public DatabaseLockBackend::acquire($name, $timeout = 30.0)
Acquires a lock.
Parameters
string $name: Lock name. Limit of name's length is 255 characters.
float $timeout: (optional) Lock lifetime in seconds. Defaults to 30.0.
Return value
bool
Overrides LockBackendInterface::acquire
File
- core/lib/Drupal/Core/Lock/DatabaseLockBackend.php, line 44
Class
- DatabaseLockBackend
- Defines the database lock backend. This is the default backend in Drupal.
Namespace
Drupal\Core\Lock
Code
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 | public function acquire($name, $timeout = 30.0) { // Insure that the timeout is at least 1 ms. $timeout = max($timeout, 0.001); $expire = microtime(TRUE) + $timeout; if (isset($this->locks[$name])) { // Try to extend the expiration of a lock we already acquired. $success = (bool) $this->database->update('semaphore') ->fields(array('expire' => $expire)) ->condition('name', $name) ->condition('value', $this->getLockId()) ->execute(); if (!$success) { // The lock was broken. unset($this->locks[$name]); } return $success; } else { // Optimistically try to acquire the lock, then retry once if it fails. // The first time through the loop cannot be a retry. $retry = FALSE; // We always want to do this code at least once. do { try { $this->database->insert('semaphore') ->fields(array( 'name' => $name, 'value' => $this->getLockId(), 'expire' => $expire, )) ->execute(); // We track all acquired locks in the global variable. $this->locks[$name] = TRUE; // We never need to try again. $retry = FALSE; } catch (IntegrityConstraintViolationException $e) { // Suppress the error. If this is our first pass through the loop, // then $retry is FALSE. In this case, the insert failed because some // other request acquired the lock but did not release it. We decide // whether to retry by checking lockMayBeAvailable(). This will clear // the offending row from the database table in case it has expired. $retry = $retry ? FALSE : $this->lockMayBeAvailable($name); } catch (\Exception $e) { // Create the semaphore table if it does not exist and retry. if ($this->ensureTableExists()) { // Retry only once. $retry = !$retry; } else { throw $e; } } // We only retry in case the first attempt failed, but we then broke // an expired lock. } while ($retry); } return isset($this->locks[$name]);} |
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