*/
namespace OCP\Files;
+
+use OCP\Config;
use OC\Files\Filesystem;
/**
const READ = 1;
const WRITE = 2;
+ /** @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 int $retries Number of lock retries to attempt */
- public static $retries = 40;
+ /** @var resource $handle A file handle used to maintain a lock */
+ protected $handle;
- /** @var int $retryInterval Milliseconds between retries */
- public static $retryInterval = 50;
+ /** @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
$this->path = Filesystem::normalizePath($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;
+ }
+
/**
- * @param integer $lockType A constant representing the type of lock to queue
+ * 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
+ * @param int $timeout Milliseconds to wait for a valid lock
+ * @return bool False if lock can't be acquired, true if it can.
*/
- public function addLock($lockType) {
- \OC_Log::write('lock', sprintf('INFO: Lock type %d requested for %s', $lockType, $this->path), \OC_Log::DEBUG);
+ protected function lockLockFile ( $filename, $timeout = 0 ) {
+ $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])) {
- // does lockfile exist?
- // yes
- // Acquire exclusive lock on lockfile?
- // yes
- // Delete lockfile, release lock
- // no
- // Sleep for configurable milliseconds - start over
- // no
- // Acquire shared lock on original file?
- // yes
- // Capture handle, return for action
- // no
- // Sleep for configurable milliseconds - start over
- $handle = 1;
-
- $this->stack[$lockType] = array('handle' => $handle, 'count' => 0);
- }
- $this->stack[$lockType]['count']++;
+ 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();
+ }
+ }
+
}
\ No newline at end of file
projects / nextcloud-server.git / commitdiff