Arthas Change Logger Level case scenario #847 (#1337)

tutorials/katacoda/case-ognl-update-logger-level-cn/arthas-boot.md

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+
+
+
+
+在新的`Terminal 2`里，下载`arthas-boot.jar`，再用`java -jar`命令启动：
+
+`wget https://arthas.aliyun.com/doc/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)

tutorials/katacoda/case-ognl-update-logger-level-cn/case-ognl-update-logger-level.md

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+
+
+在这个案例里，动态修改应用的Logger Level。
+
+
+### 查找UserController的ClassLoader
+
+`sc -d com.example.demo.arthas.user.UserController | grep classLoaderHash`{{execute T2}}
+
+```bash
+$ sc -d com.example.demo.arthas.user.UserController | grep classLoaderHash
+ classLoaderHash   1be6f5c3
+```
+
+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
+$ ognl -c 1be6f5c3 @com.example.demo.arthas.user.UserController@logger
+```
+
+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
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader  @org.springframework.boot.SpringApplication@logger
+@Slf4jLocationAwareLog[
+    FQCN=@String[org.apache.commons.logging.LogAdapter$Slf4jLocationAwareLog],
+    name=@String[org.springframework.boot.SpringApplication],
+    logger=@Logger[Logger[org.springframework.boot.SpringApplication]],
+]
+```
+
+`--classLoaderClass` 的值是ClassLoader的类名，只有匹配到唯一的ClassLoader实例时才能工作，目的是方便输入通用命令，而`-c <hashcode>`是动态变化的。
+
+### 用ognl获取logger
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'`{{execute T2}}
+
+```bash
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'
+@Logger[
+    serialVersionUID=@Long[5454405123156820674],
+    FQCN=@String[ch.qos.logback.classic.Logger],
+    name=@String[com.example.demo.arthas.user.UserController],
+    level=null,
+    effectiveLevelInt=@Integer[20000],
+    parent=@Logger[Logger[com.example.demo.arthas.user]],
+    childrenList=null,
+    aai=null,
+    additive=@Boolean[true],
+    loggerContext=@LoggerContext[ch.qos.logback.classic.LoggerContext[default]],
+]
+```
+
+可以知道`UserController@logger`实际使用的是logback。可以看到`level=null`，则说明实际最终的level是从`root` logger里来的。
+
+### 单独设置UserController的logger level
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger.setLevel(@ch.qos.logback.classic.Level@DEBUG)'`{{execute T2}}
+
+再次获取`UserController@logger`，可以发现已经是`DEBUG`了：
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'`{{execute T2}}
+
+```bash
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'
+@Logger[
+    serialVersionUID=@Long[5454405123156820674],
+    FQCN=@String[ch.qos.logback.classic.Logger],
+    name=@String[com.example.demo.arthas.user.UserController],
+    level=@Level[DEBUG],
+    effectiveLevelInt=@Integer[10000],
+    parent=@Logger[Logger[com.example.demo.arthas.user]],
+    childrenList=null,
+    aai=null,
+    additive=@Boolean[true],
+    loggerContext=@LoggerContext[ch.qos.logback.classic.LoggerContext[default]],
+]
+```
+
+### 修改logback的全局logger level
+
+通过获取`root` logger，可以修改全局的logger level：
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@org.slf4j.LoggerFactory@getLogger("root").setLevel(@ch.qos.logback.classic.Level@DEBUG)'`{{execute T2}}
+

tutorials/katacoda/case-ognl-update-logger-level-cn/finish.md

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+
+通过本教程基本掌握了Arthas动态更新应用Logger Level。更多高级特性，可以在下面的进阶指南里继续了解。
+
+* [Arthas进阶](https://arthas.aliyun.com/doc/arthas-tutorials?language=cn&id=arthas-advanced)
+* [Arthas Github](https://github.com/alibaba/arthas)
+* [Arthas 文档](https://arthas.aliyun.com/doc/)
+
+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)

tutorials/katacoda/case-ognl-update-logger-level-cn/index.json

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+{
+  "title": "Arthas 动态更新应用Logger Level 案例",
+  "description": "Arthas 动态更新应用Logger Level 案例",
+  "difficulty": "高级使用者",
+  "time": "10分钟",
+  "details": {
+    "steps": [
+      {
+        "title": "Start demo",
+        "text": "start-demo.md"
+      },
+      {
+        "title": "Start arthas-boot",
+        "text": "arthas-boot.md"
+      },
+      {
+        "title": "动态更新应用Logger Level",
+        "text": "case-ognl-update-logger-level.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"
+  }
+}

tutorials/katacoda/case-ognl-update-logger-level-cn/intro.md

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+
+
+
+![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。
+
+* Github: https://github.com/alibaba/arthas
+* 文档: https://arthas.aliyun.com/doc/

tutorials/katacoda/case-ognl-update-logger-level-cn/start-demo.md

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+
+
+
+
+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)

tutorials/katacoda/case-ognl-update-logger-level-en/arthas-boot.md

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+
+
+
+
+In the new `Terminal 2`, download `arthas-boot.jar` and start with the `java -jar` command:
+
+`wget https://arthas.aliyun.com/doc/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)

tutorials/katacoda/case-ognl-update-logger-level-en/case-ognl-update-logger-level.md

