http请求缓存小记

[iscarecrow]

关键词

• expires/cache-control
• if-modified-since/if-none-match
• eTag

如何进行http缓存

304缓存

1.if-modified-since/Last-Modified

client request if-modified-since: time1
server response  Last-Modified: time2
time1 = time2

2.if-none-match/ETag

client request if-modified-since: eTag1
server response ETag:eTag2
eTag1 = eTag2

200缓存

cache-control: max-age = 2592000 (s) （设置缓存时间）
expires: maybe next year

如何不进行http缓存

How to control web page caching, across all browsers?

Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0

使用场景：隐私数据, api请求

QA

一. 200 OK (from cache) 与304 Not Modified 区别

200 (from cache)

• request status 为200的情况下并没有发起请求。根据expires/cache-control判断。
• 回车访问

304

• 304的情况，http发起了请求。服务器响应。但是并不下载文件。根据if-modified-since/if-none-match确认缓存文件是否存在。
• 强刷页面

结论：time 200快于304。

cache-control:max-age=0和no-cache的区别

• What's the difference between Cache-Control: max-age=0 and no-cache?

no-cache no-store

• Why both no-cache and no-store should be used in HTTP response?
• Two Important Differences between Firefox and IE Caching

other

• if-modified-since if-none-match priority??
• if doc need cache ?? maybe no
• public && private , when to use ?

参考资料

• HTTP 缓存
• Caching Tutorial
• 一次完整的HTTP事务是怎样一个过程？