PHPMemcacheSASL for AppFog

This is a modification of ronnywang's implementation of PHPMemcacheSASL specifically for use on AppFog. As of now, this is the official reference implementation listed in the documentation. Awesome contributers include robertocr -- if you make a useful pull request, I will give you commit access.

What's the difference?

On AppFog, the connection information for your Memcachier instance is exposed through three environment variables:

echo $_ENV['MEMCACHIER_SERVERS'];  // output: xxx.ec2.memcachier.com:11211
echo $_ENV['MEMCACHIER_USERNAME']; // output: aa92mro2in
echo $_ENV['MEMCACHIER_PASSWORD']; // output: oim23in924b2NS3Iaid1x193jhe1

The format of $_ENV['MEMCACHIER_SERVERS'] is $HOST:$PORT on AppFog's PHP instances. In the AppFog Memcachier PHP docs, the example code suggests that you add a server using the syntax:

$m->addServer($_ENV["MEMCACHIER_SERVERS"], '11211');
// Evaluates as: $m->addServer(xxx.ec2.memcachier.com:11211', '11211');

This is a problem because the first argument of addServer expects the hostname without the port. I have modified the API of $m->addServer to:

$m->addServer($_ENV["MEMCACHIER_SERVERS"]);
// Evaluates as: $m->addServer(xxx.ec2.memcachier.com:11211');

This way, you do not need to parse/explode the value of $_ENV['MEMCACHIER_SERVERS'] before using it to connect to Memcachier. Other implementations (and docs) for PHPMemcacheSASL do not account for this difference in syntax, so they will be unhelpful to you if you are an AppFog client.

Implementation

First, make sure you have activated the Memcachier add-on in your AppFog console.

1. Go to the dashboard for your app
2. Click "Add-Ons" in your left navigation
3. Click "Install" under Memcachier
4. Click "Env Variables" in your left navigation. Make sure that your $_ENV['MEMCACHIER_SERVERS'], $_ENV['MEMCACHIER_USERNAME'], and $_ENV['MEMCACHIER_PASSWORD'] variables are listed.

Now you are ready to integrate Memcachier with your code. To get started, download MemcacheSASL.php and put it in your working directory. If you have another implementation of MemcacheSASL.php, you must replace it with the file from this project. In this example, I will assume MemcacheSASL.php is in the same directory:

include('MemcacheSASL.php');

$m = new MemcacheSASL;
$m->addServer(getenv('MEMCACHIER_SERVERS'));
$m->setSaslAuthData(getenv('MEMCACHIER_USERNAME'), getenv('MEMCACHIER_PASSWORD'));

You have now initiated a connection for your Memcachier server. Here is an example communication with the Memcachier server:

$m->add('test', '123');
echo $m->get('test'); // output: '123'
$m->delete('test');

This code will add a cache entry with the key 'test' and a value '123'. It will then immediately retrieve and print the value of the key 'test' (which is '123') from the cache. Finally, it will delete this cache entry.

$m->add() can also accept a third argument, $expiration, which is the lifespan of the cache entry in seconds. To set the same key/value as above with a one hour expiration, I would write:

$m->add('test', '123', 3600); // set expiration of 1hr (60s * 60m)
echo $m->get('test'); // output: '123'
$m->delete('test');

You can see the full code of this example in example.php.

Here is a production example using Memcachier to cache results from queries to a MySQL database:

include('MemcacheSASL.php');

function memcacheQuery($query, $hours = 1) {
	// Set up Memcachier connection
	$m = new MemcacheSASL;
	$m->addServer(getenv('MEMCACHIER_SERVERS'));
	$m->setSaslAuthData(getenv('MEMCACHIER_USERNAME'), getenv('MEMCACHIER_PASSWORD'));
	
	// Set key and check for existing entry
	$key = md5($query);
	$results = $m->get($key);

	// If there is no entry, make a database query
	if (!$results) {
		$request = mysql_query($query);
		while ($item = mysql_fetch_array($request)) {
			$results[] = $item;
		}
		$cache_entry = $m->add($key, $results, 60*60*$hours);
	}

	// Return array of results, or a single result
	return (count($results) > 1) ? $songs_array : $songs_array[0];
}

Revisions, Contact, and Acknowledgements

Please feel free to submit a pull request. I created this project to benefit other users, and plan to continually revise it as per my communications with them. Thanks to ronnywang for the base code and AppFog for providing an awesome hosting solution.

---

Further reading

Memcache Binary Protocol

http://code.google.com/p/memcached/wiki/BinaryProtocolRevamped

Memcache SASL Auth Protocol

http://code.google.com/p/memcached/wiki/SASLAuthProtocol

PHP Memcached class

http://php.net/manual/en/class.memcached.php