HTTP cache
role
Revisiting a web page can speed up user access and save traffic.
Caching strategies
The HTTP cache-Control header defines the Cache policy, under what conditions responses can be cached, and for how long.
A header (such as Expires) defined in the HTTP/1.1 specification that replaces a previous header (such as Expires) used to define caching policies.
Cache conditions
no store
Do not cache
no cache
Every time you use the cache, go to the server to verify that the resource is up to date.
Where can I cache it
Public
The default
privite
Only cached on the user’s browser, not on the public cache
How long
MAX-AGE
If the cache is used to request resources, the cache must be obtained from the server
Is it the latest
If it is the latest, continue to use the cache, otherwise request from the server. The cached available information is placed in HTTP Response headers
EXPIRES
The expiration date is marked.
disadvantages
If the client and server time is inconsistent, the updated file information may be incorrect.
HTTP / 1.0
LAST-MODIFIED
When the resource was last updated. Accurate to the second. When the client requests the resource again, it places this value in the request header if-modified-since to determine If it is updated.
HTTP / 1.0
disadvantages
If updates occur within seconds, there is an error.
ETAG
Returns a string identifier that changes based on the contents of the file. After the browser accepts the request header, the next request is sent as if-none-match. If the eTag value does not change, caching is used. The priority is the highest.
RESPONSE STATUS
The server gets the latest results
Back to 200
Resources read directly from the local cache
Back to 200
Use the cache after checking with the server
Back to 304
Storage location
The browser determines whether it is stored in memory cache or disk cache, depending on the brand.
How to configure
On the server, see github.com/h5bp/server…
reference
Google Document HTTP cache
Additional reading
http-cache-headers
http-cache
Pay attention to
For non-static resources, such as JSON (/user/: ID) to retrieve user information, the browser may ignore the cache.
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