mirror of
https://github.com/Combodo/iTop.git
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312 lines
9.3 KiB
PHP
312 lines
9.3 KiB
PHP
<?php
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// Copyright (C) 2013-2018 Combodo SARL
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//
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// This file is part of iTop.
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//
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// iTop is free software; you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// iTop is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with iTop. If not, see <http://www.gnu.org/licenses/>
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/**
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* Class iTopMutex
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* A class to serialize the execution of some code sections
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* Emulates the API of PECL Mutex class
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* Relies on MySQL locks because the API sem_get is not always present in the
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* installed PHP.
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*
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* @copyright Copyright (C) 2013-2018 Combodo SARL
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* @license http://opensource.org/licenses/AGPL-3.0
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*/
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class iTopMutex
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{
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protected $sName;
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/** @var bool */
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protected $bLocked; // Whether or not this instance of the Mutex is locked
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/** @var \mysqli */
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protected $hDBLink;
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protected $sDBHost;
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protected $sDBUser;
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protected $sDBPwd;
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protected $sDBName;
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protected $sDBSubname;
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protected $bDBTlsEnabled;
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protected $sDBTlsCA;
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static protected $aAcquiredLocks = array(); // Number of instances of the Mutex, having the lock, in this page
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public function __construct(
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$sName, $sDBHost = null, $sDBUser = null, $sDBPwd = null, $bDBTlsEnabled = null, $sDBTlsCA = null
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)
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{
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// Compute the name of a lock for mysql
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// Note: names are server-wide!!! So let's make the name specific to this iTop instance
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$oConfig = MetaModel::GetConfig();
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if ($oConfig === null)
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{
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$oConfig = utils::GetConfig(); // Will return an empty config when called during the setup
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}
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$this->sDBHost = is_null($sDBHost) ? $oConfig->Get('db_host') : $sDBHost;
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$this->sDBUser = is_null($sDBUser) ? $oConfig->Get('db_user') : $sDBUser;
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$this->sDBPwd = is_null($sDBPwd) ? $oConfig->Get('db_pwd') : $sDBPwd;
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$this->sDBName = $oConfig->Get('db_name');
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$sDBSubname = $oConfig->Get('db_subname');
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$this->bDBTlsEnabled = is_null($bDBTlsEnabled) ? $oConfig->Get('db_tls.enabled') : $bDBTlsEnabled;
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$this->sDBTlsCA = is_null($sDBTlsCA) ? $oConfig->Get('db_tls.ca') : $sDBTlsCA;
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$this->sName = $sName;
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if (substr($sName, -strlen($this->sDBName.$sDBSubname)) != $this->sDBName.$sDBSubname)
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{
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// If the name supplied already ends with the expected suffix
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// don't add it twice, since the setup may try to detect an already
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// running cron job by its mutex, without knowing if the config already exists or not
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$this->sName .= $this->sDBName.$sDBSubname;
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}
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// Limit the length of the name for MySQL > 5.7.5
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$this->sName = 'itop.'.md5($this->sName);
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$this->bLocked = false; // Not yet locked
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if (!array_key_exists($this->sName, self::$aAcquiredLocks))
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{
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self::$aAcquiredLocks[$this->sName] = 0;
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}
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// It is MANDATORY to create a dedicated session each time a lock is required, because
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// using GET_LOCK anytime on the same session will RELEASE the current and unique session lock (known issue)
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$this->InitMySQLSession();
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}
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/**
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* Get instance of self but with an escaped $sName
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*
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* this is meant to be used with non trusted string such as user inputs.
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*
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* @param mixed ...$aArgs smae as __construct()
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*
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* @return \iTopMutex
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* @since 2.7.0
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*
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*/
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public static function GetInstanceFromUserInput(...$aArgs)
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{
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$aArgs[0] = \CMDBSource::Quote($aArgs[0]);
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return new iTopMutex(...$aArgs);
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}
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public function __destruct()
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{
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if ($this->bLocked)
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{
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$this->Unlock();
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}
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mysqli_close($this->hDBLink);
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}
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/**
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* Acquire the mutex. Uses a MySQL lock. <b>Warn</b> : can have an abnormal behavior on MySQL clusters (see R-016204)
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*
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* @see https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
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*/
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public function Lock()
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{
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if ($this->bLocked)
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{
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// Lock already acquired
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return;
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}
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if (self::$aAcquiredLocks[$this->sName] == 0)
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{
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do
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{
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$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 3600)");
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if (is_null($res))
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{
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throw new Exception("Failed to acquire the lock '".$this->sName."'");
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}
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// $res === '1' means I hold the lock
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// $res === '0' means it timed out
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}
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while ($res !== '1');
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}
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$this->bLocked = true;
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self::$aAcquiredLocks[$this->sName]++;
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}
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/**
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* Attempt to acquire the mutex
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* @returns bool True if the mutex is acquired, false if already locked elsewhere
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*/
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public function TryLock()
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{
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if ($this->bLocked)
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{
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return true; // Already acquired
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}
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if (self::$aAcquiredLocks[$this->sName] > 0)
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{
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self::$aAcquiredLocks[$this->sName]++;
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$this->bLocked = true;
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return true;
