I have this module that a great group of guys in Malaysia have put together. But their language of choice is PHP and mine is Perl. I need to modify it slightly to integrate it. For example, I need to add my own session code so that their code knows if my user is logged in or not and who they are.

I started writing PHP but quickly started duplicating code I’d already written in Perl. Fetch the session from the database, de-serialize the session data, that sort of thing. I also ran into issues trying to recreate my Perl decryption routines in PHP. [I use non-mainstream ciphers]

Then I found ways to run Perl inside PHP and vice-versa. But I quickly realized that’s a very bad idea. Not only are you creating a new Perl or PHP interpreter for every request, but you’re still duplicating code, and you’re using a lot more memory to run interpreters in addition to what mod_php and mod_perl already run.

Eventually I settled on creating a very lightweight wrapper function in PHP called doPerl. It looks like this:

$associativeArrayResult = doPerl(functionName, associativeArrayWithParameters);

function doPerl($func, $arrayData){
 $ch = curl_init();
 $ip = '127.0.0.1';
 $postData = array(
 json => json_encode($arrayData),
 auth => 'myPassword',
 );
 curl_setopt($ch,CURLOPT_POST, TRUE);
 curl_setopt($ch,CURLOPT_POSTFIELDS, $postData);
 curl_setopt($ch, CURLOPT_URL, "http://" . $ip . "/webService/" . $func . "/");
 curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
 $output = curl_exec($ch);
 curl_close($ch);
 $data = json_decode($output, TRUE);
 return $data;
}

On the other side I have a very fast mod_perl handler that only allows connections from 127.0.0.1 (the local machine). I deserialise the incoming JSON data using Perl’s JSON::from_json(). I use eval() to execute the function name that is, as you can see above, part of the URL. I reserialize the result using Perl’s JSON::to_json($result) and send it back to the PHP app as the HTML body.

This is very very fast because all PHP and Perl code that executes is already in memory under mod_perl or mod_php. The only overhead is the connection creation, sending of packet data across the network connection and connection breakdown. Some of this is handled by your server’s hardware. [And of course the serialization/deserialization of the JSON data on both ends.]

The connection creation is a three way handshake, but because there’s no latency on the link it’s almost instantaneous. The transferring of data is faster than a network because the MTU on your lo interface (the 127.0.0.1 interface) is 16436 bytes instead of the normal 1500 bytes. That means the entire request or response fits inside a single packet. And connection termination is again just two packets from each side and because of the zero latency it’s super fast.

I use JSON because it’s less bulky than XML and on average it’s faster to parse across all languages. Both PHP and Perl’s JSON routines are ridiculously fast.

My final implementation on the PHP side is a set of wrapper classes that use the doPerl() function to do their work. Inside the classes I use caching liberally, either in instance variables, or if the data needs to persist across requests I use PHP’s excellent APC cache to store the data in shared memory.

Update: On request I’ve posted the perl web service handler for this here. The Perl code allows you to send parameters via POST using either a query parameter called ‘json’ and including escaped JSON that will get deserialized and passed to your function, or you can just use regular post style name value pairs that will be sent as a hashref to your function. I’ve included one test function called hello() in the code. Please note this web service module lets you execute arbitrary perl code in the web service module’s namespace and doesn’t filter out double colon’s, so really you can just do whatever the hell you want. So I’ve included two very simple security mechanisms that I strongly recommend you don’t remove. It only allows requests from localhost, and you must include an ‘auth’ post parameter containing a password (currently set to ‘password’). You’re going to have to implement the MM::Util::getIP() routine to make this work and it’s really just a one liner:

sub getIP {
 my $r = shift @_;
 return $r->headers_in->{'X-Forwarded-For'} ?
    $r->headers_in->{'X-Forwarded-For'} :
    $r->connection->get_remote_host();
}