public DatabaseLockBackend::lockMayBeAvailable($name)
Checks if a lock is available for acquiring.
Parameters
string $name: Lock to acquire.
Return value
bool
Overrides LockBackendInterface::lockMayBeAvailable
File
- core/lib/Drupal/Core/Lock/DatabaseLockBackend.php, line 108
Class
- DatabaseLockBackend
- Defines the database lock backend. This is the default backend in Drupal.
Namespace
Drupal\Core\Lock
Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 | public function lockMayBeAvailable($name) { try { $lock = $this->database->query('SELECT expire, value FROM {semaphore} WHERE name = :name', array(':name' => $name))->fetchAssoc(); } catch (\Exception $e) { $this->catchException($e); // If the table does not exist yet then the lock may be available. $lock = FALSE; } if (!$lock) { return TRUE; } $expire = (float) $lock['expire']; $now = microtime(TRUE); if ($now > $expire) { // We check two conditions to prevent a race condition where another // request acquired the lock and set a new expire time. We add a small // number to $expire to avoid errors with float to string conversion. return (bool) $this->database->delete('semaphore') ->condition('name', $name) ->condition('value', $lock['value']) ->condition('expire', 0.0001 + $expire, '<=') ->execute(); } return FALSE;} |
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