Apache HTTP Server Version 2.4
Description: | Provides Lua hooks into various portions of the httpd request processing |
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Status: | Experimental |
Module Identifier: | lua_module |
Source File: | mod_lua.c |
Compatibility: | 2.3 and later |
This module allows the server to be extended with scripts written in the
Lua programming language. The extension points (hooks) available with
mod_lua
include many of the hooks available to
natively compiled Apache HTTP Server modules, such as mapping requests to
files, generating dynamic responses, access control, authentication, and
authorization
More information on the Lua programming language can be found at the the Lua website.
mod_lua
is still in experimental state.
Until it is declared stable, usage and behavior may change
at any time, even between stable releases of the 2.4.x series.
Be sure to check the CHANGES file before upgrading.The basic module loading directive is
LoadModule lua_module modules/mod_lua.so
mod_lua
provides a handler named lua-script
,
which can be used with an AddHandler
directive:
AddHandler lua-script .lua
This will cause mod_lua
to handle requests for files
ending in .lua
by invoking that file's
handle
function.
For more flexibility, see LuaMapHandler
.
In the Apache HTTP Server API, the handler is a specific kind of hook
responsible for generating the response. Examples of modules that include a
handler are mod_proxy
, mod_cgi
,
and mod_status
.
mod_lua
always looks to invoke a Lua function for the handler, rather than
just evaluating a script body CGI style. A handler function looks
something like this:
example.lua -- example handler require "string" --[[ This is the default method name for Lua handlers, see the optional function-name in the LuaMapHandler directive to choose a different entry point. --]] function handle(r) r.content_type = "text/plain" r:puts("Hello Lua World!\n") if r.method == 'GET' then for k, v in pairs( r:parseargs() ) do r:puts( string.format("%s: %s\n", k, v) ) end else r:puts("Unsupported HTTP method " .. r.method) end end
This handler function just prints out the uri or form encoded arguments to a plaintext page.
This means (and in fact encourages) that you can have multiple handlers (or hooks, or filters) in the same script.
Hook functions are how modules (and Lua scripts) participate in the processing of requests. Each type of hook exposed by the server exists for a specific purpose, such as mapping requests to the filesystem, performing access control, or setting mimetypes. General purpose hooks that simply run at handy times in the request lifecycle exist as well.
Hook functions are passed the request object as their only argument.
They can return any value, depending on the hook, but most commonly
they'll return OK, DONE, or DECLINED, which you can write in lua as
apache2.OK
, apache2.DONE
, or
apache2.DECLINED
, or else an HTTP status code.
translate_name.lua -- example hook that rewrites the URI to a filesystem path. require 'apache2' function translate_name(r) if r.uri == "/translate-name" then r.filename = r.document_root .. "/find_me.txt" return apache2.OK end -- we don't care about this URL, give another module a chance return apache2.DECLINED end
translate_name2.lua --[[ example hook that rewrites one URI to another URI. It returns a apache2.DECLINED to give other URL mappers a chance to work on the substitution, including the core translate_name hook which maps based on the DocumentRoot. Note: It is currently undefined as to whether this runs before or after mod_alias. --]] require 'apache2' function translate_name(r) if r.uri == "/translate-name" then r.uri = "/find_me.txt" return apache2.DECLINED end return apache2.DECLINED end
The request_rec is mapped in as a userdata. It has a metatable which lets you do useful things with it. For the most part it has the same fields as the request_rec struct (see httpd.h until we get better docs here) many of which are writeable as well as readable. (The table fields' content can be changed, but the fields themselves cannot be set to different tables.)
