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Commit 3daf04df authored by doctrine's avatar doctrine
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Added a first implementation of a pessimistic offline locking mechanism.

parent a9ccd9dc
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Doctrine/Locking/Exception.php 0 → 100644
View file @ 3daf04df
<?PHP
/**
* Locking exception class
*
* A loking exception represents an error that occured during a locking process
* (obtain/release locks).
*/
class Doctrine_Locking_Exception extends Doctrine_Exception {}
?>
\ No newline at end of file
Doctrine/Locking/Manager/Pessimistic.php 0 → 100644
View file @ 3daf04df
<?php
/**
* Class for handling the pessimistic offline locking of {@link Doctrine_Record}s.
* Offline locking of records comes in handy where you need to make sure that
* a time-consuming task on a record or many records, which is spread over several
* page requests can't be interfered by other users.
*
* @author Roman Borschel <roman@code-factory.org>
* @license LGPL
* @since 1.0
*/
class Doctrine_Locking_Manager_Pessimistic
{
/**
* The datasource that is used by the locking manager
*
* @var PDO object
*/
private $_dataSource;
/**
* The database table name for the lock tracking
*/
private $lockTable = 'doctrine_lock_tracking';
/**
* Constructs a new locking manager object
*
* When the CREATE_TABLES attribute of the session on which the manager
* is supposed to work on is set to true, the locking table is created.
*
* @param Doctrine_Session $dataSource The database session to use
*/
public function __construct(Doctrine_Session $dataSource)
{
$this->_dataSource = $dataSource;
if($this->_dataSource->getAttribute(Doctrine::ATTR_CREATE_TABLES) === true)
{
$columns = array();
$columns['object_type'] = array('string', 50, 'notnull|primary');
$columns['object_key'] = array('string', 250, 'notnull|primary');
$columns['user_ident'] = array('string', 50, 'notnull');
$columns['timestamp_obtained'] = array('integer', 10, 'notnull');
$dataDict = new Doctrine_DataDict($this->_dataSource->getDBH());
$dataDict->createTable($this->lockTable, $columns);
}
}
/**
* Obtains a lock on a {@link Doctrine_Record}
*
* @param Doctrine_Record $record The record that has to be locked
* @param mixed $userIdent A unique identifier of the locking user
* @return boolean TRUE if the locking was successful, FALSE if another user
* holds a lock on this record
* @throws Doctrine_Locking_Exception If the locking failed due to database errors
*/
public function getLock(Doctrine_Record $record, $userIdent)
{
$objectType = $record->getTable()->getComponentName();
$key = $record->getID();
$gotLock = false;
if(is_array($key))
{
// Composite key
$key = implode('|', $key);
}
try
{
$dbh = $this->_dataSource->getDBH();
$dbh->beginTransaction();
$stmt = $dbh->prepare("INSERT INTO $this->lockTable
(object_type, object_key, user_ident, timestamp_obtained)
VALUES (:object_type, :object_key, :user_ident, :ts_obtained)");
$stmt->bindParam(':object_type', $objectType);
$stmt->bindParam(':object_key', $key);
$stmt->bindParam(':user_ident', $userIdent);
$stmt->bindParam(':ts_obtained', time());
try {
$stmt->execute();
$gotLock = true;
} catch(PDOException $pkviolation) {
// PK violation occured => existing lock!
}
if(!$gotLock)
{
$lockingUserIdent = $this->_getLockingUserIdent($objectType, $key);
if($lockingUserIdent !== null && $lockingUserIdent == $userIdent)
{
$gotLock = true; // The requesting user already has a lock
// Update timestamp
$stmt = $dbh->prepare("UPDATE $this->lockTable SET timestamp_obtained = :ts
WHERE object_type = :object_type AND
object_key = :object_key AND
user_ident = :user_ident");
$stmt->bindParam(':ts', time());
$stmt->bindParam(':object_type', $objectType);
$stmt->bindParam(':object_key', $key);
$stmt->bindParam(':user_ident', $lockingUserIdent);
$stmt->execute();
}
}
$dbh->commit();
}
catch(PDOException $pdoe)
{
$dbh->rollBack();
throw new Doctrine_Locking_Exception($pdoe->getMessage());
}
return $gotLock;
}
/**
* Releases a lock on a {@link Doctrine_Record}
*
* @param Doctrine_Record $record The record for which the lock has to be released
* @param mixed $userIdent The unique identifier of the locking user
* @return boolean TRUE if a lock was released, FALSE if no lock was released
* @throws Doctrine_Locking_Exception If the release procedure failed due to database errors
*/
public function releaseLock(Doctrine_Record $record, $userIdent)
{
$objectType = $record->getTable()->getComponentName();
$key = $record->getID();
if(is_array($key))
{
// Composite key
$key = implode('|', $key);
}
try
{
$dbh = $this->_dataSource->getDBH();
$stmt = $dbh->prepare("DELETE FROM $this->lockTable WHERE
object_type = :object_type AND
object_key = :object_key AND
user_ident = :user_ident");
$stmt->bindParam(':object_type', $objectType);
$stmt->bindParam(':object_key', $key);
$stmt->bindParam(':user_ident', $userIdent);
$stmt->execute();
$count = $stmt->rowCount();
return ($count > 0);
}
catch(PDOException $pdoe)
{
throw new Doctrine_Locking_Exception($pdoe->getMessage());
}
}
/**
* Gets the unique user identifier of a lock
*
* @param string $objectType The type of the object (component name)
* @param mixed $key The unique key of the object
* @return mixed The unique user identifier for the specified lock
* @throws Doctrine_Locking_Exception If the query failed due to database errors
*/
private function _getLockingUserIdent($objectType, $key)
{
if(is_array($key))
{
// Composite key
$key = implode('|', $key);
}
try
{
$dbh = $this->_dataSource->getDBH();
$stmt = $dbh->prepare("SELECT user_ident
FROM $this->lockTable
WHERE object_type = :object_type AND object_key = :object_key");
$stmt->bindParam(':object_type', $objectType);
$stmt->bindParam(':object_key', $key);
$success = $stmt->execute();
if(!$success)
{
throw new Doctrine_Locking_Exception("Failed to determine locking user");
}
$user_ident = $stmt->fetchColumn();
}
catch(PDOException $pdoe)
{
throw new Doctrine_Locking_Exception($pdoe->getMessage());
}
return $user_ident;
}
/**
* Releases locks older than a defined amount of seconds
*
* When called without parameters all locks older than 15 minutes are released.
*
* @param integer $age The maximum valid age of locks in seconds
* @return boolean TRUE if locks have been released, FALSE if no locks were released
* @throws Doctrine_Locking_Exception If the release process failed due to database errors
*/
public function releaseAgedLocks($age = 900)
{
$age = time() - $age;
try
{
$dbh = $this->_dataSource->getDBH();
$stmt = $dbh->prepare("DELETE FROM $this->lockTable WHERE timestamp_obtained < :age");
$stmt->bindParam(':age', $age);
$stmt->execute();
$count = $stmt->rowCount();
return ($count > 0);
}
catch(PDOException $pdoe)
{
throw new Doctrine_Locking_Exception($pdoe->getMessage());
}
}
}
?>
\ No newline at end of file
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