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 Friendica\Database\DBM;
  13 use Memcache;
  14 use dba;
  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 $fn_name Name of the lock
  52          *
  53          * @return ressource the semaphore key
  54          */
  55         private static function semaphoreKey($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                 $start = time();
  78
  79                 // The second parameter for "sem_acquire" doesn't exist before 5.6.1
  80                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
  81                         self::$semaphore[$fn_name] = sem_get(self::semaphoreKey($fn_name));
  82                         if (self::$semaphore[$fn_name]) {
  83                                 return sem_acquire(self::$semaphore[$fn_name], ($timeout == 0));
  84                         }
  85                 }
  86
  87                 $memcache = self::connectMemcache();
  88                 if (is_object($memcache)) {
  89                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
  90
  91                         do {
  92                                 // We only lock to be sure that nothing happens at exactly the same time
  93                                 dba::lock('locks');
  94                                 $lock = $memcache->get($cachekey);
  95
  96                                 if (!is_bool($lock)) {
  97                                         $pid = (int)$lock;
  98
  99                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 100                                         // Or we do want to lock something that was already locked by us.
 101                                         if (!posix_kill($pid, 0) || ($pid == getmypid())) {
 102                                                 $lock = false;
 103                                         }
 104                                 }
 105                                 if (is_bool($lock)) {
 106                                         $memcache->set($cachekey, getmypid(), MEMCACHE_COMPRESSED, 300);
 107                                         $got_lock = true;
 108                                 }
 109
 110                                 dba::unlock();
 111
 112                                 if (!$got_lock && ($timeout > 0)) {
 113                                         usleep(rand(10000, 200000));
 114                                 }
 115                         } while (!$got_lock && ((time() - $start) < $timeout));
 116
 117                         return $got_lock;
 118                 }
 119
 120                 do {
 121                         dba::lock('locks');
 122                         $lock = dba::select('locks', array('locked', 'pid'), array('name' => $fn_name), array('limit' => 1));
 123
 124                         if (DBM::is_result($lock)) {
 125                                 if ($lock['locked']) {
 126                                         // When the process id isn't used anymore, we can safely claim the lock for us.
 127                                         if (!posix_kill($lock['pid'], 0)) {
 128                                                 $lock['locked'] = false;
 129                                         }
 130                                         // We want to lock something that was already locked by us? So we got the lock.
 131                                         if ($lock['pid'] == getmypid()) {
 132                                                 $got_lock = true;
 133                                         }
 134                                 }
 135                                 if (!$lock['locked']) {
 136                                         dba::update('locks', array('locked' => true, 'pid' => getmypid()), array('name' => $fn_name));
 137                                         $got_lock = true;
 138                                 }
 139                         } elseif (!DBM::is_result($lock)) {
 140                                 dba::insert('locks', array('name' => $fn_name, 'locked' => true, 'pid' => getmypid()));
 141                                 $got_lock = true;
 142                         }
 143
 144                         dba::unlock();
 145
 146                         if (!$got_lock && ($timeout > 0)) {
 147                                 usleep(rand(100000, 2000000));
 148                         }
 149                 } while (!$got_lock && ((time() - $start) < $timeout));
 150
 151                 return $got_lock;
 152         }
 153
 154         /**
 155          * @brief Removes a lock if it was set by us
 156          *
 157          * @param string $fn_name Name of the lock
 158          */
 159         public static function remove($fn_name) {
 160                 if (function_exists('sem_get') && version_compare(PHP_VERSION, '5.6.1', '>=')) {
 161                         if (empty(self::$semaphore[$fn_name])) {
 162                                 return false;
 163                         } else {
 164                                 $success = @sem_release(self::$semaphore[$fn_name]);
 165                                 unset(self::$semaphore[$fn_name]);
 166                                 return $success;
 167                         }
 168                 }
 169
 170                 $memcache = self::connectMemcache();
 171                 if (is_object($memcache)) {
 172                         $cachekey = get_app()->get_hostname().";lock:".$fn_name;
 173                         $lock = $memcache->get($cachekey);
 174
 175                         if (!is_bool($lock)) {
 176                                 if ((int)$lock == getmypid()) {
 177                                         $memcache->delete($cachekey);
 178                                 }
 179                         }
 180                         return;
 181                 }
 182
 183                 dba::update('locks', array('locked' => false, 'pid' => 0), array('name' => $fn_name, 'pid' => getmypid()));
 184                 return;
 185         }
 186
 187         /**
 188          * @brief Removes all lock that were set by us
 189          */
 190         public static function removeAll() {
 191                 $memcache = self::connectMemcache();
 192                 if (is_object($memcache)) {
 193                         // We cannot delete all cache entries, but this doesn't matter with memcache
 194                         return;
 195                 }
 196
 197                 dba::update('locks', array('locked' => false, 'pid' => 0), array('pid' => getmypid()));
 198                 return;
 199         }
 200 }