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AbsoLUAtion » History » Revision 14

Revision 13 (nitrox, 2009-03-03 10:39) → Revision 14/30 (exe, 2009-05-15 06:11)

h1. AbsoLUAtion - The powerful combo of Lighttpd + Lua 

 {{>toc}} 

 We want to build a central resource for Lighttpd + Lua as this is one of the biggest advantages Lighttpd has over other webservers. It's useful, handy, simple and sometimes a quite powerful combo which gives you some additional flexibility and offers you solutions to small and big problems other httpds can't solve! 

 Again we hope you - the users of lighty - support this page by contributing links, code-snippets or simply offer your lua scripts with small descriptions of what they do and how it helps lighty to do stuff you want it to do. 


 h1. What's needed for this to work? 

 * A [[DevelSubversion|recent]] version of Lighttpd 
 * [[lighttpd:Docs:ModMagnet|mod_magnet]] 
 * Lua (v5.0 or better v5.1, your distro´s should have this) http://www.lua.org 

 h1. How to get it up and running 

 [[lighttpd:Docs:ModMagnet|Documentation mod_magnet]] 

 h1. Links 

 Link collection (Description -> Link). 

 * darix is maintaining the cleanurl.lua at http://pixel.global-banlist.de/ 
 * Jippi is maintaining the bundle.lua at http://www.cakephp.nu/faster-page-loads-bundle-your-css-and-javascript-lighttpd-mod_magnet-lua 
 * http://www.sitepoint.com/blogs/2007/04/10/faster-page-loads-bundle-your-css-and-javascript/ 
 * Google CodeSearch is great for looking Lua examples. http://www.google.com/codesearch start your queries with "lang:lua" 
 * WP-Supercache http://tempe.st/2008/04/lighttpd-and-wp-supercache-now-you-can/ 

 Dead links? You don´t like to be listed here? Please remove it. Thanks! 

 h1. Code-Snippets 

 *The is_file/is_dir dilemma* 

 Known from Apache´s .htaccess: 

 <pre> 
 RewriteCond %{REQUEST_FILENAME} !-f 
 RewriteCond %{REQUEST_FILENAME} !-d 
 RewriteRule ^(.*)$ index.php?q=$1 [L,QSA] 
 </pre> 

 As lighttpd doesn´t provide this is_file/is_dir check out of the box, again mod_magnet comes into play. 

 I took the example for drupal from darix site (http://nordisch.org/2007/2/6/drupal-on-lighttpd-with-clean-urls): 

 Lets assume drupal is already installed under http://example.com/drupal/ you now add the magnet part to it. 

 <pre> 
 $HTTP["url"] =~ "^/drupal" { 
     # we only need index.php here. 
     index-file.names = ( "index.php" ) 
     # for clean urls 
     magnet.attract-physical-path-to = ( "/etc/lighttpd/drupal.lua" ) 
 } 
 </pre> 

 The drupal.lua: 

 <pre> 
 -- little helper function 
 function file_exists(path) 
   local attr = lighty.stat(path) 
   if (attr) then 
       return true 
   else 
       return false 
   end 
 end 
 function removePrefix(str, prefix) 
   return str:sub(1,#prefix+1) == prefix.."/" and str:sub(#prefix+2) 
 end 

 -- prefix without the trailing slash 
 local prefix = '/drupal' 

 -- the magic ;) 
 if (not file_exists(lighty.env["physical.path"])) then 
     -- file still missing. pass it to the fastcgi backend 
     request_uri = removePrefix(lighty.env["uri.path"], prefix) 
     if request_uri then 
       lighty.env["uri.path"]            = prefix .. "/index.php" 
       local uriquery = lighty.env["uri.query"] or "" 
       lighty.env["uri.query"] = uriquery .. (uriquery ~= "" and "&" or "") .. "q=" .. request_uri 
       lighty.env["physical.rel-path"] = lighty.env["uri.path"] 
       lighty.env["request.orig-uri"]    = lighty.env["request.uri"] 
       lighty.env["physical.path"]       = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"] 
     end 
 end 
 -- fallthrough will put it back into the lighty request loop 
 -- that means we get the 304 handling for free. ;) 
 </pre> 


 *Overwrite default mime-type/content-type* 

 Add "magnet.attract-physical-path-to = ( "/path-to/change-ctype.lua" )" to lighttpd.conf and save the following as "change-ctype.lua" 
 <pre> 
  if (string.match(lighty.env["physical.rel-path"], ".swf")) then 
     lighty.header["Content-Type"] = "text/html" 
 </pre> 


 *Sending text-files as HTML* 

 This is a bit simplistic, but it illustrates the idea: Take a text-file and cover it in a "< pre >" tag. 

