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mod_lua - Apache HTTP Server Version 2.4









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Apache HTTP Server Version 2.4



Apache > HTTP Server > Documentation > Version 2.4 > Modules

Apache Module mod_lua

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Description:Provides Lua hooks into various portions of the httpd
request processing
Status:Experimental
ModuleIdentifier:lua_module
SourceFile:mod_lua.c
Compatibility:2.3 and later
Summary

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.

Warning
This module holds a great deal of power over httpd, which is both a 
strength and a potential security risk. It is not 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.



Topics

 Basic Configuration
 Writing Handlers
 Writing Authorization Providers
 Writing Hooks
 Data Structures
 Built in functions
 Logging Functions
 apache2 Package
 Modifying contents with Lua filters
 Database connectivity
Directives

 LuaAuthzProvider
 LuaCodeCache
 LuaHookAccessChecker
 LuaHookAuthChecker
 LuaHookCheckUserID
 LuaHookFixups
 LuaHookInsertFilter
 LuaHookLog
 LuaHookMapToStorage
 LuaHookTranslateName
 LuaHookTypeChecker
 LuaInherit
 LuaInputFilter
 LuaMapHandler
 LuaOutputFilter
 LuaPackageCPath
 LuaPackagePath
 LuaQuickHandler
 LuaRoot
 LuaScope

Bugfix checklisthttpd changelogKnown issuesReport a bugSee also

Comments


Basic Configuration

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 a SetHandler or
AddHandler directive:

<Files "*.lua">
    SetHandler lua-script
</Files>



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.




Writing Handlers
 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"

    if r.method == 'GET' then
        r:puts("Hello Lua World!\n")
        for k, v in pairs( r:parseargs() ) do
            r:puts( string.format("%s: %s\n", k, v) )
        end
    elseif r.method == 'POST' then
        r:puts("Hello Lua World!\n")
        for k, v in pairs( r:parsebody() ) do
            r:puts( string.format("%s: %s\n", k, v) )
        end
    elseif r.method == 'PUT' then
-- use our own Error contents
        r:puts("Unsupported HTTP method " .. r.method)
        r.status = 405
        return apache2.OK
    else
-- use the ErrorDocument
        return 501
    end
    return apache2.OK
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.




Writing Authorization Providers


mod_authz_core 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
Require directive gives
the name of the responsible authorization provider. For any
Require line,
mod_authz_core 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.

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 apache2.AUTHZ_DENIED_NO_USER.
This will cause authentication to proceed and the authz provider to be
called a second time.

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:


authz_provider.lua

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


The following configuration registers this function as provider
foo and configures it for URL /:
LuaAuthzProvider foo authz_provider.lua authz_check_foo
<Location "/">
  Require foo 10.1.2.3 john_doe
</Location>




Writing Hooks

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 file system,
performing access control, or setting mime types:


        Hook phase
        mod_lua directive
        Description
    

        Quick handler
        LuaQuickHandler
        This is the first hook that will be called after a request has 
            been mapped to a host or virtual host
    

        Translate name
        LuaHookTranslateName
        This phase translates the requested URI into a filename on the 
            system. Modules such as mod_alias and
            mod_rewrite operate in this phase.
    

        Map to storage
        LuaHookMapToStorage
        This phase maps files to their physical, cached or external/proxied storage. 
            It can be used by proxy or caching modules
    

        Check Access
        LuaHookAccessChecker
        This phase checks whether a client has access to a resource. This 
            phase is run before the user is authenticated, so beware.
        
    

        Check User ID
        LuaHookCheckUserID
        This phase it used to check the negotiated user ID
    

        Check Authorization
        LuaHookAuthChecker or 
            LuaAuthzProvider
        This phase authorizes a user based on the negotiated credentials, such as 
            user ID, client certificate etc.
        
    

        Check Type
        LuaHookTypeChecker
        This phase checks the requested file and assigns a content type and 
            a handler to it
    

        Fixups
        LuaHookFixups
        This is the final "fix anything" phase before the content handlers 
            are run. Any last-minute changes to the request should be made here.
    

