lib/private/Lock/DBLockingProvider.php
<?php
/**
* @author Individual IT Services <info@individual-it.net>
* @author Markus Goetz <markus@woboq.com>
* @author Morris Jobke <hey@morrisjobke.de>
* @author Robin Appelman <icewind@owncloud.com>
* @author Roeland Jago Douma <rullzer@owncloud.com>
*
* @copyright Copyright (c) 2018, ownCloud GmbH
* @license AGPL-3.0
*
* This code is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License, version 3,
* along with this program. If not, see <http://www.gnu.org/licenses/>
*
*/
namespace OC\Lock;
use Doctrine\DBAL\Exception\UniqueConstraintViolationException;
use OC\DB\QueryBuilder\Literal;
use OCP\AppFramework\Utility\ITimeFactory;
use OCP\DB\QueryBuilder\IQueryBuilder;
use OCP\IDBConnection;
use OCP\ILogger;
use OCP\Lock\ILockingProvider;
use OCP\Lock\LockedException;
/**
* Locking provider that stores the locks in the database
*/
class DBLockingProvider extends AbstractLockingProvider {
/**
* @var \OCP\IDBConnection
*/
private $connection;
/**
* @var \OCP\ILogger
*/
private $logger;
/**
* @var \OCP\AppFramework\Utility\ITimeFactory
*/
private $timeFactory;
private $sharedLocks = [];
/**
* Check if we have an open shared lock for a path
*
* @param string $path
* @return bool
*/
protected function isLocallyLocked($path) {
return isset($this->sharedLocks[$path]) && $this->sharedLocks[$path];
}
/**
* Mark a locally acquired lock
*
* @param string $path
* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
*/
protected function markAcquire($path, $type) {
parent::markAcquire($path, $type);
if ($type === self::LOCK_SHARED) {
$this->sharedLocks[$path] = true;
}
}
/**
* Change the type of an existing tracked lock
*
* @param string $path
* @param int $targetType self::LOCK_SHARED or self::LOCK_EXCLUSIVE
*/
protected function markChange($path, $targetType) {
parent::markChange($path, $targetType);
if ($targetType === self::LOCK_SHARED) {
$this->sharedLocks[$path] = true;
} elseif ($targetType === self::LOCK_EXCLUSIVE) {
$this->sharedLocks[$path] = false;
}
}
/**
* @param \OCP\IDBConnection $connection
* @param \OCP\ILogger $logger
* @param \OCP\AppFramework\Utility\ITimeFactory $timeFactory
* @param int $ttl
*/
public function __construct(IDBConnection $connection, ILogger $logger, ITimeFactory $timeFactory, $ttl = 3600) {
$this->connection = $connection;
$this->logger = $logger;
$this->timeFactory = $timeFactory;
$this->ttl = $ttl;
}
/**
* Insert a file locking row if it does not exist.
*
* @param string $path
* @param int $lock
* @return int number of inserted rows
*/
protected function initLockField($path, $lock = 0) {
$expire = $this->getExpireTime();
try {
$rows = $this->connection->insertIfNotExist(
'*PREFIX*file_locks',
['key' => $path, 'lock' => $lock, 'ttl' => $expire],
['key'] // NOTE: see *PREFIX*file_locks/lock_key_index
);
if ($rows === 0) {
// likely to happen when called multiple times
$this->logger->debug(
"Lock {$path}/{$lock} already exists"
);
}
return $rows;
} catch (UniqueConstraintViolationException $e) {
// most likely race condition but make sure to log the error in case it is application level error
$this->logger->error(
"Attempt to add lock {$path}/{$lock} failed"
);
$this->logger->logException($e);
return 0;
}
}
/**
* @return int
*/
protected function getExpireTime() {
return $this->timeFactory->getTime() + $this->ttl;
}
/**
* @param string $path
* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
* @return bool
*/
public function isLocked($path, $type) {
if ($this->hasAcquiredLock($path, $type)) {
return true;
}
$query = $this->connection->prepare('SELECT `lock` from `*PREFIX*file_locks` WHERE `key` = ?');
$query->execute([$path]);
$lockValue = (int)$query->fetchColumn();
if ($type === self::LOCK_SHARED) {
if ($this->isLocallyLocked($path)) {
// if we have a shared lock we kept open locally but it's released we always have at least 1 shared lock in the db
