path: root/docs/manual/mod/mod_lua.xml

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<modulesynopsis metafile="mod_lua.xml.meta">

<name>mod_lua</name>

<description>Provides Lua hooks into various portions of the httpd
request processing</description>
<status>Experimental</status>
<sourcefile>mod_lua.c</sourcefile>
<identifier>lua_module</identifier>
<compatibility>2.3 and later</compatibility>

<summary>
<p>This module allows the server to be extended with scripts written in the
Lua programming language.  The extension points (hooks) available with
<module>mod_lua</module> 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</p>

<p>More information on the Lua programming language can be found at the
<a href="http://www.lua.org/">the Lua website</a>.</p>

<note><code>mod_lua</code> 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.</note>

<note type="warning"><title>Warning</title>
<p>This module holds a great deal of power over httpd, which is both a 
strength and a potential security risk. It is <strong>not</strong> recommended 
that you use this module on a server that is shared with users you do not 
trust, as it can be abused to change the internal workings of httpd.</p>
</note>

</summary>

<section id="basicconf"><title>Basic Configuration</title>

<p>The basic module loading directive is</p>

<highlight language="config">
    LoadModule lua_module modules/mod_lua.so
</highlight>

<p>
<code>mod_lua</code> provides a handler named <code>lua-script</code>,
which can be used with an <code>AddHandler</code> directive:</p>

<highlight language="config">
AddHandler lua-script .lua
</highlight>

<p>
This will cause <code>mod_lua</code> to handle requests for files
ending in <code>.lua</code> by invoking that file's
<code>handle</code> function.
</p>

<p>For more flexibility, see <directive>LuaMapHandler</directive>.
</p>

</section>

<section id="writinghandlers"><title>Writing Handlers</title>
<p> 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 <module>mod_proxy</module>, <module>mod_cgi</module>,
and <module>mod_status</module>.</p>

<p><code>mod_lua</code> 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:</p>


<highlight language="lua">
<strong>example.lua</strong><br/>
-- 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
    elseif r.method == 'POST' then
        for k, v in pairs( r:parsebody() ) do
            r:puts( string.format("%s: %s\n", k, v) )
        end
    else
        r:puts("Unsupported HTTP method " .. r.method)
    end
end
</highlight>

<p>
This handler function just prints out the uri or form encoded
arguments to a plaintext page.
</p>

<p>
This means (and in fact encourages) that you can have multiple
handlers (or hooks, or filters) in the same script.
</p>

</section>

<section id="writingauthzproviders">
<title>Writing Authorization Providers</title>

<p><module>mod_authz_core</module> provides a high-level interface to
authorization that is much easier to use than using into the relevant
hooks directly. The first argument to the
<directive module="mod_authz_core">Require</directive> directive gives
the name of the responsible authorization provider. For any
<directive module="mod_authz_core">Require</directive> line,
<module>mod_authz_core</module> will call the authorization provider
of the given name, passing the rest of the line as parameters. The
provider will then check authorization and pass the result as return
value.</p>

<p>The authz provider is normally called before authentication. If it needs to
know the authenticated user name (or if the user will be authenticated at
all), the provider must return <code>apache2.AUTHZ_DENIED_NO_USER</code>.
This will cause authentication to proceed and the authz provider to be
called a second time.</p>

<p>The following authz provider function takes two arguments, one ip
address and one user name. It will allow access from the given ip address
without authentication, or if the authenticated user matches the second
argument:</p>

<highlight language="lua">
<strong>authz_provider.lua</strong><br/>

require 'apache2'

function authz_check_foo(r, ip, user)
    if r.useragent_ip == ip then
        return apache2.AUTHZ_GRANTED
    elseif r.user == nil then
        return apache2.AUTHZ_DENIED_NO_USER
    elseif r.user == user then
        return apache2.AUTHZ_GRANTED
    else
        return apache2.AUTHZ_DENIED
    end
end
</highlight>

<p>The following configuration registers this function as provider
<code>foo</code> and configures it for URL <code>/</code>:</p>
<highlight language="config">
LuaAuthzProvider foo authz_provider.lua authz_check_foo
&lt;Location /&gt;
  Require foo 10.1.2.3 john_doe
&lt;/Location&gt;
</highlight>