        Content handler
        fx. .lua files or through LuaMapHandler
        This is where the content is handled. Files are read, parsed, some are run, 
            and the result is sent to the client
    

        Logging
        LuaHookLog
        Once a request has been handled, it enters several logging phases, 
            which logs the request in either the error or access log. Mod_lua
            is able to hook into the start of this and control logging output.
    


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
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: 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



Data Structures


request_rec
        
        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 writable 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
          Description
        

          allowoverrides
          string
          no
          The AllowOverride options applied to the current request.
        

          ap_auth_type
          string
          no
          If an authentication check was made, this is set to the type 
          of authentication (f.x. basic)
        

          args
          string
          yes
          The query string arguments extracted from the request 
            (f.x. foo=bar&name=johnsmith)
        

          assbackwards
          boolean
          no
          Set to true if this is an HTTP/0.9 style request 
            (e.g. GET /foo (with no headers) )
        

          auth_name
          string
          no
          The realm name used for authorization (if applicable).
        

          banner
          string
          no
          The server banner, f.x. Apache HTTP Server/2.4.3 openssl/0.9.8c
        

          basic_auth_pw
          string
          no
          The basic auth password sent with this request, if any
        

          canonical_filename
          string
          no
          The canonical filename of the request
        

          content_encoding
          string
          no
          The content encoding of the current request
        

          content_type
          string
          yes
          The content type of the current request, as determined in the 
            type_check phase (f.x. image/gif or text/html)
        

          context_prefix
          string
          no
          
        

          context_document_root
          string
          no
          
        

          document_root
          string
          no
          The document root of the host
        

          err_headers_out
          table
          no
          MIME header environment for the response, printed even on errors and
            persist across internal redirects
        

          filename
          string
          yes
          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.
        

          handler
          string
          yes
          The name of the handler that should serve this request, f.x. 
            lua-script if it is to be served by mod_lua. This is typically set by the 
            AddHandler or SetHandler 
            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.
            
        

          headers_in
          table
          yes
          MIME header environment from the request. This contains headers such as Host, 
            User-Agent, Referer and so on.
        

          headers_out
          table
          yes
          MIME header environment for the response.
        

          hostname
          string
          no
          The host name, as set by the Host: header or by a full URI.
        

          is_https
          boolean
          no
          Whether or not this request is done via HTTPS
        

          is_initial_req
          boolean
          no
          Whether this request is the initial request or a sub-request
        

          limit_req_body
          number
          no
          The size limit of the request body for this request, or 0 if no limit.
        

          log_id
          string
          no
          The ID to identify request in access and error log.
        

          method
          string
          no
          The request method, f.x. GET or POST.
        

          notes
          table
          yes
          A list of notes that can be passed on from one module to another.
        

          options
          string
          no
          The Options directive applied to the current request.
        

          path_info
          string
          no
          The PATH_INFO extracted from this request.
        

          port
          number
          no
          The server port used by the request.
        

          protocol
          string
          no
          The protocol used, f.x. HTTP/1.1
        

          proxyreq
          string
          yes
          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.
        

          range
          string
          no
          The contents of the Range: header.
        

          remaining
          number
          no
          The number of bytes remaining to be read from the request body.
        

          server_built
          string
          no
          The time the server executable was built.
        

          server_name
          string
          no
          The server name for this request.
        

          some_auth_required
          boolean
          no
          Whether some authorization is/was required for this request.
        

          subprocess_env
          table
          yes
          The environment variables set for this request.
        

          started
          number
          no
          The time the server was (re)started, in seconds since the epoch (Jan 1st, 1970)
        

          status
          number
          yes
          The (current) HTTP return code for this request, f.x. 200 or 404.
        

          the_request
          string
          no
          The request string as sent by the client, f.x. GET /foo/bar HTTP/1.1.
        

          unparsed_uri
          string
          no
          The unparsed URI of the request
        

          uri
          string
          yes
          The URI after it has been parsed by httpd
        

          user
          string
          yes
          If an authentication check has been made, this is set to the name of the authenticated user.
        

          useragent_ip
          string
          no
          The IP of the user agent making the request
        

           
    


