http protocol

HTTP/2 头部压缩技术介绍

rfc7540

Head-of-Line Blocking in QUIC and HTTP/3: The Details

Introduction to HTTP/2

HTTP/2 头部压缩技术介绍

HTTP/2.0 Header Compression（上）

队头阻塞（Head-of-Line blocking）

http structure

1. start line: GET /background.png HTTP/1.1
2. Header:
   1. provide extra message
   2. tell the brower do sth(cache)
3. body: json, xml,etc.

content-type

cache-control

load local cache directly

cache-control, expire before the time, it will load local;

cache-control:

1. public: allow proxy to cache the data(default value)
2. private: only local browser can cache the data
3. no-cache: it must go through valiation with origin server;
4. no-store: can’t cache
5. max-age=xxx;

validate the resource from server

If-Modified-Since: compare resource time If-None-Match: compare resource ta ;

if same, return 304; otherwise 200

http2

what:

1. multiplex: add http2 frame heade
2. header compresee:small size header

multiplex

Head-of-Line Blocking: 队列前部阻塞后部

why: http 基于content-length来区分消息的边界， 这要求数据必须是串行的

solve: http2 frame，

1. 基于frame id and flag分割消息
2. 不同资源被交叉发送

http2 frame header: frame filed:

1. Stream Identifier
2. type:
   1. data: 0x0
   2. headers 0x1
3. flags:
   1. END_STREAM
   2. END_HEADERS

example: a.js 2byte b.js 2byte header frame1, data frame1 header frame1, data frame2 data frame1, data frame2

![[Pasted image 20221220164804.png]]

mutiplex strategy: 1111， 2222

1. fair：12121212
2. 加权(2权重是1两倍): 22122122111

heder compression

使用index代替字段 header.key, header

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3

:method GET = 2 = 00000010 
:method POST = 3 = 00000011
:path / = 4 = 00000100 

huffman coding:

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2
3
4

A:0 
B:10 
C:110 
D:111

http keep alive

what: http 未关闭 tcp connection 而 让 tcp connection alive

http keep alive 基于 tcp-keep-alive 实现的吗: http 未关闭 tcp connection,此时 tcp 短时间 就是alive, 长时间的alive 才需要 tcp keep alive

restful api

what:   REpresentational State Transfer， 表现层状态转移 是一种架构风格， 遵循一定的指导原则与约束

restful vs http: restful 不一定 基于http 实现， 基于 http实现 叫做： HTTP-based RESTful API

methods:

1. Create — POST
2. Read/Retrieve — GET
3. Update — PUT/PATCH
4. Delete — DELETE

example

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   // get all prodducets
   Method: GET
   Endpoint: https://fakestoreapi.com/products

   // retrieve product with id 12
   Method: GET
   ENDPOINT: https://fakestoreapi.com/products/12

   // add new produects
   Method: POST
   ENDPOINT: https://fakestoreapi.com/products
   Data:  {} //Data in form of JSON

   //To update a product resource with id 10
   Method: PUT
   ENDPOINT: https://fakestoreapi.com/products/10
   Data:  {} //Data in form of JSON

   //To delete a resource with id 5:
   Method: DELETE
   ENDPOINT: https://fakestoreapi.com/products/5

URL , URI

URI： A Uniform Resource Identifier URL : A Uniform Resource Locator, schema+URI