iOS HTTP/2 Server Push 探索
<p style="text-align:center"><img src="https://simg.open-open.com/show/afca5c2b7192f4e40f11a3b7ecc0b439.jpg"></p> <p>当用户的浏览器和服务器在建立链接后，服务器主动将一些资源推送给浏览器并缓存起来，这样当浏览器接下来请求这些资源时就直接从缓存中读取，不会在从服务器上拉了，提升了速率。举一个例子就是：</p> <p>假如一个页面有3个资源文件index.html,index.css,index.js,当浏览器请求index.html的时候，服务器不仅返回index.html的内容，同时将index.css和index.js的内容push给浏览器，当浏览器下次请求这2两个文件时就可以直接从缓存中读取了。</p> <p>如下图所示:</p> <p><img src="https://simg.open-open.com/show/aa8b031fe1d90a815df4358d8a6321fc.png"></p> <h2>HTTP/2 Server Push 原理是什么</h2> <p>要想了解server push原理，首先要理解一些概念。我们知道HTTP/2传输的格式并不像HTTP1使用文本来传输，而是启用了二进制帧(Frames)格式来传输，和server push相关的帧主要分成这几种类型：</p> <ol> <li>HEADERS frame(请求返回头帧):这种帧主要携带的http请求头信息，和HTTP1的header类似。</li> <li>DATA frames(数据帧) :这种帧存放真正的数据content，用来传输。</li> <li>PUSH_PROMISE frame(推送帧):这种帧是由server端发送给client的帧，用来表示server push的帧，这种帧是实现server push的主要帧类型。</li> <li>RST_STREAM(取消推送帧):这种帧表示请求关闭帧，简单讲就是当client不想接受某些资源或者接受timeout时会向发送方发送此帧，和PUSH_PROMISE frame一起使用时表示拒绝或者关闭server push。</li> </ol> <p>(PS:HTTP/2相关的帧其实包括 10种帧 ，正是因为底层数据格式的改变，才为HTTP/2带来许多的特性，帧的引入不仅有利于压缩数据，也有利于数据的安全性和可靠传输性。)</p> <p>了解了相关的帧类型，下面就是具体server push的实现过程了：</p> <ol> <li>由多路复用我们可以知道HTTP/2中对于同一个域名的请求会使用一条tcp链接而用不同的stream ID来区分各自的请求。</li> <li>当client使用stream 1请求index.html时，server正常处理index.html的请求，并可以得知index.html页面还将要会请求index.css和index.js。</li> <li>server使用stream 1发送PUSH_PROMISE frame给client告诉client我这边可以使用stream 2来推送index.js和stream 3来推送index.css资源。</li> <li>server使用stream 1正常的发送HEADERS frame和DATA frames将index.html的内容返回给client。</li> <li>client接收到PUSH_PROMISE frame得知stream 2和stream 3来接收推送资源。</li> <li>server拿到index.css和index.js便会发送HEADERS frame和DATA frames将资源发送给client。</li> <li>client拿到push的资源后会缓存起来当请求这个资源时会从直接从从缓存中读取。</li> </ol> <h2>Server Push 怎么用</h2> <h2>使用 nghttp2 调试 HTTP/2 流量</h2> <p>查看 HTTP/2 流量的几种方式</p> <ul> <li>在 Chrome 地址栏输入 chrome://net-internals/#http2 ，使用 Chrome 自带的 HTTP/2 调试工具；<br> 使用方便，但受限于 Chrome 浏览器，对于 Chrome 不支持的 h2c（HTTP/2 Cleartext，没有部署 TLS 的 HTTP/2）协议无能为力。同时，这个工具显示的信息经过了解析和筛选，不够全面。</li> <li>使用 Wireshark 调试 HTTP/2 流量；<br> Wireshark 位于服务端和浏览器之间，充当的是中间人角色，用它查看 HTTP/2 over HTTPS 流量时，必须拥有网站私钥或者借助浏览器共享对称密钥，才能解密 TLS 流量，配置起来比较麻烦。</li> </ul> <p>nghttp2，是一个用 C 实现的 HTTP/2 库，支持 h2c。它可以做为其它软件的一部分，为其提供 HTTP/2 相关功能（例如 curl 的 HTTP/2 功能就是用的 nghttp2）。除此之外，它还提供了四个有用的 HTTP/2 工具：</p> <ul> <li>nghttp：HTTP/2 客户端；</li> <li>nghttpd：HTTP/2 服务端；</li> <li>nghttpx：HTTP/2 代理，提供 HTTP/1、HTTP/2 等协议之间的转换；</li> <li>h2load：HTTP/2 性能测试工具；</li> </ul> <h3>nghttp2 安装</h3> <p>先来用 brew 看一下有没有 nghttp 相关的库：</p> <pre> <code class="language-objectivec">~ brew search nghttp nghttp2 </code></pre> <p>看来是有 nghttp2 的，再用 brew 看下需要安装哪些环境：</p> <pre> <code class="language-objectivec">~ brew info nghttp2 nghttp2: stable 1.21.0 (bottled), HEAD HTTP/2 C Library https://nghttp2.org/ Not installed From: https://github.com/Homebrew/homebrew-core/blob/master/Formula/nghttp2.rb ==> Dependencies Build: sphinx-doc ✘, pkg-config ✔, cunit ✘ Required: c-ares ✘, libev ✘, openssl ✔, libevent ✘, jansson ✘, boost ✘, spdylay ✘ Recommended: jemalloc ✘ ==> Requirements Optional: python3 ✔ ==> Options --with-examples Compile and install example programs --with-python3 Build python3 bindings --without-docs Don't build man pages --without-jemalloc Build without jemalloc support --HEAD Install HEAD version </code></pre> <p>看来需要的依赖还挺多。