Built in functions

The request_rec object has (at least) the following methods:

r:flush()   -- flushes the output buffer.
            -- Returns true if the flush was successful, false otherwise.

while we_have_stuff_to_send do
    r:puts("Bla bla bla\n") -- print something to client
    r:flush() -- flush the buffer (send to client)
    r.usleep(500000) -- fake processing time for 0.5 sec. and repeat
end


r:addoutputfilter(name|function) -- add an output filter:

r:addoutputfilter("fooFilter") -- add the fooFilter to the output stream


r:sendfile(filename) -- sends an entire file to the client, using sendfile if supported by the current platform:

if use_sendfile_thing then
    r:sendfile("/var/www/large_file.img")
end


r:parseargs() -- returns two tables; one standard key/value table for regular GET data, 
              -- and one for multi-value data (fx. foo=1&foo=2&foo=3):

local GET, GETMULTI = r:parseargs()
r:puts("Your name is: " .. GET['name'] or "Unknown")


r:parsebody([sizeLimit]) -- parse the request body as a POST and return two lua tables,
                         -- just like r:parseargs().
                         -- An optional number may be passed to specify the maximum number 
                         -- of bytes to parse. Default is 8192 bytes:
                 
local POST, POSTMULTI = r:parsebody(1024*1024)
r:puts("Your name is: " .. POST['name'] or "Unknown")


r:puts("hello", " world", "!") -- print to response body, self explanatory


r:write("a single string") -- print to response body, self explanatory


r:escape_html("<html>test</html>") -- Escapes HTML code and returns the escaped result


r:base64_encode(string) -- Encodes a string using the Base64 encoding standard:

local encoded = r:base64_encode("This is a test") -- returns VGhpcyBpcyBhIHRlc3Q=


r:base64_decode(string) -- Decodes a Base64-encoded string:

local decoded = r:base64_decode("VGhpcyBpcyBhIHRlc3Q=") -- returns 'This is a test'


r:md5(string) -- Calculates and returns the MD5 digest of a string (binary safe):

local hash = r:md5("This is a test") -- returns ce114e4501d2f4e2dcea3e17b546f339


r:sha1(string) -- Calculates and returns the SHA1 digest of a string (binary safe):

local hash = r:sha1("This is a test") -- returns a54d88e06612d820bc3be72877c74f257b561b19


r:escape(string) -- URL-Escapes a string:

local url = "http://foo.bar/1 2 3 & 4 + 5"
local escaped = r:escape(url) -- returns 'http%3a%2f%2ffoo.bar%2f1+2+3+%26+4+%2b+5'


r:unescape(string) -- Unescapes an URL-escaped string:

local url = "http%3a%2f%2ffoo.bar%2f1+2+3+%26+4+%2b+5"
local unescaped = r:unescape(url) -- returns 'http://foo.bar/1 2 3 & 4 + 5'


r:construct_url(string) -- Constructs an URL from an URI

local url = r:construct_url(r.uri)


r.mpm_query(number) -- Queries the server for MPM information using ap_mpm_query:

local mpm = r.mpm_query(14)
if mpm == 1 then
    r:puts("This server uses the Event MPM")
end


r:expr(string) -- Evaluates an expr string.

if r:expr("%{HTTP_HOST} =~ /^www/") then
    r:puts("This host name starts with www")
end


r:scoreboard_process(a) -- Queries the server for information about the process at position a:

local process = r:scoreboard_process(1)
r:puts("Server 1 has PID " .. process.pid)


r:scoreboard_worker(a, b) -- Queries for information about the worker thread, b, in process a:

local thread = r:scoreboard_worker(1, 1)
r:puts("Server 1's thread 1 has thread ID " .. thread.tid .. " and is in " .. thread.status .. " status")



r:clock() -- Returns the current time with microsecond precision


r:requestbody(filename) -- Reads and returns the request body of a request.
                -- If 'filename' is specified, it instead saves the
                -- contents to that file:
                
local input = r:requestbody()
r:puts("You sent the following request body to me:\n")
r:puts(input)


r:add_input_filter(filter_name) -- Adds 'filter_name' as an input filter


r.module_info(module_name) -- Queries the server for information about a module

local mod = r.module_info("mod_lua.c")
if mod then
    for k, v in pairs(mod.commands) do
       r:puts( ("%s: %s\n"):format(k,v)) -- print out all directives accepted by this module
    end
end


r:loaded_modules() -- Returns a list of modules loaded by httpd:

for k, module in pairs(r:loaded_modules()) do
    r:puts("I have loaded module " .. module .. "\n")
end


r:runtime_dir_relative(filename) -- Compute the name of a run-time file (e.g., shared memory "file") 
                         -- relative to the appropriate run-time directory.


