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 require_once 'include/dba.php';
  18
  19 /**
  20  * @brief This class contain Functions for preventing parallel execution of functions
  21  */
  22 class Lock
  23 {
  24         private static $semaphore = array();
  25
  26         /**
  27          * @brief Check for memcache and open a connection if configured
  28          *
  29          * @return object|boolean The memcache object - or "false" if not successful
  30          */
  31         private static function connectMemcache()
  32         {
  33                 if (!function_exists('memcache_connect')) {
  34                         return false;
  35                 }
  36
  37                 if (!Config::get('system', 'memcache')) {
  38                         return false;
  39                 }
  40
  41                 $memcache_host = Config::get('system', 'memcache_host', '127.0.0.1');
  42                 $memcache_port = Config::get('system', 'memcache_port', 11211);
  43
  44                 $memcache = new Memcache;
  45
  46                 if (!$memcache->connect($memcache_host, $memcache_port)) {
  47                         return false;
  48                 }
  49
  50                 return $memcache;
  51         }
  52
  53         /**
  54          * @brief Creates a semaphore key
  55          *
  56          * @param string $fn_name Name of the lock
  57          *
  58          * @return ressource the semaphore key
  59          */
  60         private static function semaphoreKey($fn_name)
  61         {
  62                 $temp = get_temppath();
  63
  64                 $file = $temp.'/'.$fn_name.'.sem';
  65
  66                 if (!file_exists($file)) {
  67                         file_put_contents($file, $fn_name);
  68                 }
  69
  70                 return ftok($file, 'f');
  71         }
  72
  73         /**
  74          * @brief Sets a lock for a given name
  75          *
  76          * @param string  $fn_name Name of the lock
  77          * @param integer $timeout Seconds until we give up
  78          *
  79          * @return boolean Was the lock successful?
  80          */
  81         public static function set($fn_name, $timeout = 120)
  82         {
  83                 $got_lock = false;
  84                 $start = time();
  85
  86                 // The second parameter for "sem_acquire" doesn't exist before 5.6.1
  87                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
  88                         self::$semaphore[$fn_name] = sem_get(self::semaphoreKey($fn_name));
  89                         if (self::$semaphore[$fn_name]) {
  90                                 return sem_acquire(self::$semaphore[$fn_name], ($timeout == 0));
  91                         }
  92                 }
  93
  94                 $memcache = self::connectMemcache();
  95                 if (is_object($memcache)) {
  96                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
  97
  98                         do {
  99                                 // We only lock to be sure that nothing happens at exactly the same time
 100                                 dba::lock('locks');
 101                                 $lock = $memcache->get($cachekey);
 102
 103                                 if (!is_bool($lock)) {
 104                                         $pid = (int)$lock;
 105
 106                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 107                                         // Or we do want to lock something that was already locked by us.
 108                                         if (!posix_kill($pid, 0) || ($pid == getmypid())) {
 109                                                 $lock = false;
 110                                         }
 111                                 }
 112                                 if (is_bool($lock)) {
 113                                         $memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
 114                                         $got_lock = true;
 115                                 }
 116
 117                                 dba::unlock();
 118
 119                                 if (!$got_lock && ($timeout > 0)) {
 120                                         usleep(rand(10000, 200000));
 121                                 }
 122                         } while (!$got_lock && ((time() - $start) < $timeout));
 123
 124                         return $got_lock;
 125                 }
 126
 127                 do {
 128                         dba::lock('locks');
 129                         $lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
 130
 131                         if (DBM::is_result($lock)) {
 132                                 if ($lock['locked']) {
 133                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 134                                         if (!posix_kill($lock['pid'], 0)) {
 135                                                 $lock['locked'] = false;
 136                                         }
 137                                         // We want to lock something that was already locked by us? So we got the lock.
 138                                         if ($lock['pid'] == getmypid()) {
 139                                                 $got_lock = true;
 140                                         }
 141                                 }
 142                                 if (!$lock['locked']) {
 143                                         dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
 144                                         $got_lock = true;
 145                                 }
 146                         } elseif (!DBM::is_result($lock)) {
 147                                 dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
 148                                 $got_lock = true;
 149                         }
 150
 151                         dba::unlock();
 152
 153                         if (!$got_lock && ($timeout > 0)) {
 154                                 usleep(rand(100000, 2000000));
 155                         }
 156                 } while (!$got_lock && ((time() - $start) < $timeout));
 157
 158                 return $got_lock;
 159         }
 160
 161         /**
 162          * @brief Removes a lock if it was set by us
 163          *
 164          * @param string $fn_name Name of the lock
 165          * @return mixed
 166          */
 167         public static function remove($fn_name)
 168         {
 169                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
 170                         if (empty(self::$semaphore[$fn_name])) {
 171                                 return false;
 172                         } else {
 173                                 $success = @sem_release(self::$semaphore[$fn_name]);
 174                                 unset(self::$semaphore[$fn_name]);
 175                                 return $success;
 176                         }
 177                 }
 178
 179                 $memcache = self::connectMemcache();
 180                 if (is_object($memcache)) {
 181                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
 182                         $lock = $memcache->get($cachekey);
 183
 184                         if (!is_bool($lock)) {
 185                                 if ((int)$lock == getmypid()) {
 186                                         $memcache->delete($cachekey);
 187                                 }
 188                         }
 189                         return;
 190                 }
 191
 192                 dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
 193                 return;
 194         }
 195
 196         /**
 197          * @brief Removes all lock that were set by us
 198          * @return void
 199          */
 200         public static function removeAll()
 201         {
 202                 $memcache = self::connectMemcache();
 203                 if (is_object($memcache)) {
 204                         // We cannot delete all cache entries, but this doesn't matter with memcache
 205                         return;
 206                 }
 207
 208                 dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
 209                 return;
 210         }
 211 }