabc/spring-boot-inside/raw/master/demo-arthas-spring-boot/demo-arthas-spring-boot.jar
+java -jar demo-arthas-spring-boot.jar`{{execute T1}}
+
+`demo-arthas-spring-boot`是一个很简单的spring boot应用，源代码：[查看](https://github.com/hengyunabc/spring-boot-inside/tree/master/demo-arthas-spring-boot)
+
+启动之后，可以访问80端口： https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com
+
+![Demo Web](/arthas/scenarios/common-resources/assets/demo-web.png)
diff --git a/tutorials/katacoda/command-classloader-en/arthas-boot.md b/tutorials/katacoda/command-classloader-en/arthas-boot.md
@@ -0,0 +1,16 @@
+
+
+
+
+In the new `Terminal 2`, download `arthas-boot.jar` and start with the `java -jar` command:
+
+`wget https://arthas.aliyun.com/arthas-boot.jar
+java -jar arthas-boot.jar`{{execute T2}}
+
+`arthas-boot` is the launcher for `Arthas`. It lists all the Java processes, and the user can select the target process to be diagnosed.
+
+Select the first process, type `1`{{execute T2}} ，then type `Enter`：
+
+After the Attach is successful, Arthas LOGO is printed. Enter `help`{{execute T2}} for more help.
+
+![Arthas Boot](/arthas/scenarios/common-resources/assets/arthas-boot.png)