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egroupware/phpgwapi/inc/class.egw_session_memcache.inc.php

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PHP
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<?php
/**
* eGroupWare API - memcache session handler
*
* Fixes a problem of the buildin session handler of the memcache pecl extension,
* which can NOT work with sessions > 1MB. This handler splits the session-data
* in 1MB chunk, so memcache can handle them. For the first chunk we use an identical
* key (just the session-id) as the original memcache session handler. For the further
* chunks we add -2, -3, ... so other code (eg. the SyncML code from Horde) can
* open the session, if it's size is < 1MB.
*
* To enable it, you need to set session.save_handler to 'memcache',
* session.save_path to 'tcp://host:port[,tcp://host2:port,...]',
* as you have to do it with the original handler PLUS adding the following
* to your header.inc.php:
*
* $GLOBALS['egw_info']['server']['session_handler'] = 'egw_session_memcache';
*
* @link http://www.egroupware.org
* @author Ralf Becker <RalfBecker-AT-outdoor-training.de>
* @package api
* @subpackage session
* @copyright (c) 2007-8 by Ralf Becker <RalfBecker-AT-outdoor-training.de>
* @license http://opensource.org/licenses/gpl-license.php GPL - GNU General Public License
* @version $Id$
*/
// needed for check_load_extension (session-handler gets included before regular include via the header.inc.php)
require_once(EGW_API_INC.'/common_functions.inc.php');
/**
* File based php sessions or all other build in handlers configures via session_module_name() or php.ini: session.save_handler
*
* Contains static methods to list or count 'files' sessions (does not work under Debian, were session.save_path is not searchable!)
*/
class egw_session_memcache
{
/**
* Debug level: 0 = none, 1 = some, 2 = all
*/
const DEBUG = 0;
/**
* Instance of Memcache
*
* @var Memcache
*/
private static $memcache;
/**
* are the string functions overloaded by their mbstring variants
*
* @var boolean
*/
private static $mbstring_func_overload;
/**
* Initialise the session-handler (session_set_save_handler()), if necessary
*/
public static function init_session_handler()
{
self::$mbstring_func_overload = @extension_loaded('mbstring') && (ini_get('mbstring.func_overload') & 2);
// session needs to be closed before objects get destroyed, as this session-handler is an object ;-)
register_shutdown_function('session_write_close');
}
/**
* Open session
*
* @param string $save_path
* @param string $session_name
* @return boolean
*/
public static function open($save_path, $session_name)
{
check_load_extension('memcache',true); // true = throw exception if not loadable
self::$memcache = new Memcache;
foreach(explode(',',$save_path) as $path)
{
$parts = parse_url($path);
self::$memcache->addServer($parts['host'],$parts['port']); // todo parse query
}
return true;
}
/**
* Close session
*
* @return boolean
*/
public static function close()
{
return is_object(self::$memcache) ? self::$memcache->close() : false;
}
/**
* Size of a single memcache junk
*
* 1024*1024 is too big, maybe some account-info needs to be added
*/
const MEMCACHED_MAX_JUNK = 1024000;
/**
* Read session data
*
* According to a commentary on php.net (session_set_save_handler) this function has to return
* a string, if the session-id is NOT found, not false. Returning false terminates the script
* with a fatal error!
