Translate VisualDL front-end & back-end info (#421)

docs/develop/how_to_dev_backend_cn.md

 # 后台指南
 
-VisualDL has three components.
-1. The Python/C++ SDK that logs the data during training.
-1. The single page client side app that visualizes training data.
-1. The server powered by Flask, reads the log data and delivers it to the client side app for displaying graphs (scalars/histograms) and embeddings.
+VisualDL有三个功能模块.
+1. 在训练过程中用来记录日志数据的 Python/C++ SDK。
+1. 用来可视化训练数据的客户端单页面应用。
+1. 后端 Flask 服务器，用来读取日志数据并提供给前端应用，以便前端可以展示各类图标，如柱状图，嵌入图等等.
 
-This doc will go over Backend / SDK structure with development guide.
+这篇文档用来介绍 后端/SDK 的架构，以及指导用户自行开发。
 
-For front end architecture and development guide, looks [here](https://github.com/PaddlePaddle/VisualDL/blob/develop/docs/how_to_dev_frontend_en.md)
+关于前端的架构和开发指南，请看 [这里](https://github.com/PaddlePaddle/VisualDL/blob/develop/docs/how_to_dev_frontend_cn.md)
 
 
-## Code structure
+## 代码结构
 
-All backend and sdk logic is under visualdl sub directory
+所有后端和 SDK 的逻辑都在 visualdl 子文件夹里面
 
 ```
 ├── build
@@ -27,20 +27,21 @@ All backend and sdk logic is under visualdl sub directory
     └── utils    - Helper function and classes
 ```
 
-## Development
+## 开发
 
-Any code changes in ```server``` folder, simply run
+任何在 ```server``` 文件夹里代码的改动，都可以通过运行以下命令
 
 ```
 python visualdl/server/visualDL --logdir={LOG_DIR} --port=8080
 ```
-to restart flask server
+来重启 Flask 服务器
 
-Notice if you install visualDL from pip install wheel, make sure resetting PYTHONPATH to get the command work.
+需要注意的是如果你通过 `pip install wheel` 来安装 visualDL, 请确认重置 PYTHONPATH，以便是的上述命令可以运行。
 
-Any code changes in ```logic```, ```python```, ```storage```, ```utils``` is modified, need to rebuild core.so or sdk to get effect.
+任何在 ```logic```, ```python```, ```storage```, ```utils``` 中的代码修改，都需要重新 build core.so 或 SDK 来确保生效。
+
+要么运行 VisualDL/build.sh 脚本来重新安装所有组件，要么安装特定的目标组件如下：
 
-Either run VisualDL/build.sh that builds everything or a target like this
 ```
 mkdir {VisualDL_ROOT}/build
 cd build
@@ -49,12 +50,12 @@ make {TARGET MODULE}
 ```
 
 
-## Tests
+## 测试
 
-Modification in SDK API or any major function should be adding test cases.
+任何关于 SDK API 或其他核心组件的修改都必须提供相应的测试案例。
 
 
-In {VisualDL_ROOT}/CMakeList.txt, we have a list of test files as target
+在 {VisualDL_ROOT}/CMakeList.txt 中，我们有一个测试文件清单
 
 ```
 add_executable(vl_test
@@ -70,7 +71,7 @@ add_executable(vl_test
         )
 ```
 
-Add new test cases in corresponding files where code is modified or create new test files. You can make vl_test target and just run vl_test executable for all test cases.
+在相应被修改的代码文件处添加测试用例或者新的测试文件。你可以制作 vl_test 目标或者运行 vl_test 可执行文件来运行所有测试案例。
 
 ```
 mkdir {VisualDL_ROOT}/build
@@ -80,45 +81,45 @@ make vl_test
 ./vl_test
 ```
 
-## Backend / SDK architecture
+## 后端 / SDK 架构
 
-### Server
+### 服务器
 
-- Implement a server using a lightweight framework Flask, provides two services:
-  - Host a main application with support of a front end web app
-  - Provide a series of HTTP end points, using JSON for front end data communication
-- ```visualDL``` : main app entry point
-  - defines server arguments and config
-  - provides API and router for front end
-- ```lib.py``` : delegate wrapper for function calls
-  - read and cache log data
-  - convert data to JSON
-  - retry mechanism
-- ```graph.py``` and ```onnx```
-  - graph.py defines the logic to read and parse onnx model file
-  - create edges and nodes as JSON format for front end to read
-  - onnx folder contains onnx protobuf interface that ports from onnx repo
+- 采用轻量级 Flask 框架来搭建服务器并提供以下两种服务
+  - 搭建主程序来支持前端应用
+  - 提供一系列 HTTP 访问点，通过返回的 JSON 来和前端沟通
+- ```visualDL``` : 主程序入口
+  - 定义了服务器参数
+  - 给前端提供 API 和 路由匹配
+- ```lib.py``` : 调用库函数的入口
+  - 读取并缓存日志数据
+  - 把数据变成 JSON
+  - 重试机制
+- ```graph.py``` 和 ```onnx```
+  - graph.py 定义了读取和解析 ONNX 模型文件的逻辑
+  - 给前端提供具有结点和边信息的图模型JSON
+  - ONNX 文件夹包含从 ONNX 代码库移植来的 ONNX Protobuf 接口
 