</section>

<section id="writinghooks"><title>Writing Hooks</title>

<p>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:</p>

<table border="1" style="zebra">
    <tr>
        <th>Hook phase</th>
        <th>mod_lua directive</th>
        <th>Description</th>
    </tr>
    <tr>
        <td>Quick handler</td>
        <td><directive module="mod_lua">LuaQuickHandler</directive></td>
        <td>This is the first hook that will be called after a request has 
            been mapped to a host or virtual host</td>
    </tr>
    <tr>
        <td>Translate name</td>
        <td><directive module="mod_lua">LuaHookTranslateName</directive></td>
        <td>This phase translates the requested URI into a filename on the 
            system. Modules such as <module>mod_alias</module> and
            <module>mod_rewrite</module> operate in this phase.</td>
    </tr>
    <tr>
        <td>Map to storage</td>
        <td><directive module="mod_lua">LuaHookMapToStorage</directive></td>
        <td>This phase maps files to their physical, cached or external/proxied storage. 
            It can be used by proxy or caching modules</td>
    </tr>
    <tr>
        <td>Check Access</td>
        <td><directive module="mod_lua">LuaHookAccessChecker</directive></td>
        <td>This phase checks whether a client has access to a resource. This 
            phase is run before the user is authenticated, so beware.
        </td>
    </tr>
    <tr>
        <td>Check User ID</td>
        <td><directive module="mod_lua">LuaHookCheckUserID</directive></td>
        <td>This phase it used to check the negotiated user ID</td>
    </tr>
    <tr>
        <td>Check Authorization</td>
        <td><directive module="mod_lua">LuaHookAuthChecker</directive> or 
            <directive module="mod_lua">LuaAuthzProvider</directive></td>
        <td>This phase authorizes a user based on the negotiated credentials, such as 
            user ID, client certificate etc.
        </td>
    </tr>
    <tr>
        <td>Check Type</td>
        <td><directive module="mod_lua">LuaHookTypeChecker</directive></td>
        <td>This phase checks the requested file and assigns a content type and 
            a handler to it</td>
    </tr>
    <tr>
        <td>Fixups</td>
        <td><directive module="mod_lua">LuaHookFixups</directive></td>
        <td>This is the final "fix anything" phase before the content handlers 
            are run. Any last-minute changes to the request should be made here.</td>
    </tr>
    <tr>
        <td>Content handler</td>
        <td>fx. <code>.lua</code> files or through <directive module="mod_lua">LuaMapHandler</directive></td>
        <td>This is where the content is handled. Files are read, parsed, some are run, 
            and the result is sent to the client</td>
    </tr>
    <tr>
        <td>Logging</td>
        <td>(none)</td>
        <td>Once a request has been handled, it enters several logging phases, 
            which logs the request in either the error or access log</td>
    </tr>

</table>

<p>Hook functions are passed the request object as their only argument 
(except for LuaAuthzProvider, which also gets passed the arguments from 
the Require directive).
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
<code>apache2.OK</code>, <code>apache2.DONE</code>, or
<code>apache2.DECLINED</code>, or else an HTTP status code.</p>


<highlight language="lua">
<strong>translate_name.lua</strong><br/>
-- 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
</highlight>


<highlight language="lua">
<strong>translate_name2.lua</strong><br/>
--[[ 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: Use the early/late flags in the directive to make it run 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
</highlight>
</section>

<section id="datastructures"><title>Data Structures</title>

<dl>
<dt>request_rec</dt>
        <dd>
        <p>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, 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.)</p>

        <table border="1" style="zebra">

        <tr>
          <th><strong>Name</strong></th>
          <th><strong>Lua type</strong></th>
          <th><strong>Writable</strong></th>
          <th><strong>Description</strong></th>
        </tr>
        <tr>
          <td><code>allowoverrides</code></td>
          <td>string</td>
          <td>no</td>
          <td>The AllowOverride options applied to the current request.</td>
        </tr>
        <tr>
          <td><code>ap_auth_type</code></td>
          <td>string</td>
          <td>no</td>
          <td>If an authentication check was made, this is set to the type 
          of authentication (f.x. <code>basic</code>)</td>
        </tr>
        <tr>
          <td><code>args</code></td>
          <td>string</td>
          <td>yes</td>
          <td>The query string arguments extracted from the request 
            (f.x. <code>foo=bar&amp;name=johnsmith</code>)</td>
        </tr>
        <tr>
          <td><code>assbackwards</code></td>
          <td>boolean</td>
          <td>no</td>
          <td>Set to true if this is an HTTP/0.9 style request 
            (e.g. <code>GET /foo</code> (with no headers) )</td>
        </tr>
        <tr>
          <td><code>auth_name</code></td>
          <td>string</td>
          <td>no</td>
          <td>The realm name used for authorization (if applicable).</td>
        </tr>
        <tr>
          <td><code>banner</code></td>
          <td>string</td>
          <td>no</td>
          <td>The server banner, f.x. <code>Apache HTTP Server/2.4.3 openssl/0.9.8c</code></td>
        </tr>
        <tr>
          <td><code>basic_auth_pw</code></td>
          <td>string</td>
          <td>no</td>
          <td>The basic auth password sent with this request, if any</td>
        </tr>
        <tr>
          <td><code>canonical_filename</code></td>
          <td>string</td>
          <td>no</td>
          <td>The canonical filename of the request</td>
        </tr>
        <tr>
          <td><code>content_encoding</code></td>
          <td>string</td>
          <td>no</td>
          <td>The content encoding of the current request</td>
        </tr>
        <tr>
          <td><code>content_type</code></td>
          <td>string</td>
          <td>yes</td>
          <td>The content type of the current request, as determined in the 
            type_check phase (f.x. <code>image/gif</code> or <code>text/html</code>)</td>
        </tr>
        <tr>
          <td><code>context_prefix</code></td>
          <td>string</td>
          <td>no</td>
          <td></td>
        </tr>
        <tr>
          <td><code>context_document_root</code></td>
          <td>string</td>
          <td>no</td>
          <td></td>
        </tr>