Name | Lua type | Writable |
---|---|---|
ap_auth_type |
string | no |
args |
string | yes |
assbackwards |
boolean | no |
canonical_filename |
string | no |
content_encoding |
string | no |
content_type |
string | yes |
context_prefix |
string | no |
context_document_root |
string | no |
document_root |
string | no |
err_headers_out |
table | no |
filename |
string | yes |
handler |
string | yes |
headers_in |
table | yes |
headers_out |
table | yes |
hostname |
string | no |
log_id |
string | no |
method |
string | no |
notes |
table | yes |
path_info |
string | no |
protocol |
string | no |
proxyreq |
string | yes |
range |
string | no |
subprocess_env |
table | yes |
status |
number | yes |
the_request |
string | no |
unparsed_uri |
string | no |
uri |
string | yes |
user |
string | yes |
useragent_ip |
string | no |
The request_rec has (at least) the following methods:
r:addoutputfilter(name|function) -- add an output filter
r:parseargs() -- returns a lua table containing the request's query string arguments
r:puts("hello", " world", "!") -- print to response body
r:write("a single string") -- print to response body
-- examples of logging messages
r:trace1("This is a trace log message") -- trace1 through trace8 can be used
r:debug("This is a debug log message")
r:info("This is an info log message")
r:notice("This is a notice log message")
r:warn("This is a warn log message")
r:err("This is an err log message")
r:alert("This is an alert log message")
r:crit("This is a crit log message")
r:emerg("This is an emerg log message")
A package named apache2
is available with (at least) the following contents.
mod_proxy
(Other HTTP status codes are not yet implemented.)
Description: | Provide a hook for the access_checker phase of request processing |
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Syntax: | LuaHookAccessChecker /path/to/lua/script.lua hook_function_name [early|late] |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Compatibility: | The optional third argument is supported in 2.3.15 and later |
Add your hook to the access_checker phase. An access checker hook function usually returns OK, DECLINED, or HTTP_FORBIDDEN.
The optional arguments "early" or "late" control when this script runs relative to other modules.
Description: | Provide a hook for the auth_checker phase of request processing |
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Syntax: | LuaHookAuthChecker /path/to/lua/script.lua hook_function_name [early|late] |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Compatibility: | The optional third argument is supported in 2.3.15 and later |
Invoke a lua function in the auth_checker phase of processing a request. This can be used to implement arbitrary authentication and authorization checking. A very simple example:
require 'apache2' -- fake authcheck hook -- If request has no auth info, set the response header and -- return a 401 to ask the browser for basic auth info. -- If request has auth info, don't actually look at it, just -- pretend we got userid 'foo' and validated it. -- Then check if the userid is 'foo' and accept the request. function authcheck_hook(r) -- look for auth info auth = r.headers_in['Authorization'] if auth ~= nil then -- fake the user r.user = 'foo' end if r.user == nil then r:debug("authcheck: user is nil, returning 401") r.err_headers_out['WWW-Authenticate'] = 'Basic realm="WallyWorld"' return 401 elseif r.user == "foo" then r:debug('user foo: OK') else r:debug("authcheck: user='" .. r.user .. "'") r.err_headers_out['WWW-Authenticate'] = 'Basic realm="WallyWorld"' return 401 end return apache2.OK end
The optional arguments "early" or "late" control when this script runs relative to other modules.
Description: | Provide a hook for the check_user_id phase of request processing |
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Syntax: | LuaHookCheckUserID /path/to/lua/script.lua hook_function_name [early|late] |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Compatibility: | The optional third argument is supported in 2.3.15 and later |
...
The optional arguments "early" or "late" control when this script runs relative to other modules.
Description: | Provide a hook for the fixups phase of request processing |
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Syntax: | LuaHookFixups /path/to/lua/script.lua hook_function_name |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Just like LuaHookTranslateName, but executed at the fixups phase
Description: | Provide a hook for the insert_filter phase of request processing |
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Syntax: | LuaHookInsertFilter /path/to/lua/script.lua hook_function_name |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Not Yet Implemented
Description: | Provide a hook for the map_to_storage phase of request processing |
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Syntax: | LuaHookMapToStorage /path/to/lua/script.lua hook_function_name |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
...
