第1部分　向HTTP/2靠攏
第1章　萬維網(wǎng)與HTTP....................................................................................................3
1.1　萬維網(wǎng)的原理 .......................................................................................................3
1.1.1　因特網(wǎng)與萬維網(wǎng) .......................................................................................4
1.1.2　打開網(wǎng)頁時(shí)會(huì)發(fā)生什么 ...........................................................................5
1.2　什么是HTTP .........................................................................................................9
1.3　HTTP的語法和歷史 ...........................................................................................16
1.3.1　HTTP/0.9 .................................................................................................16
1.3.2　HTTP/1.0 .................................................................................................17
1.3.3　HTTP/1.1 .................................................................................................23
1.4　HTTPS簡介 .........................................................................................................29
1.5　查看、發(fā)送和接收HTTP消息的工具 ...............................................................32
1.5.1　瀏覽器開發(fā)者工具 .................................................................................32
1.5.2　發(fā)送 HTTP 請求 .....................................................................................34
1.5.3　其他工具 .................................................................................................35
總結(jié) ..............................................................................................................................36
第2章　通向HTTP/2之路...............................................................................................37
2.1　HTTP/1.1和當(dāng)前的萬維網(wǎng) .................................................................................38
2.1.1　HTTP/1.1 根本的性能問題 ....................................................................40
2.1.2　HTTP/1.1 管道化 ....................................................................................42
2.1.3　網(wǎng)絡(luò)性能瀑布流圖 .................................................................................43
2.2　解決HTTP/1.1性能問題的方案 .........................................................................45
2.2.1　使用多個(gè) HTTP 連接 .............................................................................46
2.2.2　發(fā)送更少的請求 .....................................................................................49
2.2.3　HTTP/1 性能優(yōu)化總結(jié) ...........................................................................50
2.3　HTTP/1.1的其他問題 .........................................................................................50
2.4　實(shí)際案例 .............................................................................................................51
2.4.1　示例網(wǎng)站 1: amazon.com .......................................................................52
2.4.2　示例網(wǎng)站 2 ： imgur.com .........................................................................56
2.4.3　這個(gè)問題究竟有多嚴(yán)重 .........................................................................57
2.5　從HTTP/1.1到HTTP/2 ........................................................................................58
2.5.1　SPDY .......................................................................................................58
2.5.2　HTTP/2 ....................................................................................................61
2.6　HTTP/2對Web性能的影響 .................................................................................62
2.6.1　展示 HTTP/2 能力的絕佳示例 ..............................................................62
2.6.2　對 HTTP/2 提升性能的期望 ..................................................................65
2.6.3　HTTP/1.1 的一些性能變通方法可能是反模式 ....................................70
總結(jié) ..............................................................................................................................70
第3章　升級到HTTP/2. ..................................................................................................72
3.1　HTTP/2的支持 ....................................................................................................72
3.1.1　瀏覽器對 HTTP/2 的支持 ......................................................................73
3.1.2　服務(wù)器對 HTTP/2 的支持 ......................................................................78
3.1.3　兼容不支持 HTTP/2 的情況 ..................................................................80
3.2　網(wǎng)站開啟HTTP/2的方法 ....................................................................................81
3.2.1　在 Web 服務(wù)器上開啟 HTTP/2..............................................................81
3.2.2　反向代理實(shí)現(xiàn) HTTP/2 ...........................................................................84
3.2.3　通過 CDN 實(shí)現(xiàn) HTTP/2 ........................................................................87
3.2.4　小結(jié) .........................................................................................................89
3.3　常見問題 .............................................................................................................89
總結(jié) ..............................................................................................................................93
第2部分　使用HTTP/2
第4章　HTTP/2協(xié)議基礎(chǔ)...............................................................................................97
4.1　為什么是HTTP/2而不是HTTP/1.2 ....................................................................97
4.1.1　使用二進(jìn)制格式替換文本格式 .............................................................99
4.1.2　多路復(fù)用代替同步請求 .......................................................................100
4.1.3　流的優(yōu)先級和流量控制 .......................................................................103
4.1.4　首部壓縮 ...............................................................................................104
4.1.5　服務(wù)端推送 ...........................................................................................105
4.2　如何創(chuàng)建一個(gè)HTTP/2連接 ..............................................................................105
4.2.1　使用 HTTPS 協(xié)商 .................................................................................106
4.2.2　使用 HTTP upgrade 首部 .....................................................................113
4.2.3　使用先驗(yàn)知識(shí) .......................................................................................116
4.2.4　HTTP Alternative Services ....................................................................117
4.2.5　HTTP/2 前奏消息 .................................................................................117