r:server_info() -- Returns a table containing server information, such as 
                -- the name of the httpd executable file, mpm used etc.


r:set_document_root(file_path) -- Sets the document root for the request to file_path




r:set_context_info(prefix, docroot) -- Sets the context prefix and context document root for a request


r:os_escape_path(file_path) -- Converts an OS path to a URL in an OS dependent way


r:escape_logitem(string) -- Escapes a string for logging


r.strcmp_match(string, pattern) -- Checks if 'string' matches 'pattern' using strcmp_match (globs).
                        -- fx. whether 'www.example.com' matches '*.example.com':
                        
local match = r.strcmp_match("foobar.com", "foo*.com")
if match then 
    r:puts("foobar.com matches foo*.com")
end


r:set_keepalive() -- Sets the keepalive status for a request. Returns true if possible, false otherwise.


r:make_etag() -- Constructs and returns the etag for the current request.


r:send_interim_response(clear) -- Sends an interim (1xx) response to the client.
                       -- if 'clear' is true, available headers will be sent and cleared.


r:custom_response(status_code, string) -- Construct and set a custom response for a given status code.
                               -- This works much like the ErrorDocument directive:
                               
r:custom_response(404, "Baleted!")


r.exists_config_define(string) -- Checks whether a configuration definition exists or not:

if r.exists_config_define("FOO") then
    r:puts("httpd was probably run with -DFOO, or it was defined in the configuration")
end


r:state_query(string) -- Queries the server for state information


r:stat(filename [,wanted]) -- Runs stat() on a file, and returns a table with file information:

local info = r:stat("/var/www/foo.txt")
if info then
    r:puts("This file exists and was last modified at: " .. info.modified)
end


r:regex(string, pattern [,flags]) -- Runs a regular expression match on a string, returning captures if matched:

local matches = r:regex("foo bar baz", [[foo (\w+) (\S*)]])
if matches then
    r:puts("The regex matched, and the last word captured ($2) was: " .. matches[2])
end

-- Example ignoring case sensitivity:
local matches = r:regex("FOO bar BAz", [[(foo) bar]], 1)

-- Flags can be a bitwise combination of:
-- 0x01: Ignore case
-- 0x02: Multiline search


r.usleep(number_of_microseconds) -- Puts the script to sleep for a given number of microseconds.


r:dbacquire(dbType[, dbParams]) -- Acquires a connection to a database and returns a database class.
                        -- See 'Database connectivity' for details.


r:ivm_set("key", value) -- Set an Inter-VM variable to hold a specific value.
                        -- These values persist even though the VM is gone or not being used,
                        -- and so should only be used if MaxConnectionsPerChild is > 0
                        -- Values can be numbers, strings and booleans, and are stored on a 
                        -- per process basis (so they won't do much good with a prefork mpm)
                        
r:ivm_get("key")        -- Fetches a variable set by ivm_set. Returns the contents of the variable
                        -- if it exists or nil if no such variable exists.
                        