</p> <p>使用 brew 安装 nghttp2 ：</p> <pre> <code class="language-objectivec">brew install nghttp2 </code></pre> <p>一切妥当后，nghttp2 提供的几个工具就可以直接用了。</p> <h3>nghttp</h3> <p>nghttp 做为一个功能完整的 HTTP/2 客户端，非常适合用来查看和调试 HTTP/2 流量。它支持的参数很多，通过官方文档或者 nghttp -h 都能查看。最常用几个参数如下：</p> <ul> <li>-v, –verbose，输出完整的 debug 信息；</li> <li>-n, –null-out，丢弃下载的数据；</li> <li>-a, –get-assets，下载 html 中的 css、js、image 等外链资源；</li> <li>-H, –header = < HEADER >，添加请求头部字段，如 -H’:method: PUT’；</li> <li>-u, –upgrade，使用 HTTP 的 Upgrade 机制来协商 HTTP/2 协议，用于 h2c，详见下面的例子；</li> </ul> <p>以下是使用 nghttp 访问 <a href="/misc/goto?guid=4959747148189018288" rel="nofollow,noindex">https://h2o.examp1e.net</a> 的结果。从调试信息中可以清晰看到 h2c 协商以及 Server Push 的整个过程：</p> <pre> <code class="language-objectivec">nghttp -nv 'https://h2o.examp1e.net' [ 0.201] Connected The negotiated protocol: h2 [ 1.180] send SETTINGS frame <length=12, flags=0x00, stream_id=0> (niv=2) [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] [ 1.180] send PRIORITY frame <length=5, flags=0x00, stream_id=3> (dep_stream_id=0, weight=201, exclusive=0) [ 1.180] send PRIORITY frame <length=5, flags=0x00, stream_id=5> (dep_stream_id=0, weight=101, exclusive=0) [ 1.180] send PRIORITY frame <length=5, flags=0x00, stream_id=7> (dep_stream_id=0, weight=1, exclusive=0) [ 1.180] send PRIORITY frame <length=5, flags=0x00, stream_id=9> (dep_stream_id=7, weight=1, exclusive=0) [ 1.180] send PRIORITY frame <length=5, flags=0x00, stream_id=11> (dep_stream_id=3, weight=1, exclusive=0) [ 1.180] send HEADERS frame <length=39, flags=0x25, stream_id=13> ; END_STREAM | END_HEADERS | PRIORITY (padlen=0, dep_stream_id=11, weight=16, exclusive=0) ; Open new stream :method: GET :path: / :scheme: https :authority: h2o.examp1e.net accept: */* accept-encoding: gzip, deflate user-agent: nghttp2/1.21.1 [ 1.373] recv SETTINGS frame <length=12, flags=0x00, stream_id=0> (niv=2) [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] [SETTINGS_INITIAL_WINDOW_SIZE(0x04):16777216] [ 1.373] recv SETTINGS frame <length=0, flags=0x01, stream_id=0> ; ACK (niv=0) [ 1.373] recv (stream_id=13) :method: GET [ 1.373] recv (stream_id=13) :scheme: https [ 1.373] recv (stream_id=13) :authority: h2o.examp1e.net [ 1.373] recv (stream_id=13) :path: /search/jquery-1.9.1.min.js [ 1.373] recv (stream_id=13) accept: */* [ 1.373] recv (stream_id=13) accept-encoding: gzip, deflate [ 1.373] recv (stream_id=13) user-agent: nghttp2/1.21.1 [ 1.373] recv PUSH_PROMISE frame <length=59, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=2) [ 1.373] recv (stream_id=2) :status: 200 [ 1.373] recv (stream_id=2) server: h2o/2.2.0-beta2 [ 1.373] recv (stream_id=2) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.373] recv (stream_id=2) content-type: application/javascript [ 1.373] recv (stream_id=2) last-modified: Thu, 14 May 2015 04:10:14 GMT [ 1.373] recv (stream_id=2) etag: "55542026-169d5" [ 1.373] recv (stream_id=2) accept-ranges: bytes [ 1.373] recv (stream_id=2) x-http2-push: pushed [ 1.373] recv (stream_id=2) content-length: 92629 [ 1.373] recv HEADERS frame <length=126, flags=0x04, stream_id=2> ; END_HEADERS (padlen=0) ; First push response header [ 1.373] recv (stream_id=13) :method: GET [ 1.373] recv (stream_id=13) :scheme: https [ 1.373] recv (stream_id=13) :authority: h2o.examp1e.net [ 1.373] recv (stream_id=13) :path: /search/oktavia-jquery-ui.js [ 1.373] recv (stream_id=13) accept: */* [ 1.373] recv (stream_id=13) accept-encoding: gzip, deflate [ 1.373] recv (stream_id=13) user-agent: nghttp2/1.21.1 [ 1.373] recv PUSH_PROMISE frame <length=33, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=4) [ 1.373] recv (stream_id=4) :status: 200 [ 1.373] recv (stream_id=4) server: h2o/2.2.0-beta2 [ 1.373] recv (stream_id=4) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.373] recv (stream_id=4) content-type: application/javascript [ 1.373] recv (stream_id=4) last-modified: Thu, 14 May 2015 04:10:14 GMT [ 1.373] recv (stream_id=4) etag: "55542026-1388" [ 1.373] recv (stream_id=4) accept-ranges: bytes [ 1.374] recv (stream_id=4) x-http2-push: pushed [ 1.374] recv (stream_id=4) content-length: 5000 [ 1.374] recv HEADERS frame <length=28, flags=0x04, stream_id=4> ; END_HEADERS (padlen=0) ; First push response header [ 1.374] recv (stream_id=13) :method: GET [ 1.374] recv (stream_id=13) :scheme: https [ 1.374] recv (stream_id=13) :authority: h2o.examp1e.net [ 1.374] recv (stream_id=13) :path: /search/oktavia-english-search.js [ 1.374] recv (stream_id=13) accept: */* [ 1.374] recv (stream_id=13) accept-encoding: gzip, deflate [ 1.374] recv (stream_id=13) user-agent: nghttp2/1.21.1 [ 1.374] recv PUSH_PROMISE frame <length=35, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=6) [ 1.374] recv (stream_id=6) :status: 200 [ 1.374] recv (stream_id=6) server: h2o/2.2.0-beta2 [ 1.374] recv (stream_id=6) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.374] recv (stream_id=6) content-type: application/javascript [ 1.374] recv (stream_id=6) last-modified: Thu, 14 May 2015 04:10:14 GMT [ 1.374] recv (stream_id=6) etag: "55542026-34dd6" [ 1.374] recv (stream_id=6) accept-ranges: bytes [ 1.374] recv (stream_id=6) x-http2-push: pushed [ 1.374] recv (stream_id=6) content-length: 216534 [ 1.374] recv HEADERS frame <length=31, flags=0x04, stream_id=6> ; END_HEADERS (padlen=0) ; First push response header [ 1.374] recv (stream_id=13) :method: GET [ 1.374] recv (stream_id=13) :scheme: https [ 1.374] recv (stream_id=13) :authority: h2o.examp1e.net [ 1.374] recv (stream_id=13) :path: /assets/style.css [ 1.374] recv (stream_id=13) accept: */* [ 1.374] recv (stream_id=13) accept-encoding: gzip, deflate [ 1.374] recv (stream_id=13) user-agent: nghttp2/1.21.1 [ 1.374] recv PUSH_PROMISE frame <length=24, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=8) [ 1.374] recv (stream_id=8) :status: 200 [ 1.374] recv (stream_id=8) server: h2o/2.2.0-beta2 [ 1.374] recv (stream_id=8) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.374] recv (stream_id=8) content-type: text/css [ 1.374] recv (stream_id=8) last-modified: Tue, 20 Sep 2016 05:27:06 GMT [ 1.374] recv (stream_id=8) etag: "57e0c8aa-1586" [ 1.374] recv (stream_id=8) accept-ranges: bytes [ 1.374] recv (stream_id=8) x-http2-push: pushed [ 1.374] recv (stream_id=8) content-length: 5510 [ 1.374] recv HEADERS frame <length=58, flags=0x04, stream_id=8> ; END_HEADERS (padlen=0) ; First push response header [ 1.374] recv (stream_id=13) :method: GET [ 1.374] recv (stream_id=13) :scheme: https [ 1.374] recv (stream_id=13) :authority: