library/Zend/Search/Lucene/LockManager.php

   1 <?php
   2 /**
   3  * Zend Framework
   4  *
   5  * LICENSE
   6  *
   7  * This source file is subject to the new BSD license that is bundled
   8  * with this package in the file LICENSE.txt.
   9  * It is also available through the world-wide-web at this URL:
  10  * http://framework.zend.com/license/new-bsd
  11  * If you did not receive a copy of the license and are unable to
  12  * obtain it through the world-wide-web, please send an email
  13  * to license@zend.com so we can send you a copy immediately.
  14  *
  15  * @category   Zend
  16  * @package    Zend_Search_Lucene
  17  * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
  18  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  19  * @version    $Id: LockManager.php 16971 2009-07-22 18:05:45Z mikaelkael $
  20  */
  21
  22 /** Zend_Search_Lucene_Storage_Directory */
  23 require_once 'Zend/Search/Lucene/Storage/Directory.php';
  24
  25 /** Zend_Search_Lucene_Storage_File */
  26 require_once 'Zend/Search/Lucene/Storage/File.php';
  27
  28 /**
  29  * This is an utility class which provides index locks processing functionality
  30  *
  31  * @category   Zend
  32  * @package    Zend_Search_Lucene
  33  * @copyright  Copyright (c) 2005-2009 Zend Technologies USA Inc. (http://www.zend.com)
  34  * @license    http://framework.zend.com/license/new-bsd     New BSD License
  35  */
  36 class Zend_Search_Lucene_LockManager
  37 {
  38     /**
  39      * consts for name of file to show lock status
  40      */
  41     const WRITE_LOCK_FILE                = 'write.lock.file';
  42     const READ_LOCK_FILE                 = 'read.lock.file';
  43     const READ_LOCK_PROCESSING_LOCK_FILE = 'read-lock-processing.lock.file';
  44     const OPTIMIZATION_LOCK_FILE         = 'optimization.lock.file';
  45
  46     /**
  47      * Obtain exclusive write lock on the index
  48      *
  49      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
  50      * @return Zend_Search_Lucene_Storage_File
  51      * @throws Zend_Search_Lucene_Exception
  52      */
  53     public static function obtainWriteLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
  54     {
  55         $lock = $lockDirectory->createFile(self::WRITE_LOCK_FILE);
  56         if (!$lock->lock(LOCK_EX)) {
  57             require_once 'Zend/Search/Lucene/Exception.php';
  58             throw new Zend_Search_Lucene_Exception('Can\'t obtain exclusive index lock');
  59         }
  60         return $lock;
  61     }
  62
  63     /**
  64      * Release exclusive write lock
  65      *
  66      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
  67      */
  68     public static function releaseWriteLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
  69     {
  70         $lock = $lockDirectory->getFileObject(self::WRITE_LOCK_FILE);
  71         $lock->unlock();
  72     }
  73
  74     /**
  75      * Obtain the exclusive "read escalation/de-escalation" lock
  76      *
  77      * Required to protect the escalate/de-escalate read lock process
  78      * on GFS (and potentially other) mounted filesystems.
  79      *
  80      * Why we need this:
  81      *  While GFS supports cluster-wide locking via flock(), it's
  82      *  implementation isn't quite what it should be.  The locking
  83      *  semantics that work consistently on a local filesystem tend to
  84      *  fail on GFS mounted filesystems.  This appears to be a design defect
  85      *  in the implementation of GFS.  How this manifests itself is that
  86      *  conditional promotion of a shared lock to exclusive will always
  87      *  fail, lock release requests are honored but not immediately
  88      *  processed (causing erratic failures of subsequent conditional
  89      *  requests) and the releasing of the exclusive lock before the
  90      *  shared lock is set when a lock is demoted (which can open a window
  91      *  of opportunity for another process to gain an exclusive lock when
  92      *  it shoudln't be allowed to).
  93      *
  94      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
  95      * @return Zend_Search_Lucene_Storage_File
  96      * @throws Zend_Search_Lucene_Exception
  97      */
  98     private static function _startReadLockProcessing(Zend_Search_Lucene_Storage_Directory $lockDirectory)
  99     {
 100         $lock = $lockDirectory->createFile(self::READ_LOCK_PROCESSING_LOCK_FILE);
 101         if (!$lock->lock(LOCK_EX)) {
 102             require_once 'Zend/Search/Lucene/Exception.php';
 103             throw new Zend_Search_Lucene_Exception('Can\'t obtain exclusive lock for the read lock processing file');
 104         }
 105         return $lock;
 106     }
 107
 108     /**
 109      * Release the exclusive "read escalation/de-escalation" lock
 110      *
 111      * Required to protect the escalate/de-escalate read lock process
 112      * on GFS (and potentially other) mounted filesystems.