-- An example getter/setter that saves a global variable outside the VM:
function handle(r)
    -- First VM to call this will get no value, and will have to create it
    local foo = r:ivm_get("cached_data")
    if not foo then
        foo = do_some_calcs() -- fake some return value
        r:ivm_set("cached_data", foo) -- set it globally
    end
    r:puts("Cached data is: ", foo)
end


r:htpassword(string [,algorithm [,cost]]) -- Creates a password hash from a string.
                                          -- algorithm: 0 = APMD5 (default), 1 = SHA, 2 = BCRYPT, 3 = CRYPT.
                                          -- cost: only valid with BCRYPT algorithm (default = 5).


r:mkdir(dir [,mode]) -- Creates a directory and sets mode to optional mode paramter.


r:mkrdir(dir [,mode]) -- Creates directories recursive and sets mode to optional mode paramter.


r:rmdir(dir) -- Removes a directory.


r:touch(file [,mtime]) -- Sets the file modification time to current time or to optional mtime msec value.


r:get_direntries(dir) -- Returns a table with all directory entries.

function handle(r)
  local dir = r.context_document_root
  for _, f in ipairs(r:get_direntries(dir)) do
    local info = r:stat(dir .. "/" .. f)
    if info then
      local mtime = os.date(fmt, info.mtime / 1000000)
      local ftype = (info.filetype == 2) and "[dir] " or "[file]"
      r:puts( ("%s %s %10i %s\n"):format(ftype, mtime, info.size, f) )
    end
  end
end


r.date_parse_rfc(string) -- Parses a date/time string and returns seconds since epoche.


r:getcookie(key) -- Gets a HTTP cookie


r:setcookie{
  key = [key],
  value = [value],
  expires = [expiry],
  secure = [boolean],
  httponly = [boolean],
  path = [path],
  domain = [domain]
} -- Sets a HTTP cookie, for instance:

r:setcookie{
  key = "cookie1",
  value = "HDHfa9eyffh396rt",
  expires = os.time() + 86400,
  secure = true
}


r:wsupgrade() -- Upgrades a connection to WebSockets if possible (and requested):
if r:wsupgrade() then -- if we can upgrade:
    r:wswrite("Welcome to websockets!") -- write something to the client
    r:wsclose()  -- goodbye!
end


r:wsread() -- Reads a WebSocket frame from a WebSocket upgraded connection (see above):

local line, isFinal = r:wsread() -- isFinal denotes whether this is the final frame.
                                 -- If it isn't, then more frames can be read
r:wswrite("You wrote: " .. line)


r:wswrite(line) -- Writes a frame to a WebSocket client:
r:wswrite("Hello, world!")


r:wsclose() -- Closes a WebSocket request and terminates it for httpd:

if r:wsupgrade() then
    r:wswrite("Write something: ")
    local line = r:wsread() or "nothing"
    r:wswrite("You wrote: " .. line);
    r:wswrite("Goodbye!")
    r:wsclose()
end




Logging Functions

-- 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")




apache2 Package
A package named apache2 is available with (at least) the following contents.

  apache2.OK
  internal constant OK.  Handlers should return this if they've
  handled the request.
  apache2.DECLINED
  internal constant DECLINED.  Handlers should return this if
  they are not going to handle the request.
  apache2.DONE
  internal constant DONE.
  apache2.version
  Apache HTTP server version string
  apache2.HTTP_MOVED_TEMPORARILY
  HTTP status code
  apache2.PROXYREQ_NONE, apache2.PROXYREQ_PROXY, apache2.PROXYREQ_REVERSE, apache2.PROXYREQ_RESPONSE
  internal constants used by mod_proxy
  apache2.AUTHZ_DENIED, apache2.AUTHZ_GRANTED, apache2.AUTHZ_NEUTRAL, apache2.AUTHZ_GENERAL_ERROR, apache2.AUTHZ_DENIED_NO_USER
  internal constants used by mod_authz_core


(Other HTTP status codes are not yet implemented.)


Modifying contents with Lua filters
    
    
    Filter functions implemented via LuaInputFilter 
    or LuaOutputFilter 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:
    
    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



Database connectivity
    
    
    Mod_lua implements a simple database feature for querying and running commands
    on the most popular database engines (mySQL, PostgreSQL, FreeTDS, ODBC, SQLite, Oracle)
    as well as mod_dbd.
    