*
* @param string $id
* @return string|boolean false on error, '' for not found session otherwise session data
*/
public static function read($id)
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." READ start $id:");
if (!self::_acquire_and_wait($id)) return false;
for($data='',$n=0; ($read = self::$memcache->get($id.($n?'-'.$n:''))); ++$n)
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." read $id:$n:".print_r(self::_bytes($read),true));
$data .= $read;
}
self::_release($id);
return $data;
}
/**
* Write session data
*
* @param string $id
* @param string $sess_data
* @return boolean
*/
public static function write($id, $sess_data)
{
$lifetime = (int)ini_get('session.gc_maxlifetime');
if ($id == 'no-session')
{
return true; // no need to save
}
// give anon sessions only a lifetime of 10min
if (is_object($GLOBALS['egw']->session) && $GLOBALS['egw']->session->session_flags == 'A' ||
$GLOBALS['egw_info']['flags']['currentapp'] == 'groupdav')
{
$lifetime = 600;
}
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." WRITE start $id:");
if (!self::_acquire_and_wait($id)) return false;
for($n=$i=0,$len=self::_bytes($sess_data); $i < $len; $i += self::MEMCACHED_MAX_JUNK,++$n)
{
if (self::DEBUG > 1) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." in :$n write $id:$i:".print_r(self::_bytes($sess_data),true));
if (!self::$memcache->set($id.($n?'-'.$n:''),self::_cut_bytes($sess_data,$i,self::MEMCACHED_MAX_JUNK),0,$lifetime)) {
self::_release($id);
return false;
}
}
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." DELETE :$n");
for($n=$n; self::$memcache->delete($id.($n?'-'.$n:'')); ++$n) ;
self::_release($id);
return true;
}
/**
* semaphore to gard against conflicting writes, destroying the session-data
*
* @param string $id
* @return boolean
*/
private static function _acquire_and_wait($id)
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE :$id");
$i=0;
// Acquire lock for 3 seconds, after that i should have done my job
while(!self::$memcache->add($id.'-lock',1,0,3))
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE Lock Loop :$id:$i");
usleep(100000);
$i++;
if ($i > 40)
{
if (self::DEBUG > 1) error_log("\n memcache ".print_r(getenv('HOSTNAME'),true).$_SERVER["REQUEST_TIME"]." blocked :$id");
// Could not acquire lock after 3 seconds, Continue, and pretend the locking process get stuck
// return false;A
break;
}
}
if($i > 1)
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE LOOP $i :$id");
}
if (self::DEBUG > 0) error_log("\n memcache ".print_r(getenv('HOSTNAME'),true).$_SERVER["REQUEST_TIME"]." Lock ACQUIRED $i:$id");
return true;
}
/**
* Release semaphore
*
* @param string $id
* @return boolean
*/
private static function _release($id)
{
if (self::DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." RELEASE :$id");
return self::$memcache->delete($id.'-lock');
}
/**
* mbstring.func_overload safe strlen
*
* @param string $data
* @return int
*/
private static function _bytes(&$data)
{
return self::$mbstring_func_overload ? mb_strlen($data,'ascii') : strlen($data);
}
/**
* mbstring.func_overload safe substr
*
* @param string $data
* @param int $offset
* @param int $len
* @return string
*/
private static function _cut_bytes(&$data,$offset,$len=null)
{
if (self::DEBUG > 1) error_log("\n memcache in cutbyte mb $id:$n:".print_r(mb_substr($data,$offset,$len,'ascii'),true));
if (self::DEBUG > 1) error_log("\n memcache in cutbyte norm $id:$n:".print_r(substr($data,$offset,$len),true));
return self::$mbstring_func_overload ? mb_substr($data,$offset,$len,'ascii') : substr($data,$offset,$len);
}
/**
* Destroy a session
*
* @param string $id
* @return boolean
*/
public static function destroy($id)
{
if (!self::_acquire_and_wait($id)) return false;
for($n=0; self::$memcache->delete($id.($n?'-'.$n:'')); ++$n)
{
if (self::DEBUG > 0) error_log("******* memcache destroy $id:$n:");
}
self::_release($id);
return $n > 0;
}
/**
* Run garbade collection
*
* @param int $maxlifetime
*/
public static function gc($maxlifetime)
{
// done by memcached itself
}
}
function init_session_handler()
{
$ses = 'egw_session_memcache';
$ret = session_set_save_handler(
array($ses,'open'),
array($ses,'close'),
array($ses,'read'),
array($ses,'write'),
array($ses,'destroy'),
array($ses,'gc'));
if (!$ret) error_log(__METHOD__.'() session_set_save_handler(...)='.(int)$ret.', session_module_name()='.session_module_name().' *******************************');
}
init_session_handler();
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