CRM/Core/Lock.php

   1 <?php
   2 /*
   3  +--------------------------------------------------------------------+
   4  | Copyright CiviCRM LLC. All rights reserved.                        |
   5  |                                                                    |
   6  | This work is published under the GNU AGPLv3 license with some      |
   7  | permitted exceptions and without any warranty. For full license    |
   8  | and copyright information, see https://civicrm.org/licensing       |
   9  +--------------------------------------------------------------------+
  10  */
  11
  12 /**
  13  *
  14  * @package CRM
  15  * @copyright CiviCRM LLC https://civicrm.org/licensing
  16  * $Id$
  17  *
  18  */
  19 class CRM_Core_Lock implements \Civi\Core\Lock\LockInterface {
  20
  21   /**
  22    * This variable (despite it's name) roughly translates to 'lock that we actually care about'.
  23    *
  24    * Prior to version 5.7.5 mysql only supports a single named lock. This variable is
  25    * part of the skullduggery involved in 'say it's no so Frank'.
  26    *
  27    * See further comments on the aquire function.
  28    *
  29    * @var bool
  30    */
  31   public static $jobLog = FALSE;
  32
  33   /**
  34    * lets have a 3 second timeout for now
  35    */
  36   const TIMEOUT = 3;
  37
  38   /**
  39    * @var bool
  40    */
  41   protected $_hasLock = FALSE;
  42
  43   protected $_name;
  44
  45   protected $_id;
  46
  47   /**
  48    * Use MySQL's GET_LOCK(). Locks are shared across all Civi instances
  49    * on the same MySQL server.
  50    *
  51    * @param string $name
  52    *   Symbolic name for the lock. Names generally look like
  53    *   "worker.mailing.EmailProcessor" ("{category}.{component}.{AdhocName}").
  54    *
  55    *   Categories: worker|data|cache|...
  56    *   Component: core|mailing|member|contribute|...
  57    * @return \Civi\Core\Lock\LockInterface
  58    */
  59   public static function createGlobalLock($name) {
  60     return new static($name, NULL, TRUE);
  61   }
  62
  63   /**
  64    * Use MySQL's GET_LOCK(), but apply prefixes to the lock names.
  65    * Locks are unique to each instance of Civi.
  66    *
  67    * @param string $name
  68    *   Symbolic name for the lock. Names generally look like
  69    *   "worker.mailing.EmailProcessor" ("{category}.{component}.{AdhocName}").
  70    *
  71    *   Categories: worker|data|cache|...
  72    *   Component: core|mailing|member|contribute|...
  73    * @return \Civi\Core\Lock\LockInterface
  74    */
  75   public static function createScopedLock($name) {
  76     return new static($name);
  77   }
  78
  79   /**
  80    * Use MySQL's GET_LOCK(), but conditionally apply prefixes to the lock names
  81    * (if civimail_server_wide_lock is disabled).
  82    *
  83    * @param string $name
  84    *   Symbolic name for the lock. Names generally look like
  85    *   "worker.mailing.EmailProcessor" ("{category}.{component}.{AdhocName}").
  86    *
  87    *   Categories: worker|data|cache|...
  88    *   Component: core|mailing|member|contribute|...
  89    * @return \Civi\Core\Lock\LockInterface
  90    * @deprecated
  91    */
  92   public static function createCivimailLock($name) {
  93     $serverWideLock = \Civi::settings()->get('civimail_server_wide_lock');
  94     return new static($name, NULL, $serverWideLock);
  95   }
  96
  97   /**
  98    * Initialize the constants used during lock acquire / release
  99    *
 100    * @param string $name
 101    *   Symbolic name for the lock. Names generally look like
 102    *   "worker.mailing.EmailProcessor" ("{category}.{component}.{AdhocName}").
 103    *
 104    *   Categories: worker|data|cache|...
 105    *   Component: core|mailing|member|contribute|...
 106    * @param int $timeout
 107    *   The number of seconds to wait to get the lock. 1 if not set.
 108    * @param bool $serverWideLock
 109    *   Should this lock be applicable across your entire mysql server.
 110    *   this is useful if you have multiple sites running on the same
 111    *   mysql server and you want to limit the number of parallel cron
 112    *   jobs - CRM-91XX
 113    */
 114   public function __construct($name, $timeout = NULL, $serverWideLock = FALSE) {
 115     $config = CRM_Core_Config::singleton();
 116     $dsnArray = DB::parseDSN($config->dsn);
 117     $database = $dsnArray['database'];
 118     $domainID = CRM_Core_Config::domainID();
 119     if ($serverWideLock) {
 120       $this->_name = $name;
 121     }
 122     else {
 123       $this->_name = $database . '.' . $domainID . '.' . $name;
 124     }
 125     // MySQL 5.7 doesn't like long lock names so creating a lock id
 126     $this->_id = sha1($this->_name);
 127     if (defined('CIVICRM_LOCK_DEBUG')) {
 128       CRM_Core_Error::debug_log_message('trying to construct lock for ' . $this->_name . '(' . $this->_id . ')');
 129     }
 130     $this->_timeout = $timeout !== NULL ? $timeout : self::TIMEOUT;
 131   }
 132
 133   public function __destruct() {
 134     $this->release();
 135   }
 136
 137   /**
 138    * Acquire lock.
 139    *
 140    * The advantage of mysql locks is that they can be used across processes. However, only one
 141    * can be used at once within a process. An attempt to use a second one within a process
 142    * prior to mysql 5.7.5 results in the first being released.
