├── CONTRIBUTING.md ├── LICENSE ├── README.md ├── __init__.py ├── backend ├── __init__.py └── for_django.py └── frontend ├── for_angular.js └── for_angular_externs.js /CONTRIBUTING.md: -------------------------------------------------------------------------------- 1 | Want to contribute? Great! First, read this page (including the small print at the end). 2 | 3 | ### Before you contribute 4 | Before we can use your code, you must sign the 5 | [Google Individual Contributor License Agreement] 6 | (https://cla.developers.google.com/about/google-individual) 7 | (CLA), which you can do online. The CLA is necessary mainly because you own the 8 | copyright to your changes, even after your contribution becomes part of our 9 | codebase, so we need your permission to use and distribute your code. We also 10 | need to be sure of various other things—for instance that you'll tell us if you 11 | know that your code infringes on other people's patents. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright 2016 The angular-dual-http Authors. 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | # The dual-http Solution 2 | 3 | Render your page with cached data, 4 | then fetch up-to-date data from server and update the page. 5 | 6 | This solution contains both frontend code and backend code. 7 | It works in the following way: 8 | 9 | - The browser begins with sending an http request, allowing browser cache. 10 | - Either cached data or server responded data comes back. 11 | - A callback function gets called to allow the user (you) 12 | to render the webpage. 13 | - If the previous data came from browser cache, 14 | a subsequent http request that bypasses the cache is sent. 15 | - Another callback function is called to notify the user 16 | to update the content of the webpage. 17 | 18 | It is a special header that both the http request and the response carry 19 | that makes it possible for us to detect whether the response comes from cache, 20 | because the backend always responses with the exact `x-echo` value 21 | as the request has. Example: 22 | 23 | First request: 24 | 25 | GET /api/data HTTP/1.1 26 | host: example.com 27 | x-echo: 456 28 | 29 | Gets a response: 30 | 31 | 200 OK 32 | x-echo: 123 33 | cache-control: private, max-age=31536000 34 | {"data": "actual data"} 35 | 36 | Noting the difference of the `x-echo` values, 37 | the frontend realizes that the response must be from browser cache. 38 | It then issues a second request immediately: 39 | 40 | GET /api/data HTTP/1.1 41 | host: example.com 42 | x-echo: 789 43 | cache-control: max-age=0 44 | 45 | Because of `max-age=0`, the browser cache gets bypassed. 46 | The server gets the request and has to respond. 47 | 48 | 200 OK 49 | x-echo: 789 50 | cache-control: private, max-age=31536000 51 | {"data": "some new data"} 52 | 53 | This time `x-echo` values match. 54 | 55 | ## Usage 56 | 57 | This solution supports AngularJS as frontend framework 58 | and django as backend framework. More framework supports are on the way. 59 | 60 | AngularJS: 61 | 62 | var mod = angular.module('...NAME...', ['ngDualHttp']); 63 | mod.controller('...NAME...', function(dualHttp) { 64 | dualHttp.get('/api/data') 65 | .onCacheFetched(onCacheSucceed) 66 | .onServerResponded(onServerSucceed, onFail); 67 | function onCacheSucceed(response) {...} 68 | function onServerSucceed(response) {...} 69 | function onFail(response) {...} 70 | }); 71 | 72 | django: 73 | 74 | # settings.py: 75 | MIDDLEWARE_CLASSES = ( 76 | '...YOUR.PATH...dualhttp.backend.for_django.EchoHeaderMiddleware', 77 | ) 78 | 79 | Enjoy! 