================
Plugin Interface
================

------------
Module: core
------------

:Author: Jan Kneschke
:Date: $Date: 2005-03-28T08:30:05.699628Z $
:Revision: $Revision: 227 $

:abstract:
  The plugin interface is an integral part of lighttpd which
  provides a flexible way to add specific functionality to lighttpd.
  
.. meta::
  :keywords: lighttpd, plugins
  
.. contents:: Table of Contents

Description
===========

Plugins allow you to enhance the functionality of lighttpd without
changing the core of the webserver. They can be loaded at startup time 
and can change virtually any aspect of the behaviour of the webserver.

Plugin Entry Points
-------------------

lighttpd has 16 hooks which are used in different states of the 
execution of the request:

Serverwide hooks
````````````````

:init_:
  called when the plugin is loaded
:cleanup_:
  called when the plugin is unloaded
:set_defaults_:
  called when the configuration has to be processed
:handle_trigger_:
  called once a second
:handle_sighup_:
  called when the server received a SIGHUP

Connectionwide hooks
````````````````````

Most of these hooks are called in ``http_response_prepare()`` after some 
fields in the connection structure are set.

:handle_uri_raw_:
  called after uri.path_raw, uri.authority and uri.scheme are set
:handle_uri_clean_:
  called after uri.path (a clean URI without .. and %20) is set
:handle_docroot_:
  called at the end of the logical path handle to get a docroot 
:handle_subrequest_start_:
  called if the physical path is set up and checked
:handle_subrequest_:
  called at the end of ``http_response_prepare()``
:handle_physical_path_:
  called after the physical path is created and no other handler is 
  found for this request
:handle_request_done_:
  called when the request is done
:handle_connection_close_:
  called if the connection has to be closed
:handle_joblist_:
  called after the connection_state_engine is left again and plugin
  internal handles have to be called
:connection_reset_:
  called if the connection structure has to be cleaned up 


Plugin Interface
----------------

\*_plugin_init
``````````````

Every plugin has a uniquely-named function which is called after the 
plugin is loaded. It is used to set up the ``plugin`` structure with 
some useful data:

- name of the plugin ``name``
- all hooks 

The field ``data`` and ``lib`` should not be touched in the init function. 
``lib`` is the library handler from dlopen and ``data`` will be the storage
of the internal plugin data.

:returns:
  0 (not handled)

init
````

The first real call of a plugin function is the init hook which is used 
to set up the internal plugin data. The internal plugin is assigned the 
``data`` field mentioned in the \*_plugin_init description. 

:returns:
  a pointer to the internal plugin data.

cleanup
```````

The cleanup hook is called just before the plugin is unloaded. It is meant 
to free all buffers allocated in ``init`` or somewhere else in the plugin
which are still not freed and to close all handles which were opened and
are not closed yet.

:returns:
  HANDLER_GO_ON if ok (not handled)

set_defaults
````````````

set_defaults is your entry point into the configfile parsing. It should 
pass a list of options to ``config_insert_values`` and check if
the plugin configuration is valid. If it is not valid yet, it should 
set useful defaults or return with HANDLER_ERROR and an error message.

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR will terminate lighttpd
  
connection_reset
````````````````

called at the end of each request

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  
handle_trigger
``````````````

called once a second

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  
handle_sighup
`````````````

called if a SIGHUP is received (cycling logfiles, ...)

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  
handle_uri_raw
``````````````

called after uri_raw is set

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  
handle_uri_clean
````````````````

called after uri.path is set

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  
handle_docroot
``````````````

called when a docroot is needed

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  
handle_subrequest_start
```````````````````````

called after physical.path is set

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  
handle_subrequest
`````````````````

called if subrequest_start requested a COMEBACK or a WAIT_FOR_EVENT

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  
handle_physical_path
````````````````````

called after physical.path is set

:returns:
  HANDLER_GO_ON if ok
  HANDLER_FINISHED if the final output is prepared
  
  HANDLER_ERROR on error
  

handle_request_done
```````````````````

called at the end of the request (logging, statistics, ...)

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  
handle_connection_close
```````````````````````

called if the connection is terminated

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  
handle_joblist
``````````````

called if the state of the connection has changed

:returns:
  HANDLER_GO_ON if ok
  
  HANDLER_ERROR on error
  

