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lock.php 10.08 KiB
<?php
/**
*
* This library is free software; you can redistribute it and/or
* modify it under the terms of the GNU AFFERO GENERAL PUBLIC LICENSE
* License as published by the Free Software Foundation; either
* version 3 of the License, or any later version.
*
* This library 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 along with this library. If not, see <http://www.gnu.org/licenses/>.
*
*/
namespace OC\Files;
use OCP\Config;
use OC\Files\Filesystem;
use OCP\Files\LockNotAcquiredException;
/**
* Class Lock
* @package OC\Files
*/
class Lock implements \OCP\Files\Lock {
/** @var int $retries Number of lock retries to attempt */
public static $retries = 40;
/** @var int $retryInterval Milliseconds between retries */
public static $retryInterval = 50;
/** @var string $path Filename of the file as represented in storage */
protected $path;
/** @var array $stack A stack of lock data */
protected $stack = array();
/** @var resource $handle A file handle used to maintain a lock */
protected $handle;
/** @var string $lockFile Filename of the lock file */
protected $lockFile;
/** @var resource $lockFileHandle The file handle used to maintain a lock on the lock file */
protected $lockFileHandle;
/**
* Constructor for the lock instance
* @param string $path Absolute pathname for a local file on which to obtain a lock
*/
public function __construct($path) {
$this->path = Filesystem::normalizePath($path);
}
protected function obtainReadLock($existingHandle = null) {
\OC_Log::write('lock', sprintf('INFO: Read lock requested for %s', $this->path), \OC_Log::DEBUG);
$timeout = Lock::$retries;
// Re-use an existing handle or get a new one
if(empty($existingHandle)) {
$handle = fopen($this->path, 'r');
}
else {
$handle = $existingHandle;
}
do {
if($this->isLockFileLocked($this->getLockFile($this->path))) {
\OC_Log::write('lock', sprintf('INFO: Read lock has locked lock file %s for %s', $this->getLockFile($this->path), $this->path), \OC_Log::DEBUG);
do {
usleep(Lock::$retryInterval);
$timeout--;
} while($this->isLockFileLocked($this->getLockFile($this->path)) && $timeout > 0);
\OC_Log::write('lock', sprintf('INFO: Lock file %s has become unlocked for %s', $this->getLockFile($this->path), $this->path), \OC_Log::DEBUG);
}
} while ((!$lockReturn = flock($handle, LOCK_SH | LOCK_NB, $wouldBlock)) && $timeout > 0);
if ($wouldBlock == true || $lockReturn == false || $timeout <= 0) {
\OC_Log::write('lock', sprintf('FAIL: Failed to acquire read lock for %s', $this->path), \OC_Log::DEBUG);
return false;
}
$this->handle = $handle;
\OC_Log::write('lock', sprintf('PASS: Acquired read lock for %s', $this->path), \OC_Log::DEBUG);
return true;
}
protected function obtainWriteLock($existingHandle = null) {
\OC_Log::write('lock', sprintf('INFO: Write lock requested for %s', $this->path), \OC_Log::DEBUG);
// Re-use an existing handle or get a new one
if (empty($existingHandle)) {
$handle = fopen($this->path, 'c');
}
else {
$handle = $existingHandle;
}
// If the file doesn't exist, but we can create a lock for it
if (!file_exists($this->path) && $this->lockLockFile($this->path)) {
$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock);
if ($lockReturn == false || $wouldBlock == true) {
\OC_Log::write('lock', sprintf('FAIL: Write lock failed, unable to exclusively lock new file %s', $this->path), \OC_Log::DEBUG);
return false;
}
$this->handle = $handle;
return true;
}
// Since this file does exist, wait for locks to release to get an exclusive lock
$timeout = Lock::$retries;
$haveBlock = false;
while ((!$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock)) && $timeout > 0) {
// We don't have a lock on the original file, try to get a lock on its lock file
if ($haveBlock || $haveBlock = $this->lockLockFile($this->lockFile)) {
usleep(Lock::$retryInterval);
}
else {
\OC_Log::write('lock', sprintf('FAIL: Write lock failed, unable to lock original %s or lock file', $this->path), \OC_Log::DEBUG);
return false;
}
$timeout--;
}
if ($wouldBlock == true || $lockReturn == false) {
\OC_Log::write('lock', sprintf('FAIL: Write lock failed due to timeout on %s', $this->path), \OC_Log::DEBUG);
return false;
}
\OC_Log::write('lock', sprintf('PASS: Write lock succeeded on %s', $this->path), \OC_Log::DEBUG);
return true;
}
/**
* Create a lock file and lock it
* Sets $this->lockFile to the specified lock file, indicating that the lock file is IN USE for this lock instance
* Also sets $this->lockFileHandle to a file handle of the lock file * @param string $filename The name of the file to lock
* @return bool False if lock can't be acquired, true if it can.