80 | -------------------------------------------------------------------------------- /__init__.py: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/google/dualhttp/d78c8860f243e0c5250b526b0990058a69a9077d/__init__.py -------------------------------------------------------------------------------- /backend/__init__.py: -------------------------------------------------------------------------------- https://raw.githubusercontent.com/google/dualhttp/d78c8860f243e0c5250b526b0990058a69a9077d/backend/__init__.py -------------------------------------------------------------------------------- /backend/for_django.py: -------------------------------------------------------------------------------- 1 | # Copyright 2016 Google Inc. All Rights Reserved. 2 | # 3 | # Licensed under the Apache License, Version 2.0 (the "License"); 4 | # you may not use this file except in compliance with the License. 5 | # You may obtain a copy of the License at 6 | # 7 | # http://www.apache.org/licenses/LICENSE-2.0 8 | # 9 | # Unless required by applicable law or agreed to in writing, software 10 | # distributed under the License is distributed on an "AS IS" BASIS, 11 | # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 | # See the License for the specific language governing permissions and 13 | # limitations under the License. 14 | 15 | 16 | class EchoHeaderMiddleware(object): 17 | 18 | def process_response(self, request, response): 19 | """Put a "x-echo" header to response with same value from request.""" 20 | echo = request.META.get('HTTP_X_ECHO', '') 21 | if echo: 22 | response['x-echo'] = echo 23 | return response 24 | -------------------------------------------------------------------------------- /frontend/for_angular.js: -------------------------------------------------------------------------------- 1 | /** 2 | * @license 3 | * Copyright 2016 Google Inc. All Rights Reserved. 4 | * 5 | * Licensed under the Apache License, Version 2.0 (the "License"); 6 | * you may not use this file except in compliance with the License. 7 | * You may obtain a copy of the License at 8 | * 9 | * http://www.apache.org/licenses/LICENSE-2.0 10 | * 11 | * Unless required by applicable law or agreed to in writing, software 12 | * distributed under the License is distributed on an "AS IS" BASIS, 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 | * See the License for the specific language governing permissions and 15 | * limitations under the License. 16 | */ 17 | 18 | (function() { 19 | 'use strict'; 20 | 21 | 22 | /** 23 | * A Promise-like object that you use onCacheFetched() and onServerResponded() 24 | * in place of then(). 25 | */ 26 | class DualPromise { 27 | constructor($q) { 28 | this.$$cacheDeferred = $q.defer(); 29 | this.$$serverDeferred = $q.defer(); 30 | } 31 | 32 | onCacheFetched(resolveCallback) { 33 | this.$$cacheDeferred.promise.then(resolveCallback); 34 | return this; 35 | } 36 | 37 | onServerResponded(resolveCallback, opt_rejectCallback) { 38 | this.$$serverDeferred.promise.then(resolveCallback, opt_rejectCallback); 39 | return this; 40 | } 41 | 42 | finally(callback) { 43 | this.$$serverDeferred.promise.finally(callback); 44 | return this; 45 | } 46 | } 47 | 48 | 49 | /** 50 | * Issues http request *twice*. 51 | * 52 | * First request allows fetching from browser cache, which enables UI to 53 | * render sooner. Second request is meant to sent to the server only when 54 | * first request comes from cache. It makes sure the data is up-to-date. 55 | * 56 | * Example usage: 57 | * dualHttp.get('/api/data') 58 | * .onCacheFetched(onCacheSucceed) 59 | * .onServerResponded(onServerSucceed, onFail); 60 | * function onCacheSucceed(response) {...} 61 | * function onServerSucceed(response) {...} 62 | * function onFail(response) {...} 63 | */ 64 | class DualHttpService { 65 | static get $inject() { return ['$http', '$q']; } 66 | 67 | constructor($http, $q) { 68 | this.http_ = $http; 69 | this.q_ = $q; 70 | } 71 | 72 | 73 | /** 74 | * Performs GET requests. It's just like AngularJS's $http.get() method, 75 | * except that this returns a DualPromise object, while $http.get() returns 76 | * a standard AngularJS Promise. 