Description: | Provide a hook for the translate name phase of request processing |
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Syntax: | LuaHookTranslateName /path/to/lua/script.lua hook_function_name [early|late] |
Context: | server config, virtual host |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Compatibility: | The optional third argument is supported in 2.3.15 and later |
Add a hook (at APR_HOOK_MIDDLE) to the translate name phase of request processing. The hook function receives a single argument, the request_rec, and should return a status code, which is either an HTTP error code, or the constants defined in the apache2 module: apache2.OK, apache2.DECLINED, or apache2.DONE.
For those new to hooks, basically each hook will be invoked until one of them returns apache2.OK. If your hook doesn't want to do the translation it should just return apache2.DECLINED. If the request should stop processing, then return apache2.DONE.
Example:
# httpd.conf LuaHookTranslateName /scripts/conf/hooks.lua silly_mapper
-- /scripts/conf/hooks.lua -- require "apache2" function silly_mapper(r) if r.uri == "/" then r.filename = "/var/www/home.lua" return apache2.OK else return apache2.DECLINED end end
This directive is not valid in <Directory>
, <Files>
, or htaccess
context.
The optional arguments "early" or "late" control when this script runs relative to other modules.
Description: | Provide a hook for the type_checker phase of request processing |
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Syntax: | LuaHookTypeChecker /path/to/lua/script.lua hook_function_name |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
...
Description: | Controls how parent configuration sections are merged into children |
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Syntax: | LuaInherit none|parent-first|parent-last |
Default: | LuaInherit parent-first |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Compatibility: | 2.4.0 and later |
By default, if LuaHook* directives are used in overlapping Directory or Location configuration sections, the scripts defined in the more specific section are run after those defined in the more generic section (LuaInherit parent-first). You can reverse this order, or make the parent context not apply at all.
In previous 2.3.x releases, the default was effectively to ignore LuaHook* directives from parent configuration sections.
Description: | Map a path to a lua handler |
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Syntax: | LuaMapHandler uri-pattern /path/to/lua/script.lua [function-name] |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
This directive matches a uri pattern to invoke a specific handler function in a specific file. It uses PCRE regular expressions to match the uri, and supports interpolating match groups into both the file path and the function name be careful writing your regular expressions to avoid security issues.
LuaMapHandler /(\w+)/(\w+) /scripts/$1.lua handle_$2
This would match uri's such as /photos/show?id=9 to the file /scripts/photos.lua and invoke the handler function handle_show on the lua vm after loading that file.
LuaMapHandler /bingo /scripts/wombat.lua
This would invoke the "handle" function, which is the default if no specific function name is provided.
Description: | Add a directory to lua's package.cpath |
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Syntax: | LuaPackageCPath /path/to/include/?.soa |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Add a path to lua's shared library search path. Follows the same conventions as lua. This just munges the package.cpath in the lua vms.
Description: | Add a directory to lua's package.path |
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Syntax: | LuaPackagePath /path/to/include/?.lua |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Add a path to lua's module search path. Follows the same conventions as lua. This just munges the package.path in the lua vms.
LuaPackagePath /scripts/lib/?.lua LuaPackagePath /scripts/lib/?/init.lua
Description: | Provide a hook for the quick handler of request processing |
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Syntax: | LuaQuickHandler /path/to/script.lua hook_function_name |
Context: | server config, virtual host |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
...
This directive is not valid in <Directory>
, <Files>
, or htaccess
context.
Description: | Specify the base path for resolving relative paths for mod_lua directives |
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Syntax: | LuaRoot /path/to/a/directory |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Specify the base path which will be used to evaluate all relative paths within mod_lua. If not specified they will be resolved relative to the current working directory, which may not always work well for a server.
Description: | One of once, request, conn, thread -- default is once |
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Syntax: | LuaScope once|request|conn|thread |
Default: | LuaScope once |
Context: | server config, virtual host, directory, .htaccess |
Override: | All |
Status: | Experimental |
Module: | mod_lua |
Specify the lifecycle scope of the Lua interpreter which will be used by handlers in this "Directory." The default is "once"