    The example below shows how to acquire a database handle and return information from a table:
    function handle(r)
    -- Acquire a database handle
    local database, err = r:dbacquire("mysql", "server=localhost,user=someuser,pass=somepass,dbname=mydb")
    if not err then
        -- Select some information from it
        local results, err = database:select(r, "SELECT `name`, `age` FROM `people` WHERE 1")
        if not err then
            local rows = results(0) -- fetch all rows synchronously
            for k, row in pairs(rows) do
                r:puts( string.format("Name: %s, Age: %s<br/>", row[1], row[2]) )
            end
        else
            r:puts("Database query error: " .. err)
        end
        database:close()
    else
        r:puts("Could not connect to the database: " .. err)
    end
end

    
    To utilize mod_dbd, specify mod_dbd
    as the database type, or leave the field blank:
    
    local database = r:dbacquire("mod_dbd")

    Database object and contained functions
        
        The database object returned by dbacquire has the following methods:
        Normal select and query from a database:
    -- Run a statement and return the number of rows affected:
local affected, errmsg = database:query(r, "DELETE FROM `tbl` WHERE 1")

-- Run a statement and return a result set that can be used synchronously or async:
local result, errmsg = database:select(r, "SELECT * FROM `people` WHERE 1")

        Using prepared statements (recommended):
    -- Create and run a prepared statement:
local statement, errmsg = database:prepare(r, "DELETE FROM `tbl` WHERE `age` > %u")
if not errmsg then
    local result, errmsg = statement:query(20) -- run the statement with age > 20
end

-- Fetch a prepared statement from a DBDPrepareSQL directive:
local statement, errmsg = database:prepared(r, "someTag")
if not errmsg then
    local result, errmsg = statement:select("John Doe", 123) -- inject the values "John Doe" and 123 into the statement
end

        Escaping values, closing databases etc:
    -- Escape a value for use in a statement:
local escaped = database:escape(r, [["'|blabla]])

-- Close a database connection and free up handles:
database:close()

-- Check whether a database connection is up and running:
local connected = database:active()

    
    Working with result sets
    
    The result set returned by db:select or by the prepared statement functions 
    created through db:prepare can be used to
    fetch rows synchronously or asynchronously, depending on the row number specified:
    result(0) fetches all rows in a synchronous manner, returning a table of rows.
    result(-1) fetches the next available row in the set, asynchronously.
    result(N) fetches row number N, asynchronously:
    
    -- fetch a result set using a regular query:
local result, err = db:select(r, "SELECT * FROM `tbl` WHERE 1")

local rows = result(0) -- Fetch ALL rows synchronously
local row = result(-1) -- Fetch the next available row, asynchronously
local row = result(1234) -- Fetch row number 1234, asynchronously
local row = result(-1, true) -- Fetch the next available row, using row names as key indexes.

    One can construct a function that returns an iterative function to iterate over all rows 
    in a synchronous or asynchronous way, depending on the async argument:
    
    function rows(resultset, async)
    local a = 0
    local function getnext()
        a = a + 1
        local row = resultset(-1)
        return row and a or nil, row
    end
    if not async then
        return pairs(resultset(0))
    else
        return getnext, self
    end
end

local statement, err = db:prepare(r, "SELECT * FROM `tbl` WHERE `age` > %u")
if not err then
     -- fetch rows asynchronously:
    local result, err = statement:select(20)
    if not err then
        for index, row in rows(result, true) do
            ....
        end
    end

     -- fetch rows synchronously:
    local result, err = statement:select(20)
    if not err then
        for index, row in rows(result, false) do
            ....
        end
    end
end

    
    Closing a database connection
        

    Database handles should be closed using database:close() when they are no longer
    needed. If you do not close them manually, they will eventually be garbage collected and 
    closed by mod_lua, but you may end up having too many unused connections to the database 
    if you leave the closing up to mod_lua. Essentially, the following two measures are
    the same:
    
    -- Method 1: Manually close a handle
local database = r:dbacquire("mod_dbd")
database:close() -- All done

-- Method 2: Letting the garbage collector close it
local database = r:dbacquire("mod_dbd")
database = nil -- throw away the reference
collectgarbage() -- close the handle via GC

    
    Precautions when working with databases
    
    Although the standard query and run functions are freely 
    available, it is recommended that you use prepared statements whenever possible, to 
    both optimize performance (if your db handle lives on for a long time) and to minimize 
    the risk of SQL injection attacks. run and query should only
    be used when there are no variables inserted into a statement (a static statement). 
    When using dynamic statements, use db:prepare or db:prepared.
    
