koa和egg项目webpack热更新实现

迷南。 2021-12-24 15:21 357阅读 0赞

## 背景 ##

在用Node.js+Webpack构建的方式进行开发时, 我们希望能实现修改代码能实时刷新页面UI的效果.  
这个特性webpack本身是支持的, 而且基于koa也有现成的koa-webpack-hot-middleware 和 koa-webpack-dev-middleware 封装好的组件支持.  
不过这里如果需要支持Node.js服务器端修改代码自动重启webpack自动编译功能就需要cluster来实现.

今天这里要讲的是如何在koa和egg应用实现Node.js应用重启中的webpack热更新功能. 要实现egg项目中webpack友好的开发体验, 需要解决如下三个问题.

## 问题 ##

*  如何解决Node.js服务器端代码修改应用重启避免webpack重新编译.
 *  如何访问js,css,image等静态资源.
 *  如何处理本地开发webpack热更新内存存储读取和线上应用本机文件读取逻辑分离.

## 基于koa的webpack编译和热更新实现 ##

在koa项目中, 通过koa-webpack-dev-middleware和koa-webpack-hot-middleware可以实现webpack编译内存存储和热更新功能, 代码如下:

const compiler = webpack(webpackConfig);
    const devMiddleware = require('koa-webpack-dev-middleware')(compiler, options);
    const hotMiddleware = require('koa-webpack-hot-middleware')(compiler, options);
    app.use(devMiddleware);
    app.use(hotMiddleware);

如果按照上面实现, 可以满足修改修改客户端代码实现webpack自动变编译和UI界面热更新的功能, 但如果是修改Node.js服务器端代码重启后就会发现webpack会重新编译,  
这不是我们要的效果.原因是因为middleware是依赖app的生命周期, 当app销毁时, 对应webpack compiler实例也就没有了, 重启时会重新执行middleware初始化工作.  
针对这个我们可以通过Node.js cluster实现, 大概思路如下:

#### 通过cluster worker 启动App应用 ####

if (cluster.isWorker) {
      const koa = require('koa');
        app.listen(8888, () =>{
            app.logger.info('The server is running on port: 9999');
        });
    }

#### 通过cluster master 启动一个新的koa应用, 并启动 webpack 编译. ####

#### 通过chokidar库监听文件夹的文件修改, 然后重启worker, 这样就能保证webpack compiler实例不被销毁. ####

#### worker 通过`process.send` 向 master 发现消息, `process.on` 监听 master返回的消息 ####

*  首先我们看看本地文件读取的实现, 在context上面挂载readFile方法, 进行view render时, 调用`app.context.readFile` 方法.

app.context.readFile = function(fileName){
      const filePath = path.join(config.baseDir, config.staticDir, fileName);
      return new Promise((resolve, reject) =>{
        fs.readFile(filePath, CHARSET, function(err, data){
          if (err) {
            reject(err);
          } else {
            resolve(data);
          }
        });
      });
    };

*  通过覆写worker `app.context.readFile` 方法, 这样进行本地开发时,开启该插件就可以无缝的从webpack编译内存系统里面读取文件

app.context.readFile = (fileName) =>{
      return new Promise((resolve, reject) =>{
        process.send({ action: Constant.EVENT_FILE_READ, fileName });
        process.on(Constant.EVENT_MESSAGE, (msg) =>{
          resolve(msg.content);
        });
      });
    };

#### master 通过监听worker发过来的消息, 获取webpack编译进度和读取webpack compiler内存系统文件内容 ####

cluster.on(Constant.EVENT_MESSAGE, (worker, msg) =>{
            switch (msg.action) {
                case Constant.EVENT_WEBPACK_BUILD_STATE: {
                    const data = {
                        action: Constant.EVENT_WEBPACK_BUILD_STATE,
                        state: app.webpack_client_build_success && app.webpack_server_build_success
                    };
                    worker.send(data);
                    break;
                }
                case Constant.EVENT_FILE_READ: {
                    const fileName = msg.fileName;
                    try {
                        const compiler = app.compiler;
                        const filePath = path.join(compiler.outputPath, fileName);
                        const content = app.compiler.outputFileSystem.readFileSync(filePath).toString(Constant.CHARSET);
                        worker.send({ fileName, content });
                    } catch (e) {
                        console.log(`read file ${fileName} error`, e.toString());
                    }
                    break;
                }
                default:
                    break;
            }
    });

## 基于egg的webpack编译和热更新实现 ##

通过上面koa的实现思路, egg实现就更简单了. 因为egg已经内置了worker和agent通信机制以及自动重启功能.

