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