        <tr>
          <td><code>document_root</code></td>
          <td>string</td>
          <td>no</td>
          <td>The document root of the host</td>
        </tr>
        <tr>
          <td><code>err_headers_out</code></td>
          <td>table</td>
          <td>no</td>
          <td>MIME header environment for the response, printed even on errors and
            persist across internal redirects</td>
        </tr>
        <tr>
          <td><code>filename</code></td>
          <td>string</td>
          <td>yes</td>
          <td>The file name that the request maps to, f.x. /www/example.com/foo.txt. This can be 
            changed in the translate-name or map-to-storage phases of a request to allow the 
            default handler (or script handlers) to serve a different file than what was requested.</td>
        </tr>
        <tr>
          <td><code>handler</code></td>
          <td>string</td>
          <td>yes</td>
          <td>The name of the <a href="../handler.html">handler</a> that should serve this request, f.x. 
            <code>lua-script</code> if it is to be served by mod_lua. This is typically set by the 
            <directive module="mod_mime">AddHandler</directive> or <directive module="core">SetHandler</directive> 
            directives, but could also be set via mod_lua to allow another handler to serve up a specific request 
            that would otherwise not be served by it.
            </td>
        </tr>

        <tr>
          <td><code>headers_in</code></td>
          <td>table</td>
          <td>yes</td>
          <td>MIME header environment from the request. This contains headers such as <code>Host, 
            User-Agent, Referer</code> and so on.</td>
        </tr>
        <tr>
          <td><code>headers_out</code></td>
          <td>table</td>
          <td>yes</td>
          <td>MIME header environment for the response.</td>
        </tr>
        <tr>
          <td><code>hostname</code></td>
          <td>string</td>
          <td>no</td>
          <td>The host name, as set by the <code>Host:</code> header or by a full URI.</td>
        </tr>
        <tr>
          <td><code>is_https</code></td>
          <td>boolean</td>
          <td>no</td>
          <td>Whether or not this request is done via HTTPS</td>
        </tr>
        <tr>
          <td><code>is_initial_req</code></td>
          <td>boolean</td>
          <td>no</td>
          <td>Whether this request is the initial request or a sub-request</td>
        </tr>
        <tr>
          <td><code>limit_req_body</code></td>
          <td>number</td>
          <td>no</td>
          <td>The size limit of the request body for this request, or 0 if no limit.</td>
        </tr>
        <tr>
          <td><code>log_id</code></td>
          <td>string</td>
          <td>no</td>
          <td>The ID to identify request in access and error log.</td>
        </tr>
        <tr>
          <td><code>method</code></td>
          <td>string</td>
          <td>no</td>
          <td>The request method, f.x. <code>GET</code> or <code>POST</code>.</td>
        </tr>
        <tr>
          <td><code>notes</code></td>
          <td>table</td>
          <td>yes</td>
          <td>A list of notes that can be passed on from one module to another.</td>
        </tr>
        <tr>
          <td><code>options</code></td>
          <td>string</td>
          <td>no</td>
          <td>The Options directive applied to the current request.</td>
        </tr>
        <tr>
          <td><code>path_info</code></td>
          <td>string</td>
          <td>no</td>
          <td>The PATH_INFO extracted from this request.</td>
        </tr>
        <tr>
          <td><code>port</code></td>
          <td>number</td>
          <td>no</td>
          <td>The server port used by the request.</td>
        </tr>
        <tr>
          <td><code>protocol</code></td>
          <td>string</td>
          <td>no</td>
          <td>The protocol used, f.x. <code>HTTP/1.1</code></td>
        </tr>
        <tr>
          <td><code>proxyreq</code></td>
          <td>string</td>
          <td>yes</td>
          <td>Denotes whether this is a proxy request or not. This value is generally set in 
            the post_read_request/translate_name phase of a request.</td>
        </tr>
        <tr>
          <td><code>range</code></td>
          <td>string</td>
          <td>no</td>
          <td>The contents of the <code>Range:</code> header.</td>
