src/Util/Lock.php

   1 <?php
   2 /**
   3  * @file src/Util/Lock.php
   4  */
   5 namespace Friendica\Util;
   6
   7 /**
   8  * @file src/Util/Lock.php
   9  * @brief Functions for preventing parallel execution of functions
  10  */
  11
  12 use Friendica\Core\Config;
  13 use Friendica\Database\DBM;
  14 use Memcache;
  15 use dba;
  16
  17 /**
  18  * @brief This class contain Functions for preventing parallel execution of functions
  19  */
  20 class Lock
  21 {
  22         private static $semaphore = array();
  23
  24         /**
  25          * @brief Check for memcache and open a connection if configured
  26          *
  27          * @return object|boolean The memcache object - or "false" if not successful
  28          */
  29         private static function connectMemcache()
  30         {
  31                 if (!function_exists('memcache_connect')) {
  32                         return false;
  33                 }
  34
  35                 if (!Config::get('system', 'memcache')) {
  36                         return false;
  37                 }
  38
  39                 $memcache_host = Config::get('system', 'memcache_host', '127.0.0.1');
  40                 $memcache_port = Config::get('system', 'memcache_port', 11211);
  41
  42                 $memcache = new Memcache;
  43
  44                 if (!$memcache->connect($memcache_host, $memcache_port)) {
  45                         return false;
  46                 }
  47
  48                 return $memcache;
  49         }
  50
  51         /**
  52          * @brief Creates a semaphore key
  53          *
  54          * @param string $fn_name Name of the lock
  55          *
  56          * @return ressource the semaphore key
  57          */
  58         private static function semaphoreKey($fn_name)
  59         {
  60                 $temp = get_temppath();
  61
  62                 $file = $temp.'/'.$fn_name.'.sem';
  63
  64                 if (!file_exists($file)) {
  65                         file_put_contents($file, $function);
  66                 }
  67
  68                 return ftok($file, 'f');
  69         }
  70
  71         /**
  72          * @brief Sets a lock for a given name
  73          *
  74          * @param string  $fn_name Name of the lock
  75          * @param integer $timeout Seconds until we give up
  76          *
  77          * @return boolean Was the lock successful?
  78          */
  79         public static function set($fn_name, $timeout = 120)
  80         {
  81                 $got_lock = false;
  82                 $start = time();
  83
  84                 // The second parameter for "sem_acquire" doesn't exist before 5.6.1
  85                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
  86                         self::$semaphore[$fn_name] = sem_get(self::semaphoreKey($fn_name));
  87                         if (self::$semaphore[$fn_name]) {
  88                                 return sem_acquire(self::$semaphore[$fn_name], ($timeout == 0));
  89                         }
  90                 }
  91
  92                 $memcache = self::connectMemcache();
  93                 if (is_object($memcache)) {
  94                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
  95
  96                         do {
  97                                 // We only lock to be sure that nothing happens at exactly the same time
  98                                 dba::lock('locks');
  99                                 $lock = $memcache->get($cachekey);
 100
 101                                 if (!is_bool($lock)) {
 102                                         $pid = (int)$lock;
 103
 104                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 105                                         // Or we do want to lock something that was already locked by us.
 106                                         if (!posix_kill($pid, 0) || ($pid == getmypid())) {
 107                                                 $lock = false;
 108                                         }
 109                                 }
 110                                 if (is_bool($lock)) {
 111                                         $memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
 112                                         $got_lock = true;
 113                                 }
 114
 115                                 dba::unlock();
 116
 117                                 if (!$got_lock && ($timeout > 0)) {
 118                                         usleep(rand(10000, 200000));
 119                                 }
 120                         } while (!$got_lock && ((time() - $start) < $timeout));
 121
 122                         return $got_lock;
 123                 }
 124
 125                 do {
 126                         dba::lock('locks');
 127                         $lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
 128
 129                         if (DBM::is_result($lock)) {
 130                                 if ($lock['locked']) {
 131                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 132                                         if (!posix_kill($lock['pid'], 0)) {
 133                                                 $lock['locked'] = false;
 134                                         }
 135                                         // We want to lock something that was already locked by us? So we got the lock.
 136                                         if ($lock['pid'] == getmypid()) {
 137                                                 $got_lock = true;
 138                                         }
 139                                 }
 140                                 if (!$lock['locked']) {
 141                                         dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
 142                                         $got_lock = true;
 143                                 }
 144                         } elseif (!DBM::is_result($lock)) {
 145                                 dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
 146                                 $got_lock = true;
 147                         }
 148
 149                         dba::unlock();
 150
 151                         if (!$got_lock && ($timeout > 0)) {
 152                                 usleep(rand(100000, 2000000));
 153                         }
 154                 } while (!$got_lock && ((time() - $start) < $timeout));
 155
 156                 return $got_lock;
 157         }
 158
 159         /**
 160          * @brief Removes a lock if it was set by us
 161          *
 162          * @param string $fn_name Name of the lock
 163          * @return mixed
 164          */
 165         public static function remove($fn_name)
 166         {
 167                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
 168                         if (empty(self::$semaphore[$fn_name])) {
 169                                 return false;
 170                         } else {
 171                                 $success = @sem_release(self::$semaphore[$fn_name]);
 172                                 unset(self::$semaphore[$fn_name]);
 173                                 return $success;
 174                         }
 175                 }
 176
 177                 $memcache = self::connectMemcache();
 178                 if (is_object($memcache)) {
 179                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
 180                         $lock = $memcache->get($cachekey);
 181
 182                         if (!is_bool($lock)) {
 183                                 if ((int)$lock == getmypid()) {
 184                                         $memcache->delete($cachekey);
 185                                 }
 186                         }
 187                         return;
 188                 }
 189
 190                 dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
 191                 return;
 192         }
 193
 194         /**
 195          * @brief Removes all lock that were set by us
 196          * @return void
 197          */
 198         public static function removeAll()
 199         {
 200                 $memcache = self::connectMemcache();
 201                 if (is_object($memcache)) {
 202                         // We cannot delete all cache entries, but this doesn't matter with memcache
 203                         return;
 204                 }
 205
 206                 dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
 207                 return;
 208         }
 209 }