# Apache模块 mod_cache
| [说明](#calibre_link-11) | 基于URI键的内容动态缓冲(内存或磁盘) |
| --- | --- |
| [状态](#calibre_link-12) | 扩展(E) |
| [模块名](#calibre_link-13) | cache_module |
| [源文件](#calibre_link-14) | mod_cache.c |
### 概述
This module should be used with care and can be used to circumvent `Allow`和`Deny` directives. You should not enable caching for any content to which you wish to limit access by client host name, address or environment variable.
`mod_cache` implements an [RFC 2616](http://www.ietf.org/rfc/rfc2616.txt) compliant HTTP content cache that can be used to cache either local or proxied content. `mod_cache` requires the services of one or more storage management modules. Two storage management modules are included in the base Apache distribution:
`mod_disk_cache`
implements a disk based storage manager.
`mod_mem_cache`
implements a memory based storage manager. `mod_mem_cache` can be configured to operate in two modes: caching open file descriptors or caching objects in heap storage. `mod_mem_cache` can be used to cache locally generated content or to cache backend server content for `mod_proxy` when configured using `ProxyPass` (aka <dfn class="calibre27">reverse proxy</dfn>)
Content is stored in and retrieved from the cache using URI based keys. Content with access protection is not cached.
## Related Modules and Directives
相关模块
* `mod_disk_cache`
* `mod_mem_cache`
相关指令
* `CacheRoot`
* `CacheSize`
* `CacheDirLevels`
* `CacheDirLength`
* `CacheMinFileSize`
* `CacheMaxFileSize`
* `MCacheSize`
* `MCacheMaxObjectCount`
* `MCacheMinObjectSize`
* `MCacheMaxObjectSize`
* `MCacheRemovalAlgorithm`
* `MCacheMaxStreamingBuffer`
## Sample Configuration
### Sample httpd.conf
```
#
# Sample Cache Configuration
#
LoadModule cache_module modules/mod_cache.so
<IfModule mod_cache.c>
#LoadModule disk_cache_module modules/mod_disk_cache.so
# If you want to use mod_disk_cache instead of mod_mem_cache,
# uncomment the line above and comment out the LoadModule line below.
<IfModule mod_disk_cache.c>
CacheRoot c:/cacheroot
CacheEnable disk /
CacheDirLevels 5
CacheDirLength 3
</IfModule>
LoadModule mem_cache_module modules/mod_mem_cache.so
<IfModule mod_mem_cache.c>
CacheEnable mem /
MCacheSize 4096
MCacheMaxObjectCount 100
MCacheMinObjectSize 1
MCacheMaxObjectSize 2048
</IfModule>
# When acting as a proxy, don't cache the list of security updates
CacheDisable http://security.update.server/update-list/
</IfModule>
```
## CacheDefaultExpire 指令
| [说明](#calibre_link-18) | The default duration to cache a document when no expiry date is specified. |
| --- | --- |
| [语法](#calibre_link-19) | `CacheDefaultExpire seconds` |
| [默认值](#calibre_link-24) | `CacheDefaultExpire 3600 (one hour)` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
`CacheDefaultExpire` directive specifies a default time, in seconds, to cache a document if neither an expiry date nor last-modified date are provided with the document. The value specified with the `CacheMaxExpire` directive does _not_ override this setting.
```
CacheDefaultExpire 86400
```
## CacheDisable 指令
| [说明](#calibre_link-18) | Disable caching of specified URLs |
| --- | --- |
| [语法](#calibre_link-19) | `CacheDisable url-string` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
`CacheDisable` directive instructs `mod_cache` to _not_ cache urls at or below url-string.
