CRM/Core/Lock.php

   1 <?php
   2 /*
   3  +--------------------------------------------------------------------+
   4  | CiviCRM version 4.4                                                |
   5  +--------------------------------------------------------------------+
   6  | Copyright CiviCRM LLC (c) 2004-2013                                |
   7  +--------------------------------------------------------------------+
   8  | This file is a part of CiviCRM.                                    |
   9  |                                                                    |
  10  | CiviCRM is free software; you can copy, modify, and distribute it  |
  11  | under the terms of the GNU Affero General Public License           |
  12  | Version 3, 19 November 2007 and the CiviCRM Licensing Exception.   |
  13  |                                                                    |
  14  | CiviCRM is distributed in the hope that it will be useful, but     |
  15  | WITHOUT ANY WARRANTY; without even the implied warranty of         |
  16  | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.               |
  17  | See the GNU Affero General Public License for more details.        |
  18  |                                                                    |
  19  | You should have received a copy of the GNU Affero General Public   |
  20  | License and the CiviCRM Licensing Exception along                  |
  21  | with this program; if not, contact CiviCRM LLC                     |
  22  | at info[AT]civicrm[DOT]org. If you have questions about the        |
  23  | GNU Affero General Public License or the licensing of CiviCRM,     |
  24  | see the CiviCRM license FAQ at http://civicrm.org/licensing        |
  25  +--------------------------------------------------------------------+
  26 */
  27
  28 /**
  29  *
  30  * @package CRM
  31  * @copyright CiviCRM LLC (c) 2004-2013
  32  * $Id$
  33  *
  34  */
  35 class CRM_Core_Lock {
  36
  37   // lets have a 3 second timeout for now
  38   CONST TIMEOUT = 3;
  39
  40   protected $_hasLock = FALSE;
  41
  42   protected $_name;
  43
  44   /**
  45    * Initialize the constants used during lock acquire / release
  46    *
  47    * @param string  $name name of the lock. Please prefix with component / functionality
  48    *                      e.g. civimail.cronjob.JOB_ID
  49    * @param int     $timeout the number of seconds to wait to get the lock. 1 if not set
  50    * @param boolean $serverWideLock should this lock be applicable across your entire mysql server
  51    *                                this is useful if you have mutliple sites running on the same
  52    *                                mysql server and you want to limit the number of parallel cron
  53    *                                jobs - CRM-91XX
  54    *
  55    * @return object the lock object
  56    *
  57    */
  58   function __construct($name, $timeout = NULL, $serverWideLock = FALSE) {
  59     $config = CRM_Core_Config::singleton();
  60     $dsnArray = DB::parseDSN($config->dsn);
  61     $database = $dsnArray['database'];
  62     $domainID = CRM_Core_Config::domainID();
  63     if ($serverWideLock) {
  64       $this->_name = $name;
  65     }
  66     else {
  67       $this->_name = $database . '.' . $domainID . '.' . $name;
  68     }
  69     if (defined('CIVICRM_LOCK_DEBUG')) {
  70       CRM_Core_Error::debug_log_message('trying to construct lock for ' . $this->_name);
  71     }
  72     static $jobLog = FALSE;
  73     if ($jobLog && CRM_Core_DAO::singleValueQuery("SELECT IS_USED_LOCK( '{$jobLog}')")) {
  74       return $this->hackyHandleBrokenCode($jobLog);
  75     }
  76     if (stristr($name, 'civimail.job.')) {
  77       $jobLog = $this->_name;
  78     }
  79     //if (defined('CIVICRM_LOCK_DEBUG')) {
  80     //CRM_Core_Error::debug_var('backtrace', debug_backtrace());
  81     //}
  82     $this->_timeout = $timeout !== NULL ? $timeout : self::TIMEOUT;
  83
  84     $this->acquire();
  85   }
  86
  87   function __destruct() {
  88     $this->release();
  89   }
  90
  91   function acquire() {
  92     if (defined('CIVICRM_LOCK_DEBUG')) {
  93       CRM_Core_Error::debug_log_message('acquire lock for ' . $this->_name);
  94     }
  95     if (!$this->_hasLock) {
  96       $query = "SELECT GET_LOCK( %1, %2 )";
  97       $params = array(
  98         1 => array($this->_name, 'String'),
  99         2 => array($this->_timeout, 'Integer'),
 100       );
 101       $res = CRM_Core_DAO::singleValueQuery($query, $params);
 102       if ($res) {
 103         $this->_hasLock = TRUE;
 104       }
 105     }
 106     return $this->_hasLock;
 107   }
 108
 109   function release() {
 110     if ($this->_hasLock) {
 111       $this->_hasLock = FALSE;
 112
 113       $query = "SELECT RELEASE_LOCK( %1 )";
 114       $params = array(1 => array($this->_name, 'String'));
 115       return CRM_Core_DAO::singleValueQuery($query, $params);
 116     }
 117   }
 118
 119   function isFree() {
 120     $query = "SELECT IS_FREE_LOCK( %1 )";
 121     $params = array(1 => array($this->_name, 'String'));
 122     return CRM_Core_DAO::singleValueQuery($query, $params);
 123   }
 124
 125   function isAcquired() {
 126     return $this->_hasLock;
 127   }
 128
 129   /**
 130    * CRM-12856 locks were originally set up for jobs, but the concept was extended to caching & groups without
 131    * understanding that would undermine the job locks (because grabbing a lock implicitly releases existing ones)
 132    * this is all a big hack to mitigate the impact of that - but should not be seen as a fix. Not sure correct fix
 133    * but maybe locks should be used more selectively? Or else we need to handle is some cool way that Tim is yet to write :-)
 134    * if we are running in the context of the cron log then we would rather die (or at least let our process die)
 135    * than release that lock - so if the attempt is being made by setCache or something relatively trivial
 136    * we'll just return TRUE, but if it's another job then we will crash as that seems 'safer'
 137    *
 138    * @param string $jobLog
 139    * @throws CRM_Core_Exception
 140    * @return boolean
 141    */
 142   function hackyHandleBrokenCode($jobLog) {
 143     if (stristr($this->_name, 'job')) {
 144       throw new CRM_Core_Exception('lock aquisition for ' . $this->_name . 'attempted when ' . $jobLog . 'is not released');
 145     }
 146     if (defined('CIVICRM_LOCK_DEBUG')) {
 147       CRM_Core_Error::debug_log_message('(CRM-12856) faking lock for ' . $this->_name);
 148     }
 149     $this->_hasLock = TRUE;
 150     return TRUE;
 151   }
 152 }
 153