 
-### Logic & SDK
+### 逻辑和 SDK
 
 #### Python SDK
-- ```pybind.cc``` : create python interface from C++ layer
-- ```storage.py``` : ```LogReader``` and ```LogWriter``` APIs of Python SDK that maps to pybind
+- ```pybind.cc``` : 为 C++ 创建 Python 接口
+- ```storage.py``` : Python SDK 的 ```LogReader``` 和 ```LogWriter``` API，对应于 pybind
 
 #### C++ SDK
 - ```sdk.h```
-  - defines ```LogReader``` and ```LogWriter``` APIs of C++ SDK
-  - defines feature components such as ```Scalar```, ```Histogram```, ```Image``` and their corresponding component```Reader```
-- ```sdk.cc``` : implements ```Reader``` to use ```Storage``` layer for reading and writing
-
-#### Information Container
-- Currently it just handles logic of sync cycle (when to write)
-
-#### Storage
-- Defines log data format as following:
-  - ```Storage``` : main set of data with different modes such as "train" or "test", contain multiple ```Tablet```
-  - ```Tablet``` : group a single type of data with ```tag```. One tablet will only represent one data type such as scalar, histogram, image and contains multiple ```Record```. For example one tablet represents a line in scalar chart.
-  - ```Record``` : represent any data structure for any component
-- Handles the actual logic to serialize to disk and deserialize from disk
-- ```storage.proto```: protobuf file that defines the exact interface to be read/write
+  - 定义了 ```LogReader``` 和 ```LogWriter``` 的 C++ SDK 的API
+  - 定义了诸如```Scalar```, ```Histogram```, ```Image``` 的功能模块以及它们相应的 ```Reader```
+- ```sdk.cc``` : 实现了 ```Reader``` 以便使用 ```Storage``` 层来完成读和写
+
+#### 信息容器
+- 目前我们仅仅处理写操作时的同步逻辑
+
+#### 存储
+- 定义日志数据的格式如下：
+  - ```Storage``` : 主数据存储地， 包含不同模式，比如 "train" 或 "test", 包含多个 ```Tablet```
+  - ```Tablet``` : 把同一个数据类型用 ```tag``` 打包. 一个面板只代表一个数据类型，比如 ‘数值’， ‘柱状图’， ‘图像’。 可以包含多个 ```Record```。 比如，一个面板可以表达在 ‘数值’ 图像中的一条线。
+  - ```Record``` : 最小单位，代表任何功能模块中的任何数据结构。
+- 处理和磁盘之间的 序列化/去序列化 传输
+- ```storage.proto```: 用来定义确切 读/写 接口的 protobuf 文件。

docs/develop/how_to_dev_frontend_cn.md

 # 前端指南
 
-VisualDL has three components.
-1. The Python/C++ SDK that logs the data during training.
-1. The single page client side app that visualized training data.
-1. The server (powered on Flask) that reads the logs data and delivers it to the client side app for displaying graphs (scalars/histograms) and embeddings.
+VisualDL有三个功能模块.
+1. 在训练过程中用来记录日志数据的 Python/C++ SDK。
+1. 用来可视化训练数据的客户端单页面应用。
+1. 后端 Flask 服务器，用来读取日志数据并提供给前端应用，以便前端可以展示各类图标，如柱状图，嵌入图等等.
 
-This article will go over the basic web-app architecture and development guide.
+这篇文档用来介绍前端的架构，以及指导用户自行开发。
 
-## TL;DR
-If you are not interested in the details of mumbo jumbo and want to start development as soon as possible, please run the following commands.
+## 长话短说
+如果您不关心细节，而是想马上开始开发，请运行以下命令。
 
-To clone the repo and to prepare the environment
+克隆代码库以及准备开发环境
 ```bash
 git clone git@github.com:PaddlePaddle/VisualDL.git
 cd VisualDL
@@ -19,60 +19,62 @@ pip install -r requirements.txt
 # Set up the node dependencies and the VisualDL SDK
 ./scripts/setup_dev_env.sh
 ```
-To run the dev server and start coding
+运行开发服务器，开始码代码喽~
 ```bash
 ./scripts/start_dev_server.sh --logdir=<LOG_DIR>
 ```
-The script will run a dev server at `http://0.0.0.0:8040`. Open a browser and navigate to `http://0.0.0.0:8040/` to see it
+这个脚本会在 `http://0.0.0.0:8040` 启动一个开发服务器。打开浏览器，来到 `http://0.0.0.0:8040/`，您就可以发现开发版的 VisualDL 啦~
 
