Apache HTTP Server Version 2.4

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# Apache Module mod_cache_socache

Description: | Shared object cache (socache) based storage module for the HTTP caching filter.
Status: | Extension
Module Identifier: | cache_socache_module
Source File: | mod_cache_socache.c

### Summary

`mod_cache_socache` implements a shared object cache (socache) based storage manager for `mod_cache`.

The headers and bodies of cached responses are combined, and stored underneath a single key in the shared object cache. A number of implementations of shared object caches are available to choose from.

Multiple content negotiated responses can be stored concurrently, however the caching of partial content is not yet supported by this module.

    # Turn on caching
    CacheSocache shmcb
    CacheSocacheMaxSize 102400
    <Location "/foo">
        CacheEnable socache
    </Location>

    # Fall back to the disk cache
    CacheSocache shmcb
    CacheSocacheMaxSize 102400
    <Location "/foo">
        CacheEnable socache
        CacheEnable disk
    </Location>

### Note:

`mod_cache_socache` requires the services of `mod_cache`, which must be loaded before `mod_cache_socache`.

### Directives

### Bugfix checklist

- httpd changelog
- Known issues
- Report a bug

### See also

- `mod_cache`
- `mod_cache_disk`
- Caching Guide

## CacheSocache Directive

Description: | The shared object cache implementation to use
Syntax: | `CacheSocache type[:args]`
Context: | server config, virtual host
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocache` directive defines the name of the shared object cache implementation to use, followed by optional arguments for that implementation. A number of implementations of shared object caches are available to choose from.

    CacheSocache shmcb

## CacheSocacheMaxSize Directive

Description: | The maximum size (in bytes) of an entry to be placed in the cache
Syntax: | `CacheSocacheMaxSize bytes`
Default: | `CacheSocacheMaxSize 102400`
Context: | server config, virtual host, directory, .htaccess
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocacheMaxSize` directive sets the maximum size, in bytes, for the combined headers and body of a document to be considered for storage in the cache. The value must be at least 1024 bytes. The larger the headers that are stored alongside the body, the smaller the body may be.

The `mod_cache_socache` module will only attempt to cache responses that have an explicit content length, or that are small enough to be written in one pass. This is done to allow the `mod_cache_disk` module to have an opportunity to cache responses larger than those cacheable within `mod_cache_socache`.

    CacheSocacheMaxSize 102400

## CacheSocacheMaxTime Directive

Description: | The maximum time (in seconds) for a document to be placed in the cache
Syntax: | `CacheSocacheMaxTime seconds`
Default: | `CacheSocacheMaxTime 86400`
Context: | server config, virtual host, directory, .htaccess
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocacheMaxTime` directive sets the maximum freshness lifetime, in seconds, for a document to be stored in the cache. This value overrides the freshness lifetime defined for the document by the HTTP protocol.

    CacheSocacheMaxTime 86400

## CacheSocacheMinTime Directive

Description: | The minimum time (in seconds) for a document to be placed in the cache
Syntax: | `CacheSocacheMinTime seconds`
Default: | `CacheSocacheMinTime 600`
Context: | server config, virtual host, directory, .htaccess
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocacheMinTime` directive sets the amount of seconds beyond the freshness lifetime of the response that the response should be cached for in the shared object cache. If a response is only stored for its freshness lifetime, there will be no opportunity to revalidate the response to make it fresh again.

    CacheSocacheMinTime 600

## CacheSocacheReadSize Directive

Description: | The minimum size (in bytes) of the document to read and be cached before sending the data downstream
Syntax: | `CacheSocacheReadSize bytes`
Default: | `CacheSocacheReadSize 0`
Context: | server config, virtual host, directory, .htaccess
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocacheReadSize` directive sets the minimum amount of data, in bytes, to be read from the backend before the data is sent to the client. The default of zero causes all data read of any size to be passed downstream to the client immediately as it arrives. Setting this to a higher value causes the disk cache to buffer at least this amount before sending the result to the client. This can improve performance when caching content from a slow reverse proxy.

This directive only takes effect when the data is being saved to the cache, as opposed to data being served from the cache.

    CacheSocacheReadSize 102400

## CacheSocacheReadTime Directive

Description: | The minimum time (in milliseconds) that should elapse while reading before data is sent downstream
Syntax: | `CacheSocacheReadTime milliseconds`
Default: | `CacheSocacheReadTime 0`
Context: | server config, virtual host, directory, .htaccess
Status: | Extension
Module: | mod_cache_socache
Compatibility: | Available in Apache 2.4.5 and later

The `CacheSocacheReadTime` directive sets the minimum amount of elapsed time that should pass before making an attempt to send data downstream to the client. During the time period, data will be buffered before sending the result to the client. This can improve performance when caching content from a reverse proxy.

The default of zero disables this option.

This directive only takes effect when the data is being saved to the cache, as opposed to data being served from the cache. It is recommended that this option be used alongside the `CacheSocacheReadSize` directive to ensure that the server does not buffer excessively should data arrive faster than expected.

    CacheSocacheReadTime 1000