src/Core/Lock/SemaphoreLock.php

   1 <?php
   2
   3 namespace Friendica\Core\Lock;
   4
   5 use Friendica\Core\BaseLock;
   6 use Friendica\Core\Cache\Duration;
   7
   8 class SemaphoreLock extends BaseLock
   9 {
  10         private static $semaphore = [];
  11
  12         public function __construct()
  13         {
  14                 if (!function_exists('sem_get')) {
  15                         throw new \Exception('Semaphore lock not supported');
  16                 }
  17         }
  18
  19         /**
  20          * (@inheritdoc)
  21          */
  22         private static function semaphoreKey($key)
  23         {
  24                 $success = true;
  25
  26                 $temp = get_temppath();
  27
  28                 $file = $temp . '/' . $key . '.sem';
  29
  30                 if (!file_exists($file)) {
  31                         $success = !empty(file_put_contents($file, $key));
  32                 }
  33
  34                 return $success ? ftok($file, 'f') : false;
  35         }
  36
  37         /**
  38          * (@inheritdoc)
  39          */
  40         public function acquire($key, $timeout = 120, $ttl = Duration::FIVE_MINUTES)
  41         {
  42                 self::$semaphore[$key] = sem_get(self::semaphoreKey($key));
  43                 if (!empty(self::$semaphore[$key])) {
  44                         if ((bool)sem_acquire(self::$semaphore[$key], ($timeout === 0))) {
  45                                 $this->markAcquire($key);
  46                                 return true;
  47                         }
  48                 }
  49
  50                 return false;
  51         }
  52
  53         /**
  54          * (@inheritdoc)
  55          *
  56          * @param bool $override not necessary parameter for semaphore locks since the lock lives as long as the execution
  57          *                       of the using function
  58          */
  59         public function release($key, $override = false)
  60         {
  61                 $success = false;
  62
  63                 if (!empty(self::$semaphore[$key])) {
  64                         try {
  65                                 $success = @sem_release(self::$semaphore[$key]);
  66                                 unset(self::$semaphore[$key]);
  67                                 $this->markRelease($key);
  68                         } catch (\Exception $exception) {
  69                                 $success = false;
  70                         }
  71                 }
  72
  73                 return $success;
  74         }
  75
  76         /**
  77          * (@inheritdoc)
  78          */
  79         public function isLocked($key)
  80         {
  81                 return isset(self::$semaphore[$key]);
  82         }
  83
  84         /**
  85          * {@inheritDoc}
  86          */
  87         public function getName()
  88         {
  89                 return Type::SEMAPHORE;
  90         }
  91
  92         /**
  93          * {@inheritDoc}
  94          */
  95         public function getLocks(string $prefix = '')
  96         {
  97                 // We can just return our own semaphore keys, since we don't know
  98                 // the state of other semaphores, even if the .sem files exists
  99                 $keys = array_keys(self::$semaphore);
 100
 101                 if (empty($prefix)) {
 102                         return $keys;
 103                 } else {
 104                         $result = [];
 105
 106                         foreach ($keys as $key) {
 107                                 if (strpos($key, $prefix) === 0) {
 108                                         array_push($result, $key);
 109                                 }
 110                         }
 111
 112                         return $result;
 113                 }
 114         }
 115
 116         /**
 117          * {@inheritDoc}
 118          */
 119         public function releaseAll($override = false)
 120         {
 121                 // Semaphores are just alive during a run, so there is no need to release
 122                 // You can just release your own locks
 123                 return parent::releaseAll($override);
 124         }
 125 }