由于附加了 DevTools，超时计时器终止服务工作线程被取消

Question

OS: Windows 10 专业版
网络包：1.14.0
sw-precache-webpack-插件：0.9.1
sw-预缓存：5.0.0

所以，我启动了我的网站，但有一段时间没有主动做任何事情，然后在 devTools 中生成了上面指定的错误消息。如果执行某些过程，则不会出现错误

我的React代码如下：

webpack.config.prod.js

var path = require('path');
var webpack = require('webpack');
var SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin');

module.exports = {
  devtool: 'source-map',
  context: __dirname,
  entry: {
    main: path.resolve(__dirname, './client/app'),
  },
  output: {
    path: path.join(__dirname, '/public'),
    filename: 'bundle.js',
    publicPath: '/public/'
  },
  plugins: [
    new webpack.optimize.OccurenceOrderPlugin(),
    new webpack.DefinePlugin({
      'process.env': {
        'NODE_ENV': "'production'"
      }
    }),
    new webpack.optimize.UglifyJsPlugin({
      compressor: {
        warnings: false
      }
    }),
    new SWPrecacheWebpackPlugin(
      {
        cacheId: 'flamingoCity',
        filename: 'my-service-worker.js',
        stripPrefix: path.join(__dirname, 'public').replace(/\/g,"/"),
        maximumFileSizeToCacheInBytes: 6194304,
        minify: true,
        runtimeCaching: [{
          handler: 'cacheFirst',
          urlPattern: /[.]mp3$/,
        }],
      }
    ),
  ],
  module: {
    loaders: [
    // js
    {
      test: /\.js$/,
      loaders: ['babel'],
      include: path.join(__dirname, 'client')
    },
    // CSS
    { 
      test: /\.styl$/, 
      include: path.join(__dirname, 'client'),
      loader: 'style-loader!css-loader!stylus-loader'
    }
    ]
  }
};

app.js

/*
  Import Dependencies
*/
import React from 'react';
import { render } from 'react-dom';
import { Provider } from 'react-redux';
import { Router, Route, IndexRoute } from 'react-router'
import 'babel-polyfill';

/*
  Import Components
*/
import App from './components/App';
import Single from './components/Single';
import PhotoGrid from './components/PhotoGrid';

/* Import CSS */
import css from  './styles/style.styl';

/* Import our data store */
import store, { history } from './store';

/*
  Error Logging
*/

import Raven from 'raven-js';
import { sentry_url } from './data/config';
if(window) {
  Raven.config(sentry_url).install();
}

/*
  Register Service Worker
*/

if('serviceWorker' in navigator  && process.env.NODE_ENV === 'production') {
  navigator.serviceWorker.register('./my-service-worker.js').then(function(reg) {
  // updatefound is fired if my-service-worker.js changes.
  reg.onupdatefound = function() {
    // The updatefound event implies that reg.installing is set; see
    // https://slightlyoff.github.io/ServiceWorker/spec/service_worker/index.html#service-worker-container-updatefound-event
    var installingWorker = reg.installing;

    installingWorker.onstatechange = function() {
      switch (installingWorker.state) {
        case 'installed':
          if (navigator.serviceWorker.controller) {
            // At this point, the old content will have been purged and the fresh content will
            // have been added to the cache.
            // It's the perfect time to display a "New content is available; please refresh."
            // message in the page's interface.
            console.log('New or updated content is available.');
          } else {
            // At this point, everything has been precached.
            // It's the perfect time to display a "Content is cached for offline use." message.
            console.log('Content is now available offline!');
          }
          break;

        case 'redundant':
          console.error('The installing service worker became redundant.');
          break;
      }
    };
  };
  }).catch(function(e) {
    console.error('Error during service worker registration:', e);
  });
}

/*
  Rendering
  This is where we hook up the Store with our actual component and the router
*/
render(
  <Provider store={store}>
    { /* Tell the Router to use our enhanced history */ }
    <Router history={history}>
      <Route path="/" component={App}>
        <IndexRoute component={PhotoGrid} />
        <Route path="/view/:postId" component={Single}></Route>
      </Route>
    </Router>
  </Provider>,
  document.getElementById('root')
);

这里有什么问题？

Answer 1

通常情况下，闲置的服务工作者会被积极杀死作为一种优化，以防止代码在不需要时运行在后台运行。

Chrome 采取措施检测 DevTools 是否打开，当打开时，不会自动杀死 service worker。假设是，如果开发人员正在使用 DevTools，他们可能正在调试或以其他方式检查 service worker 的行为，杀死 service worker 会使开发人员感到沮丧。

延长 service worker 的生命周期以前是默默地完成的，但是 as described here，对于过去的几个版本 Chrome，消息

Service Worker termination by a timeout timer was canceled because DevTools is attached.

被记录到控制台，让开发人员知道服务工作者通常会被杀死，但是由于 DevTools 处于打开状态，杀死它的作业被取消了。

您可能会问，这有什么区别？为什么要让开发人员知道某些事情并没有发生？

指出这一点的动机是让开发人员知道真实用户在生产中会遇到的事情（即 service worker 重复 killed/restarted）在这个调试环境中不会发生。如果开发人员编写了导致有问题的 Service Worker 代码，这就会有所不同。很容易编写假设全局状态将始终存在的代码，并且在运行打开 DevTools 时工作（因为 service worker 永远不会被杀死），然后在生产中无法工作。

Answer 2

var path = require('path');
var webpack = require('webpack');
var SWPrecacheWebpackPlugin = require('sw-precache-webpack-plugin');

module.exports = {
  devtool: 'source-map',
  context: __dirname,
  entry: {
    main: path.resolve(__dirname, './client/app'),
  },
  output: {
    path: path.join(__dirname, '/public'),
    filename: 'bundle.js',
    publicPath: '/public/'
  },
  plugins: [
    new webpack.optimize.OccurenceOrderPlugin(),
    new webpack.DefinePlugin({
      'process.env': {
        'NODE_ENV': "'production'"
      }
    }),
    new webpack.optimize.UglifyJsPlugin({
      compressor: {
        warnings: false
      }
    }),
    new SWPrecacheWebpackPlugin(
      {
        cacheId: 'flamingoCity',
        filename: 'my-service-worker.js',
        stripPrefix: path.join(__dirname, 'public').replace(/\/g,"/"),
        maximumFileSizeToCacheInBytes: 6194304,
        minify: true,
        runtimeCaching: [{
          handler: 'cacheFirst',
          urlPattern: /[.]mp3$/,
        }],
      }
    ),
  ],
  module: {
    loaders: [
    // js
    {
      test: /\.js$/,
      loaders: ['babel'],
      include: path.join(__dirname, 'client')
    },
    // CSS
    { 
      test: /\.styl$/, 
      include: path.join(__dirname, 'client'),
      loader: 'style-loader!css-loader!stylus-loader'
    }
    ]
  }
};

由于附加了 DevTools，超时计时器终止服务工作线程被取消

Service Worker termination by a timeout timer was canceled because DevTools is attached

javascript

reactjs

service-worker

sw-precache