 113      *
 114      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 115      */
 116     private static function _stopReadLockProcessing(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 117     {
 118         $lock = $lockDirectory->getFileObject(self::READ_LOCK_PROCESSING_LOCK_FILE);
 119         $lock->unlock();
 120     }
 121
 122
 123     /**
 124      * Obtain shared read lock on the index
 125      *
 126      * It doesn't block other read or update processes, but prevent index from the premature cleaning-up
 127      *
 128      * @param Zend_Search_Lucene_Storage_Directory $defaultLockDirectory
 129      * @return Zend_Search_Lucene_Storage_File
 130      * @throws Zend_Search_Lucene_Exception
 131      */
 132     public static function obtainReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 133     {
 134         $lock = $lockDirectory->createFile(self::READ_LOCK_FILE);
 135         if (!$lock->lock(LOCK_SH)) {
 136             require_once 'Zend/Search/Lucene/Exception.php';
 137             throw new Zend_Search_Lucene_Exception('Can\'t obtain shared reading index lock');
 138         }
 139         return $lock;
 140     }
 141
 142     /**
 143      * Release shared read lock
 144      *
 145      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 146      */
 147     public static function releaseReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 148     {
 149         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
 150         $lock->unlock();
 151     }
 152
 153     /**
 154      * Escalate Read lock to exclusive level
 155      *
 156      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 157      * @return boolean
 158      */
 159     public static function escalateReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 160     {
 161         self::_startReadLockProcessing($lockDirectory);
 162
 163         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
 164
 165         // First, release the shared lock for the benefit of GFS since
 166         // it will fail the conditional request to promote the lock to
 167         // "exclusive" while the shared lock is held (even when we are
 168         // the only holder).
 169         $lock->unlock();
 170
 171         // GFS is really poor.  While the above "unlock" returns, GFS
 172         // doesn't clean up it's tables right away (which will potentially
 173         // cause the conditional locking for the "exclusive" lock to fail.
 174         // We will retry the conditional lock request several times on a
 175         // failure to get past this.  The performance hit is negligible
 176         // in the grand scheme of things and only will occur with GFS
 177         // filesystems or if another local process has the shared lock
 178         // on local filesystems.
 179         for ($retries = 0; $retries < 10; $retries++) {
 180             if ($lock->lock(LOCK_EX, true)) {
 181                 // Exclusive lock is obtained!
 182                 self::_stopReadLockProcessing($lockDirectory);
 183                 return true;
 184             }
 185
 186             // wait 1 microsecond
 187             usleep(1);
 188         }
 189
 190         // Restore lock state
 191         $lock->lock(LOCK_SH);
 192
 193         self::_stopReadLockProcessing($lockDirectory);
 194         return false;
 195     }
 196
 197     /**
 198      * De-escalate Read lock to shared level
 199      *
 200      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 201      */
 202     public static function deEscalateReadLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 203     {
 204         $lock = $lockDirectory->getFileObject(self::READ_LOCK_FILE);
 205         $lock->lock(LOCK_SH);
 206     }
 207
 208     /**
 209      * Obtain exclusive optimization lock on the index
 210      *
 211      * Returns lock object on success and false otherwise (doesn't block execution)
 212      *
 213      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 214      * @return mixed
 215      */
 216     public static function obtainOptimizationLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 217     {
 218         $lock = $lockDirectory->createFile(self::OPTIMIZATION_LOCK_FILE);
 219         if (!$lock->lock(LOCK_EX, true)) {
 220             return false;
 221         }
 222         return $lock;
 223     }
 224
 225     /**
 226      * Release exclusive optimization lock
 227      *
 228      * @param Zend_Search_Lucene_Storage_Directory $lockDirectory
 229      */
 230     public static function releaseOptimizationLock(Zend_Search_Lucene_Storage_Directory $lockDirectory)
 231     {
 232         $lock = $lockDirectory->getFileObject(self::OPTIMIZATION_LOCK_FILE);
 233         $lock->unlock();
 234     }
 235
 236 }