src/Util/Lock/DatabaseLockDriver.php

   1 <?php
   2
   3 namespace Friendica\Util\Lock;
   4
   5 use dba;
   6 use Friendica\Database\DBM;
   7
   8 /**
   9  * Locking driver that stores the locks in the database
  10  */
  11 class DatabaseLockDriver implements ILockDriver
  12 {
  13         /**
  14          * @brief Sets a lock for a given name
  15          *
  16          * @param string  $key      The Name of the lock
  17          * @param integer $timeout  Seconds until we give up
  18          *
  19          * @return boolean Was the lock successful?
  20          */
  21         public function acquireLock($key, $timeout = 120)
  22         {
  23                 $got_lock = false;
  24                 $start = time();
  25
  26                 do {
  27                         dba::lock('locks');
  28                         $lock = dba::selectFirst('locks', ['locked', 'pid'], ['name' => $key]);
  29
  30                         if (DBM::is_result($lock)) {
  31                                 if ($lock['locked']) {
  32                                         // When the process id isn't used anymore, we can safely claim the lock for us.
  33                                         if (!posix_kill($lock['pid'], 0)) {
  34                                                 $lock['locked'] = false;
  35                                         }
  36                                         // We want to lock something that was already locked by us? So we got the lock.
  37                                         if ($lock['pid'] == getmypid()) {
  38                                                 $got_lock = true;
  39                                         }
  40                                 }
  41                                 if (!$lock['locked']) {
  42                                         dba::update('locks', ['locked' => true, 'pid' => getmypid()], ['name' => $key]);
  43                                         $got_lock = true;
  44                                 }
  45                         } elseif (!DBM::is_result($lock)) {
  46                                 dba::insert('locks', ['name' => $key, 'locked' => true, 'pid' => getmypid()]);
  47                                 $got_lock = true;
  48                         }
  49
  50                         dba::unlock();
  51
  52                         if (!$got_lock && ($timeout > 0)) {
  53                                 usleep(rand(100000, 2000000));
  54                         }
  55                 } while (!$got_lock && ((time() - $start) < $timeout));
  56
  57                 return $got_lock;
  58         }
  59
  60         /**
  61          * @brief Removes a lock if it was set by us
  62          *
  63          * @param string $key Name of the lock
  64          *
  65          * @return mixed
  66          */
  67         public function releaseLock($key)
  68         {
  69                 dba::update('locks', ['locked' => false, 'pid' => 0], ['name' => $key, 'pid' => getmypid()]);
  70
  71                 return;
  72         }
  73
  74         /**
  75          * @brief Removes all lock that were set by us
  76          *
  77          * @return void
  78          */
  79         public function releaseAll()
  80         {
  81                 dba::update('locks', ['locked' => false, 'pid' => 0], ['pid' => getmypid()]);
  82         }
  83 }