File indexing completed on 2024-05-26 06:03:23

 <?php
 /**
  * Zend Framework
  *
  * LICENSE
  *
  * This source file is subject to the new BSD license that is bundled
  * with this package in the file LICENSE.txt.
  * It is also available through the world-wide-web at this URL:
  * http://framework.zend.com/license/new-bsd
  * If you did not receive a copy of the license and are unable to
  * obtain it through the world-wide-web, please send an email
  * to license@zend.com so we can send you a copy immediately.
  *
  * @category   Zend
  * @package    Zend_Search_Lucene
  * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  * @version    $Id$
  */
 
 /** Zend_Search_Lucene_Storage_Directory */
 // require_once 'Zend/Search/Lucene/Storage/Directory.php';
 
 /** Zend_Search_Lucene_Storage_File */
 // require_once 'Zend/Search/Lucene/Storage/File.php';
 
 /**
  * This is an utility class which provides index locks processing functionality
  *
  * @category   Zend
  * @package    Zend_Search_Lucene
  * @copyright  Copyright (c) 2005-2015 Zend Technologies USA Inc. (http://www.zend.com)
  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  */
 class Zend_Search_Lucene_LockManager
 {
     /**
      * consts for name of file to show lock status
      */
     const WRITE_LOCK_FILE                = 'write.lock.file';
     const READ_LOCK_FILE                 = 'read.lock.file';
     const READ_LOCK_PROCESSING_LOCK_FILE = 'read-lock-processing.lock.file';
     const OPTIMIZATION_LOCK_FILE         = 'optimization.lock.file';
 
     /**
      * Obtain exclusive write lock on the index
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      * @return Zend_Search_Lucene_Storage_File
      * @throws Zend_Search_Lucene_Exception
      */
     public static function obtainWriteLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->createFile(self::WRITE_LOCK_FILE);
         if (!$lock->lock(LOCK_EX)) {
             // require_once 'Zend/Search/Lucene/Exception.php';
             throw new Zend_Search_Lucene_Exception('Can\'t obtain exclusive index lock');
         }
         return $lock;
     }
 
     /**
      * Release exclusive write lock
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      */
     public static function releaseWriteLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->getFileObject(self::WRITE_LOCK_FILE);
         $lock->unlock();
     }
 
     /**
      * Obtain the exclusive "read escalation/de-escalation" lock
      *
      * Required to protect the escalate/de-escalate read lock process
      * on GFS (and potentially other) mounted filesystems.
      *
      * Why we need this:
      *  While GFS supports cluster-wide locking via flock(), it's
      *  implementation isn't quite what it should be.  The locking
      *  semantics that work consistently on a local filesystem tend to
      *  fail on GFS mounted filesystems.  This appears to be a design defect
      *  in the implementation of GFS.  How this manifests itself is that
      *  conditional promotion of a shared lock to exclusive will always
      *  fail, lock release requests are honored but not immediately
      *  processed (causing erratic failures of subsequent conditional
      *  requests) and the releasing of the exclusive lock before the
      *  shared lock is set when a lock is demoted (which can open a window
      *  of opportunity for another process to gain an exclusive lock when
      *  it shoudln't be allowed to).
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      * @return Zend_Search_Lucene_Storage_File
      * @throws Zend_Search_Lucene_Exception
      */
     private static function _startReadLockProcessing(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->createFile(self::READ_LOCK_PROCESSING_LOCK_FILE);
         if (!$lock->lock(LOCK_EX)) {
             // require_once 'Zend/Search/Lucene/Exception.php';
             throw new Zend_Search_Lucene_Exception('Can\'t obtain exclusive lock for the read lock processing file');
         }
         return $lock;
     }
 
     /**
      * Release the exclusive "read escalation/de-escalation" lock
      *
      * Required to protect the escalate/de-escalate read lock process
      * on GFS (and potentially other) mounted filesystems.
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      */
     private static function _stopReadLockProcessing(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->getFileObject(self::READ_LOCK_PROCESSING_LOCK_FILE);
         $lock->unlock();
     }
 
 
     /**
      * Obtain shared read lock on the index
      *
      * It doesn't block other read or update processes, but prevent index from the premature cleaning-up
      *
      * @param Zend_Search_Lucene_Storage_Directory $defaultLockDirectory
      * @return Zend_Search_Lucene_Storage_File
      * @throws Zend_Search_Lucene_Exception
      */
     public static function obtainReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->createFile(self::READ_LOCK_FILE);
         if (!$lock->lock(LOCK_SH)) {
             // require_once 'Zend/Search/Lucene/Exception.php';
             throw new Zend_Search_Lucene_Exception('Can\'t obtain shared reading index lock');
         }
         return $lock;
     }
 
     /**
      * Release shared read lock
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      */
     public static function releaseReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
         $lock->unlock();
     }
 
     /**
      * Escalate Read lock to exclusive level
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      * @return boolean
      */
     public static function escalateReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         self::_startReadLockProcessing($lockDirectory);
 
         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
 
         // First, release the shared lock for the benefit of GFS since
         // it will fail the conditional request to promote the lock to
         // "exclusive" while the shared lock is held (even when we are
         // the only holder).
         $lock->unlock();
 
         // GFS is really poor.  While the above "unlock" returns, GFS
         // doesn't clean up it's tables right away (which will potentially
         // cause the conditional locking for the "exclusive" lock to fail.
         // We will retry the conditional lock request several times on a
         // failure to get past this.  The performance hit is negligible
         // in the grand scheme of things and only will occur with GFS
         // filesystems or if another local process has the shared lock
         // on local filesystems.
         for ($retries = 0; $retries < 10; $retries++) {
             if ($lock->lock(LOCK_EX, true)) {
                 // Exclusive lock is obtained!
                 self::_stopReadLockProcessing($lockDirectory);
                 return true;
             }
 
             // wait 1 microsecond
             usleep(1);
         }
 
         // Restore lock state
         $lock->lock(LOCK_SH);
 
         self::_stopReadLockProcessing($lockDirectory);
         return false;
     }
 
     /**
      * De-escalate Read lock to shared level
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      */
     public static function deEscalateReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
         $lock->lock(LOCK_SH);
     }
 
     /**
      * Obtain exclusive optimization lock on the index
      *
      * Returns lock object on success and false otherwise (doesn't block execution)
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      * @return mixed
      */
     public static function obtainOptimizationLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->createFile(self::OPTIMIZATION_LOCK_FILE);
         if (!$lock->lock(LOCK_EX, true)) {
             return false;
         }
         return $lock;
     }
 
     /**
      * Release exclusive optimization lock
      *
      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
      */
     public static function releaseOptimizationLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
     {
         $lock = $lockDirectory->getFileObject(self::OPTIMIZATION_LOCK_FILE);
         $lock->unlock();
     }
 
 }