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• Memcached protocol support

  15 novembre 2013, par Mikko Koppanen — Imagick

  For the past few days I’ve been adding Memcached binary protocol support to PECL memcached extension. The protocol handler provides a high-level abstraction for acting as a memcached server. There are quite a few things still missing and only binary protocol is supported at the moment, but the code seems to work reasonably well in small-scale testing.

  I am not sure whether this is useful for anyone, but at least it allows things such as quick prototyping of network servers, exposing sqlite database over memcached protocol etc.

  The code is quite simple and implementing a simple server responding to get and set would look roughly like the following :

  php

  < view plain text >

  1. < ?php
  2. // Create new server instance
  3. $server = new MemcachedServer() ;
  4.  
  5. // Create a simple storage class
  6. class Storage {
  7.   private $values = array () ;
  8.   
  9.   public function set ($key, $value, $expiration) {
  10.     $this->values [$key] = array (’value’ => $value,
  11.                    ’expires’ => time () + $expiration) ;
  12.   }
  13.  
  14.   public function get ($key) {
  15.     if (isset ($this->values [$key])) {
  16.       if ($this->values [$key] [’expires’] < time ()) {
  17.         unset ($this->values [$key]) ;
  18.         return null ;
  19.       }
  20.       return $this->values [$key] [’value’] ;
  21.     }
  22.     else
  23.       return null ;
  24.   }
  25. }
  26.  
  27. $storage = new Storage () ;
  28.  
  29. // Set callback for get command
  30. $server->on (Memcached: :ON_GET,
  31.        function ($client_id, $key, &$value, &$flags, &$cas) use ($storage) {
  32.          echo "Getting key=[$key]" . PHP_EOL ;
  33.          if (($value = $storage->get ($key))  != null)
  34.            return Memcached: :RESPONSE_SUCCESS ;
  35.  
  36.          return Memcached: :RESPONSE_KEY_ENOENT ;
  37.        }) ;
  38.  
  39. // Set callback for set command
  40. $server->on (Memcached: :ON_SET,
  41.        function ($client_id, $key, $value, $flags, $expiration, $cas, &$result_cas) use ($storage) {
  42.          echo "Setting key=[$key] value=[$value]" . PHP_EOL ;
  43.          $storage->set ($key, $value, $expiration) ;
  44.          return Memcached: :RESPONSE_SUCCESS ;
  45.        }) ;
  46.  
  47. // Run the server on localhost, port 3434. Will block
  48. $server->run ("127.0.0.1:3434") ;
  49.  ?>

  And the client that communicates with the server :

  php

  < view plain text >

  1. < ?php
  2.  
  3. $cache = new Memcached() ;
  4. $cache->setOption(Memcached: :OPT_BINARY_PROTOCOL, true) ;
  5. $cache->setOption(Memcached: :OPT_COMPRESSION, false) ;
  6. $cache->addServer(’localhost’, 3434) ;
  7.  
  8. $cache->set (’set_key1’, ’This is the first key’, 10) ;
  9. var_dump ($cache->get (’set_key1’)) ;
  10.  
  11. $cache->set (’set_key2’, ’This is the second key’, 2) ;
  12. var_dump ($cache->get (’set_key2’)) ;
  13.  ?>

  The code is still work in progress but it’s available in github : https://github.com/mkoppanen/php-memcached/tree/feature-server. Note that you need to compile libmemcached with –enable-libmemcachedprotocol and the PECL memcached extension with –enable-memcached-protocol.

• Working on images asynchronously

  15 décembre 2013, par Mikko Koppanen — Imagick, PHP stuff

  To get my quota on buzzwords for the day we are going to look at using ZeroMQ and Imagick to create a simple asynchronous image processing system. Why asynchronous ? First of all, separating the image handling from a interactive PHP scripts allows us to scale the image processing separately from the web heads. For example we could do the image processing on separate servers, which have SSDs attached and more memory. In this example making the images available to all worker nodes is left to the reader.

  Secondly, separating the image processing from a web script can provide more responsive experience to the user. This doesn’t necessarily mean faster, but let’s say in a multiple image upload scenario this method allows the user to do something else on the site while we process the images in the background. This can be beneficial especially in cases where users upload hundreds of images at a time. To achieve a simple distributed image processing infrastructure we are going to use ZeroMQ for communicating between different components and Imagick to work on the images.