        </tr>
        <tr>
          <td><code>remaining</code></td>
          <td>number</td>
          <td>no</td>
          <td>The number of bytes remaining to be read from the request body.</td>
        </tr>
        <tr>
          <td><code>server_built</code></td>
          <td>string</td>
          <td>no</td>
          <td>The time the server executable was built.</td>
        </tr>
        <tr>
          <td><code>server_name</code></td>
          <td>string</td>
          <td>no</td>
          <td>The server name for this request.</td>
        </tr>
        <tr>
          <td><code>some_auth_required</code></td>
          <td>boolean</td>
          <td>no</td>
          <td>Whether some authorization is/was required for this request.</td>
        </tr>
        <tr>
          <td><code>subprocess_env</code></td>
          <td>table</td>
          <td>yes</td>
          <td>The environment variables set for this request.</td>
        </tr>
        <tr>
          <td><code>started</code></td>
          <td>number</td>
          <td>no</td>
          <td>The time the server was (re)started, in seconds since the epoch (Jan 1st, 1970)</td>
        </tr>
        <tr>
          <td><code>status</code></td>
          <td>number</td>
          <td>yes</td>
          <td>The (current) HTTP return code for this request, f.x. <code>200</code> or <code>404</code>.</td>
        </tr>
        <tr>
          <td><code>the_request</code></td>
          <td>string</td>
          <td>no</td>
          <td>The request string as sent by the client, f.x. <code>GET /foo/bar HTTP/1.1</code>.</td>
        </tr>
        <tr>
          <td><code>unparsed_uri</code></td>
          <td>string</td>
          <td>no</td>
          <td>The unparsed URI of the request</td>
        </tr>
        <tr>
          <td><code>uri</code></td>
          <td>string</td>
          <td>yes</td>
          <td>The URI after it has been parsed by httpd</td>
        </tr>
        <tr>
          <td><code>user</code></td>
          <td>string</td>
          <td>yes</td>
          <td>If an authentication check has been made, this is set to the name of the authenticated user.</td>
        </tr>
        <tr>
          <td><code>useragent_ip</code></td>
          <td>string</td>
          <td>no</td>
          <td>The IP of the user agent making the request</td>
        </tr>
        </table>

        <p>The request_rec has (at least) the following methods:</p>

        <highlight language="lua">
        r:flush() -- flushes the output buffer
        </highlight>

        <highlight language="lua">
        r:addoutputfilter(name|function) -- add an output filter
        </highlight>

        <highlight language="lua">
        r:sendfile(filename) -- sends an entire file to the client, using sendfile if supported by the current platform
        </highlight>

        <highlight language="lua">
        r:parseargs() -- returns a Lua table containing the request's query string arguments
        </highlight>

        <highlight language="lua">
r:parsebody([sizeLimit]) -- parse the request body as a POST and return a lua table.
                         -- An optional number may be passed to specify the maximum number 
                         -- of bytes to parse. Default is 8192 bytes.
        </highlight>

        <highlight language="lua">
        r:puts("hello", " world", "!") -- print to response body
        </highlight>

        <highlight language="lua">
        r:write("a single string") -- print to response body
        </highlight>

        <highlight language="lua">
        r:escape_html("&lt;html&gt;test&lt;/html&gt;") -- Escapes HTML code and returns the escaped result
        </highlight>
        </dd>
    </dl>

</section>

<section id="logging"><title>Logging Functions</title>

<highlight language="lua">
        -- examples of logging messages<br />
        r:trace1("This is a trace log message") -- trace1 through trace8 can be used <br />
        r:debug("This is a debug log message")<br />
        r:info("This is an info log message")<br />
        r:notice("This is a notice log message")<br />
        r:warn("This is a warn log message")<br />
        r:err("This is an err log message")<br />
        r:alert("This is an alert log message")<br />
        r:crit("This is a crit log message")<br />
        r:emerg("This is an emerg log message")<br />
</highlight>