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}
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$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 0)");
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if (is_null($res))
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{
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throw new Exception("Failed to acquire the lock '".$this->sName."'");
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}
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// $res === '1' means I hold the lock
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// $res === '0' means it timed out
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if ($res === '1')
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{
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$this->bLocked = true;
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self::$aAcquiredLocks[$this->sName]++;
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}
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if (($res !== '1') && ($res !== '0'))
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{
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$sMsg = 'GET_LOCK('.$this->sName.', 0) returned: '.var_export($res, true).'. Expected values are: 0, 1 or null';
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IssueLog::Error($sMsg);
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throw new Exception($sMsg);
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}
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return ($res !== '0');
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}
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/**
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* Check if the mutex is locked WITHOUT TRYING TO ACQUIRE IT
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* @returns bool True if the mutex is in use, false otherwise
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*/
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public function IsLocked()
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{
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if ($this->bLocked)
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{
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return true; // Already acquired
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}
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if (self::$aAcquiredLocks[$this->sName] > 0)
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{
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return true;
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}
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$res = $this->QueryToScalar("SELECT IS_FREE_LOCK('".$this->sName."')"); // IS_FREE_LOCK detects some error cases that IS_USED_LOCK do not detect
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if (is_null($res))
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{
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$sMsg = "MySQL Error, IS_FREE_LOCK('".$this->sName."') returned null. Error (".mysqli_errno($this->hDBLink).") = '".mysqli_error($this->hDBLink)."'";
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IssueLog::Error($sMsg);
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throw new Exception($sMsg);
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}
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else if ($res == '1')
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{
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// Lock is free
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return false;
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}
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return true;
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}
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/**
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* Release the mutex
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*/
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public function Unlock()
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{
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if (!$this->bLocked)
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{
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// ??? the lock is not acquired, exit
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return;
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}
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if (self::$aAcquiredLocks[$this->sName] == 0)
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{
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return; // Safety net
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}
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if (self::$aAcquiredLocks[$this->sName] == 1)
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{
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$res = $this->QueryToScalar("SELECT RELEASE_LOCK('".$this->sName."')");
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}
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$this->bLocked = false;
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self::$aAcquiredLocks[$this->sName]--;
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}
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/**
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* Initialize database connection. Mandatory attributes must be already set !
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*
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* @throws \Exception
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* @throws \MySQLException
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*
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* @since 2.7.5 3.0.0 N°3968 specify `wait_timeout` for the mutex dedicated connection
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*/
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public function InitMySQLSession()
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{
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$sServer = $this->sDBHost;
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$sUser = $this->sDBUser;
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$sPwd = $this->sDBPwd;
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$sSource = $this->sDBName;
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$bTlsEnabled = $this->bDBTlsEnabled;
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$sTlsCA = $this->sDBTlsCA;
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$this->hDBLink = CMDBSource::GetMysqliInstance($sServer, $sUser, $sPwd, $sSource, $bTlsEnabled, $sTlsCA, false);
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if (!$this->hDBLink) {
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throw new MySQLException('Could not connect to the DB server '.mysqli_connect_error().' (mysql errno: '.mysqli_connect_errno(), array('host' => $sDBHost, 'user' => $sDBUser));
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}
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// Make sure that the server variable `wait_timeout` is at least 86400 seconds for this connection,
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// since the lock will be released if/when the connection times out.
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// Source https://dev.mysql.com/doc/refman/5.7/en/locking-functions.html :
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// > A lock obtained with GET_LOCK() is released explicitly by executing RELEASE_LOCK() or implicitly when your session terminates
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//
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// BEWARE: If you want to check the value of this variable, when run from an interactive console `SHOW VARIABLES LIKE 'wait_timeout'`
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// will actually returns the value of the variable `interactive_timeout` which may be quite different.
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$sSql = "SHOW VARIABLES LIKE 'wait_timeout'";
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$result = mysqli_query($this->hDBLink, $sSql);
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if (!$result) {
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throw new Exception("Failed to issue MySQL query '".$sSql."': ".mysqli_error($this->hDBLink).' (mysql errno: '.mysqli_errno($this->hDBLink).')');
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}
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if ($aRow = mysqli_fetch_array($result, MYSQLI_BOTH)) {
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$iTimeout = (int)$aRow[1];
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} else {
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mysqli_free_result($result);
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throw new Exception("No result for query '".$sSql."'");
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}
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mysqli_free_result($result);
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if ($iTimeout < 86400) {
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$result = mysqli_query($this->hDBLink, 'SET SESSION wait_timeout=86400');
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if ($result === false) {
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throw new Exception("Failed to issue MySQL query '".$sSql."': ".mysqli_error($this->hDBLink).' (mysql errno: '.mysqli_errno($this->hDBLink).')');
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}
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}
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}
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protected function QueryToScalar($sSql)
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{
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$result = mysqli_query($this->hDBLink, $sSql);
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if (!$result)
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{
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throw new Exception("Failed to issue MySQL query '".$sSql."': ".mysqli_error($this->hDBLink).' (mysql errno: '.mysqli_errno($this->hDBLink).')');
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}
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if ($aRow = mysqli_fetch_array($result, MYSQLI_BOTH))
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{
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$res = $aRow[0];
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}
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else
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{
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mysqli_free_result($result);
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throw new Exception("No result for query '".$sSql."'");
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}
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mysqli_free_result($result);
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return $res;
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}
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}
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