mod_cache

说明	基于URI键的内容动态缓冲(内存或磁盘)
状态	扩展(E)
模块名	cache_module
源文件	mod_cache.c

概述

这个模块使会绕过Allow和Deny设置的访问控制。所以，你不应该缓冲任何根据这两个指令设置了访问控制的内容。

mod_cache实现了一个RFC 2616兼容的HTTP本地缓存或HTTP代理缓存。mod_cache需要一个或多个存储管理模块提供的服务才能正常工作。目前官方发布的存储管理模块有两个：

mod_disk_cache

一个基于磁盘的存储管理模块。

mod_mem_cache

一个基于内存的存储管理模块。mod_mem_cache可以被配置为两种不同的操作模式：①缓存打开的文件描述符；②在堆(heap)上缓存对象。mod_mem_cache既可以用于缓存本地生成的内容，也可以用于为反向代理模式下的mod_proxy(参见ProxyPass)缓存后端服务器输出的内容。

内容将被以基于URI的索引存入和检出，但是并不保存相应的访问控制信息。

更多的细节、讨论、实例，可以参考缓冲指南。

相关模块和指令

相关模块	相关指令
mod_disk_cache mod_mem_cache	CacheRoot CacheSize CacheDirLevels CacheDirLength CacheMinFileSize CacheMaxFileSize MCacheSize MCacheMaxObjectCount MCacheMinObjectSize MCacheMaxObjectSize MCacheRemovalAlgorithm MCacheMaxStreamingBuffer

示范配置

httpd.conf 示例

#
# 缓存示范配置
#
LoadModule cache_module modules/mod_cache.so

<IfModule mod_cache.c>
#LoadModule disk_cache_module modules/mod_disk_cache.so
# 如果你想使用mod_disk_cache代替mod_mem_cache的话，
# 那么就取消上面的注释，并将下面的LoadModule行加上注释
<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>

# 在充当代理的时候，不缓存update-list下的内容
CacheDisable http://security.update.server/update-list/
</IfModule>

CacheDefaultExpire 指令

说明	默认缓存有效期(秒)
语法	CacheDefaultExpire seconds
默认值	CacheDefaultExpire 3600 (一小时)
作用域	server config, virtual host
状态	扩展(E)
模块	mod_cache

CacheDefaultExpire指令设置了那些既没有包含"Expires"或"Cache-Control"头，也没有包含"Last-Modified"头的缓存对象的默认有效期(按秒计)。CacheMaxExpire指令的值并不会覆盖这里的设置。

CacheDefaultExpire 86400

CacheDisable 指令

说明	禁止缓存某些特定的URL
语法	CacheDisable url-string
作用域	server config, virtual host
状态	扩展(E)
模块	mod_cache

CacheDisable指令表示禁止缓存url-string自身以及所有以url-string开头的URL。

示例

CacheDisable /local_files

CacheEnable 指令

说明	使用特定的存储类型缓存某些特定的URL
语法	CacheEnable cache_type url-string
作用域	server config, virtual host
状态	扩展(E)
模块	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	Ignore request to not serve cached content to client
语法	CacheIgnoreCacheControl On|Off
默认值	CacheIgnoreCacheControl Off
作用域	server config, virtual host
状态	扩展(E)
模块	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	Do not store the given HTTP header(s) in the cache.
语法	CacheIgnoreHeaders header-string [header-string] ...
默认值	CacheIgnoreHeaders None
作用域	server config, virtual host
状态	扩展(E)
模块	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	Ignore the fact that a response has no Last Modified header.
语法	CacheIgnoreNoLastMod On|Off
默认值	CacheIgnoreNoLastMod Off
作用域	server config, virtual host
状态	扩展(E)
模块	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

CacheIgnoreQueryString 指令

说明	Ignore query string when caching
语法	CacheIgnoreQueryString On|Off
默认值	CacheIgnoreQueryString Off
作用域	server config, virtual host
状态	Extension
模块	mod_cache
兼容性	Available in Apache 2.2.6 and later

Ordinarily, requests with query string parameters are cached separately for each unique query string. This is according to RFC 2616/13.9 done only if an expiration time is specified. The CacheIgnoreQueryString directive tells the cache to cache requests even if no expiration time is specified, and to reply with a cached reply even if the query string differs. From a caching point of view the request is treated as if having no query string when this directive is enabled.

CacheIgnoreQueryString On

CacheLastModifiedFactor 指令

说明	The factor used to compute an expiry date based on the LastModified date.
语法	CacheLastModifiedFactor float
默认值	CacheLastModifiedFactor 0.1
作用域	server config, virtual host
状态	扩展(E)
模块	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	The maximum time in seconds to cache a document
语法	CacheMaxExpire seconds
默认值	CacheMaxExpire 86400 (one day)
作用域	server config, virtual host
状态	扩展(E)
模块	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	Attempt to cache requests or responses that have been marked as no-store.
语法	CacheStoreNoStore On|Off
默认值	CacheStoreNoStore Off
作用域	server config, virtual host
状态	扩展(E)
模块	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	Attempt to cache responses that the server has marked as private
语法	CacheStorePrivate On|Off
默认值	CacheStorePrivate Off
作用域	server config, virtual host
状态	扩展(E)
模块	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