src/Core/Lock.php

   1 <?php
   2
   3 /**
   4  * @file src/Core/Lock.php
   5  * @brief Functions for preventing parallel execution of functions
   6  */
   7
   8 namespace Friendica\Core;
   9
  10 use Friendica\Core\Cache\CacheDriverFactory;
  11 use Friendica\Core\Cache\IMemoryCacheDriver;
  12
  13 /**
  14  * @brief This class contain Functions for preventing parallel execution of functions
  15  */
  16 class Lock
  17 {
  18         /**
  19          * @var Lock\ILockDriver;
  20          */
  21         static $driver = null;
  22
  23         public static function init()
  24         {
  25                 $lock_driver = Config::get('system', 'lock_driver', 'default');
  26
  27                 try {
  28                         switch ($lock_driver) {
  29                                 case 'memcache':
  30                                 case 'memcached':
  31                                 case 'redis':
  32                                         $cache_driver = CacheDriverFactory::create($lock_driver);
  33                                         if ($cache_driver instanceof IMemoryCacheDriver) {
  34                                                 self::$driver = new Lock\CacheLockDriver($cache_driver);
  35                                         }
  36                                         break;
  37
  38                                 case 'database':
  39                                         self::$driver = new Lock\DatabaseLockDriver();
  40                                         break;
  41
  42                                 case 'semaphore':
  43                                         self::$driver = new Lock\SemaphoreLockDriver();
  44                                         break;
  45
  46                                 default:
  47                                         self::useAutoDriver();
  48                         }
  49                 } catch (\Exception $exception) {
  50                         Logger::log('Driver \'' . $lock_driver . '\' failed - Fallback to \'useAutoDriver()\'');
  51                         self::useAutoDriver();
  52                 }
  53         }
  54
  55         /**
  56          * @brief This method tries to find the best - local - locking method for Friendica
  57          *
  58          * The following sequence will be tried:
  59          * 1. Semaphore Locking
  60          * 2. Cache Locking
  61          * 3. Database Locking
  62          *
  63          */
  64         private static function useAutoDriver() {
  65
  66                 // 1. Try to use Semaphores for - local - locking
  67                 if (function_exists('sem_get')) {
  68                         try {
  69                                 self::$driver = new Lock\SemaphoreLockDriver();
  70                                 return;
  71                         } catch (\Exception $exception) {
  72                                 Logger::log('Using Semaphore driver for locking failed: ' . $exception->getMessage());
  73                         }
  74                 }
  75
  76                 // 2. Try to use Cache Locking (don't use the DB-Cache Locking because it works different!)
  77                 $cache_driver = Config::get('system', 'cache_driver', 'database');
  78                 if ($cache_driver != 'database') {
  79                         try {
  80                                 $lock_driver = CacheDriverFactory::create($cache_driver);
  81                                 if ($lock_driver instanceof IMemoryCacheDriver) {
  82                                         self::$driver = new Lock\CacheLockDriver($lock_driver);
  83                                 }
  84                                 return;
  85                         } catch (\Exception $exception) {
  86                                 Logger::log('Using Cache driver for locking failed: ' . $exception->getMessage());
  87                         }
  88                 }
  89
  90                 // 3. Use Database Locking as a Fallback
  91                 self::$driver = new Lock\DatabaseLockDriver();
  92         }
  93
  94         /**
  95          * Returns the current cache driver
  96          *
  97          * @return Lock\ILockDriver;
  98          */
  99         private static function getDriver()
 100         {
 101                 if (self::$driver === null) {
 102                         self::init();
 103                 }
 104
 105                 return self::$driver;
 106         }
 107
 108         /**
 109          * @brief Acquires a lock for a given name
 110          *
 111          * @param string  $key Name of the lock
 112          * @param integer $timeout Seconds until we give up
 113          * @param integer $ttl The Lock lifespan, must be one of the Cache constants
 114          *
 115          * @return boolean Was the lock successful?
 116          */
 117         public static function acquire($key, $timeout = 120, $ttl = Cache::FIVE_MINUTES)
 118         {
 119                 return self::getDriver()->acquireLock($key, $timeout, $ttl);
 120         }
 121
 122         /**
 123          * @brief Releases a lock if it was set by us
 124          *
 125          * @param string $key Name of the lock
 126          * @return void
 127          */
 128         public static function release($key)
 129         {
 130                 self::getDriver()->releaseLock($key);
 131         }
 132
 133         /**
 134          * @brief Releases all lock that were set by us
 135          * @return void
 136          */
 137         public static function releaseAll()
 138         {
 139                 self::getDriver()->releaseAll();
 140         }
 141 }