 Config-file 

 <pre> 
   magnet.attract-physical-path-to = (server.docroot + "/readme.lua") 
 </pre> 

 readme.lua 

 <pre> 
   lighty.content = { "<pre>", { filename = "/README" }, "</pre>" } 
   lighty.header["Content-Type"] = "text/html" 
  
   return 200 
 </pre> 


 *Simple maintenance script* 

 You need three files, maint.up, maint.down and maint.html. 
 maint.html holds a simple html-page of what you want to display to your users while in maintenance-mode. 

 Add "magnet.attract-physical-path-to = ( "/path-to-your/maint.lua" )" to your lighttpd.conf, best is global section or within a host-section of your config, e.g. a board/forum/wiki you know a maintenance-mode is needed from time to time. If you want to switch to maintenance-mode, just copy maint.down to maint.lua in your "/path-to-your/" location, and lighty will display your maint.html to all users - without restarting anything - this can be done on-the-fly. Work is done and all is up again? Copy maint.up to maint.lua in your "/path-to-your/" location. Whats maint.up doing? Nothing, just going on with normal file serving :-) 

 maint.up - all is up, user will see normal pages 

 <pre> 
 -- This is empty, nothing to do. 
 </pre> 

 maint.down - lighty will show the maintenance page -> maint.html 

 <pre> 
 -- lighty.header["X-Maintenance-Mode"] = "1" 
 -- uncomment the above if you want to add the header 
 lighty.content = { { filename = "/path-to-your/maint.html" } } 
 lighty.header["Content-Type"] = "text/html" 
 return 503 
 -- or return 200 if you want 
 </pre> 


 *mod_flv_streaming* 

 Config-file 

 <pre> 
   magnet.attract-physical-path-to = (server.docroot + "/flv-streaming.lua") 
 </pre> 

 flv-streaming.lua 

 <pre> 
   if (lighty.env["uri.query"]) then 
     -- split the query-string 
     get = {} 
     for k, v in string.gmatch(lighty.env["uri.query"], "(%w+)=(%w+)") do 
       get[k] = v 
     end 
       
     header="" 
     if (get and get["start"]) then 
       start = tonumber(get["start"]) 
     else 
       start=0 
     end 

     -- send te FLV header only when seeking + a seek into the file 
     if (start ~= nil and start > 0) then 
       header="FLV\1\1\0\0\0\9\0\0\0\9" 
     end 

     lighty.content = { header ,  
        { filename = lighty.env["physical.path"], offset = start } } 
     lighty.header["Content-Type"] = "video/x-flv" 

     return 200 
    
   end 
 </pre> 

 You can also use a backend like php to use your own authorization or stuff like mod_secdl. Just activate x-rewrite in the backend configuration and use a header like  

 <pre> 
   header("X-Rewrite-URI: flvstreaming?start=" . $start . "&path=" . $path); 
 </pre> 

 The request is restarted and in the lua, you can catch the non-existing uri with the following code (wrap it between the example below):: 

 <pre> 
   if (string.find(lighty.env["uri.path"],"/flvstreaming") then 
     <flv streaming lua code> 
   end 
 </pre> 

 In the future, there will be a new magnet for response headers, maybe you can give your own headers like:: 

 <pre> 
   header("X-StreamMyFlv: $path"); 
 </pre> 

 to lua and use the header data as parameter for the streaming. 


 *selecting a random file from a directory* 

 Say, you want to send a random file (ad-content) from a directory.  

 To simplify the code and to improve the performance we define: 

 * all images have the same format (e.g. image/png) 
 * all images use increasing numbers starting from 1 
 * a special index-file names the highest number 

 Config 

 <pre> 
   server.modules += ( "mod_magnet" ) 
   magnet.attract-physical-path-to = ("random.lua") 
 </pre> 

 random.lua 

 <pre> 
   dir = lighty.env["physical.path"] 

   f = assert(io.open(dir .. "/index", "r")) 
   maxndx = f:read("*all") 
   f:close() 

   ndx = math.random(maxndx) 

   lighty.content = { { filename = dir .. "/" .. ndx }} 
   lighty.header["Content-Type"] = "image/png" 

   return 200   
 </pre> 


 *denying illegal character sequences in the URL* 

 Instead of implementing mod_security, you might just want to apply filters on the content and deny special sequences that look like SQL injection.  

 A common injection is using UNION to extend a query with another SELECT query. 