*  worker和agent通信机制: [https://eggjs.org/zh-cn/core/cluster-and-ipc.html][https_eggjs.org_zh-cn_core_cluster-and-ipc.html]
 *  实现egg项目服务器代码修改项目自动重启的功能可以使用[egg-development][]插件.

#### app.js (worker) 通过 检测webpack 编译进度 ####

*  通过`app.messenger.sendToAgent` 向agent发送消息
 *  通过`app.messenger.on` 监听agent发送过来的消息

app.use(function* (next) {
      if (app.webpack_server_build_success && app.webpack_client_build_success) {
        yield* next;
      } else {
        const serverData = yield new Promise(resolve => {
          this.app.messenger.sendToAgent(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, {
            webpackBuildCheck: true,
          });
          this.app.messenger.on(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, data => {
            resolve(data);
          });
        });
        app.webpack_server_build_success = serverData.state;
    
        const clientData = yield new Promise(resolve => {
          this.app.messenger.sendToAgent(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, {
            webpackBuildCheck: true,
          });
          this.app.messenger.on(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, data => {
            resolve(data);
          });
        });
    
        app.webpack_client_build_success = clientData.state;
    
        if (!(app.webpack_server_build_success && app.webpack_client_build_success)) {
          if (app.webpack_loading_text) {
            this.body = app.webpack_loading_text;
          } else {
            const filePath = path.resolve(__dirname, './lib/template/loading.html');
            this.body = app.webpack_loading_text = fs.readFileSync(filePath, 'utf8');
          }
        } else {
          yield* next;
        }
      }
    });
    
    app.messenger.on(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, data => {
      app.webpack_server_build_success = data.state;
    });
    
    app.messenger.on(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, data => {
      app.webpack_client_build_success = data.state;
    });

#### agent.js 启动koa实例和webpack编译流程 ####

这里client和server编译单独启动koa实例, 而不是一个是因为在测试时发现编译会导致热更新冲突.

*  启动webpack client 编译模式, 负责编译browser运行文件(js,css,image等静态资源)

'use strict';
    
    const webpack = require('webpack');
    const koa = require('koa');
    const cors = require('kcors');
    const app = koa();
    app.use(cors());
    const Constant = require('./constant');
    const Utils = require('./utils');
    
    module.exports = agent => {
    
      const config = agent.config.webpack;
      const webpackConfig = config.clientConfig;
      const compiler = webpack([webpackConfig]);
    
      compiler.plugin('done', compilation => {
        // Child extract-text-webpack-plugin:
        compilation.stats.forEach(stat => {
          stat.compilation.children = stat.compilation.children.filter(child => {
            return child.name !== 'extract-text-webpack-plugin';
          });
        });
        agent.messenger.sendToApp(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, { state: true });
        agent.webpack_client_build_success = true;
      });
    
      const devMiddleware = require('koa-webpack-dev-middleware')(compiler, {
        publicPath: webpackConfig.output.publicPath,
        stats: {
          colors: true,
          children: true,
          modules: false,
          chunks: false,
          chunkModules: false,
        },
        watchOptions: {
          ignored: /node_modules/,
        },
      });
    
      const hotMiddleware = require('koa-webpack-hot-middleware')(compiler, {
        log: false,
        reload: true,
      });
    
      app.use(devMiddleware);
      app.use(hotMiddleware);
    
      app.listen(config.port, err => {
        if (!err) {
          agent.logger.info(`start webpack client build service: http://127.0.0.1:${config.port}`);
        }
      });
    
      agent.messenger.on(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, () => {
        agent.messenger.sendToApp(Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, { state: agent.webpack_client_build_success });
      });
    
      agent.messenger.on(Constant.EVENT_WEBPACK_READ_CLIENT_FILE_MEMORY, data => {
        const fileContent = Utils.readWebpackMemoryFile(compiler, data.filePath);
        if (fileContent) {
          agent.messenger.sendToApp(Constant.EVENT_WEBPACK_READ_CLIENT_FILE_MEMORY_CONTENT, {
            fileContent,
          });
        } else {
          agent.logger.error(`webpack client memory file[${data.filePath}] not exist!`);
          agent.messenger.sendToApp(Constant.EVENT_WEBPACK_READ_CLIENT_FILE_MEMORY_CONTENT, {
            fileContent: '',
          });
        }
      });
    };

