src/Util/Lock/MemcacheLockDriver.php

   1 <?php
   2
   3 namespace Friendica\Util\Lock;
   4
   5 use Friendica\Core\Cache;
   6 use dba;
   7
   8 class MemcacheLockDriver implements ILockDriver
   9 {
  10         /**
  11          *
  12          * @brief Sets a lock for a given name
  13          *
  14          * @param string $key The Name of the lock
  15          * @param integer $timeout Seconds until we give up
  16          *
  17          * @return boolean Was the lock successful?
  18          */
  19         public function acquireLock($key, $timeout = 120)
  20         {
  21                 $got_lock = false;
  22                 $start = time();
  23
  24                 $cachekey = get_app()->get_hostname() . ";lock:" . $key;
  25
  26                 do {
  27                         // We only lock to be sure that nothing happens at exactly the same time
  28                         dba::lock('locks');
  29                         $lock = Cache::get($cachekey);
  30
  31                         if (!is_bool($lock)) {
  32                                 $pid = (int)$lock;
  33
  34                                 // When the process id isn't used anymore, we can safely claim the lock for us.
  35                                 // Or we do want to lock something that was already locked by us.
  36                                 if (!posix_kill($pid, 0) || ($pid == getmypid())) {
  37                                         $lock = false;
  38                                 }
  39                         }
  40                         if (is_bool($lock)) {
  41                                 Cache::set($cachekey, getmypid(), 300);
  42                                 $got_lock = true;
  43                         }
  44
  45                         dba::unlock();
  46
  47                         if (!$got_lock && ($timeout > 0)) {
  48                                 usleep(rand(10000, 200000));
  49                         }
  50                 } while (!$got_lock && ((time() - $start) < $timeout));
  51
  52                 return $got_lock;
  53         }
  54
  55         /**
  56          * @brief Removes a lock if it was set by us
  57          *
  58          * @param string $key Name of the lock
  59          *
  60          * @return mixed
  61          */
  62         public function releaseLock($key)
  63         {
  64                 $cachekey = get_app()->get_hostname() . ";lock:" . $key;
  65                 $lock = Cache::get($cachekey);
  66
  67                 if (!is_bool($lock)) {
  68                         if ((int)$lock == getmypid()) {
  69                                 Cache::delete($cachekey);
  70                         }
  71                 }
  72
  73                 return;
  74         }
  75
  76         /**
  77          * @brief Removes all lock that were set by us
  78          *
  79          * @return void
  80          */
  81         public function releaseAll()
  82         {
  83                 // We cannot delete all cache entries, but this doesn't matter with memcache
  84                 return;
  85         }
  86 }