 <pre> 
   if (string.find(lighty.env["request.uri"], "UNION%s")) then 
     return 400 
   end 
 </pre> 




 *Traffic Quotas* 

 If you only allow your virtual hosts a certain amount for traffic each month and want to disable them if the traffic is reached, perhaps this helps: 

 <pre> 
   host_blacklist = { ["www.example.org"] = 0 } 

   if (host_blacklist[lighty.request["Host"]]) then 
     return 404 
   end 
 </pre> 

 Just add the hosts you want to blacklist into the blacklist table in the shown way. 

 *Complex rewrites* 

 If you want to implement caching on your document-root and only want to regenerate content if the requested file doesn't exist, you can attract the physical.path: 

 <pre> 
   magnet.attract-physical-path-to = ( server.document-root + "/rewrite.lua" ) 
 </pre> 

 rewrite.lua 

 <pre> 
   attr = lighty.stat(lighty.env["physical.path"]) 

   if (not attr) then 
     -- we couldn't stat() the file for some reason 
     -- let the backend generate it 

     lighty.env["uri.path"] = "/dispatch.fcgi" 
     lighty.env["physical.rel-path"] = lighty.env["uri.path"] 
     lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"] 
   end 
 </pre> 


 *Extension rewrites* 

 If you want to hide your file extensions (like .php) you can attract the physical.path: 

 <pre> 
   magnet.attract-physical-path-to = ( server.document-root + "/rewrite.lua" ) 
 </pre> 

 rewrite.lua 

 <pre> 
   attr = lighty.stat(lighty.env["physical.path"] .. ".php") 

   if (attr) then 
     lighty.env["uri.path"] = lighty.env["uri.path"] .. ".php" 
     lighty.env["physical.rel-path"] = lighty.env["uri.path"] 
     lighty.env["physical.path"] = lighty.env["physical.doc-root"] .. lighty.env["physical.rel-path"] 
   end 
 </pre> 


 *User tracking* 

 ... or how to store data globally in the script-context: 

 Each script has its own script-context. When the script is started it only contains the lua-functions and the special lighty.* name-space. If you want to save data between script runs, you can use the global-script context: 

 <pre> 
   if (nil == _G["usertrack"]) then 
     _G["usertrack"] = {} 
   end 
   if (nil == _G["usertrack"][lighty.request["Cookie"]]) then 
     _G["usertrack"][lighty.request["Cookie"]] 
   else  
     _G["usertrack"][lighty.request["Cookie"]] = _G["usertrack"][lighty.request["Cookie"]] + 1 
   end 

   print _G["usertrack"][lighty.request["Cookie"]] 
 </pre> 

 The global-context is per script. If you update the script without restarting the server, the context will still be maintained. 

 h1. Fight DDoS 
 If your Server is under high load because of someone is flooding you with requests, a little bit lua might help you. ;) In our case we've got a lot of requests without a User-Agent in the request header. 
 <pre>if ( lighty.request["User-Agent"]== nil ) then 
         file = io.open ("ips.txt","a") 
         file:write(lighty.env["request.remote-ip"]) 
         file:write("\n") 
         file:close() 
         return 200 
 end</pre> 

 The field request.remote-ip is available since Lighttpd 1.4.23. The file ips.txt must be writeable by the lighttpd user (www-data). The bad guys in the ips.txt file can be dropped into the firewall with a little shell script. 

 


 h1. Small Helpers 

  ... 

 h1. other solutions 

 *external-static* 

 I´ve seen this nice solution somewhere where they host some files locally on their machines. If popularity gets to high, files are too big or for whatever reasons the files are moved to i think it was amazon´s S3 or akamai for faster serving or to cope with high traffic. You still can use your hostname, urls, collect stats from your logs - your users are just redirected with a 302 to the files they ask for. 

 2008-11-17: Found the source: http://blog.innerfence.com/2008/05/31/presto-move-content-to-s3-with-no-code-changes/ 

   Request -> check for local copy -> 302 (if not stored locally) -> let users download from a big pipe 

 Add the following to your lighttpd.conf: 
 <pre> 
 $HTTP["url"] =~ "^/static/[^/]+[.]gif([?].*)?$" { #match the files you want this to work for 
   magnet.attract-physical-path-to = ( "/path-to-your/external-static.lua" ) 
 } 
 </pre> 

 Save the following to external-static.lua: 
 <pre> 
  local filename = lighty.env["physical.path"] 
  local stat = lighty.stat( filename ) 
   if not stat then 
    local static_name = string.match( filename, "static/([^/]+)$" ) 
    lighty.header["Location"] = "http://<new-location-with-big-pipes>/" .. static_name 
  return 302 
 end  
 </pre>