src/Core/Lock/SemaphoreLock.php

   1 <?php
   2
   3 namespace Friendica\Core\Lock;
   4
   5 use Friendica\Core\Cache;
   6
   7 class SemaphoreLock extends Lock
   8 {
   9         private static $semaphore = [];
  10
  11         public function __construct()
  12         {
  13                 if (!function_exists('sem_get')) {
  14                         throw new \Exception('Semaphore lock not supported');
  15                 }
  16         }
  17
  18         /**
  19          * (@inheritdoc)
  20          */
  21         private static function semaphoreKey($key)
  22         {
  23                 $success = true;
  24
  25                 $temp = get_temppath();
  26
  27                 $file = $temp . '/' . $key . '.sem';
  28
  29                 if (!file_exists($file)) {
  30                         $success = !empty(file_put_contents($file, $key));
  31                 }
  32
  33                 return $success ? ftok($file, 'f') : false;
  34         }
  35
  36         /**
  37          * (@inheritdoc)
  38          */
  39         public function acquireLock($key, $timeout = 120, $ttl = Cache\Cache::FIVE_MINUTES)
  40         {
  41                 self::$semaphore[$key] = sem_get(self::semaphoreKey($key));
  42                 if (!empty(self::$semaphore[$key])) {
  43                         if ((bool)sem_acquire(self::$semaphore[$key], ($timeout === 0))) {
  44                                 $this->markAcquire($key);
  45                                 return true;
  46                         }
  47                 }
  48
  49                 return false;
  50         }
  51
  52         /**
  53          * (@inheritdoc)
  54          *
  55          * @param bool $override not necessary parameter for semaphore locks since the lock lives as long as the execution
  56          *                       of the using function
  57          */
  58         public function releaseLock($key, $override = false)
  59         {
  60                 $success = false;
  61
  62                 if (!empty(self::$semaphore[$key])) {
  63                         try {
  64                                 $success = @sem_release(self::$semaphore[$key]);
  65                                 unset(self::$semaphore[$key]);
  66                                 $this->markRelease($key);
  67                         } catch (\Exception $exception) {
  68                                 $success = false;
  69                         }
  70                 }
  71
  72                 return $success;
  73         }
  74
  75         /**
  76          * (@inheritdoc)
  77          */
  78         public function isLocked($key)
  79         {
  80                 return isset(self::$semaphore[$key]);
  81         }
  82
  83         /**
  84          * {@inheritDoc}
  85          */
  86         public function getName()
  87         {
  88                 return self::TYPE_SEMAPHORE;
  89         }
  90
  91         /**
  92          * {@inheritDoc}
  93          */
  94         public function getLocks(string $prefix = '')
  95         {
  96                 // We can just return our own semaphore keys, since we don't know
  97                 // the state of other semaphores, even if the .sem files exists
  98                 $keys = array_keys(self::$semaphore);
  99
 100                 if (empty($prefix)) {
 101                         return $keys;
 102                 } else {
 103                         $result = [];
 104
 105                         foreach ($keys as $key) {
 106                                 if (strpos($key, $prefix) === 0) {
 107                                         array_push($result, $key);
 108                                 }
 109                         }
 110
 111                         return $result;
 112                 }
 113         }
 114
 115         /**
 116          * {@inheritDoc}
 117          */
 118         public function releaseAll($override = false)
 119         {
 120                 // Semaphores are just alive during a run, so there is no need to release
 121                 // You can just release your own locks
 122                 return parent::releaseAll($override);
 123         }
 124 }