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.
const cluster = require('cluster');
const chokidar = require('chokidar');
if (cluster.isMaster) {
const koa = require('koa');
const app = koa();
const compiler = webpack([clientWebpackConfig,serverWebpackConfig]);
const devMiddleware = require('koa-webpack-dev-middleware')(compiler);
const hotMiddleware = require('koa-webpack-hot-middleware')(compiler);
app.use(devMiddleware);
app.use(hotMiddleware);
let worker = cluster.fork();
chokidar.watch(config.dir, config.options).on('change', path =>{
console.log(`${path} changed`);
worker.kill();
worker = cluster.fork().on('listening', (address) =>{
console.log(`[master] listening: worker ${worker.id}, pid:${worker.process.pid} ,Address:${address.address } :${address.port}`);
});
});
}
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.
const watchConfig = {
dir: [ 'controller', 'middleware', 'lib', 'model', 'app.js', 'index.js' ],
options: {}
};
let worker = cluster.fork();
chokidar.watch(watchConfig.dir, watchConfig.options).on('change', path =>{
console.log(`${path} changed`);
worker && worker.kill();
worker = cluster.fork().on('listening', (address) =>{
console.log(`[master] listening: worker ${worker.id}, pid:${worker.process.pid} ,Address:${address.address } :${address.port}`);
});
});
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/...
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
const WEBPACK = Symbol('Application#webpack');
module.exports = {
get webpack() {
if (!this[WEBPACK]) {
this[WEBPACK] = new FileSystem(this);
}
return this[WEBPACK];
},
};
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:
const Engine = require('../../lib/engine');
const VUE_ENGINE = Symbol('Application#vue');
module.exports = {
get vue() {
if (!this[VUE_ENGINE]) {
this[VUE_ENGINE] = new Engine(this);
}
return this[VUE_ENGINE];
},
};
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
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