Session Server - Maintaing State between several Servers

SessionServer :: Maintaining state between several servers Stephan Schmidt 1&1 Internet AG

Agenda The need for a session server ext/sockets and ext/pcntl Using Net_Server Designing a protocol Architecture of HTTP_SessionServer Building a client Integrating the built-in session functions The future

Why Sessions? HTTP is stateless Requests operate in a sandbox Two requests of the same user may be handled by different apache processes Modern applications require a state Authentication Shopping carts User tracking

PHP sessions Built-in functions since PHP4 Data associated with a user is stored on the server Unique Session-Id for each active user, passed between requests Stores data on the filesystem (other containers are possible) Shared Memory Database

Disadvantages Data is stored on the web server only accessible via PHP only accessible from this server applications must run on this server no clusters size may be limited (size of /tmp or shared memory segment)

The Solution Store session data in one central location accessible from any server accessible by any application accessible by any programming language no overhead (like when using a RDBMS or web service) access must be simple

Session Server Stores key value pairs for sessions Daemon that is awaiting connections may be accessed using fsockopen(), fwrite() and fread() very simple protocol Store data on the filesystem, just like PHP's session functions, but need not be on the webserver

Building a server with PHP ext/sockets allows you to create daemons: $fd = socket_create( AF_INET, SOCK_STREAM, SOL_TCP ); if(!is_resource($fd)) { die('Could not create socket.'); } socket_bind( $fd, 'localhost', 9090 ); socket_listen( $fd, 10 ); $newFd = socket_accept( $fd ); $text = "Hello world!\n"; socket_write( $newFd, $text, strlen( $text ) ); socket_close($newFd); socket_close($fd);

Building a server with PHP (2) run this script in with PHP-CLI $ php myServer.php open a new terminal and execute $ telnet localhost 9090 schst@rot3:schst> telnet localhost 9090 Trying 127.0.0.1... Connected to localhost. Escape character is '^]'. Hello world! Connection closed by foreign host. schst@rot3:schst>

Building a server with PHP (3) ext/sockets provides more functions receive data from client using socket_read() set options get information about the client socket_accept() halts script execution Limited to one connection at a time May keep more than one connection open using socket_select() but still sequential

Making use of ext/pcntl Implements the Unix style of process creation signal handling process termination That means current process can be copied at runtime parent-process may stop children Not available on Windows

Making use of ext/pcntl (2) $children = 5; for ($i=1; $i<=$children; $i++) { $pid = pcntl_fork(); if ($pid === -1) { exit('Could not fork child.'); } elseif ($pid) { continue; } else { printf("new process created: %s\n",getmypid()); break; } } // do not exit while(true) { sleep(5); }

Making use of ext/pcntl (3) pcntl_fork() forks process and returns new process id If pcntl_fork() returns '0' (zero), current process is the child If master-process is stopped, all children are stopped as well Child-Processes may be stopped without stopping the parent

Making use of ext/pcntl (4) run this script in with PHP-CLI $ php myFork.php schst@rot3:schst> php5 myFork.php new process created: 30923 new process created: 30924 new process created: 30925 new process created: 30926 new process created: 30927

Making use of ext/pcntl (5) Take a look at the processes $ ps fax | grep myFork schst@rot3:schst> ps fax | grep myFork 30922 pts/0 S+ 0:00 | \_ php5 myFork.php 30923 pts/0 S+ 0:00 | \_ php5 myFork.php 30924 pts/0 S+ 0:00 | \_ php5 myFork.php 30925 pts/0 S+ 0:00 | \_ php5 myFork.php 30926 pts/0 S+ 0:00 | \_ php5 myFork.php 30927 pts/0 S+ 0:00 | \_ php5 myFork.php Kill one process $ kill 30923

Confused by low-level code? Use PEAR::Net_Server! Provides generic server class. Has support for pcntl_fork() Triggers callbacks on events New client connects Client sends data Client disconnects …

Using Net_Server class Net_Server_Handler_Talkback extends Net_Server_Handler { function onConnect($clientId = 0) { $this->_server->sendData($clientId,"Welcome to my server\n"); } function onReceiveData($clientId = 0, $data = '') { $this->_server->sendData($clientId, "You said: $data"); } } $server = &Net_Server::create('Fork', 'localhost', 9090); $handler = &new Net_Server_Handler_Talkback; $server->setCallbackObject($handler); $server->start();