h2o.examp1e.net [ 1.374] recv (stream_id=13) :path: /assets/searchstyle.css [ 1.374] recv (stream_id=13) accept: */* [ 1.374] recv (stream_id=13) accept-encoding: gzip, deflate [ 1.374] recv (stream_id=13) user-agent: nghttp2/1.21.1 [ 1.374] recv PUSH_PROMISE frame <length=28, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=10) [ 1.374] recv (stream_id=10) :status: 200 [ 1.374] recv (stream_id=10) server: h2o/2.2.0-beta2 [ 1.374] recv (stream_id=10) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.374] recv (stream_id=10) content-type: text/css [ 1.374] recv (stream_id=10) last-modified: Tue, 20 Sep 2016 05:27:06 GMT [ 1.374] recv (stream_id=10) etag: "57e0c8aa-8dd" [ 1.374] recv (stream_id=10) accept-ranges: bytes [ 1.374] recv (stream_id=10) x-http2-push: pushed [ 1.374] recv (stream_id=10) content-length: 2269 [ 1.374] recv HEADERS frame <length=27, flags=0x04, stream_id=10> ; END_HEADERS (padlen=0) ; First push response header [ 1.374] recv (stream_id=13) :status: 200 [ 1.374] recv (stream_id=13) server: h2o/2.2.0-beta2 [ 1.374] recv (stream_id=13) date: Mon, 10 Apr 2017 06:30:29 GMT [ 1.374] recv (stream_id=13) link: </search/jquery-1.9.1.min.js>; rel=preload [ 1.374] recv (stream_id=13) link: </search/oktavia-jquery-ui.js>; rel=preload [ 1.374] recv (stream_id=13) link: </search/oktavia-english-search.js>; rel=preload [ 1.374] recv (stream_id=13) link: </assets/style.css>; rel=preload [ 1.374] recv (stream_id=13) link: </assets/searchstyle.css>; rel=preload [ 1.374] recv (stream_id=13) cache-control: no-cache [ 1.374] recv (stream_id=13) content-type: text/html [ 1.374] recv (stream_id=13) last-modified: Wed, 05 Apr 2017 06:55:14 GMT [ 1.374] recv (stream_id=13) etag: "58e494d2-1665" [ 1.374] recv (stream_id=13) accept-ranges: bytes [ 1.374] recv (stream_id=13) set-cookie: h2o_casper=AmgAAAAAAAAAAAAYxfEYAAABSA; Path=/; Expires=Tue, 01 Jan 2030 00:00:00 GMT; Secure [ 1.374] recv (stream_id=13) content-length: 5733 [ 1.374] recv HEADERS frame <length=304, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0) ; First response header [ 1.375] send SETTINGS frame <length=0, flags=0x01, stream_id=0> ; ACK (niv=0) [ 1.566] recv DATA frame <length=16137, flags=0x00, stream_id=2> [ 1.567] recv DATA frame <length=5000, flags=0x01, stream_id=4> ; END_STREAM [ 1.567] recv DATA frame <length=4915, flags=0x00, stream_id=6> [ 1.766] recv DATA frame <length=2829, flags=0x00, stream_id=8> [ 1.766] recv DATA frame <length=2269, flags=0x01, stream_id=10> ; END_STREAM [ 1.766] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=33120) [ 1.767] recv DATA frame <length=9065, flags=0x00, stream_id=2> [ 1.970] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 1.970] recv DATA frame <length=2681, flags=0x01, stream_id=8> ; END_STREAM [ 1.971] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=2> (window_size_increment=33855) [ 1.971] recv DATA frame <length=10072, flags=0x00, stream_id=2> [ 2.172] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 2.172] recv DATA frame <length=4248, flags=0x00, stream_id=2> [ 2.173] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 2.173] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34002) [ 2.173] recv DATA frame <length=4248, flags=0x00, stream_id=2> [ 