</section>

<section id="apache2"><title>apache2 Package</title>
<p>A package named <code>apache2</code> is available with (at least) the following contents.</p>
<dl>
  <dt>apache2.OK</dt>
  <dd>internal constant OK.  Handlers should return this if they've
  handled the request.</dd>
  <dt>apache2.DECLINED</dt>
  <dd>internal constant DECLINED.  Handlers should return this if
  they are not going to handle the request.</dd>
  <dt>apache2.DONE</dt>
  <dd>internal constant DONE.</dd>
  <dt>apache2.version</dt>
  <dd>Apache HTTP server version string</dd>
  <dt>apache2.HTTP_MOVED_TEMPORARILY</dt>
  <dd>HTTP status code</dd>
  <dt>apache2.PROXYREQ_NONE, apache2.PROXYREQ_PROXY, apache2.PROXYREQ_REVERSE, apache2.PROXYREQ_RESPONSE</dt>
  <dd>internal constants used by <module>mod_proxy</module></dd>
  <dt>apache2.AUTHZ_DENIED, apache2.AUTHZ_GRANTED, apache2.AUTHZ_NEUTRAL, apache2.AUTHZ_GENERAL_ERROR, apache2.AUTHZ_DENIED_NO_USER</dt>
  <dd>internal constants used by <module>mod_authz_core</module></dd>

</dl>
<p>(Other HTTP status codes are not yet implemented.)</p>
</section>

<section id="modifying_buckets">
    <title>Modifying contents with Lua filters</title>
    <p>
    Filter functions implemented via <directive module="mod_lua">LuaInputFilter</directive> 
    or <directive module="mod_lua">LuaOutputFilter</directive> are designed as 
    three-stage non-blocking functions using coroutines to suspend and resume a 
    function as buckets are sent down the filter chain. The core structure of 
    such a function is:
    </p>
    <highlight language="lua">
function filter(r)
    -- Our first yield is to signal that we are ready to receive buckets.
    -- Before this yield, we can set up our environment, check for conditions,
    -- and, if we deem it necessary, decline filtering a request alltogether:
    if something_bad then
        return -- This would skip this filter.
    end
    -- Regardless of whether we have data to prepend, a yield MUST be called here.
    -- Note that only output filters can prepend data. Input filters must use the 
    -- final stage to append data to the content.
    coroutine.yield([optional header to be prepended to the content])
    
    -- After we have yielded, buckets will be sent to us, one by one, and we can 
    -- do whatever we want with them and then pass on the result.
    -- Buckets are stored in the global variable 'bucket', so we create a loop
    -- that checks if 'bucket' is not nil:
    while bucket ~= nil do
        local output = mangle(bucket) -- Do some stuff to the content
        coroutine.yield(output) -- Return our new content to the filter chain
    end

    -- Once the buckets are gone, 'bucket' is set to nil, which will exit the 
    -- loop and land us here. Anything extra we want to append to the content
    -- can be done by doing a final yield here. Both input and output filters 
    -- can append data to the content in this phase.
    coroutine.yield([optional footer to be appended to the content])
end
    </highlight>
</section>

<directivesynopsis>
<name>LuaRoot</name>
<description>Specify the base path for resolving relative paths for mod_lua directives</description>
<syntax>LuaRoot /path/to/a/directory</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>

<usage>
    <p>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.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaScope</name>
<description>One of once, request, conn, thread -- default is once</description>
<syntax>LuaScope once|request|conn|thread|server [min] [max]</syntax>
<default>LuaScope once</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>

<usage>
    <p>Specify the lifecycle scope of the Lua interpreter which will
    be used by handlers in this "Directory." The default is "once"</p>

   <dl>
    <dt>once:</dt> <dd>use the interpreter once and throw it away.</dd>

    <dt>request:</dt> <dd>use the interpreter to handle anything based on
             the same file within this request, which is also
             request scoped.</dd>

    <dt>conn:</dt> <dd>Same as request but attached to the connection_rec</dd>

    <dt>thread:</dt> <dd>Use the interpreter for the lifetime of the thread 
            handling the request (only available with threaded MPMs).</dd>

    <dt>server:</dt>  <dd>This one is different than others because the
            server scope is quite long lived, and multiple threads
            will have the same server_rec. To accommodate this,
            server scoped Lua states are stored in an apr
            resource list. The <code>min</code> and <code>max</code> arguments 
            specify the minimum and maximum number of Lua states to keep in the 
            pool.</dd>
   </dl>
    <p>
    Generally speaking, the <code>thread</code> and <code>server</code> scopes 
    execute roughly 2-3 times faster than the rest, because they don't have to 
    spawn new Lua states on every request (especially with the event MPM, as 
    even keepalive requests will use a new thread for each request). If you are 
    satisfied that your scripts will not have problems reusing a state, then 
    the <code>thread</code> or <code>server</code> scopes should be used for 
    maximum performance. While the <code>thread</code> scope will provide the 
    fastest responses, the <code>server</code> scope will use less memory, as 
    states are pooled, allowing f.x. 1000 threads to share only 100 Lua states, 
    thus using only 10% of the memory required by the <code>thread</code> scope.
    </p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaMapHandler</name>
<description>Map a path to a lua handler</description>
<syntax>LuaMapHandler uri-pattern /path/to/lua/script.lua [function-name]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
    <p>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.</p>
   <example><title>Examples:</title>
   <highlight language="config">
    LuaMapHandler /(\w+)/(\w+) /scripts/$1.lua handle_$2
    </highlight>
   </example>
        <p>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.</p>