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+
+In this case, show how to dynamically modify the Logger Level.
+
+### Find the ClassLoader of the UserController
+
+`sc -d com.example.demo.arthas.user.UserController | grep classLoaderHash`{{execute T2}}
+
+```bash
+$ sc -d com.example.demo.arthas.user.UserController | grep classLoaderHash
+ classLoaderHash   1be6f5c3
+```
+
+Please write down your classLoaderHash here since it's dynamic. In the case here, it's `1be6f5c3`.
+
+if you use`-c`, you have to manually type hashcode by `-c <hashcode>`.
+
+```bash
+$ ognl -c 1be6f5c3 @com.example.demo.arthas.user.UserController@logger
+```
+
+For classloader with only one instance, it can be specified by `--classLoaderClass` using class name, which is more convenient to use.
+
+```bash
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader  @org.springframework.boot.SpringApplication@logger
+@Slf4jLocationAwareLog[
+    FQCN=@String[org.apache.commons.logging.LogAdapter$Slf4jLocationAwareLog],
+    name=@String[org.springframework.boot.SpringApplication],
+    logger=@Logger[Logger[org.springframework.boot.SpringApplication]],
+]
+```
+
+The value of `--classloaderclass` is the class name of classloader. It can only work when it matches a unique classloader instance. The purpose is to facilitate the input of general commands. However, `-c <hashcode>` is dynamic.
+
+### Use ognl command to get the logger
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'`{{execute T2}}
+
+```bash
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'
+@Logger[
+    serialVersionUID=@Long[5454405123156820674],
+    FQCN=@String[ch.qos.logback.classic.Logger],
+    name=@String[com.example.demo.arthas.user.UserController],
+    level=null,
+    effectiveLevelInt=@Integer[20000],
+    parent=@Logger[Logger[com.example.demo.arthas.user]],
+    childrenList=null,
+    aai=null,
+    additive=@Boolean[true],
+    loggerContext=@LoggerContext[ch.qos.logback.classic.LoggerContext[default]],
+]
+```
+
+The user can know that `UserController@logger` actually uses logback. Because `level=null`, the actual final level is from the `root` logger.
+
+### Change the logger level of UserController
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger.setLevel(@ch.qos.logback.classic.Level@DEBUG)'`{{execute T2}}
+
+Get `UserController@logger` again, the user can see that it is already `DEBUG`:
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'`{{execute T2}}
+
+```bash
+$ ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@com.example.demo.arthas.user.UserController@logger'
+@Logger[
+    serialVersionUID=@Long[5454405123156820674],
+    FQCN=@String[ch.qos.logback.classic.Logger],
+    name=@String[com.example.demo.arthas.user.UserController],
+    level=@Level[DEBUG],
+    effectiveLevelInt=@Integer[10000],
+    parent=@Logger[Logger[com.example.demo.arthas.user]],
+    childrenList=null,
+    aai=null,
+    additive=@Boolean[true],
+    loggerContext=@LoggerContext[ch.qos.logback.classic.LoggerContext[default]],
+]
+```
+
+### Change the global logger level of the logback
+
+By getting the `root` logger, the user can modify the global logger level:
+
+`ognl --classLoaderClass org.springframework.boot.loader.LaunchedURLClassLoader '@org.slf4j.LoggerFactory@getLogger("root").setLevel(@ch.qos.logback.classic.Level@DEBUG)'`{{execute T2}}
+

tutorials/katacoda/case-ognl-update-logger-level-en/finish.md

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+
+Through this tutorial, you can know how to Change Logger Level. More advanced features can be found in the Advanced Guide below.
+
+* [Arthas Advanced](https://arthas.aliyun.com/doc/arthas-tutorials?language=en&id=arthas-advanced)
+* [Arthas Github](https://github.com/alibaba/arthas)
+* [Arthas Documentation](https://arthas.aliyun.com/doc/en)

tutorials/katacoda/case-ognl-update-logger-level-en/index.json

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+{
+  "title": "Arthas Change Logger Level",
+  "description": "Arthas Change Logger Level",
+  "difficulty": "expert",
+  "time": "10 minutes",
+  "details": {
+    "steps": [
+      {
+        "title": "Start demo",
+        "text": "start-demo.md"
+      },
+      {
+        "title": "Start arthas-boot",
+        "text": "arthas-boot.md"
+      },
+      {
+        "title": "Change Logger Level",
+        "text": "case-ognl-update-logger-level.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"
+  }
+}

tutorials/katacoda/case-ognl-update-logger-level-en/intro.md

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+
+
+
+![Arthas](https://arthas.aliyun.com/doc/_images/arthas.png)
+
+`Arthas` is a Java diagnostic tool open-sourced by Alibaba middleware team. Arthas helps developers in trouble-shooting issues in production environment for Java based applications without modifying code or restarting servers.
+
+`Arthas` supports JDK 6+, supports Linux/Mac/Windows.
+
+* Github: https://github.com/alibaba/arthas
+* Documentation: https://arthas.aliyun.com/doc/en

tutorials/katacoda/case-ognl-update-logger-level-en/start-demo.md

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+
+
+
+
+Download `demo-arthas-spring-boot.jar`, and start with `java -jar` command:
+
+`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` is a simple Spring Boot demo, the source code here: [View](https://github.com/hengyunabc/spring-boot-inside/tree/master/demo-arthas-spring-boot)
+
+After booting, access port 80: https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com
+
+![Demo Web](/arthas/scenarios/common-resources/assets/demo-web.png)