The Proxy Interface¶

• Table of contents
• The Proxy Interface
  • • Description
    • Options
    • Example
    • Troubleshooting
    • Enhancements

Module: mod_proxy

Description¶

Options¶

lighttpd provides the Proxy support via the proxy-module (mod_proxy) which provides 3 options in the config-file:

• proxy.debug: a value between 0 and 65535 to set the debug-level in the Proxy module. Currently only 0 and 1 are used. Use 1 to enable some debug output, 0 to disable it. Note: Use 'enable|disable' in v1.4.13.
• proxy.balance: might be one of 'hash', 'round-robin' or 'fair' (default).
  'round-robin' chooses another host for each request, 'hash' is generating a hash over the request-uri and makes sure
  that the same request URI is sent to always the same host. That can increase the performance of the backend servers
  a lot due to higher cache-locality. 'fair' is the normal load-based, passive balancing.
• proxy.server: tell the module where to send Proxy requests to. Every file-extension can have its own handler. Load-balancing is done by specifying multiple handles for the same extension.

Structure of proxy.server section:

    ( <extension> => 
      ( [ <name> => ]
        ( "host" => <string> ,
          "port" => <integer> ),
        ( "host" => <string> ,
          "port" => <integer> )
      ),
      <extension> => ... 
    )

• <extension>: is the file-extension or prefix (if started with "/"); can be empty ("") to match all requests
• <name>: optional name that shows up in the generated statistics of mod_status, useful for indicating which backend handler processed this extension
• "host": is ip of the proxy server DO not use hostnames here! only IP addresses
• "port": is tcp-port on the "host" used by the proxy server (default: 80)

e.g.:

    proxy.server = ( ".jsp" =>
                       ( ( 
                           "host" => "10.0.0.242",
                           "port" => 81
                         ) )
                     )

Example¶

Using lighttpd + mod_proxy in front of 8 Squids which handle the caching of dynamic content for you. All requests for the host www.example.org should be forwarded to the proxy. All proxies listen on port 80 for requests.

  $HTTP["host"] == "www.example.org" {
    proxy.balance = "hash" 
    proxy.server  = ( "" => ( ( "host" => "10.0.0.10" ),
                              ( "host" => "10.0.0.11" ),
                              ( "host" => "10.0.0.12" ),
                              ( "host" => "10.0.0.13" ),
                              ( "host" => "10.0.0.14" ),
                              ( "host" => "10.0.0.15" ),
                              ( "host" => "10.0.0.16" ),
                              ( "host" => "10.0.0.17" ) ) )
  }

If one of the hosts goes down the all requests for this one server are moved equally to the other servers. If you want to know more about the algorithm used here, "google" for 'Microsoft CARP'.

Troubleshooting¶

If you are getting:

2007-05-02 09:45:48: (mod_proxy.c.397) connect failed: 8 Network is unreachable 101 
  2007-05-02 09:45:48: (mod_proxy.c.871) proxy-server disabled: blabla.com 80 8 
  2007-05-02 09:45:48: (mod_proxy.c.1229) no proxy-handler found for: /

Check if you have used an IP address for the proxy address. Hostnames are not allowed there!

Enhancements¶

Remove HTTP headers X-Forwarded-For, X-Host, X-Forwarded-Proto, replace HTTP headers Host with proxy hostname ("name", then "host") from headers, and support hostnames by gethostbyname. You can get the patch from this page.

    ( "" => 
      ( "nkbbs.org" # name
        ( "host" => "202.113.16.117",
          "port" => 80
        )
      )
    )

In the configuration of above, this will replace Host with "nkbbs.org"(name). But if the name is shorter than the shortest hostname("g.cn"?), mod_proxy will use Host as "host".