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 Friendica\Core\Config;
  12 use Memcache;
  13 use dba;
  14 use dbm;
  15
  16 /**
  17  * @brief This class contain Functions for preventing parallel execution of functions
  18  */
  19 class Lock {
  20         private static $semaphore = array();
  21
  22        /**
  23          * @brief Check for memcache and open a connection if configured
  24          *
  25          * @return object|boolean The memcache object - or "false" if not successful
  26          */
  27         private static function connectMemcache() {
  28                 if (!function_exists('memcache_connect')) {
  29                         return false;
  30                 }
  31
  32                 if (!Config::get('system', 'memcache')) {
  33                         return false;
  34                 }
  35
  36                 $memcache_host = Config::get('system', 'memcache_host', '127.0.0.1');
  37                 $memcache_port = Config::get('system', 'memcache_port', 11211);
  38
  39                 $memcache = new Memcache;
  40
  41                 if (!$memcache->connect($memcache_host, $memcache_port)) {
  42                         return false;
  43                 }
  44
  45                 return $memcache;
  46         }
  47
  48         /**
  49          * @brief Creates a semaphore key
  50          *
  51          * @param string $fn_name Name of the lock
  52          *
  53          * @return ressource the semaphore key
  54          */
  55         private static function semaphore_key($fn_name) {
  56                 $temp = get_temppath();
  57
  58                 $file = $temp.'/'.$fn_name.'.sem';
  59
  60                 if (!file_exists($file)) {
  61                         file_put_contents($file, $function);
  62                 }
  63
  64                 return ftok($file, 'f');
  65         }
  66
  67         /**
  68          * @brief Sets a lock for a given name
  69          *
  70          * @param string $fn_name Name of the lock
  71          * @param integer $timeout Seconds until we give up
  72          *
  73          * @return boolean Was the lock successful?
  74          */
  75         public static function set($fn_name, $timeout = 120) {
  76                 $got_lock = false;
  77                 $start = time();
  78
  79                 if (function_exists('sem_get')) {
  80                         self::$semaphore[$fn_name] = sem_get(self::semaphore_key($fn_name));
  81                         if (self::$semaphore[$fn_name]) {
  82                                 return sem_acquire(self::$semaphore[$fn_name], ($timeout == 0));
  83                         }
  84                 }
  85
  86                 $memcache = self::connectMemcache();
  87                 if (is_object($memcache)) {
  88                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
  89
  90                         do {
  91                                 // We only lock to be sure that nothing happens at exactly the same time
  92                                 dba::lock('locks');
  93                                 $lock = $memcache->get($cachekey);
  94
  95                                 if (!is_bool($lock)) {
  96                                         $pid = (int)$lock;
  97
  98                                         // When the process id isn't used anymore, we can safely claim the lock for us.
  99                                         // Or we do want to lock something that was already locked by us.
 100                                         if (!posix_kill($pid, 0) || ($pid == getmypid())) {
 101                                                 $lock = false;
 102                                         }
 103                                 }
 104                                 if (is_bool($lock)) {
 105                                         $memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
 106                                         $got_lock = true;
 107                                 }
 108
 109                                 dba::unlock();
 110
 111                                 if (!$got_lock && ($timeout > 0)) {
 112                                         usleep(rand(10000, 200000));
 113                                 }
 114                         } while (!$got_lock && ((time() - $start) < $timeout));
 115
 116                         return $got_lock;
 117                 }
 118
 119                 do {
 120                         dba::lock('locks');
 121                         $lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
 122
 123                         if (dbm::is_result($lock)) {
 124                                 if ($lock['locked']) {
 125                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 126                                         if (!posix_kill($lock['pid'], 0)) {
 127                                                 $lock['locked'] = false;
 128                                         }
 129                                         // We want to lock something that was already locked by us? So we got the lock.
 130                                         if ($lock['pid'] == getmypid()) {
 131                                                 $got_lock = true;
 132                                         }
 133                                 }
 134                                 if (!$lock['locked']) {
 135                                         dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
 136                                         $got_lock = true;
 137                                 }
 138                         } elseif (!dbm::is_result($lock)) {
 139                                 dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
 140                                 $got_lock = true;
 141                         }
 142
 143                         dba::unlock();
 144
 145                         if (!$got_lock && ($timeout > 0)) {
 146                                 usleep(rand(100000, 2000000));
 147                         }
 148                 } while (!$got_lock && ((time() - $start) < $timeout));
 149
 150                 return $got_lock;
 151         }
 152
 153         /**
 154          * @brief Removes a lock if it was set by us
 155          *
 156          * @param string $fn_name Name of the lock
 157          */
 158         public static function remove($fn_name) {
 159                 if (function_exists('sem_get') && self::$semaphore[$fn_name]) {
 160                         return @sem_release(self::$semaphore[$fn_name]);
 161                 }
 162
 163                 $memcache = self::connectMemcache();
 164                 if (is_object($memcache)) {
 165                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
 166                         $lock = $memcache->get($cachekey);
 167
 168                         if (!is_bool($lock)) {
 169                                 if ((int)$lock == getmypid()) {
 170                                         $memcache->delete($cachekey);
 171                                 }
 172                         }
 173                         return;
 174                 }
 175
 176                 dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
 177                 return;
 178         }
 179
 180         /**
 181          * @brief Removes all lock that were set by us
 182          */
 183         public static function removeAll() {
 184                 $memcache = self::connectMemcache();
 185                 if (is_object($memcache)) {
 186                         // We cannot delete all cache entries, but this doesn't matter with memcache
 187                         return;
 188                 }
 189
 190                 dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
 191                 return;
 192         }
 193 }