*/
protected function lockLockFile ( $filename ) {
$lockFile = $this->getLockFile($filename);
\OC_Log::write('lock', sprintf('INFO: Locking lock file %s for %s', $lockFile, $filename), \OC_Log::DEBUG);
// If we already manage the lockfile, success
if(!empty($this->lockFile)) {
\OC_Log::write('lock', sprintf('PASS: Lock file %s was locked by this request for %s', $lockFile, $filename), \OC_Log::DEBUG);
return true;
}
// Check if the lockfile exists, and if not, try to create it
\OC_Log::write('lock', sprintf('INFO: Does lock file %s already exist? %s', $lockFile, file_exists($lockFile) ? 'yes' : 'no'), \OC_Log::DEBUG);
$handle = fopen($lockFile, 'c');
if(!$handle) {
\OC_Log::write('lock', sprintf('FAIL: Could not create lock file %s', $lockFile), \OC_Log::DEBUG);
return false;
}
// Attempt to acquire lock on lock file
$wouldBlock = false;
$timeout = self::$retries;
// Wait for lock over timeout
while((!$lockReturn = flock($handle, LOCK_EX | LOCK_NB, $wouldBlock)) && $timeout > 0) {
\OC_Log::write('lock', sprintf('FAIL: Could not acquire lock on lock file %s, %s timeout increments remain.', $lockFile, $timeout), \OC_Log::DEBUG);
usleep(self::$retryInterval);
$timeout--;
}
if ($wouldBlock == true || $lockReturn == false) {
\OC_Log::write('lock', sprintf('FAIL: Could not acquire lock on lock file %s', $lockFile), \OC_Log::DEBUG);
return false;
}
fwrite($handle, $filename);
\OC_Log::write('lock', sprintf('PASS: Wrote filename to lock lock file %s', $lockFile), \OC_Log::DEBUG);
$this->lockFile = $lockFile;
$this->lockFileHandle = $handle;
return true;
}
/**
* Add a lock of a specific type to the stack
* @param integer $lockType A constant representing the type of lock to queue
* @param null|resource $existingHandle An existing file handle from an fopen()
* @throws LockNotAcquiredException
*/
public function addLock($lockType, $existingHandle = null) {
if(!isset($this->stack[$lockType])) {
switch($lockType) {
case Lock::READ:
$result = $this->obtainReadLock($existingHandle);
break;
case Lock::WRITE:
$result = $this->obtainWriteLock($existingHandle);
break;
default:
$result = false;
break;
}
if($result) {
$this->stack[$lockType] = 0;
}
else {
throw new LockNotAcquiredException($this->path, $lockType);
}
}
\OC_Log::write('lock', sprintf('INFO: Incrementing lock type %d count for %s', $lockType, $this->path), \OC_Log::DEBUG);
$this->stack[$lockType]++;
}
/**
* Release locks on handles and files
*/
public function release($lockType) {
if(isset($this->stack[$lockType])) {
$this->stack[$lockType]--;
if($this->stack[$lockType] <= 0) {
unset($this->stack[$lockType]);
}
}
if(count($this->stack) == 0) {
// No more locks needed on this file, release the handle and/or lockfile
$this->releaseAll();
}
return true;
}
/**
* Get the lock file associated to a file
* @param string $filename The filename of the file to create a lock file for
* @return string The filename of the lock file
*/
public static function getLockFile($filename) {
static $locksDir = false;
if(!$locksDir) {
$dataDir = Config::getSystemValue('datadirectory');
$locksDir = $dataDir . '/.locks';
if(!file_exists($locksDir)) {
mkdir($locksDir);
}
}
$filename = Filesystem::normalizePath($filename);
return $locksDir . '/' . sha1($filename) . '.lock';
}
/**
* Determine if a file has an associated and flocked lock file
* @param string $lockFile The filename of the lock file to check
* @return bool True if the lock file is flocked
*/
protected function isLockFileLocked($lockFile) {
if(file_exists($lockFile)) {
if($handle = fopen($lockFile, 'c')) {
if($lock = flock($handle, LOCK_EX | LOCK_NB)) {
// Got lock, not blocking, release and unlink
unlink($lockFile);
fclose($handle);
flock($lock, LOCK_UN);
return false;
}
else {
return true;
}
}
else {
return true;
}
}
return false;
}
/** * Release all queued locks on the file
* @return bool
*/
public function releaseAll() {
$this->stack = array();
\OC_Log::write('lock', sprintf('INFO: Releasing locks on %s', $this->path), \OC_Log::DEBUG);
if (!empty($this->handle) && is_resource($this->handle)) {
flock($this->handle, LOCK_UN);
\OC_Log::write('lock', sprintf('INFO: Released lock handle %s on %s', $this->handle, $this->path), \OC_Log::DEBUG);
$this->handle = null;
}
if (!empty($this->lockFile) && file_exists($this->lockFile)) {
unlink($this->lockFile);
\OC_Log::write('lock', sprintf('INFO: Released lock file %s on %s', $this->lockFile, $this->path), \OC_Log::DEBUG);
$this->lockFile = null;
}
\OC_Log::write('lock', sprintf('FREE: Released locks on %s', $this->path), \OC_Log::DEBUG);
return true;
}
public function __destruct() {
// Only releaseAll if we have locks to release
if(!empty($this->handle) || !empty($this->lockFile)) {
\OC_Log::write('lock', sprintf('INFO: Destroying locks on %s', $this->path), \OC_Log::DEBUG);
$this->releaseAll();
}
}
}