<highlight language="config">
    LuaMapHandler /bingo /scripts/wombat.lua
</highlight>
        <p>This would invoke the "handle" function, which
        is the default if no specific function name is
        provided.</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaPackagePath</name>
<description>Add a directory to lua's package.path</description>
<syntax>LuaPackagePath /path/to/include/?.lua</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
    <usage><p>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.</p>

    <example><title>Examples:</title>
    <highlight language="config">
LuaPackagePath /scripts/lib/?.lua
LuaPackagePath /scripts/lib/?/init.lua
    </highlight>
    </example>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaPackageCPath</name>
<description>Add a directory to lua's package.cpath</description>
<syntax>LuaPackageCPath /path/to/include/?.soa</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>

<usage>
    <p>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.</p>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaCodeCache</name>
<description>Configure the compiled code cache.</description>
<syntax>LuaCodeCache stat|forever|never</syntax>
<default>LuaCodeCache stat</default>
<contextlist>
<context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>

<usage><p>
    Specify the behavior of the in-memory code cache. The default
    is stat, which stats the top level script (not any included
    ones) each time that file is needed, and reloads it if the
    modified time indicates it is newer than the one it has
    already loaded. The other values cause it to keep the file
    cached forever (don't stat and replace) or to never cache the
    file.</p>

    <p>In general stat or forever is good for production, and stat or never
    for development.</p>

    <example><title>Examples:</title>
    <highlight language="config">
LuaCodeCache stat
LuaCodeCache forever
LuaCodeCache never
    </highlight>
    </example>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookTranslateName</name>
<description>Provide a hook for the translate name phase of request processing</description>
<syntax>LuaHookTranslateName  /path/to/lua/script.lua  hook_function_name [early|late]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<override>All</override>
<compatibility>The optional third argument is supported in 2.3.15 and later</compatibility>

<usage><p>
    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. </p>

    <p>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.</p>

    <p>Example:</p>

<highlight language="config">
# httpd.conf
LuaHookTranslateName /scripts/conf/hooks.lua silly_mapper
</highlight>

<highlight language="lua">
-- /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
</highlight>

   <note><title>Context</title><p>This directive is not valid in <directive
   type="section" module="core">Directory</directive>, <directive
   type="section" module="core">Files</directive>, or htaccess
   context.</p></note>

   <note><title>Ordering</title><p>The optional arguments "early" or "late" 
   control when this script runs relative to other modules.</p></note>

</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookFixups</name>
<description>Provide a hook for the fixups phase of a request
processing</description>
<syntax>LuaHookFixups  /path/to/lua/script.lua hook_function_name</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<usage>
<p>
    Just like LuaHookTranslateName, but executed at the fixups phase
</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookMapToStorage</name>
<description>Provide a hook for the map_to_storage phase of request processing</description>
<syntax>LuaHookMapToStorage  /path/to/lua/script.lua hook_function_name</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
    <usage>
    <p>Like <directive>LuaHookTranslateName</directive> but executed at the 
    map-to-storage phase of a request. Modules like mod_cache run at this phase,
    which makes for an interesting example on what to do here:</p>
    <highlight language="config">
    LuaHookMapToStorage /path/to/lua/script.lua check_cache
    </highlight>
    <highlight language="lua">
require"apache2"
cached_files = {}

function read_file(filename) 
    local input = io.open(filename, "r")
    if input then
        local data = input:read("*a")
        cached_files[filename] = data
        file = cached_files[filename]
        input:close()
    end
    return cached_files[filename]
end

function check_cache(r)
    if r.filename:match("%.png$") then -- Only match PNG files
        local file = cached_files[r.filename] -- Check cache entries
        if not file then
            file = read_file(r.filename)  -- Read file into cache
        end
        if file then -- If file exists, write it out
            r.status = 200
            r:write(file)
            r:info(("Sent %s to client from cache"):format(r.filename))
            return apache2.DONE -- skip default handler for PNG files
        end
    end
    return apache2.DECLINED -- If we had nothing to do, let others serve this.
end
    </highlight>