*  启动webpack server 编译模式, 负责编译服务器端Node运行文件

'use strict';
    
    const webpack = require('webpack');
    const koa = require('koa');
    const cors = require('kcors');
    const app = koa();
    app.use(cors());
    const Constant = require('./constant');
    const Utils = require('./utils');
    
    module.exports = agent => {
      const config = agent.config.webpack;
      const serverWebpackConfig = config.serverConfig;
      const compiler = webpack([serverWebpackConfig]);
    
      compiler.plugin('done', () => {
        agent.messenger.sendToApp(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, { state: true });
        agent.webpack_server_build_success = true;
      });
    
      const devMiddleware = require('koa-webpack-dev-middleware')(compiler, {
        publicPath: serverWebpackConfig.output.publicPath,
        stats: {
          colors: true,
          children: true,
          modules: false,
          chunks: false,
          chunkModules: false,
        },
        watchOptions: {
          ignored: /node_modules/,
        },
      });
    
      app.use(devMiddleware);
    
      app.listen(config.port + 1, err => {
        if (!err) {
          agent.logger.info(`start webpack server build service: http://127.0.0.1:${config.port + 1}`);
        }
      });
    
      agent.messenger.on(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, () => {
        agent.messenger.sendToApp(Constant.EVENT_WEBPACK_SERVER_BUILD_STATE, { state: agent.webpack_server_build_success });
      });
    
      agent.messenger.on(Constant.EVENT_WEBPACK_READ_SERVER_FILE_MEMORY, data => {
        const fileContent = Utils.readWebpackMemoryFile(compiler, data.filePath);
        if (fileContent) {
          agent.messenger.sendToApp(Constant.EVENT_WEBPACK_READ_SERVER_FILE_MEMORY_CONTENT, {
            fileContent,
          });
        } else {
          // agent.logger.error(`webpack server memory file[${data.filePath}] not exist!`);
          agent.messenger.sendToApp(Constant.EVENT_WEBPACK_READ_SERVER_FILE_MEMORY_CONTENT, {
            fileContent: '',
          });
        }
      });
    };

*  挂载 webpack 内存读取实例到`app`上面, 方便业务扩展实现, 代码如下:

我们通过worker向agent发送消息, 就可以从webpack内存获取文件内容, 下面简单封装一下:

class FileSystem {
    
      constructor(app) {
        this.app = app;
      }
    
      readClientFile(filePath, fileName) {
        return new Promise(resolve => {
          this.app.messenger.sendToAgent(Constant.EVENT_WEBPACK_READ_CLIENT_FILE_MEMORY, {
            filePath,
            fileName,
          });
          this.app.messenger.on(Constant.EVENT_WEBPACK_READ_CLIENT_FILE_MEMORY_CONTENT, data => {
            resolve(data.fileContent);
          });
        });
      }
    
      readServerFile(filePath, fileName) {
        return new Promise(resolve => {
          this.app.messenger.sendToAgent(Constant.EVENT_WEBPACK_READ_SERVER_FILE_MEMORY, {
            filePath,
            fileName,
          });
          this.app.messenger.on(Constant.EVENT_WEBPACK_READ_SERVER_FILE_MEMORY_CONTENT, data => {
            resolve(data.fileContent);
          });
        });
      }
    }

在app/extend/application.js 挂载webpack实例

#### 本地开发webpack热更新内存存储读取和线上应用文件读取逻辑分离 ####

基于上面编译流程实现和webpack实例, 我们很容易实现koa方式的本地开发和线上运行代码分离. 下面我们就以vue 服务器渲染render实现为例:

在egg-view插件开发规范中,我们会在ctx上面挂载render方法, render方法会根据文件名进行文件读取, 模板与数据编译, 从而实现模板的渲染.如下就是controller的调用方式:

exports.index = function* (ctx) {
      yield ctx.render('index/index.js', Model.getPage(1, 10));
    };

其中最关键的一步是根据文件名进行文件读取, 只要view插件设计时, 把文件读取的方法暴露出来(例如上面的koa的readFile),就可以实现本地开发webpack热更新内存存储读取.

