src/Util/Lock.php

   1 <?php
   2
   3 namespace Friendica\Util;
   4
   5 /**
   6  * @file src/Util/Lock.php
   7  * @brief Functions for preventing parallel execution of functions
   8  *
   9  */
  10
  11 use dba;
  12 use dbm;
  13
  14 /**
  15  * @brief This class contain Functions for preventing parallel execution of functions
  16  */
  17 class Lock {
  18
  19         /**
  20          * @brief Sets a lock for a given name
  21          *
  22          * @param string $fn_name Name of the lock
  23          * @param integer $timeout Seconds until we give up
  24          * @param integer $wait_sec Time between to lock attempts
  25          *
  26          * @return boolean Was the lock successful?
  27          */
  28         public static function set($fn_name, $timeout = 30, $wait_sec = 2) {
  29                 if ($wait_sec == 0) {
  30                         $wait_sec = 2;
  31                 }
  32
  33                 $got_lock = false;
  34                 $start = time();
  35
  36                 do {
  37                         dba::p("LOCK TABLE `locks` WRITE");
  38                         $lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
  39
  40                         if (dbm::is_result($lock)) {
  41                                 if ($lock['locked']) {
  42                                         // When the process id isn't used anymore, we can safely claim the lock for us.
  43                                         if (!posix_kill($lock['pid'], 0)) {
  44                                                 $lock['locked'] = false;
  45                                         }
  46                                         // We want to lock something that was already locked by us? So we got the lock.
  47                                         if ($lock['pid'] == getmypid()) {
  48                                                 $got_lock = true;
  49                                         }
  50                                 }
  51                                 if (!$lock['locked']) {
  52                                         dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
  53                                         $got_lock = true;
  54                                 }
  55                         } elseif (!dbm::is_result($lock)) {
  56                                 dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
  57                                 $got_lock = true;
  58                         }
  59
  60                         dba::p("UNLOCK TABLES");
  61
  62                         if (!$got_lock) {
  63                                 sleep($wait_sec);
  64                         }
  65                 } while (!$got_lock AND ((time() - $start) < $timeout));
  66
  67                 return $got_lock;
  68         }
  69
  70         /**
  71          * @brief Removes a lock if it was set by us
  72          *
  73          * @param string $fn_name Name of the lock
  74          */
  75         public static function remove($fn_name) {
  76                 dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
  77                 return;
  78         }
  79 }