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Member "drupal-8.9.10/core/lib/Drupal/Core/Lock/LockBackendAbstract.php" (26 Nov 2020, 2242 Bytes) of package /linux/www/drupal-8.9.10.tar.gz:


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    1 <?php
    2 
    3 namespace Drupal\Core\Lock;
    4 
    5 /**
    6  * Non backend related common methods implementation for lock backends.
    7  *
    8  * @ingroup lock
    9  */
   10 abstract class LockBackendAbstract implements LockBackendInterface {
   11 
   12   /**
   13    * Current page lock token identifier.
   14    *
   15    * @var string
   16    */
   17   protected $lockId;
   18 
   19   /**
   20    * Existing locks for this page.
   21    *
   22    * @var array
   23    */
   24   protected $locks = [];
   25 
   26   /**
   27    * {@inheritdoc}
   28    */
   29   public function wait($name, $delay = 30) {
   30     // Pause the process for short periods between calling
   31     // lock_may_be_available(). This prevents hitting the database with constant
   32     // database queries while waiting, which could lead to performance issues.
   33     // However, if the wait period is too long, there is the potential for a
   34     // large number of processes to be blocked waiting for a lock, especially
   35     // if the item being rebuilt is commonly requested. To address both of these
   36     // concerns, begin waiting for 25ms, then add 25ms to the wait period each
   37     // time until it reaches 500ms. After this point polling will continue every
   38     // 500ms until $delay is reached.
   39 
   40     // $delay is passed in seconds, but we will be using usleep(), which takes
   41     // microseconds as a parameter. Multiply it by 1 million so that all
   42     // further numbers are equivalent.
   43     $delay = (int) $delay * 1000000;
   44 
   45     // Begin sleeping at 25ms.
   46     $sleep = 25000;
   47     while ($delay > 0) {
   48       // This function should only be called by a request that failed to get a
   49       // lock, so we sleep first to give the parallel request a chance to finish
   50       // and release the lock.
   51       usleep($sleep);
   52       // After each sleep, increase the value of $sleep until it reaches
   53       // 500ms, to reduce the potential for a lock stampede.
   54       $delay = $delay - $sleep;
   55       $sleep = min(500000, $sleep + 25000, $delay);
   56       if ($this->lockMayBeAvailable($name)) {
   57         // No longer need to wait.
   58         return FALSE;
   59       }
   60     }
   61     // The caller must still wait longer to get the lock.
   62     return TRUE;
   63   }
   64 
   65   /**
   66    * {@inheritdoc}
   67    */
   68   public function getLockId() {
   69     if (!isset($this->lockId)) {
   70       $this->lockId = uniqid(mt_rand(), TRUE);
   71     }
   72     return $this->lockId;
   73   }
   74 
   75 }