How to use Apache mod_expires and mod_headers to implement file caching and mod_deflate compressed output

1. Use mod_deflate module to compress output (start gzip)

Enablemod_deflate

Add

in httpd.conf. By default, all output needs to be compressed, and only some are excluded.

2. Use Apache mod_expires and mod_headers to implement file caching

Openmod_expires Use mod_expires with mod_headers

, in httpd. conf, add

Using mod_headers, add

to httpd.conf
3.Cache-Control description:

#The cache of web pages is controlled by the "Cache-control" in the HTTP message header. Commonly used Values ​​include private, no-cache, max-age, must-revalidate, etc. The default is private. Its function is divided into the following situations according to different re-browsing methods:

(1) Open a new window
The value is private, no-cache, must-revalidate, then the server will be accessed again when a new window is opened.
If a max-age value is specified, the server will not be accessed again within this value, for example:
Cache-control: max-age=5 (indicates 5 seconds after accessing this web page) Accessing again within seconds will not go to the server)
(2) Press Enter in the address bar
If the value is private or must-revalidate, the server will only be accessed the first time, and will not be accessed again.
If the value is no-cache, it will be accessed every time.
If the value is max-age, it will not be accessed again before expiration.
(3) Press the back button
If the value is private, must-revalidate, max-age, it will not be accessed again.
If the value is no-cache, it will be accessed repeatedly every time
( 4) Press the refresh button
No matter what the value is, it will be accessed repeatedly
Cache-Control (regular header, HTTP1.1)
.public: (Response header only)
Response: Inform cachers of any channel that the response can be cached unconditionally.
.private (Only For the response header)
Response: Inform the cacher (as far as I know, it refers to the user agent, the local cache of common browsers. The user also refers to the system user. But perhaps, it should not be excluded that some gateways can Identify each end user), only cache the response for a single user. And you can specify a certain field. For example, private - "username", the header content named username in the response header will not be shared and cached.
.no-cache:
Request: Inform the cacher that the original request must be forwarded exactly as it is, and inform any cachers not to directly use your cached copy to fool people. You need to go Forward my request and verify your cache (if any). Corresponding noun: end-to-end reloading.
Response: Allow cachers to cache copies. So its actual value is to always force cachers to calibrate Verify the freshness of the cache. Once freshness is confirmed, you can use the cached copy as a response. no-cache, you can also specify an included field, such as a typical application, no-cache=Set-Cookie. The result of this is to inform Cache, for the Set-Cookie field, you should not use cached content. Instead, use Xindi. Other content can be cached.
.no-store:
Request: inform, request and responses are prohibited from being cached. (Perhaps for privacy reasons)
Response: Same as above.
.max-age:
Request: Force response cacher, according to this value, Verify freshness. That is, compare it with its own Age value and the request time. If the max-age value is exceeded, server-side verification is forced to ensure that a fresh response is returned. Its function is essentially similar to traditional Expires. But the difference is that Expires is compared based on a specific date value. Once the cacher's own time is inaccurate, the result may be wrong. Max-age obviously does not have this problem. Max-age also has a higher priority than Expires.
Response: Similar to the above, except that the sender is different.
.max-stale:
Request: Meaning, I allow the cacher to send one, and it will not expire A stale cache that exceeds the specified number of seconds.
Response: Same as above.
.must-revalidate (response header only)
Response: Meaning, if the cache is past fresh period, you must re-verify instead of trying to return a cache that is not in the fresh period. The difference from no-cache is that no-cache completely ignores the concept of fresh period and always forces re-validation. In theory, must-revalidate is more Saves traffic, but compared to no-cache, it may not always be so accurate. Because even if the cacher thinks it is fresh, there is no guarantee that the server has not been updated. If the cacher is a caching proxy server, if it tries to When revalidating, if the original server cannot be connected, a stale copy in the cache is not allowed to be returned. Instead, a 504 Gateway timeout.
.proxy-revalidate(only Response header)
Response: The restriction is similar to must-revalidate. The difference is the scope of the acceptor. proxy-revalidate is to exclude the user agent's cache. That is, its rules do not apply to the user agent's local Cache.
.min-fresh(request header only)
Request: Inform the cacher that if the current time plus the value of min-fresh exceeds the expiration time of the cache, a new one will be given to me. In fact, I personally feel that its function is somewhat similar to max-age. But it is larger. The difference is semantic.
.only-if-cached: (only request header)
Request: Inform the cacher that I want the content to come from the cache, and I don’t care about being cached. Cache response, whether it is fresh.
.s-maxage(response header only)
Response: The only difference from max-age is that s-maxage only applies to shared cache . does not refer to the local cache of the user agent, such as the cache for a single user. In addition, s-maxage has a higher priority than max-age..cache-extension (cache-extension is a general name. It refers to All custom, or extended, instructions, both the client and the server can customize and extend Cache-Control related instructions.) Then, in fact, we can do this Cache-Control:max-age=300, custom-directive = xxx, public. In this way, we define an extension directive collectively called cache-extension. If the corresponding client or server does not recognize this directive, it will be ignored.
.no-transform
Request: Tell the agent not to change the media type, such as jpg, you changed it to png.
Response: Same as above.

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