Facebook has been working a lot, Cassandra, Scribe, u name it. The new kid from Facebook is Hiphop PHP which is an automated system that converts PHP to C++

HipHop programmatically transforms your PHP source code into highly optimized C++ and then uses g++ to compile it.

Read More here: HipHop

HTTP is a stateless protocol. Which means that every request the browser makes to the server cant be identified by the server as a subsequent request of that user/IP/browser or a brand new request.

HTTP doesn’t understand who is requesting. So how do sessions manage to make HTTP look intelligent? The Answer lies in the request-response model with data.

When a normal request is made, eg my website, the minimalistic data passed by the client/browser is this

GET / HTTP/1.1
Host: ruturaj.net

The server responds by giving the output. But when a developer does a session_start();, What actually happens is, the PHP engine sets a PHPSESSID cookie. This data is sent from the Server as Set-Cookie header. So the response goes somewhat like this

HTTP/1.x 200 OK
Date: xxxx
Set-Cookie: PHPSESSID=<32charhexvalue>; expires=xxxx
...

Now considering the browser does accept the cookies, it saves the PHPSESSID cookie. Consequently the server also creates a file in the specified directory (by default on Linux as /tmp) as /tmp/sess_32charid.

Now when another request is made by the user/browser, the Cookie header is passed through the GET request back to the server, something like this…

GET /session2.php HTTP/1.1
Host: ruturaj.net
Cookie: PHPSESSID=<32charid>; othercookies=othervalues;

The session2.php, for example, is setting a value of name in session, by this

$_SESSION['name'] = $name_obtained_from_somewhere;

Now as the script finishes, the script flushes all the $_SESSION data into the /tmp/sess_32charid file associated to that session id. It saves all the data in the serialized format

Consider the browser makes another request to session3.php where $_SESSION['name'] is echoed. Now when the request is made, just like previous case, the PHPSESSID is passed in the cookie.

Now as mandated by php.net, that every page where sessions should be needed, a session_start(); is required. So as soon this function is invoked, PHP checks if the browser’s request had any PHPSESSID cookie sent in the header, as it was sent in our case, PHP Engine will open /tmp/sess_32charid file (with the same session id) and unserialize the contents of the file. It then assigns the values of the unserialized data structures to the $_SESSION variable.

The simple echo $_SESSION['name']; will now be able to output the name!! Sessions working…

On a session_destroy();, PHP sends a destructive, previous timestamp cookie for PHPSESSID and unlinks or deletes the /tmp/sess_32charid file. This ensures that no reference of that session is left.

References

• http://in3.php.net/manual/en/session.configuration.php

I’d put some efforts to make scribed logging work with PHP, what I did was follow python’s example script “scribe_cat”. And made a similar PHP Script out of it, I’d to create many PHP scripts out of n number of .thrift files. Anyways I’ve got a working example. Here it is.

<?php
/*
 * As found on http://highscalability.com/product-scribe-facebooks-scalable-logging-system
        $messages = array();
        $entry = new LogEntry;
        $entry->category = "buckettest";
        $entry->message = "something very interesting happened";
        $messages []= $entry;
        $result = $conn->Log($messages);
*/

$GLOBALS['THRIFT_ROOT'] = './includes';

include_once $GLOBALS['THRIFT_ROOT'] . '/scribe.php';
include_once $GLOBALS['THRIFT_ROOT'] . '/transport/TSocket.php';
include_once $GLOBALS['THRIFT_ROOT'] . '/transport/TFramedTransport.php';
include_once $GLOBALS['THRIFT_ROOT'] . '/protocol/TBinaryProtocol.php';
//include_once '/usr/local/src/releases/scribe-2.0/src/gen-php/scribe.php';

$msg1['category'] = 'keyword';
$msg1['message'] = "This is some message for the category\n";
$msg2['category'] = 'keyword';
$msg2['message'] = "Some other message for the category\n";
$entry1 = new LogEntry($msg1);
$entry2 = new LogEntry($msg2);
$messages = array($entry1, $entry2);

$socket = new TSocket('localhost', 1464, true);
$transport = new TFramedTransport($socket);
$protocol = new TBinaryProtocol($transport, false, false);
$scribe_client = new scribeClient($protocol, $protocol);

$transport->open();
$scribe_client->Log($messages);
$transport->close();

You can have as many messages or entries into one log, as I’ve demonstrated or tried above, please change the corresponding scribed’s host and port values. I’ve attached a working file and all the required includes generated by scribe. Except for the above script everything is generated by Scribe/Thrift.