Mercurial > hg > isophonics-drupal-site
view core/lib/Drupal/Core/Lock/LockBackendAbstract.php @ 19:fa3358dc1485 tip
Add ndrum files
author | Chris Cannam |
---|---|
date | Wed, 28 Aug 2019 13:14:47 +0100 |
parents | 4c8ae668cc8c |
children |
line wrap: on
line source
<?php namespace Drupal\Core\Lock; /** * Non backend related common methods implementation for lock backends. * * @ingroup lock */ abstract class LockBackendAbstract implements LockBackendInterface { /** * Current page lock token identifier. * * @var string */ protected $lockId; /** * Existing locks for this page. * * @var array */ protected $locks = []; /** * {@inheritdoc} */ public function wait($name, $delay = 30) { // Pause the process for short periods between calling // lock_may_be_available(). This prevents hitting the database with constant // database queries while waiting, which could lead to performance issues. // However, if the wait period is too long, there is the potential for a // large number of processes to be blocked waiting for a lock, especially // if the item being rebuilt is commonly requested. To address both of these // concerns, begin waiting for 25ms, then add 25ms to the wait period each // time until it reaches 500ms. After this point polling will continue every // 500ms until $delay is reached. // $delay is passed in seconds, but we will be using usleep(), which takes // microseconds as a parameter. Multiply it by 1 million so that all // further numbers are equivalent. $delay = (int) $delay * 1000000; // Begin sleeping at 25ms. $sleep = 25000; while ($delay > 0) { // This function should only be called by a request that failed to get a // lock, so we sleep first to give the parallel request a chance to finish // and release the lock. usleep($sleep); // After each sleep, increase the value of $sleep until it reaches // 500ms, to reduce the potential for a lock stampede. $delay = $delay - $sleep; $sleep = min(500000, $sleep + 25000, $delay); if ($this->lockMayBeAvailable($name)) { // No longer need to wait. return FALSE; } } // The caller must still wait longer to get the lock. return TRUE; } /** * {@inheritdoc} */ public function getLockId() { if (!isset($this->lockId)) { $this->lockId = uniqid(mt_rand(), TRUE); } return $this->lockId; } }