2.577] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 2.578] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 2.579] recv DATA frame <length=12762, flags=0x00, stream_id=6> [ 2.777] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 2.777] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=33241) [ 2.778] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 3.177] recv DATA frame <length=8505, flags=0x00, stream_id=2> [ 3.177] recv DATA frame <length=5667, flags=0x00, stream_id=6> [ 3.177] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=33993) [ 3.177] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 3.177] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 3.378] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 3.579] recv DATA frame <length=11343, flags=0x00, stream_id=6> [ 3.580] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34002) [ 3.580] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=2> (window_size_increment=33984) [ 3.583] recv DATA frame <length=7086, flags=0x00, stream_id=2> [ 3.779] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 4.186] recv DATA frame <length=7086, flags=0x00, stream_id=2> [ 4.186] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 4.186] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 4.395] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 4.396] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 4.602] recv DATA frame <length=5667, flags=0x00, stream_id=6> [ 4.602] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=33993) [ 4.602] recv DATA frame <length=2829, flags=0x00, stream_id=2> [ 4.602] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=33975) [ 4.808] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 4.809] recv DATA frame <length=6379, flags=0x01, stream_id=2> ; END_STREAM [ 5.010] recv DATA frame <length=3536, flags=0x00, stream_id=6> [ 5.420] recv DATA frame <length=8505, flags=0x00, stream_id=6> [ 5.420] recv DATA frame <length=5667, flags=0x00, stream_id=6> [ 5.628] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 5.842] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 5.842] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 5.842] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34002) [ 5.842] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=33281) [ 6.057] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 6.273] recv DATA frame <length=8505, flags=0x00, stream_id=6> [ 6.490] recv DATA frame <length=9924, flags=0x00, stream_id=6> [ 6.490] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 6.706] recv DATA frame <length=4248, flags=0x00, stream_id=6> [ 6.706] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34002) [ 6.706] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=34002) [ 6.924] recv DATA frame <length=8505, flags=0x00, stream_id=6> [ 7.141] recv DATA frame <length=8505, flags=0x00, stream_id=6> [ 7.361] recv DATA frame <length=8505, flags=0x00, stream_id=6> [ 7.361] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34020) [ 7.574] recv DATA frame <length=9924, flags=0x00, stream_id=6> [ 7.574] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=34029) [ 7.787] recv DATA frame <length=9924, flags=0x00, stream_id=6> [ 7.787] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 