4.3　HTTP/2幀 ..........................................................................................................119
4.3.1　查看 HTTP/2 幀 ....................................................................................119
4.3.2　HTTP/2 幀數(shù)據(jù)格式 .............................................................................126
4.3.3　HTTP/2 消息流示例 .............................................................................128
4.3.4　其他幀 ...................................................................................................143
總結(jié) ............................................................................................................................148
第5章　實(shí)現(xiàn)HTTP/2推送.............................................................................................149
5.1　什么是HTTP/2服務(wù)端推送 ..............................................................................149
5.2　如何推送 ...........................................................................................................153
5.2.1　使用 HTTP link 首部推送 ....................................................................153
5.2.2　查看 HTTP/2 推送 ................................................................................156
5.2.3　使用 link 首部從下游系統(tǒng)推送 ...........................................................159
5.2.4　更早推送 ...............................................................................................162
5.2.5　使用其他方式推送 ...............................................................................168
5.3　HTTP/2推送在瀏覽器中如何運(yùn)作 ..................................................................171
5.3.1　查看推送緩存如何工作 .......................................................................172
5.3.2　使用 RST_STREAM 拒絕推送 ...........................................................175
5.4　如何實(shí)現(xiàn)條件推送 ...........................................................................................176
5.4.1　在服務(wù)端跟蹤推送的資源 ...................................................................176
5.4.2　使用 HTTP 條件請求 ...........................................................................176
5.4.3　使用基于 cookie 的推送 ......................................................................177
5.4.4　使用緩存摘要 .......................................................................................178
5.5　推送什么 ...........................................................................................................179
5.5.1　你能推送什么 .......................................................................................179
5.5.2　應(yīng)該推送什么 .......................................................................................180
5.5.3　自動(dòng)化推送 ...........................................................................................181
5.6　HTTP/2推送常見問題 ......................................................................................182
5.7　HTTP/2推送對性能的影響 ..............................................................................184
5.8　對比推送和預(yù)加載 ...........................................................................................185
5.9　HTTP/2推送的其他應(yīng)用場景 ..........................................................................188
總結(jié) ............................................................................................................................190
第6章　HTTP/2優(yōu)化....................................................................................................192
6.1　HTTP/2對Web開發(fā)者的影響 ...........................................................................192
6.2　一些HTTP/1.1優(yōu)化方法是否成了反模式 .......................................................194
6.2.1　HTTP/2 請求依然有開銷 .....................................................................194
6.2.2　HTTP/2 不是沒有限制 .........................................................................197
6.2.3　越大的資源壓縮越有效 .......................................................................199
6.2.4　帶寬限制和資源競爭 ...........................................................................201
6.2.5　域名分片 ...............................................................................................202
6.2.6　內(nèi)聯(lián)資源 ...............................................................................................203
6.2.7　總結(jié) .......................................................................................................203
6.3　在HTTP/2下依然有效的性能優(yōu)化技術(shù) ..........................................................204
6.3.1　減少要傳輸?shù)臄?shù)據(jù)量 ...........................................................................204
6.3.2　使用緩存防止重復(fù)發(fā)送數(shù)據(jù) ...............................................................211
6.3.3　Service Worker 可以大幅減少網(wǎng)絡(luò)加載 .............................................215
6.3.4　不發(fā)送不需要的內(nèi)容 ...........................................................................216
6.3.5　HTTP 資源暗示 ....................................................................................217
6.3.6　減少最后 1 公里的延遲 .......................................................................219
6.3.7　優(yōu)化 HTTPS ..........................................................................................219
6.3.8　和 HTTP 無關(guān)的性能優(yōu)化技術(shù) ...........................................................222
6.4　同時(shí)對HTTP/1.1和HTTP/2做優(yōu)化 ..................................................................222
6.4.1　計(jì)算 HTTP/2 流量 ................................................................................223
6.4.2　在服務(wù)端檢測 HTTP/2 支持 ................................................................224
6.4.3　在客戶端檢測 HTTP/2 支持 ................................................................228
6.4.4　連接合并 ...............................................................................................228
6.4.5　還要為 HTTP/1.1 的用戶優(yōu)化多久 .....................................................230
總結(jié) ............................................................................................................................231
第3部分　HTTP/2進(jìn)階
第7章　高級HTTP/2概念.............................................................................................235
7.1　流狀態(tài) ...............................................................................................................236
7.2　流量控制 ...........................................................................................................239
7.2.1　流量控制示例 .......................................................................................240
7.2.2　在服務(wù)器上設(shè)置流量控制 ...................................................................244
7.3　流優(yōu)先級 ...........................................................................................................244