-## Web App Architecture
 
-The VisualDL Web app uses multiple frameworks to help manage the project. They are
+## 前端网络应用架构
 
-1. webpack: To manage all assets
-1. npm: To manage dependencies
-1. Vue: Javascript Component framework
-1. ECharts: To pilot charts
+VisualDL 前端网络应用使用多个框架来管理项目。这些框架包括：
+
+1. webpack: 管理所有组件
+1. npm: 管理依赖性
+1. Vue: 流行的Javascript组件框架
+1. ECharts: 专业的数据可视化库
 
 ## Webpack
-webpack is a module bundler. Its main purpose is to bundle JavaScript files for usage in a browser.
+webpack 是一个模块打包框架. 它主要的工作是把前端JavaScript文件带包在一起，提供给浏览器。
 
-For a long time, web developers need to worry about backward compatibility or how to support different versions of browsers.
-webpack can help to transpile the Javascript files to the version where a browser can take. The developers don't need to implement version specific code anymore.
-It can also help to minify and uglify Javascript files. In a nutshell, webpack helps to manage all of your assets (.js, .css, .gif, .sass, etc) so you don't have to.
+很长一段时间，网络开发者不得不关心如何向后兼容以及如何支持不同的浏览器。Webpack可以把JavaScript代码同步编译到不同的版本，以便适应不同的浏览器。
+网络开发者不必再担心为了特定的浏览器而订制特定的代码版本。
+它也可以 '最小化' 和 '丑化' JavaScript文件。一句话，webpack可以帮助管理你的所有资料（.js, .css, .gif, .sass, etc）.
 
-To learn more about [webpack](https://webpack.js.org/).
+更多Webpack内容请参考[这里](https://webpack.js.org/).
 
 ## npm package
-npm is the package manager for JavaScript and is a great tool to manage multiple dependencies. To confirm that you have npm installed. Please run this command
+npm 是一个JavaScript的代码包管理器。而且是一个很优秀的管理多种依赖性的工具。请运行以下命令来确保您已经安装了 npm
+
 ``` bash
 npm -v
 ```
-If your environment does not have npm already, please [download npm](https://www.npmjs.com/get-npm).
+如果您的环境没有npm，请在 [这里](https://www.npmjs.com/get-npm) 下载.
 
-The basic packaging information is stored in `package.json`. It specifies build scripts and dependencies for each environment.
-npm reads `package.json` to build different package according to the packaging script.
-If you are not familiar with npm, please refer to the [npm documentation](https://docs.npmjs.com/) for more detail.
+基本的包裹信息在  `package.json`中。它用来定义构造脚本的依赖关系。
+npm 读取 `package.json` 来根据打包脚本构造不同的包裹。
+如果您对 npm 还不熟，请看 [这里](https://docs.npmjs.com/)。
 
-Install the necessary dependencies by running
+运行如下命令来安装所需的依赖库
 ```bash
 # Navigate to the web-app folder
 cd VisualDL/frontend
 npm install
 ```
 
-This command will go through `package.json` and install the dependencies in the local node_modules folder.
+这个命令会逐行检查`package.json`并且安装相应的依赖库到本地的 `node_modules` 文件夹里
 
 ## Vue
 
-Vue is a JavaScript component framework that helps the developer to implement web component in MVVM architecture pattern.
+Vue 是一个很潮的 JavaScript 框架。可以帮助开发者用 MVM 架构模式 开发网络组件。
 
-Vue allows you to define a self-contained view model in a .vue file and attach view model objects to DOM objects.
+Vue 允许开发者自己定义视图模型并保存在 .vue 文件里。然后把视图模型绑定到 DOM 对象上。
 
-To learn more about [Vue](https://vuejs.org/)
+更多内容参见 [这里](https://vuejs.org/)
 
 ## ECharts
 
-We use ECharts javascript library to render our charts and graphs. ECharts is a leading open source charting library that supports numerous data visualization.
+我们使用一个国内流行的 ECharts 来显示图表和图像。 ECharts 是领先的开源前端数据可视化库。它支持多种多样的数据可视化需求。
 
-To learn more about ECharts framework, please visit [ECharts](https://ecomfe.github.io/echarts-doc/public/en/index.html).
+更多关于 [ECharts](https://ecomfe.github.io/echarts-doc/public/en/index.html)的信息。