Apache module mod_proxy

### Apache HTTP Server Version 1.2

# Module mod_proxy

This module is contained in the `mod_proxy.c` file for Apache 1.1.x, or the `modules/proxy` subdirectory for Apache 1.2, and is not compiled in by default. It provides for an HTTP 1.0 caching proxy server. It is only available in Apache 1.1 and later. Common configuration questions are addressed here.

### Note:

This module was experimental in Apache 1.1.x. As of Apache 1.2, mod_proxy stability is greatly improved.

## Summary

This module implements a proxy/cache for Apache. It implements proxying capability for `FTP`, `CONNECT` (for SSL), `HTTP/0.9`, and `HTTP/1.0`. The module can be configured to connect to other proxy modules for these and other protocols.

## Directives

- ProxyRequests
- ProxyRemote
- ProxyPass
- ProxyBlock
- CacheRoot
- CacheSize
- CacheMaxExpire
- CacheDefaultExpire
- CacheLastModifiedFactor
- CacheGcInterval
- CacheDirLevels
- CacheDirLength
- NoCache

## ProxyRequests

Syntax: ProxyRequests on/off
Default: `ProxyRequests Off`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: ProxyRequest is only available in Apache 1.1 and later.

This allows or prevents Apache from functioning as a proxy server. Setting ProxyRequests to 'off' does not disable use of the ProxyPass directive.

## ProxyRemote

Syntax: ProxyRemote <match> <remote-server>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: ProxyRemote is only available in Apache 1.1 and later.

This defines remote proxies to this proxy. <match> is either the name of a URL-scheme that the remote server supports, or a partial URL for which the remote server should be used, or '*' to indicate the server should be contacted for all requests. <remote-server> is a partial URL for the remote server. Syntax:

      <remote-server> = <protocol>://<hostname>[:port]

<protocol> is the protocol that should be used to communicate with the remote server; only "http" is supported by this module. Example:

      ProxyRemote http://goodguys.com/ http://mirrorguys.com:8000
      ProxyRemote * http://cleversite.com
      ProxyRemote ftp http://ftpproxy.mydomain.com:8080

In the last example, the proxy will forward FTP requests, encapsulated as yet another HTTP proxy request, to another proxy which can handle them.

## ProxyPass

Syntax: ProxyPass <path> <url>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: ProxyPass is only available in Apache 1.1 and later.

This directive allows remote servers to be mapped into the space of the local server; the local server does not act as a proxy in the conventional sense, but appears to be a mirror of the remote server. <path> is the name of a local virtual path; <url> is a partial URL for the remote server. Suppose the local server has address http://wibble.org; then

       ProxyPass /mirror/foo http://foo.com

Will cause a local request for the http://wibble.org/mirror/foo/bar to be internally converted into a proxy request to http://foo.com/bar

## ProxyBlock

Syntax: ProxyBlock <word/host/domain list>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: ProxyBlock is only available in Apache 1.2 and later.

The ProxyBlock directive specifies a list of words, hosts and/or domains, separated by spaces. HTTP, HTTPS, and FTP document requests to matched words, hosts or domains are blocked by the proxy server. The proxy module will also attempt to determine IP addresses of list items which may be hostnames during startup, and cache them for match test as well. Example:

      ProxyBlock joes_garage.com some_host.co.uk rocky.wotsamattau.edu

'rocky.wotsamattau.edu' would also be matched if referenced by IP address.

Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.

Note also that

    ProxyBlock *

blocks connections to all sites.

## CacheRoot

Syntax: CacheRoot <directory>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheRoot is only available in Apache 1.1 and later.

Sets the name of the directory to contain cache files; this must be writable by the httpd server.

## CacheSize

Syntax: CacheSize <size>
Default: `CacheSize 5`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheSize is only available in Apache 1.1 and later.

Sets the desired space usage of the cache, in Kb (1024 byte units). Although usage may grow above this setting, the garbage collection will delete files until the usage is at or below this setting.

## CacheGcInterval

Syntax: CacheGcInterval <time>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheGcinterval is only available in Apache 1.1 and later.

Check the cache every <time> hours, and delete files if the space usage is greater than that set by CacheSize.

## CacheMaxExpire

Syntax: CacheMaxExpire <time>
Default: `CacheMaxExpire 24`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheMaxExpire is only available in Apache 1.1 and later.