Using Net_Server (2) run this script with PHP-CLI $ php myServer2.php schst@rot3:schst> php5 myServer2.php PEAR constructor called, class=Net_Server_Driver_Fork … 14:30:44 Listening on port 9090. Server started at 14:30:44 … 14:30:50 New co…on from 127.0.0.1 on port 52237, new pid: 31241 … 14:30:50 sending: "Welcome to my server" to: 127.0.0.1:52237 (pid: 31241) … 14:30:53 Received Foo from 127.0.0.1:52237 (pid: 31241) … 14:30:53 sending: "You said: Foo" to: 127.0.0.1:52237 (pid: 31241)

Building a Session Daemon Define a protocol create new session open existing session store value retrieve value some additional commands Implement a callback object start the Net_Server object

HTTP_SessionServer Out-of-the-box solution available in PEAR require_once 'HTTP/SessionServer.php'; $options = array( 'save_path' => '/tmp' ); $server = &new HTTP_SessionServer('Filesystem', $options); $server->service('localhost', 9090); Uses Net_Server with 'Fork' driver requires ext/pcntl, does not work on windows Provides a client as well

The Protocol Currently supports 13 commands: new, open, close, commit, destroy get, put, exists, remove, get_all, put_all, keys regenerate_id Structure of a command: command arg1 arg2 … Session-Id is stored after executing open or new (keeps the payload smaller)

The Protocol (2) Server sends ok or err to indicate success or failure, followed by actual result, e.g. err unknown command Data will be UTF-8 encoded enough theory, example coming up…

The protocol (3) schst@rot3:schst> telnet localhost 9090 Trying 127.0.0.1... Connected to localhost. new ok 8087127fe6cf50e89932dbf0ee8d4855 put foo bar ok put today 2004-11-09 ok keys ok foo|today get today ok 2004-11-09 close ok get foo err No session opened.

Features Different storage containers possible Open a session in read-only-mode Auto-lock a session in write-mode change mode from "write" to "read" (commit) Change the session-Id while keeping the data (for security reasons) easily extendible

Architecture of the server Net_Server HTTP_Session_Server Storage_Filesystem Custom Storage Client Client Client Client Calls onDataReceived Parses data and calls methods on storage Serializes return values

Extending SessionServer Write a new storage container In most cases open(), close(), destroy() and commit() are enough Shared Memory, RDBMS, etc. Implement new commands Extend HTTP_SessionServer Implement _cmd[CommandName] method return an array

Building a client Using fsockopen() $fp = fsockopen('localhost', 9090); fputs($fp, "new\r\n"); $result = fgets($fp, 4096); fclose($fp); Using PEAR::Net_Socket $socket = &new Net_Socket(); $socket->connect('localhost', 9090); $socket->writeLine('new'); $result = $socket->readLine(); $socket->disconnect();

Don't worry: Client included Based on PEAR::Net_Socket Very easy-to-use OO-Interface to HTTP_SessionServer Implements all supported commands Returns PEAR_Error objects on error Automatically disconnects the socket

Client example require_once 'HTTP/SessionServer/Client.php'; $session = &new HTTP_SessionServer_Client('localhost', 9090); $id = $session->create(); $session->put('time', time()); $session->put('foo', 'bar'); $keys = $session->getKeys(); $session->close(); $session2 = &new HTTP_SessionServer_Client('localhost', 9090); $session->open($id, 'r'); $time = $session2->get('time'); $session2->close();

Setting a session save handler session_set_save_handler ( string open, string close, string read, string write, string destroy, string gc) Allows you to replace the storage module for internal session functions register callbacks to open,read, write, close and destroy session data

Replacing built-in session handling HTTP_SessionServer provides needed callbacks use session_save_path() to specify host and port No other changes needed require_once 'HTTP/SessionServer/SaveHandler.php'; session_save_path('localhost:9090'); session_start();

The future Work on PHP5 version using stream_socket_server() Implement missing features garbage collection session lifetime Implement a session storage module in C to improve performance Implement more storage containers

What about msession? msession is a daemon written in C similar to HTTP_SessionServer PHP-Extension is available More information at: http://devel.mohawksoft.com/msession.html

The End Thanks for your attention. [email_address] http://www.php-tools.net

Session Server - Maintaing State between several Servers

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