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     if (defined('CIVICRM_LOCK_DEBUG')) {
  69       CRM_Core_Error::debug_log_message('trying to construct lock for ' . $this->_name);
  70     }
  71     static $jobLog = FALSE;
  72     if ($jobLog && CRM_Core_DAO::singleValueQuery("SELECT IS_USED_LOCK( '{$jobLog}')")) {
  73       return $this->hackyHandleBrokenCode($jobLog);
  74     }
  75     if (stristr($name, 'civimail.job.')) {
  76       $jobLog = $this->_name;
  77     }
  78     $this->_timeout = $timeout !== NULL ? $timeout : self::TIMEOUT;
  79
  80     $this->acquire();
  81   }
  82
  83   function __destruct() {
  84     $this->release();
  85   }
  86
  87   /**
  88    * @return bool
  89    */
  90   function acquire() {
  91     if (defined('CIVICRM_LOCK_DEBUG')) {
  92       CRM_Core_Error::debug_log_message('acquire lock for ' . $this->_name);
  93     }
  94     if (!$this->_hasLock) {
  95       $query = "SELECT GET_LOCK( %1, %2 )";
  96       $params = array(
  97         1 => array($this->_name, 'String'),
  98         2 => array($this->_timeout, 'Integer'),
  99       );
 100       $res = CRM_Core_DAO::singleValueQuery($query, $params);
 101       if ($res) {
 102         $this->_hasLock = TRUE;
 103       }
 104     }
 105     return $this->_hasLock;
 106   }
 107
 108   /**
 109    * @return null|string
 110    */
 111   function release() {
 112     if ($this->_hasLock) {
 113       $this->_hasLock = FALSE;
 114
 115       $query = "SELECT RELEASE_LOCK( %1 )";
 116       $params = array(1 => array($this->_name, 'String'));
 117       return CRM_Core_DAO::singleValueQuery($query, $params);
 118     }
 119   }
 120
 121   /**
 122    * @return null|string
 123    */
 124   function isFree() {
 125     $query = "SELECT IS_FREE_LOCK( %1 )";
 126     $params = array(1 => array($this->_name, 'String'));
 127     return CRM_Core_DAO::singleValueQuery($query, $params);
 128   }
 129
 130   /**
 131    * @return bool
 132    */
 133   function isAcquired() {
 134     return $this->_hasLock;
 135   }
 136
 137   /**
 138    * CRM-12856 locks were originally set up for jobs, but the concept was extended to caching & groups without
 139    * understanding that would undermine the job locks (because grabbing a lock implicitly releases existing ones)
 140    * this is all a big hack to mitigate the impact of that - but should not be seen as a fix. Not sure correct fix
 141    * but maybe locks should be used more selectively? Or else we need to handle is some cool way that Tim is yet to write :-)
 142    * if we are running in the context of the cron log then we would rather die (or at least let our process die)
 143    * than release that lock - so if the attempt is being made by setCache or something relatively trivial
 144    * we'll just return TRUE, but if it's another job then we will crash as that seems 'safer'
 145    *
 146    * @param string $jobLog
 147    * @throws CRM_Core_Exception
 148    * @return boolean
 149    */
 150   function hackyHandleBrokenCode($jobLog) {
 151     if (stristr($this->_name, 'job')) {
 152       throw new CRM_Core_Exception('lock aquisition for ' . $this->_name . 'attempted when ' . $jobLog . 'is not released');
 153     }
 154     if (defined('CIVICRM_LOCK_DEBUG')) {
 155       CRM_Core_Error::debug_log_message('(CRM-12856) faking lock for ' . $this->_name);
 156     }
 157     $this->_hasLock = TRUE;
 158     return TRUE;
 159   }
 160 }
 161