7.998] recv DATA frame <length=7086, flags=0x00, stream_id=6> [ 8.210] recv DATA frame <length=9924, flags=0x00, stream_id=6> [ 8.210] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=0> (window_size_increment=34011) [ 8.210] send WINDOW_UPDATE frame <length=4, flags=0x00, stream_id=6> (window_size_increment=34011) [ 8.425] recv DATA frame <length=11343, flags=0x00, stream_id=6> [ 8.426] recv DATA frame <length=2829, flags=0x00, stream_id=6> [ 8.426] recv DATA frame <length=4053, flags=0x01, stream_id=6> ; END_STREAM [ 8.631] recv DATA frame <length=4443, flags=0x00, stream_id=13> [ 8.633] recv DATA frame <length=1290, flags=0x01, stream_id=13> ; END_STREAM [ 8.633] send GOAWAY frame <length=8, flags=0x00, stream_id=0> (last_stream_id=10, error_code=NO_ERROR(0x00), opaque_data(0)=[]) </code></pre> <p>当然，我们也可以使用 grep 搜索出来 server push 的相关 stream：</p> <pre> <code class="language-objectivec">nghttp -nv 'https://h2o.examp1e.net' | grep 'PUSH_PROMISE' [ 1.582] recv PUSH_PROMISE frame <length=59, flags=0x04, stream_id=13> [ 1.582] recv PUSH_PROMISE frame <length=33, flags=0x04, stream_id=13> [ 1.582] recv PUSH_PROMISE frame <length=35, flags=0x04, stream_id=13> [ 1.582] recv PUSH_PROMISE frame <length=24, flags=0x04, stream_id=13> [ 1.582] recv PUSH_PROMISE frame <length=28, flags=0x04, stream_id=13> </code></pre> <h2>使用 NodeJS 搭建 HTTP/2 服务器</h2> <p>在大前端的时代背景下，客户端开发不会点 JavaScript 都快混不下去了，笔者前段时间在我司前端轮岗了两周，再加上之前也写过 ReactNative，但还是感觉前端变化之快领人咋舌，革命尚未结束，同志仍需努力啊。</p> <p>咱们直接上代码：</p> <pre> <code class="language-objectivec">var http2 = require('http2');// http2 var url=require('url'); // https://www.npmjs.com/package/url var fs=require('fs'); // https://www.npmjs.com/package/fs var mine=require('mine'); var path=require('path'); // 路径 var server = http2.createServer({ key: fs.readFileSync('./localhost.key'), cert: fs.readFileSync('./localhost.crt') }, function(request, response) { // var pathname = url.parse(request.url).pathname; var realPath = './push.json' ;//path.join(pathname,"push.json"); //这里设置自己的文件路径，这是该次response返回的内容; var pushArray = []; var ext = path.extname(realPath); ext = ext ? ext.slice(1) : 'unknown'; var contentType = mine[ext] || "text/plain"; if (fs.existsSync(realPath)) { console.log('success') response.writeHead(200, { 'Content-Type': contentType }); response.write(fs.readFileSync(realPath,'binary')); // 注意 push 路径必须是绝对路径，这是该次 server push 返回的内容 var pushItem = response.push('/Users/f.li/Desktop/http2-nodeServer/newpush.json', { response: { 'content-type': contentType } }); pushItem.end(fs.readFileSync('/Users/f.li/Desktop/http2-nodeServer/newpush.json','binary'),()=>{ console.log('newpush end') }); response.end(); } else { response.writeHead(404, { 'Content-Type': 'text/plain' }); response.write("This request URL " + realPath + " was not found on this server."); response.end(); } }); server.listen(3000, function() { console.log('listen on 3000'); }); </code></pre> <p>这里需要注意几点：</p> <ul> <li>创建http2的nodejs服务必须时基于https的，因为现在主流的浏览器都要支持SSL/TLS的http2，证书和私钥可以自己通过 <a href="/misc/goto?guid=4958830637256946961" rel="nofollow,noindex">OPENSSL</a> 生成。</li> <li>node http2的相关api和正常的node httpserver相同，可以直接使用。