Cachable HTTP documents will be retained for at most <time> hours without checking the origin server. Thus documents can be at most <time> hours out of date. This restriction is enforced even if an expiry date was supplied with the document.

## CacheLastModifiedFactor

Syntax: CacheLastModifiedFactor <factor>
Default: `CacheLastModifiedFactor 0.1`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheLastModifiedFactor is only available in Apache 1.1 and later.

If the origin HTTP server did not supply an expiry date for the document, then estimate one using the formula

      expiry-period = time-since-last-modification * <factor>

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 expiry-period would be longer than that set by CacheMaxExpire, then the latter takes precedence.

## CacheDirLevels

Syntax: CacheDirLevels <levels>
Default: `CacheDirLevels 3`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheDirLevels is only available in Apache 1.1 and later.

CacheDirLevels sets the number of levels of subdirectories in the cache. Cached data will be saved this many directory levels below CacheRoot.

## CacheDirLength

Syntax: CacheDirLength <length>
Default: `CacheDirLength 1`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheDirLength is only available in Apache 1.1 and later.

CacheDirLength sets the number of characters in proxy cache subdirectory names.

## CacheDefaultExpire

Syntax: CacheDefaultExpire <time>
Default: `CacheDefaultExpire 1`
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: CacheDefaultExpire is only available in Apache 1.1 and later.

If the document is fetched via a protocol that does not support expiry times, then use <time> hours as the expiry time. CacheMaxExpire does not override.

## NoCache

Syntax: NoCache <word/host/domain list>
Context: server config, virtual host
Status: Base
Module: mod_proxy
Compatibility: NoCache is only available in Apache 1.1 and later.

The NoCache directive specifies a list of words, hosts and/or domains, separated by spaces. HTTP and non-passworded FTP documents from matched words, hosts or domains are not cached by the proxy server. The proxy module will also attempt to determine IP addresses of list items which may be hostnames during startup, and cache them for match test as well. Example:

      NoCache joes_garage.com some_host.co.uk bullwinkle.wotsamattau.edu

'bullwinkle.wotsamattau.edu' would also be matched if referenced by IP address.

Note that 'wotsamattau' would also be sufficient to match 'wotsamattau.edu'.

Note also that

    NoCache *

disables caching completely.

## Common configuration topics

- Controlling access to your proxy
- Using Netscape hostname shortcuts
- Why doesn't file type xxx download via FTP?
- Why does Apache start more slowly when using the proxy module?
- Can I use the Apache proxy module with my SOCKS proxy?

## Controlling access to your proxy

You can control who can access your proxy via the normal <Directory> control block using the following example:

    <Directory proxy:*>
    <Limit GET PUT POST DELETE CONNECT OPTIONS>
    order deny,allow
    deny from [machines you'd like *not* to allow by IP address or name]
    allow from [machines you'd like to allow by IP address or name]
    </Limit>
    </Directory>

A <Files> block will also work, and is the only method known to work for all possible URLs in Apache versions earlier than 1.2b10.

## Using Netscape hostname shortcuts

There is an optional patch to the proxy module to allow Netscape-like hostname shortcuts to be used. It's available here.

## Why doesn't file type xxx download via FTP?

You probably don't have that particular file type defined as application/octet-stream in your proxy's mime.types configuration file. A useful line can be

    application/octet-stream        bin dms lha lzh exe class tgz taz

## Why does Apache start more slowly when using the proxy module?

If you're using the `ProxyBlock` or `NoCache` directives, hostnames' IP addresses are looked up and cached during startup for later match test. This may take a few seconds (or more) depending on the speed with which the hostname lookups occur.

## Can I use the Apache proxy module with my SOCKS proxy?

Yes. Just build Apache with the rule `SOCKS4=yes` in your Configuration file, and follow the instructions there. SOCKS5 capability can be added in a similar way (there's no `SOCKS5` rule yet), so use the `EXTRA_LFLAGS` definition, or build Apache normally and run it with the runsocks wrapper provided with SOCKS5, if your OS supports dynamically linked libraries.

Some users have reported problems when using SOCKS version 4.2 on Solaris. The problem was solved by upgrading to SOCKS 4.3.

Remember that you'll also have to grant access to your Apache proxy machine by permitting connections on the appropriate ports in your SOCKS daemon's configuration.

### Apache HTTP Server Version 1.2