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Mutexed memcache handler. Traps race and memcache memory conditions on large scale Fastcgi farms.

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Attribs: Stephan Becker: Code, identified the Javascript culprits
         Wim Bonis: Code, Race condition
	 Klaus Leithhoff: Code, mbstring writes a different length to that that it reads
	 Lars Volker: Code, Debug memcache slab memory,  memcache add as lock.
This commit is contained in:
Nigel Vickers 2008-02-25 14:13:45 +00:00
parent cc210e9dae
commit d81d9bce03
1 changed files with 67 additions and 4 deletions
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71
phpgwapi/inc/memcache.inc.php
View File

@ -22,6 +22,9 @@
* @version $Id$
*/
define('DEBUG',0);
define('DEBUGALL',0);
function egw_memcache_open($save_path, $session_name)
{
global $egw_memcache_obj;
@ -41,16 +44,22 @@ function egw_memcache_close()
return is_object($egw_memcache_obj) ? $egw_memcache_obj->close() : false;
}
define('MEMCACHED_MAX_JUNK',1024*1023); // 1024*1024 is too big, maybe some account-info needs to be added
define('MEMCACHED_MAX_JUNK',1024*1000); // 1024*1024 is too big, maybe some account-info needs to be added
function egw_memcache_read($id)
{
global $egw_memcache_obj;
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." READ start $id:");
if (!_acquire_and_wait($id)) return false;
for($data=false,$n=0; ($read = $egw_memcache_obj->get($id.($n?'-'.$n:''))); ++$n)
{
if (DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." read $id:$n:".print_r(_bytes($read),true));
$data .= $read;
}
_release($id);
return $data;
}
@ -64,13 +73,61 @@ function egw_memcache_write($id, $sess_data)
{
$lifetime = 600;
}
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." WRITE start $id:");
if (!_acquire_and_wait($id)) return false;
for($n=$i=0,$len=_bytes($sess_data); $i < $len; $i += MEMCACHED_MAX_JUNK,++$n)
{
if (!$egw_memcache_obj->set($id.($n?'-'.$n:''),_cut_bytes($sess_data,$i,MEMCACHED_MAX_JUNK),0,$lifetime)) return false;
if (DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." in :$n write $id:$i:".print_r(_bytes($sess_data),true));
if (!$egw_memcache_obj->set($id.($n?'-'.$n:''),_cut_bytes($sess_data,$i,MEMCACHED_MAX_JUNK),0,$lifetime)) {
_release($id);
return false;
}
}
if (DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." DELETE :$n");
for($n=$n; $egw_memcache_obj->delete($id.($n?'-'.$n:'')); ++$n) ;
_release($id);
return true;
}
function _acquire_and_wait($id)
{
global $egw_memcache_obj;
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE :$id");
$i=0;
// Acquire lock for 3 seconds, after that i should have done my job
while(!$egw_memcache_obj->add($id.'-lock',1,0,3)) {
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE Lock Loop :$id:$i");
usleep(100000);
$i++;
if ($i > 40) {
if (DEBUG > 0) 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($i>1) {
if (DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." ACQUIRE LOOP $i :$id");
}
if (DEBUG > 0) error_log("\n memcache ".print_r(getenv('HOSTNAME'),true).$_SERVER["REQUEST_TIME"]." Lock ACQUIRED $i:$id");
return true;
}
function _release($id)
{
global $egw_memcache_obj;
if (DEBUG > 0) error_log("\n memcache ".$_SERVER["REQUEST_TIME"]." RELEASE :$id");
return $egw_memcache_obj->delete($id.'-lock');
}
function _test_mbstring_func_overload()
{
return @extension_loaded('mbstring') && (ini_get('mbstring.func_overload') & 2);
@ -80,7 +137,7 @@ function _bytes(&$data)
{
global $mbstring_func_overload;
if (is_null($mbstring_func_overload)) _test_mbstring_func_overload();
if (is_null($mbstring_func_overload)) $mbstring_func_overload=_test_mbstring_func_overload();
return $mbstring_func_overload ? mb_strlen($data,'ascii') : strlen($data);
}
@ -89,7 +146,9 @@ function _cut_bytes(&$data,$offset,$len=null)
{
global $mbstring_func_overload;
if (is_null($mbstring_func_overload)) _test_mbstring_func_overload();
if (is_null($mbstring_func_overload)) $mbstring_func_overload=_test_mbstring_func_overload();
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache in cutbyte mb $id:$n:".print_r(mb_substr($data,$offset,$len,'ascii'),true));
if (DEBUG > 0 && DEBUGALL>0) error_log("\n memcache in cutbyte norm $id:$n:".print_r(substr($data,$offset,$len),true));
return $mbstring_func_overload ? mb_substr($data,$offset,$len,'ascii') : substr($data,$offset,$len);
}
@ -98,8 +157,12 @@ function egw_memcache_destroy($id)
{
global $egw_memcache_obj;
if (!_acquire_and_wait($id)) return false;
error_log("\n memcache destroy $id:$n:");
for($n=0; $egw_memcache_obj->delete($id.($n?'-'.$n:'')); ++$n) ;
_release($id);
return $n > 0;
}