</li> </ul> <p>使用 nghttp 测试一下我们的代码有没有进行 server push：</p> <pre> <code class="language-objectivec">~ nghttp -nv 'https://localhost:3000/' [ 0.007] Connected The negotiated protocol: h2 [ 0.029] recv SETTINGS frame <length=0, flags=0x00, stream_id=0> (niv=0) [ 0.029] send SETTINGS frame <length=12, flags=0x00, stream_id=0> (niv=2) [SETTINGS_MAX_CONCURRENT_STREAMS(0x03):100] [SETTINGS_INITIAL_WINDOW_SIZE(0x04):65535] [ 0.029] send SETTINGS frame <length=0, flags=0x01, stream_id=0> ; ACK (niv=0) [ 0.029] send PRIORITY frame <length=5, flags=0x00, stream_id=3> (dep_stream_id=0, weight=201, exclusive=0) [ 0.029] send PRIORITY frame <length=5, flags=0x00, stream_id=5> (dep_stream_id=0, weight=101, exclusive=0) [ 0.029] send PRIORITY frame <length=5, flags=0x00, stream_id=7> (dep_stream_id=0, weight=1, exclusive=0) [ 0.029] send PRIORITY frame <length=5, flags=0x00, stream_id=9> (dep_stream_id=7, weight=1, exclusive=0) [ 0.029] send PRIORITY frame <length=5, flags=0x00, stream_id=11> (dep_stream_id=3, weight=1, exclusive=0) [ 0.029] send HEADERS frame <length=38, flags=0x25, stream_id=13> ; END_STREAM | END_HEADERS | PRIORITY (padlen=0, dep_stream_id=11, weight=16, exclusive=0) ; Open new stream :method: GET :path: / :scheme: https :authority: localhost:3000 accept: */* accept-encoding: gzip, deflate user-agent: nghttp2/1.21.1 [ 0.043] recv SETTINGS frame <length=0, flags=0x01, stream_id=0> ; ACK (niv=0) [ 0.049] recv (stream_id=13) :status: 200 [ 0.049] recv (stream_id=13) content-type: text/plain [ 0.049] recv (stream_id=13) date: Tue, 11 Apr 2017 08:34:46 GMT [ 0.049] recv HEADERS frame <length=34, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0) ; First response header [ 0.049] recv DATA frame <length=35, flags=0x00, stream_id=13> [ 0.049] recv (stream_id=13) :method: GET [ 0.049] recv (stream_id=13) :scheme: https [ 0.050] recv (stream_id=13) :authority: localhost:3000 [ 0.050] recv (stream_id=13) :path: /Users/f.li/Desktop/http2-nodeServer/newpush.json [ 0.050] recv PUSH_PROMISE frame <length=56, flags=0x04, stream_id=13> ; END_HEADERS (padlen=0, promised_stream_id=2) [ 0.050] recv DATA frame <length=0, flags=0x01, stream_id=13> ; END_STREAM [ 0.050] recv (stream_id=2) :status: 200 [ 0.050] recv (stream_id=2) date: Tue, 11 Apr 2017 08:34:46 GMT [ 0.050] recv HEADERS frame <length=2, flags=0x04, stream_id=2> ; END_HEADERS (padlen=0) ; First push response header [ 0.050] recv DATA frame <length=21, flags=0x00, stream_id=2> [ 0.050] recv DATA frame <length=0, flags=0x01, stream_id=2> ; END_STREAM [ 0.050] send GOAWAY frame <length=8, flags=0x00, stream_id=0> (last_stream_id=2, error_code=NO_ERROR(0x00), opaque_data(0)=[]) </code></pre> <p>看到了 PUSH_PROMISE 的帧，说明进行了 server push。</p> <p>同样也可以使用chrome查看 server push，如下图所示：</p> <p><img src="https://simg.open-open.com/show/fb59bce84149feeb23b9bf6c01075c7c.png"></p> <p>服务端介绍基本完毕。下面我们来介绍一些 iOS 客户端对 Server Push 的使用。</p> <h2>iOS 使用 HTTP/2 Server Push</h2> <p>Apple 在这方面做的很好，基本实现了客户端无感调用http/2 server push。但是笔者查看了些许资料，现在只有iOS 10 支持 http/2。