add Troubleshooting HTTP request returns 404 case scenario. (#1340)

tutorials/katacoda/case-http-404-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-http-404-cn/case-http-404.md

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+
+
+在这个案例里，展示排查HTTP 404问题的技巧。
+
+访问： https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/a.txt 
+
+结果是：
+
+```
+Something went wrong: 404 Not Found
+```
+
+那么到底是哪个Servlet处理了这个请求，返回了404？
+
+### 跟踪所有的Servlet函数
+
+开始trace：
+
+`trace javax.servlet.Servlet * > /tmp/servlet.txt`{{execute T2}}
+
+访问： https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/a.txt
+
+在`Terminal 3`里，查看`/tmp/servlet.txt`的内容：
+
+`less /tmp/servlet.txt`{{execute T3}}
+
+`/tmp/servlet.txt`里的内容会比较多，需要耐心找到调用树里最长的地方。
+
+可以发现请求最终是被`freemarker`处理的：
+
+```
+`---[13.974188ms] org.springframework.web.servlet.ViewResolver:resolveViewName()
+    +---[0.045561ms] javax.servlet.GenericServlet:<init>()
+    +---[min=0.045545ms,max=0.074342ms,total=0.119887ms,count=2] org.springframework.web.servlet.view.freemarker.FreeMarkerView$GenericServletAdapter:<init>()
+    +---[0.170895ms] javax.servlet.GenericServlet:init()
+    |   `---[0.068578ms] javax.servlet.GenericServlet:init()
+    |       `---[0.021793ms] javax.servlet.GenericServlet:init()
+    `---[0.164035ms] javax.servlet.GenericServlet:getServletContext()
+```

tutorials/katacoda/case-http-404-cn/finish.md

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+
+通过本教程基本掌握了Arthas排查HTTP请求返回404。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-http-404-cn/index.json

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+{
+  "title": "Arthas 排查HTTP请求返回404 案例",
+  "description": "Arthas 排查HTTP请求返回404 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": "排查HTTP请求返回404",
+        "text": "case-http-404.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-http-404-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-http-404-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-http-404-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-http-404-en/case-http-404.md

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+
+
+In this case, the user will resolve the HTTP 404 issue.
+
+Visit: https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/a.txt 
+
+The result is:
+
+```
+Something went wrong: 404 Not Found
+```
+
+So which servlet is handle this request and returning 404?
+
+### Trace all the Servlet methods
+
+Start trace:
+
+`trace javax.servlet.Servlet * > /tmp/servlet.txt`{{execute T2}}
+
+Visit: https://[[HOST_SUBDOMAIN]]-80-[[KATACODA_HOST]].environments.katacoda.com/a.txt
+
+In `Terminal 3`, view the contents of `/tmp/servlet.txt`:
+
+`less /tmp/servlet.txt`{{execute T3}}
+
+The contents of `/tmp/servlet.txt` will be more, and you need to be patient to find the longest level in the call tree.
+
+It can be found that the request is handled by `freemarker`:
+
+```
+`---[13.974188ms] org.springframework.web.servlet.ViewResolver:resolveViewName()
+    +---[0.045561ms] javax.servlet.GenericServlet:<init>()
+    +---[min=0.045545ms,max=0.074342ms,total=0.119887ms,count=2] org.springframework.web.servlet.view.freemarker.FreeMarkerView$GenericServletAdapter:<init>()
+    +---[0.170895ms] javax.servlet.GenericServlet:init()
+    |   `---[0.068578ms] javax.servlet.GenericServlet:init()
+    |       `---[0.021793ms] javax.servlet.GenericServlet:init()
+    `---[0.164035ms] javax.servlet.GenericServlet:getServletContext()
+```

tutorials/katacoda/case-http-404-en/finish.md

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+
+Through this tutorial, you can know how to Troubleshooting HTTP request returns 404. 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-http-404-en/index.json

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+{
+  "title": "Arthas Troubleshooting HTTP request returns 404",
+  "description": "Arthas Troubleshooting HTTP request returns 404",
+  "difficulty": "expert",
+  "time": "10 minutes",
+  "details": {
+    "steps": [
+      {
+        "title": "Start demo",
+        "text": "start-demo.md"
+      },
+      {
+        "title": "Start arthas-boot",
+        "text": "arthas-boot.md"
+      },
+      {
+        "title": "Troubleshooting HTTP request returns 404",
+        "text": "case-http-404.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-http-404-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-http-404-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)