 143    *
 144    * The process here is
 145    *  1) first attempt to grab a lock for a mailing job - self::jobLog will be populated with the
 146    * lock id & a mysql lock will be created for the ID.
 147    *
 148    * If a second function in the same process attempts to grab the lock it will enter the hackyHandleBrokenCode routine
 149    * which says 'I won't break a mailing lock for you but if you are not a civimail send process I'll let you
 150    * pretend you have a lock already and you can go ahead with whatever you were doing under the delusion you
 151    * have a lock.
 152    *
 153    * @todo bypass hackyHandleBrokenCode for mysql version 5.7.5+
 154    *
 155    * If a second function in a separate process attempts to grab the lock already in use it should be rejected,
 156    * but it appears it IS allowed to grab a different lock & unlike in the same process the first lock won't be released.
 157    *
 158    * All this means CiviMail locks are first class citizens & any other process gets a 'best effort lock'.
 159    *
 160    * @todo document naming convention for CiviMail locks as this is key to ensuring they work properly.
 161    *
 162    * @param int $timeout
 163    *
 164    * @return bool
 165    * @throws \CRM_Core_Exception
 166    */
 167   public function acquire($timeout = NULL) {
 168     if (!$this->_hasLock) {
 169       if (!CRM_Utils_SQL::supportsMultipleLocks() && self::$jobLog && CRM_Core_DAO::singleValueQuery("SELECT IS_USED_LOCK( '" . self::$jobLog . "')")) {
 170         return $this->hackyHandleBrokenCode(self::$jobLog);
 171       }
 172
 173       $query = "SELECT GET_LOCK( %1, %2 )";
 174       $params = [
 175         1 => [$this->_id, 'String'],
 176         2 => [$timeout ? $timeout : $this->_timeout, 'Integer'],
 177       ];
 178       $res = CRM_Core_DAO::singleValueQuery($query, $params);
 179       if ($res) {
 180         if (defined('CIVICRM_LOCK_DEBUG')) {
 181           CRM_Core_Error::debug_log_message('acquire lock for ' . $this->_name . '(' . $this->_id . ')');
 182         }
 183         $this->_hasLock = TRUE;
 184         if (stristr($this->_name, 'data.mailing.job.')) {
 185           self::$jobLog = $this->_id;
 186         }
 187       }
 188       else {
 189         if (defined('CIVICRM_LOCK_DEBUG')) {
 190           CRM_Core_Error::debug_log_message('failed to acquire lock for ' . $this->_name . '(' . $this->_id . ')');
 191         }
 192       }
 193     }
 194     return $this->_hasLock;
 195   }
 196
 197   /**
 198    * @return null|string
 199    */
 200   public function release() {
 201     if ($this->_hasLock) {
 202       if (defined('CIVICRM_LOCK_DEBUG')) {
 203         CRM_Core_Error::debug_log_message('release lock for ' . $this->_name . '(' . $this->_id . ')');
 204       }
 205       $this->_hasLock = FALSE;
 206
 207       if (self::$jobLog == $this->_id) {
 208         self::$jobLog = FALSE;
 209       }
 210
 211       $query = "SELECT RELEASE_LOCK( %1 )";
 212       $params = [1 => [$this->_id, 'String']];
 213       return CRM_Core_DAO::singleValueQuery($query, $params);
 214     }
 215   }
 216
 217   /**
 218    * @return null|string
 219    */
 220   public function isFree() {
 221     $query = "SELECT IS_FREE_LOCK( %1 )";
 222     $params = [1 => [$this->_id, 'String']];
 223     return CRM_Core_DAO::singleValueQuery($query, $params);
 224   }
 225
 226   /**
 227    * @return bool
 228    */
 229   public function isAcquired() {
 230     return $this->_hasLock;
 231   }
 232
 233   /**
 234    * CRM-12856 locks were originally set up for jobs, but the concept was extended to caching & groups without
 235    * understanding that would undermine the job locks (because grabbing a lock implicitly releases existing ones)
 236    * this is all a big hack to mitigate the impact of that - but should not be seen as a fix. Not sure correct fix
 237    * but maybe locks should be used more selectively? Or else we need to handle is some cool way that Tim is yet to write :-)
 238    * if we are running in the context of the cron log then we would rather die (or at least let our process die)
 239    * than release that lock - so if the attempt is being made by setCache or something relatively trivial
 240    * we'll just return TRUE, but if it's another job then we will crash as that seems 'safer'
 241    *
 242    * @param string $jobLog
 243    * @throws CRM_Core_Exception
 244    * @return bool
 245    */
 246   public function hackyHandleBrokenCode($jobLog) {
 247     if (stristr($this->_name, 'job')) {
 248       CRM_Core_Error::debug_log_message('lock acquisition for ' . $this->_name . '(' . $this->_id . ')' . ' attempted when ' . $jobLog . ' is not released');
 249       throw new CRM_Core_Exception('lock acquisition for ' . $this->_name . '(' . $this->_id . ')' . ' attempted when ' . $jobLog . ' is not released');
 250     }
 251     if (defined('CIVICRM_LOCK_DEBUG')) {
 252       CRM_Core_Error::debug_log_message('(CRM-12856) faking lock for ' . $this->_name . '(' . $this->_id . ')');
 253     }
 254     $this->_hasLock = TRUE;
 255     return TRUE;
 256   }
 257
 258 }