CRM/Core/Lock.php

   1 <?php
   2 /*
   3  +--------------------------------------------------------------------+
   4  | CiviCRM version 4.5                                                |
   5  +--------------------------------------------------------------------+
   6  | Copyright CiviCRM LLC (c) 2004-2014                                |
   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) 2004-2014
  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 $serverWideLock should this lock be applicable across your entire mysql server
  51    *                                this is useful if you have multiple sites running on the same
  52    *                                mysql server and you want to limit the number of parallel cron
  53    *                                jobs - CRM-91XX
  54    *
  55    * @return \CRM_Core_Lock the lock object
  56    */
  57  function __construct($name, $timeout = NULL, $serverWideLock = FALSE) {
  58     $config   = CRM_Core_Config::singleton();
  59     $dsnArray = DB::parseDSN($config->dsn);
  60     $database = $dsnArray['database'];
  61     $domainID = CRM_Core_Config::domainID();
  62     if ($serverWideLock) {
  63       $this->_name = $name;
  64     }
  65     else {
  66       $this->_name = $database . '.' . $domainID . '.' . $name;
  67     }
  68     $this->_timeout = $timeout !== NULL ? $timeout : self::TIMEOUT;
  69
  70     $this->acquire();
  71   }
  72
  73   function __destruct() {
  74     $this->release();
  75   }
  76
  77   /**
  78    * @return bool
  79    */
  80   function acquire() {
  81     if (!$this->_hasLock) {
  82       $query = "SELECT GET_LOCK( %1, %2 )";
  83       $params = array(1 => array($this->_name, 'String'),
  84         2 => array($this->_timeout, 'Integer'),
  85       );
  86       $res = CRM_Core_DAO::singleValueQuery($query, $params);
  87       if ($res) {
  88         $this->_hasLock = TRUE;
  89       }
  90     }
  91     return $this->_hasLock;
  92   }
  93
  94   /**
  95    * @return null|string
  96    */
  97   function release() {
  98     if ($this->_hasLock) {
  99       $this->_hasLock = FALSE;
 100
 101       $query = "SELECT RELEASE_LOCK( %1 )";
 102       $params = array(1 => array($this->_name, 'String'));
 103       return CRM_Core_DAO::singleValueQuery($query, $params);
 104     }
 105   }
 106
 107   /**
 108    * @return null|string
 109    */
 110   function isFree() {
 111     $query = "SELECT IS_FREE_LOCK( %1 )";
 112     $params = array(1 => array($this->_name, 'String'));
 113     return CRM_Core_DAO::singleValueQuery($query, $params);
 114   }
 115
 116   /**
 117    * @return bool
 118    */
 119   function isAcquired() {
 120     return $this->_hasLock;
 121   }
 122 }
 123