    



LuaAuthzProvider Directive

Description:Plug an authorization provider function into mod_authz_core

Syntax:LuaAuthzProvider provider_name /path/to/lua/script.lua function_name
Context:server config
Status:Experimental
Module:mod_lua
Compatibility:2.4.3 and later

After a lua function has been registered as authorization provider, it can be used
with the Require directive:

LuaRoot "/usr/local/apache2/lua"
LuaAuthzProvider foo authz.lua authz_check_foo
<Location "/">
  Require foo johndoe
</Location>

require "apache2"
function authz_check_foo(r, who)
    if r.user ~= who then return apache2.AUTHZ_DENIED
    return apache2.AUTHZ_GRANTED
end






LuaCodeCache Directive

Description:Configure the compiled code cache.
Syntax:LuaCodeCache stat|forever|never
Default:LuaCodeCache stat
Context:server config, virtual host, directory, .htaccess
Override:All
Status:Experimental
Module:mod_lua

    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.

    In general stat or forever is good for production, and stat or never
    for development.

    Examples:LuaCodeCache stat
LuaCodeCache forever
LuaCodeCache never





LuaHookAccessChecker Directive

Description:Provide a hook for the access_checker phase of request processing
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.
   OrderingThe optional arguments "early" or "late" 
   control when this script runs relative to other modules.



LuaHookAuthChecker Directive

Description:Provide a hook for the auth_checker phase of request processing
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

   OrderingThe optional arguments "early" or "late" 
   control when this script runs relative to other modules.



LuaHookCheckUserID Directive

Description:Provide a hook for the check_user_id phase of request processing
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
...
   OrderingThe optional arguments "early" or "late" 
   control when this script runs relative to other modules.



LuaHookFixups Directive

Description:Provide a hook for the fixups phase of a request
processing
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




LuaHookInsertFilter Directive

Description:Provide a hook for the insert_filter phase of request processing
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


LuaHookLog Directive

Description:Provide a hook for the access log phase of a request
processing
Syntax:LuaHookLog  /path/to/lua/script.lua log_function_name
Context:server config, virtual host, directory, .htaccess
Override:All
Status:Experimental
Module:mod_lua


    This simple logging hook allows you to run a function when httpd enters the 
    logging phase of a request. With it, you can append data to your own logs, 
    manipulate data before the regular log is written, or prevent a log entry 
    from being created. To prevent the usual logging from happening, simply return
    apache2.DONE in your logging handler, otherwise return 
    apache2.OK to tell httpd to log as normal.

Example:
LuaHookLog "/path/to/script.lua" logger

-- /path/to/script.lua --
function logger(r)
    -- flip a coin:
    -- If 1, then we write to our own Lua log and tell httpd not to log
    -- in the main log.
    -- If 2, then we just sanitize the output a bit and tell httpd to 
    -- log the sanitized bits.

    if math.random(1,2) == 1 then
        -- Log stuff ourselves and don't log in the regular log
        local f = io.open("/foo/secret.log", "a")
        if f then
            f:write("Something secret happened at " .. r.uri .. "\n")
            f:close()
        end
        return apache2.DONE -- Tell httpd not to use the regular logging functions
    else
        r.uri = r.uri:gsub("somesecretstuff", "") -- sanitize the URI
        return apache2.OK -- tell httpd to log it.
    end
end




LuaHookMapToStorage Directive

Description:Provide a hook for the map_to_storage phase of request processing
Syntax:LuaHookMapToStorage  /path/to/lua/script.lua hook_function_name
Context:server config, virtual host, directory, .htaccess
Override:All
Status:Experimental
Module:mod_lua

    Like LuaHookTranslateName 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:
    LuaHookMapToStorage "/path/to/lua/script.lua" check_cache

    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


    


LuaHookTranslateName Directive

Description:Provide a hook for the translate name phase of request processing
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


   ContextThis directive is not valid in <Directory>, <Files>, or htaccess
   context.