</p> <p>直接上代码吧：</p> <pre> <code class="language-objectivec">#import "ViewController.h" @interface ViewController ()<NSURLSessionDelegate> @property(nonatomic,strong)NSURLSession *session; @end @implementation ViewController - (void)viewDidLoad { [super viewDidLoad]; // Do any additional setup after loading the view, typically from a nib. } #pragma mark - Touch - (void)touchesBegan:(NSSet<UITouch *> *)touches withEvent:(UIEvent *)event { [self urlSession]; } #pragma mark - 发送请求 - (void)urlSession { NSURL *url = [NSURL URLWithString:@"https://localhost:3000"]; //发送HTTPS请求是需要对网络会话设置代理的 _session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]]; NSURLSessionDataTask *dataTask = [_session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) { NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]); // 收到该次请求后，立即请求下次的内容 [self urlSessionPush]; }]; [dataTask resume]; } - (void)urlSessionPush { NSURL *url = [NSURL URLWithString:@"https://localhost:3000/Users/f.li/Desktop/http2-nodeServer/newpush.json"]; NSURLSessionDataTask *dataTask = [_session dataTaskWithURL:url completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) { NSLog(@"%@",[[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding]); }]; [dataTask resume]; } #pragma mark - URLSession Delegate - (void)URLSession:(NSURLSession *)session didReceiveChallenge:(NSURLAuthenticationChallenge *)challenge completionHandler:(void (^)(NSURLSessionAuthChallengeDisposition, NSURLCredential * _Nullable))completionHandler { // 这里还要设置下 plist 中设置 ATS if (![challenge.protectionSpace.authenticationMethod isEqualToString:@"NSURLAuthenticationMethodServerTrust"]) { return; } NSURLCredential *credential = [[NSURLCredential alloc] initWithTrust:challenge.protectionSpace.serverTrust]; completionHandler(NSURLSessionAuthChallengeUseCredential,credential); } - (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didFinishCollectingMetrics:(NSURLSessionTaskMetrics *)metrics { NSArray *fetchTypes = @[ @"Unknown", @"Network Load", @"Server Push", @"Local Cache"]; for(NSURLSessionTaskTransactionMetrics *transactionMetrics in [metrics transactionMetrics]) { NSLog(@"protocol[%@] reuse[%d] fetch:%@ - %@", [transactionMetrics networkProtocolName], [transactionMetrics isReusedConnection], fetchTypes[[transactionMetrics resourceFetchType]], [[transactionMetrics request] URL]); if([transactionMetrics resourceFetchType] == NSURLSessionTaskMetricsResourceFetchTypeServerPush) { NSLog(@"Asset was server pushed"); } } } - (void)didReceiveMemoryWarning { [super didReceiveMemoryWarning]; // Dispose of any resources that can be recreated. } @end </code></pre> <p>分别看下服务端和客户端的Log:</p> <p>客户端：</p> <pre> <code class="language-objectivec">Http2ServerPush[2525:274943] protocol[h2] reuse[0] fetch:Network Load - https://localhost:3000/ Http2ServerPush[2525:274943] {"message":" http2.0 server is ok"} Http2ServerPush[2525:274943] protocol[h2] reuse[1] fetch:Server Push - https://localhost:3000/Users/f.li/Desktop/http2-nodeServer/newpush.json Http2ServerPush[2525:274943] Asset was server pushed Http2ServerPush[2525:274943] {"message":"newPush"} </code></pre> <p>服务端：</p> <pre> <code class="language-objectivec">http2-nodeServer npm start > http2-nodeServer@1.0.0 start /Users/f.li/Desktop/http2-nodeServer > node index.js listen on 3000 success newpush end </code></pre> <p>看来确实是客户端发出了两次请求，但是服务端只响应了一次（该次响应+ server push）</p> <p> </p> <p>来自：http://www.lijianfei.cn/2017/04/11/ios-http2-server-push/</p> <p> </p> 本文由用户 jzed4573 自行上传分享，仅供网友学习交流。所有权归原作者，若您的权利被侵害，请联系管理员。
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