return $lockValue > 1;
} else {
return $lockValue > 0;
}
} elseif ($type === self::LOCK_EXCLUSIVE) {
return $lockValue === -1;
} else {
return false;
}
}
/**
* @param string $path
* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
* @throws \OCP\Lock\LockedException
*/
public function acquireLock($path, $type) {
if (\strlen($path) > 64) { // max length in file_locks
throw new \InvalidArgumentException("Lock key length too long");
}
$expire = $this->getExpireTime();
if ($type === self::LOCK_SHARED) {
if (!$this->isLocallyLocked($path)) {
$result = $this->initLockField($path, 1);
if ($result <= 0) {
$result = $this->connection->executeUpdate(
'UPDATE `*PREFIX*file_locks` SET `lock` = `lock` + 1, `ttl` = ? WHERE `key` = ? AND `lock` >= 0',
[$expire, $path]
);
}
} else {
$result = 1;
}
} else {
$existing = 0;
if ($this->hasAcquiredLock($path, ILockingProvider::LOCK_SHARED) === false && $this->isLocallyLocked($path)) {
$existing = 1;
}
$result = $this->initLockField($path, -1);
if ($result <= 0) {
$result = $this->connection->executeUpdate(
'UPDATE `*PREFIX*file_locks` SET `lock` = -1, `ttl` = ? WHERE `key` = ? AND `lock` = ?',
[$expire, $path, $existing]
);
}
}
if ($result !== 1) {
throw new LockedException($path);
}
$this->markAcquire($path, $type);
}
/**
* @param string $path
* @param int $type self::LOCK_SHARED or self::LOCK_EXCLUSIVE
*/
public function releaseLock($path, $type) {
$this->markRelease($path, $type);
// we keep shared locks till the end of the request so we can re-use them
if ($type === self::LOCK_EXCLUSIVE) {
$this->connection->executeUpdate(
'UPDATE `*PREFIX*file_locks` SET `lock` = 0 WHERE `key` = ? AND `lock` = -1',
[$path]
);
}
}
/**
* Change the type of an existing lock
*
* @param string $path
* @param int $targetType self::LOCK_SHARED or self::LOCK_EXCLUSIVE
* @throws \OCP\Lock\LockedException
*/
public function changeLock($path, $targetType) {
$expire = $this->getExpireTime();
if ($targetType === self::LOCK_SHARED) {
$result = $this->connection->executeUpdate(
'UPDATE `*PREFIX*file_locks` SET `lock` = 1, `ttl` = ? WHERE `key` = ? AND `lock` = -1',
[$expire, $path]
);
} else {
// since we only keep one shared lock in the db we need to check if we have more then one shared lock locally manually
if (isset($this->acquiredLocks['shared'][$path]) && $this->acquiredLocks['shared'][$path] > 1) {
throw new LockedException($path);
}
$result = $this->connection->executeUpdate(
'UPDATE `*PREFIX*file_locks` SET `lock` = -1, `ttl` = ? WHERE `key` = ? AND `lock` = 1',
[$expire, $path]
);
}
if ($result !== 1) {
throw new LockedException($path);
}
$this->markChange($path, $targetType);
}
/**
* cleanup empty locks
*/
public function cleanExpiredLocks() {
$expire = $this->timeFactory->getTime();
try {
$this->connection->executeUpdate(
'DELETE FROM `*PREFIX*file_locks` WHERE `ttl` < ?',
[$expire]
);
} catch (\Exception $e) {
// If the table is missing, the clean up was successful
if ($this->connection->tableExists('file_locks')) {
throw $e;
}
}
}
/**
* release all lock acquired by this instance which were marked using the mark* methods
*/
public function releaseAll() {
parent::releaseAll();
// since we keep shared locks we need to manually clean those
$lockedPaths = \array_keys($this->sharedLocks);
$lockedPaths = \array_filter($lockedPaths, function ($path) {
return $this->sharedLocks[$path];
});
$chunkedPaths = \array_chunk($lockedPaths, 100);
foreach ($chunkedPaths as $chunk) {
$builder = $this->connection->getQueryBuilder();
$query = $builder->update('file_locks')
->set('lock', $builder->createFunction('`lock` -1'))
->where($builder->expr()->in('key', $builder->createNamedParameter($chunk, IQueryBuilder::PARAM_STR_ARRAY)))
->andWhere($builder->expr()->gt('lock', new Literal(0)));
$query->execute();
}
}
}