*  vue view engine设计实现:

class Engine {
      constructor(app) {
        this.app = app;
        this.config = app.config.vue;
        this.cache = LRU(this.config.cache);
        this.fileLoader = new FileLoader(app, this.cache);
        this.renderer = vueServerRenderer.createRenderer();
        this.renderOptions = Object.assign({
          cache: this.cache,
        }, this.config.renderOptions);
      }
    
      createBundleRenderer(code, renderOptions) {
        return vueServerRenderer.createBundleRenderer(code, Object.assign({}, this.renderOptions, renderOptions));
      }
    
      * readFile(name) {
        return yield this.fileLoader.load(name);
      }
    
      render(code, data = {}, options = {}) {
        return new Promise((resolve, reject) => {
          this.createBundleRenderer(code, options.renderOptions).renderToString(data, (err, html) => {
            if (err) {
              reject(err);
            } else {
              resolve(html);
            }
          });
        });
      }
    }

*  ctx.render 方法

class View {
      constructor(ctx) {
        this.app = ctx.app;
      }
    
      * render(name, locals, options = {}) {
        // 我们通过覆写app.vue.readFile即可改变文件读取逻辑
        const code = yield this.app.vue.readFile(name);
        return this.app.vue.render(code, { state: locals }, options);
      }
    
      renderString(tpl, locals) {
        return this.app.vue.renderString(tpl, locals);
      }
    }
    
    module.exports = View;

服务器view渲染插件实现 [egg-view-vue][]

*  通过webpack实例覆写app.vue.readFile 改变从webpack内存读取文件内容.

if (app.vue) {
      app.vue.readFile = fileName => {
        const filePath = path.isAbsolute(fileName) ? fileName : path.join(app.config.view.root[0], fileName);
        if (/\.js$/.test(fileName)) {
          return app.webpack.fileSystem.readServerFile(filePath, fileName);
        }
        return app.webpack.fileSystem.readClientFile(filePath, fileName);
      };
    }
    
    app.messenger.on(app.webpack.Constant.EVENT_WEBPACK_CLIENT_BUILD_STATE, data => {
      if (data.state) {
        const filepath = app.config.webpackvue.build.manifest;
        const promise = app.webpack.fileSystem.readClientFile(filepath);
        promise.then(content => {
          fs.writeFileSync(filepath, content, 'utf8');
        });
      }
    });

webpack + vue 编译插件实现 [egg-webpack-vue][]

## egg+webpack+vue工程解决方案 ##

*  [egg-vue-webpack-boilerplate][]基于Vue多页面和单页面服务器渲染同构工程骨架项目
 *  [egg-view-vue][] egg view plugin for vue
 *  [egg-view-vue-ssr][] vue server side render solution for egg-view-vue
 *  [egg-webpack][] webpack dev server plugin for egg, support read file in memory and hot reload
 *  [egg-webpack-vue][] egg webpack building solution for vue
 *  [easywebpack][] programming instead of configuration, webpack is no longer complex

转载于:https://www.cnblogs.com/hubcarl/p/6847818.html

[https_eggjs.org_zh-cn_core_cluster-and-ipc.html]: https://eggjs.org/zh-cn/core/cluster-and-ipc.html
[egg-development]: https://github.com/eggjs/egg-development
[egg-view-vue]: https://github.com/hubcarl/egg-view-vue
[egg-webpack-vue]: https://github.com/hubcarl/egg-webpack-vue
[egg-vue-webpack-boilerplate]: https://github.com/hubcarl/egg-vue-webpack-boilerplate
[egg-view-vue-ssr]: https://github.com/hubcarl/egg-view-vue-ssr
[egg-webpack]: https://github.com/hubcarl/egg-webpack
[easywebpack]: https://github.com/hubcarl/easywebpack