77 | */ 78 | get(url, opt_config) { 79 | const dualPromise = new DualPromise(this.q_); 80 | const config = opt_config || {}; 81 | config.headers = config.headers || {}; 82 | config.headers['x-echo'] = Math.random() + ''; 83 | 84 | this.http_.get(url, config).then( 85 | this.onFirstGet_.bind(this, dualPromise, url, config), 86 | this.onFirstGet_.bind(this, dualPromise, url, config)); 87 | return dualPromise; 88 | } 89 | 90 | 91 | /** 92 | * Finds out whether the response's status code is between 200 and 299. 93 | */ 94 | isSuccess_(resp) { 95 | return 200 <= resp.status && resp.status < 300; 96 | } 97 | 98 | 99 | /** 100 | * Detects whether a response comes from browser cache, by checking if the 101 | * "x-echo" header from request and from response matches. 102 | */ 103 | isFromCache_(resp) { 104 | let fromCache = false; 105 | if (resp && resp.config && resp.config.headers['x-echo']) { 106 | const echoFromReq = resp.config.headers['x-echo']; 107 | const echoFromResp = resp.headers('x-echo'); 108 | if (echoFromResp && echoFromReq != echoFromResp) { 109 | fromCache = true; 110 | } 111 | } 112 | return fromCache; 113 | } 114 | 115 | 116 | /** 117 | * Callback function to be called when first request is done. 118 | */ 119 | onFirstGet_(dualPromise, url, config, resp) { 120 | if (this.isFromCache_(resp)) { 121 | if (this.isSuccess_(resp)) { 122 | dualPromise.$$cacheDeferred.resolve(resp); 123 | } else { 124 | dualPromise.$$cacheDeferred.reject(resp); 125 | } 126 | 127 | config = angular.extend({}, config); // Make a copy. 128 | config.headers = angular.extend({}, config.headers); 129 | config.headers['x-echo'] = Math.random() + ''; 130 | config.headers['cache-control'] = 'max-age=0'; 131 | 132 | this.http_.get(url, config).then( 133 | this.onSecondGet_.bind(this, dualPromise), 134 | this.onSecondGet_.bind(this, dualPromise)); 135 | 136 | } else { 137 | this.onSecondGet_(dualPromise, resp); 138 | } 139 | } 140 | 141 | 142 | /** 143 | * Callback function to be called when second request is done. 144 | */ 145 | onSecondGet_(dualPromise, resp) { 146 | if (this.isSuccess_(resp)) { 147 | dualPromise.$$serverDeferred.resolve(resp); 148 | } else { 149 | dualPromise.$$serverDeferred.reject(resp); 150 | } 151 | } 152 | } 153 | 154 | 155 | angular.module('ngDualHttp', []).service('dualHttp', DualHttpService); 156 | 157 | })(); 158 | -------------------------------------------------------------------------------- /frontend/for_angular_externs.js: -------------------------------------------------------------------------------- 1 | /** 2 | * @license 3 | * Copyright 2016 Google Inc. All Rights Reserved. 4 | * 5 | * Licensed under the Apache License, Version 2.0 (the "License"); 6 | * you may not use this file except in compliance with the License. 7 | * You may obtain a copy of the License at 8 | * 9 | * http://www.apache.org/licenses/LICENSE-2.0 10 | * 11 | * Unless required by applicable law or agreed to in writing, software 12 | * distributed under the License is distributed on an "AS IS" BASIS, 13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 | * See the License for the specific language governing permissions and 15 | * limitations under the License. 16 | */ 17 | 18 | /** 19 | * @externs 20 | */ 21 | 22 | 23 | class DualDefer { 24 | /** 25 | * @param {function(!angular.$http.Response): ?} resolveCallback 26 | * @return {DualDefer} 27 | */ 28 | onCacheFetched(resolveCallback) {} 29 | 30 | /** 31 | * @param {function(!angular.$http.Response): ?} resolveCallback 32 | * @param {(function(!angular.$http.Response): ?)=} opt_rejectCallback 33 | * @return {DualDefer} 34 | */ 35 | onServerResponded(resolveCallback, opt_rejectCallback) {} 36 | 37 | /** 38 | * @param {function(!angular.$http.Response): ?} callback 39 | * @return {DualDefer} 40 | */ 41 | finally(callback) {} 42 | } 43 | 44 | 45 | class DualHttpService { 46 | /** 47 | * @param {string} url 48 | * @param {angular.$http.Config=} opt_config 49 | * @return {!DualDefer} 50 | */ 51 | get(url, opt_config) {} 52 | } 53 | --------------------------------------------------------------------------------