include/lock.php

   1 <?php
   2
   3 // Provide some ability to lock a PHP function so that multiple processes
   4 // can't run the function concurrently
   5 if(! function_exists('lock_function')) {
   6 function lock_function($fn_name, $block = true, $wait_sec = 2, $timeout = 30) {
   7         if( $wait_sec == 0 )
   8                 $wait_sec = 2;  // don't let the user pick a value that's likely to crash the system
   9
  10         $got_lock = false;
  11         $start = time();
  12
  13         do {
  14                 q("LOCK TABLE `locks` WRITE");
  15                 $r = q("SELECT `locked`, `created` FROM `locks` WHERE `name` = '%s' LIMIT 1",
  16                         dbesc($fn_name)
  17                 );
  18
  19                 if((dbm::is_result($r)) AND (!$r[0]['locked'] OR (strtotime($r[0]['created']) < time() - 3600))) {
  20                         q("UPDATE `locks` SET `locked` = 1, `created` = '%s' WHERE `name` = '%s'",
  21                                 dbesc(datetime_convert()),
  22                                 dbesc($fn_name)
  23                         );
  24                         $got_lock = true;
  25                 }
  26                 elseif (! dbm::is_result($r)) {
  27                         /// @TODO the Boolean value for count($r) should be equivalent to the Boolean value of $r
  28                         q("INSERT INTO `locks` (`name`, `created`, `locked`) VALUES ('%s', '%s', 1)",
  29                                 dbesc($fn_name),
  30                                 dbesc(datetime_convert())
  31                         );
  32                         $got_lock = true;
  33                 }
  34
  35                 q("UNLOCK TABLES");
  36
  37                 if(($block) && (! $got_lock))
  38                         sleep($wait_sec);
  39
  40         } while(($block) && (! $got_lock) && ((time() - $start) < $timeout));
  41
  42         logger('lock_function: function ' . $fn_name . ' with blocking = ' . $block . ' got_lock = ' . $got_lock . ' time = ' . (time() - $start), LOGGER_DEBUG);
  43
  44         return $got_lock;
  45 }}
  46
  47
  48 if(! function_exists('block_on_function_lock')) {
  49 function block_on_function_lock($fn_name, $wait_sec = 2, $timeout = 30) {
  50         if( $wait_sec == 0 )
  51                 $wait_sec = 2;  // don't let the user pick a value that's likely to crash the system
  52
  53         $start = time();
  54
  55         do {
  56                 $r = q("SELECT locked FROM locks WHERE name = '%s' LIMIT 1",
  57                                 dbesc($fn_name)
  58                      );
  59
  60                 if (dbm::is_result($r) && $r[0]['locked'])
  61                         sleep($wait_sec);
  62
  63         } while(dbm::is_result($r) && $r[0]['locked'] && ((time() - $start) < $timeout));
  64
  65         return;
  66 }}
  67
  68
  69 if(! function_exists('unlock_function')) {
  70 function unlock_function($fn_name) {
  71         $r = q("UPDATE `locks` SET `locked` = 0, `created` = '%s' WHERE `name` = '%s'",
  72                         dbesc(NULL_DATE),
  73                         dbesc($fn_name)
  74              );
  75
  76         logger('unlock_function: released lock for function ' . $fn_name, LOGGER_DEBUG);
  77
  78         return;
  79 }}