### 示例
```
CacheDisable /local_files
```
## CacheEnable 指令
| [说明](#calibre_link-18) | Enable caching of specified URLs using a specified storage manager |
| --- | --- |
| [语法](#calibre_link-19) | `CacheEnable cache_type url-string` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
`CacheEnable` directive instructs `mod_cache` to cache urls at or below url-string. The cache storage manager is specified with the cache_type argument. cache_type `mem` instructs `mod_cache` to use the memory based storage manager implemented by `mod_mem_cache`. cache_type `disk` instructs `mod_cache` to use the disk based storage manager implemented by `mod_disk_cache`. cache_type `fd` instructs `mod_cache` to use the file descriptor cache implemented by `mod_mem_cache`.
In the event that the URL space overlaps between different `CacheEnable` directives (as in the example below), each possible storage manager will be run until the first one that actually processes the request. The order in which the storage managers are run is determined by the order of the `CacheEnable` directives in the configuration file.
```
CacheEnable mem /manual
CacheEnable fd /images
CacheEnable disk /
```
When acting as a forward proxy server, url-string can also be used to specify remote sites and proxy protocols which caching should be enabled for.
```
# Cache proxied url's
CacheEnable disk /
# Cache FTP-proxied url's
CacheEnable disk ftp://
# Cache content from www.apache.org
CacheEnable disk http://www.apache.org/
```
## CacheIgnoreCacheControl 指令
| [说明](#calibre_link-18) | Ignore request to not serve cached content to client |
| --- | --- |
| [语法](#calibre_link-19) | `CacheIgnoreCacheControl On|Off` |
| [默认值](#calibre_link-24) | `CacheIgnoreCacheControl Off` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
Ordinarily, requests containing a Cache-Control: no-cache or Pragma: no-cache header value will not be served from the cache. The `CacheIgnoreCacheControl` directive allows this behavior to be overridden. `CacheIgnoreCacheControl` On tells the server to attempt to serve the resource from the cache even if the request contains no-cache header values. Resources requiring authorization will _never_ be cached.
```
CacheIgnoreCacheControl On
```
### Warning:
This directive will allow serving from the cache even if the client has requested that the document not be served from the cache. This might result in stale content being served.
### 参见
* `CacheStorePrivate`
* `CacheStoreNoStore`
## CacheIgnoreHeaders 指令
| [说明](#calibre_link-18) | Do not store the given HTTP header(s) in the cache. |
| --- | --- |
| [语法](#calibre_link-19) | `CacheIgnoreHeaders header-string [header-string] ...` |
| [默认值](#calibre_link-24) | `CacheIgnoreHeaders None` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
According to RFC 2616, hop-by-hop HTTP headers are not stored in the cache. The following HTTP headers are hop-by-hop headers and thus do not get stored in the cache in _any_ case regardless of the setting of `CacheIgnoreHeaders`:
* `Connection`
* `Keep-Alive`
* `Proxy-Authenticate`
* `Proxy-Authorization`
* `TE`
* `Trailers`
* `Transfer-Encoding`
* `Upgrade`
`CacheIgnoreHeaders` specifies additional HTTP headers that should not to be stored in the cache. For example, it makes sense in some cases to prevent cookies from being stored in the cache.
`CacheIgnoreHeaders` takes a space separated list of HTTP headers that should not be stored in the cache. If only hop-by-hop headers not should be stored in the cache (the RFC 2616 compliant behaviour), `CacheIgnoreHeaders` can be set to `None`.
### Example 1
```
CacheIgnoreHeaders Set-Cookie
```
### Example 2
```
CacheIgnoreHeaders None
```
### Warning:
If headers like `Expires` which are needed for proper cache management are not stored due to a `CacheIgnoreHeaders` setting, the behaviour of mod_cache is undefined.
## CacheIgnoreNoLastMod 指令
| [说明](#calibre_link-18) | Ignore the fact that a response has no Last Modified header. |
| --- | --- |
| [语法](#calibre_link-19) | `CacheIgnoreNoLastMod On|Off` |
| [默认值](#calibre_link-24) | `CacheIgnoreNoLastMod Off` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
Ordinarily, documents without a last-modified date are not cached. Under some circumstances the last-modified date is removed (during `mod_include` processing for example) or not provided at all. The `CacheIgnoreNoLastMod` directive provides a way to specify that documents without last-modified dates should be considered for caching, even without a last-modified date. If neither a last-modified date nor an expiry date are provided with the document then the value specified by the `CacheDefaultExpire` directive will be used to generate an expiration date.