  The first part we are going to create is a simple “Worker” -process skeleton. Naturally for a live environment you would like to have more error handling and possibly use pcntl for process control, but for the sake of brewity the example is barebones :

  php

  < view plain text >

  1. < ?php
  2.  
  3. define (’THUMBNAIL_ADDR’, ’tcp ://127.0.0.1:5000’) ;
  4. define (’COLLECTOR_ADDR’, ’tcp ://127.0.0.1:5001’) ;
  5.  
  6. class Worker {
  7.  
  8.   private $in ;
  9.   private $out ;
  10.  
  11.   public function __construct ($in_addr, $out_addr)
  12.   {
  13.     $context = new ZMQContext () ;
  14.  
  15.     $this->in = new ZMQSocket ($context, ZMQ: :SOCKET_PULL) ;
  16.     $this->in->bind ($in_addr) ;
  17.  
  18.     $this->out = new ZMQSocket ($context, ZMQ: :SOCKET_PUSH) ;
  19.     $this->out->connect ($out_addr) ;
  20.   }
  21.  
  22.   public function work () {
  23.     while ($command = $this->in->recvMulti ()) {
  24.       if (isset ($this->commands [$command [0]])) {
  25.         echo "Received work" . PHP_EOL ;
  26.  
  27.         $callback = $this->commands [$command [0]] ;
  28.  
  29.         array_shift ($command) ;
  30.         $response = call_user_func_array ($callback, $command) ;
  31.  
  32.         if (is_array ($response))
  33.           $this->out->sendMulti ($response) ;
  34.         else
  35.           $this->out->send ($response) ;
  36.       }
  37.       else {
  38.         error_log ("There is no registered worker for $command [0]") ;
  39.       }
  40.     }
  41.   }
  42.  
  43.   public function register ($command, $callback)
  44.   {
  45.     $this->commands [$command] = $callback ;
  46.   }
  47. }
  48.  ?>

  The Worker class allows us to register commands with callbacks associated with them. In our case the Worker class doesn’t actually care or know about the parameters being passed to the actual callback, it just blindly passes them on. We are using two separate sockets in this example, one for incoming work requests and one for passing the results onwards. This allows us to create a simple pipeline by adding more workers in the mix. For example we could first have a watermark worker, which takes the original image and composites a watermark on it, passes the file onwards to thumbnail worker, which then creates different sizes of thumbnails and passes the final results to event collector.

  The next part we are going to create a is a simple worker script that does the actual thumbnailing of the images :

  php

  < view plain text >

  1. < ?php
  2. include __DIR__ . ’/common.php’ ;
  3.  
  4. // Create worker class and bind the inbound address to ’THUMBNAIL_ADDR’ and connect outbound to ’COLLECTOR_ADDR’
  5. $worker = new Worker (THUMBNAIL_ADDR, COLLECTOR_ADDR) ;
  6.  
  7. // Register our thumbnail callback, nothing special here
  8. $worker->register (’thumbnail’, function ($filename, $width, $height) {
  9.                   $info = pathinfo ($filename) ;
  10.  
  11.                   $out = sprintf ("%s/%s_%dx%d.%s",
  12.                           $info [’dirname’],
  13.                           $info [’filename’],
  14.                           $width,
  15.                           $height,
  16.                           $info [’extension’]) ;
  17.  
  18.                   $status = 1 ;
  19.                   $message = ’’ ;
  20.  
  21.                   try {
  22.                     $im = new Imagick ($filename) ;
  23.                     $im->thumbnailImage ($width, $height) ;
  24.                     $im->writeImage ($out) ;
  25.                   }
  26.                   catch (Exception $e) {
  27.                     $status = 0 ;
  28.                     $message = $e->getMessage () ;
  29.                   }
  30.  
  31.                   return array (
  32.                         ’status’  => $status,
  33.                         ’filename’ => $filename,
  34.                         ’thumbnail’ => $out,
  35.                         ’message’ => $message,
  36.                     ) ;
  37.                 }) ;
  38.  
  39. // Run the worker, will block
  40. echo "Running thumbnail worker.." . PHP_EOL ;
  41. $worker->work () ;

  As you can see from the code the thumbnail worker registers a callback for ‘thumbnail’ command. The callback does the thumbnailing based on input and returns the status, original filename and the thumbnail filename. We have connected our Workers “outbound” socket to event collector, which will receive the results from the thumbnail worker and do something with them. What the “something” is depends on you. For example you could push the response into a websocket to show immediate feeedback to the user or store the results into a database.