   OrderingThe optional arguments "early" or "late" 
   control when this script runs relative to other modules.




LuaHookTypeChecker Directive

Description:Provide a hook for the type_checker phase of request processing
Syntax:LuaHookTypeChecker  /path/to/lua/script.lua hook_function_name
Context:server config, virtual host, directory, .htaccess
Override:All
Status:Experimental
Module:mod_lua

    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:
    
    LuaHookTypeChecker "/path/to/lua/script.lua" type_checker

        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




LuaInherit Directive

Description:Controls how parent configuration sections are merged into children
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.


LuaInputFilter Directive

Description:Provide a Lua function for content input filtering
Syntax:LuaInputFilter filter_name /path/to/lua/script.lua function_name
Context:server config
Status:Experimental
Module:mod_lua
Compatibility:2.4.5 and later

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 bucket holds the buckets as they are passed 
onto the Lua script:


LuaInputFilter myInputFilter "/www/filter.lua" input_filter
<Files "*.lua">
  SetInputFilter myInputFilter
</Files>

--[[
    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("&filterSignature=1234") -- Append signature at the end
end


The input filter supports denying/skipping a filter if it is deemed unwanted:

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


See "Modifying contents with Lua 
filters" for more information.




LuaMapHandler Directive

Description:Map a path to a lua handler
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.
   Examples: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.



LuaOutputFilter Directive

Description:Provide a Lua function for content output filtering
Syntax:LuaOutputFilter filter_name /path/to/lua/script.lua function_name
Context:server config
Status:Experimental
Module:mod_lua
Compatibility:2.4.5 and later

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 bucket holds the buckets as they are passed 
onto the Lua script:


LuaOutputFilter myOutputFilter "/www/filter.lua" output_filter
<Files "*.lua">
  SetOutputFilter myOutputFilter
</Files>

--[[
    Example output filter that escapes all HTML entities in the output
]]--
function output_filter(r)
    coroutine.yield("(Handled by myOutputFilter)<br/>\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


As with the input filter, the output filter supports denying/skipping a filter 
if it is deemed unwanted:

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

Lua filters with mod_filter
 When a Lua filter is used as the underlying provider via the 
FilterProvider directive, filtering 
will only work when the filter-name is identical to the provider-name.
 


See "Modifying contents with Lua filters" for more 
information.





LuaPackageCPath Directive

Description:Add a directory to lua's package.cpath
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.




LuaPackagePath Directive

Description:Add a directory to lua's package.path
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.

    Examples:LuaPackagePath "/scripts/lib/?.lua"
LuaPackagePath "/scripts/lib/?/init.lua"




LuaQuickHandler Directive

Description:Provide a hook for the quick handler of request processing
Syntax:LuaQuickHandler /path/to/script.lua hook_function_name
Context:server config, virtual host
Override:All
Status:Experimental
Module:mod_lua

    
    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 <Location> or <Directory> are void in this phase, just as 
    URIs have not been properly parsed yet.
    
   ContextThis directive is not valid in <Directory>, <Files>, or htaccess
   context.



LuaRoot Directive

Description:Specify the base path for resolving relative paths for mod_lua directives
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.



LuaScope Directive

Description:One of once, request, conn, thread -- default is once
Syntax:LuaScope once|request|conn|thread|server [min] [max]
Default:LuaScope once
Context:server config, virtual host, directory, .htaccess
Override:All
Status:Experimental
Module:mod_lua

    Specify the life cycle scope of the Lua interpreter which will
    be used by handlers in this "Directory." The default is "once"

   
    once: use the interpreter once and throw it away.

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

    conn: Same as request but attached to the connection_rec

    thread: Use the interpreter for the lifetime of the thread 
            handling the request (only available with threaded MPMs).

    server:  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 min and max arguments 
            specify the minimum and maximum number of Lua states to keep in the 
            pool.
   
    
    Generally speaking, the thread and server 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 thread or server scopes should be used for 
    maximum performance. While the thread scope will provide the 
    fastest responses, the server 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 thread scope.
    




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CommentsNotice:This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our mailing lists.

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