    </usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookCheckUserID</name>
<description>Provide a hook for the check_user_id phase of request processing</description>
<syntax>LuaHookCheckUserID  /path/to/lua/script.lua hook_function_name [early|late]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<compatibility>The optional third argument is supported in 2.3.15 and later</compatibility>
<usage><p>...</p>
   <note><title>Ordering</title><p>The optional arguments "early" or "late" 
   control when this script runs relative to other modules.</p></note>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookTypeChecker</name>
<description>Provide a hook for the type_checker phase of request processing</description>
<syntax>LuaHookTypeChecker  /path/to/lua/script.lua hook_function_name</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
    <usage><p>
    This directive provides a hook for the type_checker phase of the request processing. 
    This phase is where requests are assigned a content type and a handler, and thus can 
    be used to modify the type and handler based on input:
    </p>
    <highlight language="config">
    LuaHookTypeChecker /path/to/lua/script.lua type_checker
    </highlight>
    <highlight language="lua">
    function type_checker(r)
        if r.uri:match("%.to_gif$") then -- match foo.png.to_gif
            r.content_type = "image/gif" -- assign it the image/gif type
            r.handler = "gifWizard"      -- tell the gifWizard module to handle this
            r.filename = r.uri:gsub("%.to_gif$", "") -- fix the filename requested
            return apache2.OK
        end

        return apache2.DECLINED
    end
    </highlight>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookAuthChecker</name>
<description>Provide a hook for the auth_checker phase of request processing</description>
<syntax>LuaHookAuthChecker  /path/to/lua/script.lua hook_function_name [early|late]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<compatibility>The optional third argument is supported in 2.3.15 and later</compatibility>
<usage>
<p>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:
</p>
<highlight language="lua">
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
</highlight>
   <note><title>Ordering</title><p>The optional arguments "early" or "late" 
   control when this script runs relative to other modules.</p></note>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookAccessChecker</name>
<description>Provide a hook for the access_checker phase of request processing</description>
<syntax>LuaHookAccessChecker  /path/to/lua/script.lua  hook_function_name [early|late]</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<compatibility>The optional third argument is supported in 2.3.15 and later</compatibility>
<usage>
<p>Add your hook to the access_checker phase.  An access checker
hook function usually returns OK, DECLINED, or HTTP_FORBIDDEN.</p>
   <note><title>Ordering</title><p>The optional arguments "early" or "late" 
   control when this script runs relative to other modules.</p></note>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaHookInsertFilter</name>
<description>Provide a hook for the insert_filter phase of request processing</description>
<syntax>LuaHookInsertFilter  /path/to/lua/script.lua hook_function_name</syntax>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
    <usage><p>Not Yet Implemented</p></usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaInherit</name>
<description>Controls how parent configuration sections are merged into children</description>
<syntax>LuaInherit none|parent-first|parent-last</syntax>
<default>LuaInherit parent-first</default>
<contextlist><context>server config</context><context>virtual host</context>
<context>directory</context><context>.htaccess</context>
</contextlist>
<override>All</override>
<compatibility>2.4.0 and later</compatibility>
    <usage><p>By default, if LuaHook* directives are used in overlapping
    Directory or Location configuration sections, the scripts defined in the
    more specific section are run <em>after</em> those defined in the more
    generic section (LuaInherit parent-first).  You can reverse this order, or
    make the parent context not apply at all.</p>
    
    <p> In previous 2.3.x releases, the default was effectively to ignore LuaHook*
    directives from parent configuration sections.</p></usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaQuickHandler</name>
<description>Provide a hook for the quick handler of request processing</description>
<syntax>LuaQuickHandler /path/to/script.lua hook_function_name</syntax>
<contextlist><context>server config</context><context>virtual host</context>
</contextlist>
<override>All</override>
<usage>
    <p>
    This phase is run immediately after the request has been mapped to a virtal host, 
    and can be used to either do some request processing before the other phases kick 
    in, or to serve a request without the need to translate, map to storage et cetera. 
    As this phase is run before anything else, directives such as <directive
   type="section" module="core">Location</directive> or <directive
   type="section" module="core">Directory</directive> are void in this phase, just as 
    URIs have not been properly parsed yet.
    </p>
   <note><title>Context</title><p>This directive is not valid in <directive
   type="section" module="core">Directory</directive>, <directive
   type="section" module="core">Files</directive>, or htaccess
   context.</p></note>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaAuthzProvider</name>
<description>Plug an authorization provider function into <module>mod_authz_core</module>
</description>
<syntax>LuaAuthzProvider provider_name /path/to/lua/script.lua function_name</syntax>
<contextlist><context>server config</context> </contextlist>
<compatibility>2.4.3 and later</compatibility>