```
CacheIgnoreNoLastMod On
```
## CacheLastModifiedFactor 指令
| [说明](#calibre_link-18) | The factor used to compute an expiry date based on the LastModified date. |
| --- | --- |
| [语法](#calibre_link-19) | `CacheLastModifiedFactor float` |
| [默认值](#calibre_link-24) | `CacheLastModifiedFactor 0.1` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
In the event that a document does not provide an expiry date but does provide a last-modified date, an expiry date can be calculated based on the time since the document was last modified. The `CacheLastModifiedFactor` directive specifies a factor to be used in the generation of this expiry date according to the following formula: `expiry-period = time-since-last-modified-date * factor expiry-date = current-date + expiry-period` For example, if the document was last modified 10 hours ago, and factor is 0.1 then the expiry-period will be set to 10*0.1 = 1 hour. If the current time was 3:00pm then the computed expiry-date would be 3:00pm + 1hour = 4:00pm. If the expiry-period would be longer than that set by `CacheMaxExpire`, then the latter takes precedence.
```
CacheLastModifiedFactor 0.5
```
## CacheMaxExpire 指令
| [说明](#calibre_link-18) | The maximum time in seconds to cache a document |
| --- | --- |
| [语法](#calibre_link-19) | `CacheMaxExpire seconds` |
| [默认值](#calibre_link-24) | `CacheMaxExpire 86400 (one day)` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
`CacheMaxExpire` directive specifies the maximum number of seconds for which cachable HTTP documents will be retained without checking the origin server. Thus, documents will be out of date at most this number of seconds. This maximum value is enforced even if an expiry date was supplied with the document.
```
CacheMaxExpire 604800
```
## CacheStoreNoStore 指令
| [说明](#calibre_link-18) | Attempt to cache requests or responses that have been marked as no-store. |
| --- | --- |
| [语法](#calibre_link-19) | `CacheStoreNoStore On|Off` |
| [默认值](#calibre_link-24) | `CacheStoreNoStore Off` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
Ordinarily, requests or responses with Cache-Control: no-store header values will not be stored in the cache. The `CacheStoreNoCache` directive allows this behavior to be overridden. `CacheStoreNoCache` On tells the server to attempt to cache the resource even if it contains no-store header values. Resources requiring authorization will _never_ be cached.
```
CacheStoreNoStore On
```
### Warning:
As described in RFC 2616, the no-store directive is intended to "prevent the inadvertent release or retention of sensitive information (for example, on backup tapes)." Enabling this option could store sensitive information in the cache. You are hereby warned.
### 参见
* `CacheIgnoreCacheControl`
* `CacheStorePrivate`
## CacheStorePrivate 指令
| [说明](#calibre_link-18) | Attempt to cache responses that the server has marked as private |
| --- | --- |
| [语法](#calibre_link-19) | `CacheStorePrivate On|Off` |
| [默认值](#calibre_link-24) | `CacheStorePrivate Off` |
| [作用域](#calibre_link-20) | server config, virtual host |
| [状态](#calibre_link-21) | 扩展(E) |
| [模块](#calibre_link-22) | mod_cache |
Ordinarily, responses with Cache-Control: private header values will not be stored in the cache. The `CacheStorePrivate` directive allows this behavior to be overridden. `CacheStorePrivate` On tells the server to attempt to cache the resource even if it contains private header values. Resources requiring authorization will _never_ be cached.
```
CacheStorePrivate On
```
### Warning:
This directive will allow caching even if the upstream server has requested that the resource not be cached. This directive is only ideal for a 'private' cache.
### 参见
* `CacheIgnoreCacheControl`
* `CacheStoreNoStore`
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