7.3.1　流依賴關(guān)系 ...........................................................................................245
7.3.2　流權(quán)重 ...................................................................................................248
7.3.3　為什么優(yōu)先級策略如此復(fù)雜 ...............................................................251
7.3.4　Web 服務(wù)器和瀏覽器中的優(yōu)先級策略 ...............................................252
7.4　HTTP/2一致性測試 ..........................................................................................255
7.4.1　服務(wù)端一致性測試 ...............................................................................255
7.4.2　客戶端一致性測試 ...............................................................................258
總結(jié) ............................................................................................................................258
第8章　HPACK首部壓縮.............................................................................................259
8.1　為什么需要首部壓縮 .......................................................................................259
8.2　壓縮的運(yùn)作方式 ...............................................................................................261
8.2.1　查表法 ...................................................................................................262
8.2.2　更高效的編碼技術(shù) ...............................................................................263
8.2.3　Lookback( 反查 ) 壓縮 .........................................................................264
8.3　HTTP正文壓縮 .................................................................................................265
8.4　HTTP/2的HPACK首部壓縮 .............................................................................267
8.4.1　HPACK 靜態(tài)表 .....................................................................................268
8.4.2　HPACK 動(dòng)態(tài)表 .....................................................................................269
8.4.3　HPACK 首部類型 .................................................................................269
8.4.4　Huffman 編碼表 ...................................................................................275
8.4.5　Huffman 編碼腳本 ...............................................................................276
8.4.6　為什么 Huffman 編碼不總是最佳的 ..................................................278
8.5　HPACK壓縮實(shí)例 ..............................................................................................279
8.6　客戶端和服務(wù)端對HPACK的實(shí)現(xiàn) ..................................................................285
8.7　HPACK的價(jià)值 ..................................................................................................287
總結(jié) ............................................................................................................................287
第4部分　HTTP的未來
第9章　TCP、QUIC和HTTP/3....................................................................................291
9.1　TCP的低效率因素，以及HTTP ......................................................................292
9.1.1　創(chuàng)建 HTTP 連接的延遲 .......................................................................293
9.1.2　TCP 擁塞控制對性能的影響...............................................................295
9.1.3　TCP 低效率因素對 HTTP/2 的影響 ...................................................303
9.1.4　優(yōu)化 TCP ...............................................................................................307
9.1.5　TCP 和 HTTP 的未來...........................................................................313
9.2　QUIC .................................................................................................................313
9.2.1　QUIC 的性能優(yōu)勢 ................................................................................315
9.2.2　QUIC 和網(wǎng)絡(luò)技術(shù)棧 ...........................................................................316
9.2.3　什么是 UDP，為什么 QUIC 基于它 ..................................................317
9.2.4　標(biāo)準(zhǔn)化 QUIC ........................................................................................320
9.2.5　HTTP/2 和 QUIC 的不同 .....................................................................322
9.2.6　QUIC 的工具 ........................................................................................325
9.2.7　QUIC 實(shí)現(xiàn) ............................................................................................327
9.2.8　你應(yīng)該使用 QUIC 嗎 ...........................................................................327
總結(jié) ............................................................................................................................328
第10章　HTTP將何去何從..........................................................................................329
10.1　關(guān)于HTTP/2的爭議，以及它沒有解決的問題 ............................................330
10.1.1　反對 SPDY 的觀點(diǎn) .............................................................................330
10.1.2　隱私問題和 HTTP 中的狀態(tài) .............................................................332
10.1.3　HTTP 和加密 ......................................................................................337
10.1.4　傳輸協(xié)議的問題 .................................................................................340
10.1.5　HTTP/2 太過于復(fù)雜 ...........................................................................344
10.1.6　HTTP/2 是一種權(quán)宜之計(jì) ...................................................................345
10.2　HTTP/2的實(shí)際應(yīng)用 ........................................................................................345
10.3　HTTP/2的未來版本，HTTP/3或者HTTP/4會(huì)帶來什么 ..............................347
10.3.1　QUIC 是 HTTP/3 嗎 ...........................................................................347
10.3.2　更進(jìn)一步改進(jìn) HTTP 二進(jìn)制協(xié)議 ....................................................348
10.3.3　在傳輸層之上進(jìn)一步優(yōu)化 HTTP ......................................................348
10.3.4　什么時(shí)候會(huì)需要新的 HTTP 版本 .....................................................351
10.3.5　如何引入未來版本的 HTTP ..............................................................352
10.4　將HTTP當(dāng)作一個(gè)更通用的傳輸協(xié)議 ...........................................................352
10.4.1　使用 HTTP 語義和消息來傳遞非 Web 流量 ....................................353
10.4.2　使用 HTTP/2 二進(jìn)制成幀層 ..............................................................354
10.4.3　使用 HTTP 啟動(dòng)另一個(gè)協(xié)議 .............................................................355
總結(jié) ............................................................................................................................359
附錄A　將常見Web服務(wù)器升級到HTTP/2...................................................................360