<usage>
<p>After a lua function has been registered as authorization provider, it can be used
with the <directive module="mod_authz_core">Require</directive> directive:</p>

<highlight language="config">
LuaRoot /usr/local/apache2/lua
LuaAuthzProvider foo authz.lua authz_check_foo
&lt;Location /&gt;
  Require foo johndoe
&lt;/Location&gt;
</highlight>
<highlight language="lua">
require "apache2"
function authz_check_foo(r, who)
    if r.user ~= who then return apache2.AUTHZ_DENIED
    return apache2.AUTHZ_GRANTED
end
</highlight>


</usage>
</directivesynopsis>


<directivesynopsis>
<name>LuaInputFilter</name>
<description>Provide a Lua function for content input filtering</description>
<syntax>LuaInputFilter filter_name /path/to/lua/script.lua function_name</syntax>
<contextlist><context>server config</context> </contextlist>
<compatibility>2.5.0 and later</compatibility>

<usage>
<p>Provides a means of adding a Lua function as an input filter. 
As with output filters, input filters work as coroutines, 
first yielding before buffers are sent, then yielding whenever 
a bucket needs to be passed down the chain, and finally (optionally) 
yielding anything that needs to be appended to the input data. The 
global variable <code>bucket</code> holds the buckets as they are passed 
onto the Lua script:
</p>

<highlight language="config">
LuaInputFilter myInputFilter /www/filter.lua input_filter
&lt;FilesMatch "\.lua&gt;
  SetInputFilter myInputFilter
&lt;/FilesMatch&gt;
</highlight>
<highlight language="lua">
--[[
    Example input filter that converts all POST data to uppercase.
]]--
function input_filter(r)
    print("luaInputFilter called") -- debug print
    coroutine.yield() -- Yield and wait for buckets
    while bucket do -- For each bucket, do...
        local output = string.upper(bucket) -- Convert all POST data to uppercase
        coroutine.yield(output) -- Send converted data down the chain
    end
    -- No more buckets available.
    coroutine.yield("&amp;filterSignature=1234") -- Append signature at the end
end
</highlight>
<p>
The input filter supports denying/skipping a filter if it is deemed unwanted:
</p>
<highlight language="lua">
function input_filter(r)
    if not good then
        return -- Simply deny filtering, passing on the original content instead
    end
    coroutine.yield() -- wait for buckets
    ... -- insert filter stuff here
end
</highlight>
<p>
See "<a href="#modifying_buckets">Modifying contents with Lua 
filters</a>" for more information.
</p>
</usage>
</directivesynopsis>

<directivesynopsis>
<name>LuaOutputFilter</name>
<description>Provide a Lua function for content output filtering</description>
<syntax>LuaOutputFilter filter_name /path/to/lua/script.lua function_name</syntax>
<contextlist><context>server config</context> </contextlist>
<compatibility>2.5.0 and later</compatibility>

<usage>
<p>Provides a means of adding a Lua function as an output filter. 
As with input filters, output filters work as coroutines, 
first yielding before buffers are sent, then yielding whenever 
a bucket needs to be passed down the chain, and finally (optionally) 
yielding anything that needs to be appended to the input data. The 
global variable <code>bucket</code> holds the buckets as they are passed 
onto the Lua script:
</p>

<highlight language="config">
LuaOutputFilter myOutputFilter /www/filter.lua output_filter
&lt;FilesMatch "\.lua&gt;
  SetOutputFilter myOutputFilter
&lt;/FilesMatch&gt;
</highlight>
<highlight language="lua">
--[[
    Example output filter that escapes all HTML entities in the output
]]--
function output_filter(r)
    coroutine.yield("(Handled by myOutputFilter)&lt;br/&gt;\n") -- Prepend some data to the output,
                                                          -- yield and wait for buckets.
    while bucket do -- For each bucket, do...
        local output = r:escape_html(bucket) -- Escape all output
        coroutine.yield(output) -- Send converted data down the chain
    end
    -- No more buckets available.
end
</highlight>
<p>
As with the input filter, the output filter supports denying/skipping a filter 
if it is deemed unwanted:
</p>
<highlight language="lua">
function output_filter(r)
    if not r.content_type:match("text/html") then
        return -- Simply deny filtering, passing on the original content instead
    end
    coroutine.yield() -- wait for buckets
    ... -- insert filter stuff here
end
</highlight>
<p>
See "<a href="#modifying_buckets">Modifying contents with Lua filters</a>" for more 
information.
</p>
</usage>
</directivesynopsis>



</modulesynopsis>