  Our example event collector will just do a var_dump on every event it receives from the thumbnailer :

  php

  < view plain text >

  1. < ?php
  2. include __DIR__ . ’/common.php’ ;
  3.  
  4. $socket = new ZMQSocket (new ZMQContext (), ZMQ: :SOCKET_PULL) ;
  5. $socket->bind (COLLECTOR_ADDR) ;
  6.  
  7. echo "Waiting for events.." . PHP_EOL ;
  8. while (($message = $socket->recvMulti ())) {
  9.   var_dump ($message) ;
  10. }
  11.  ?>

  The final piece of the puzzle is the client that pumps messages into the pipeline. The client connects to the thumbnail worker, passes on filename and desired dimensions :

  php

  < view plain text >

  1. < ?php
  2. include __DIR__ . ’/common.php’ ;
  3.  
  4. $socket = new ZMQSocket (new ZMQContext (), ZMQ: :SOCKET_PUSH) ;
  5. $socket->connect (THUMBNAIL_ADDR) ;
  6.  
  7. $socket->sendMulti (
  8.       array (
  9.         ’thumbnail’,
  10.         realpath (’./test.jpg’),
  11.         50,
  12.         50,
  13.       )
  14. ) ;
  15. echo "Sent request" . PHP_EOL ;
  16.  ?>

  After this our processing pipeline will look like this :

  

  Now, if we notice that thumbnail workers or the event collectors can’t keep up with the rate of images we are pushing through we can start scaling the pipeline by adding more processes on each layer. ZeroMQ PUSH socket will automatically round-robin between all connected nodes, which makes adding more workers and event collectors simple. After adding more workers our pipeline will look like this :

  

  Using ZeroMQ also allows us to create more flexible architectures by adding forwarding devices in the middle, adding request-reply workers etc. So, the last thing to do is to run our pipeline and see the results :

  Let’s create our test image first :

  $ convert magick:rose test.jpg
  

  From the command-line run the thumbnail script :

  $ php thumbnail.php 
  Running thumbnail worker..
  

  In a separate terminal window run the event collector :

  $ php collector.php 
  Waiting for events..
  

  And finally run the client to send the thumbnail request :

  $ php client.php 
  Sent request
  $
  

  If everything went according to the plan you should now see the following output in the event collector window :

  array(4) 
    [0]=>
    string(1) "1"
    [1]=>
    string(56) "/test.jpg"
    [2]=>
    string(62) "/test_50x50.jpg"
    [3]=>
    string(0) ""
  
  

  Happy hacking !

• Cloaked Archive Wiki

  16 mai 2011, par Multimedia Mike — General

  Google’s Chrome browser has made me phenomenally lazy. I don’t even attempt to type proper, complete URLs into the address bar anymore. I just type something vaguely related to the address and let the search engine take over. I saw something weird when I used this method to visit Archive Team’s site :

  
  
  

  There’s greater detail when you elect to view more results from the site :

  
  
  

  As the administrator of a MediaWiki installation like the one that archiveteam.org runs on, I was a little worried that they might have a spam problem. However, clicking through to any of those out-of-place pages does not indicate anything related to pharmaceuticals. Viewing source also reveals nothing amiss.

  I quickly deduced that this is a textbook example of website cloaking. This is when a website reports different content to a search engine than it reports to normal web browsers (humans, presumably). General pseudocode :

  PLAIN TEXT

  C :

  1. if (web_request.user_agent_string == CRAWLER_USER_AGENT)
  2.  return cloaked_data ;
  3. else
  4.  return real_data ;

  You can verify this for yourself using the wget command line utility :

  <br />
$ wget --quiet --user-agent="<strong>Mozilla/5.0</strong>" \<br />
 http://www.archiveteam.org/index.php?title=Geocities -O - | grep \&lt;title\&gt;<br />
&lt;title&gt;GeoCities - Archiveteam&lt;/title&gt;

  $ wget —quiet —user-agent="Googlebot/2.1"
  http://www.archiveteam.org/index.php?title=Geocities -O - | grep \<title\>
  <title>Cheap xanax | Online Drug Store, Big Discounts</title>
  

  I guess the little web prank worked because the phaux-pharma stuff got indexed. It makes we wonder if there’s a MediaWiki plugin that does this automatically.

  For extra fun, here’s a site called the CloakingDetector which purports to be able to detect whether a page employs cloaking. This is just one humble observer’s opinion, but I don’t think the site works too well :