CRON: protection against re-entrance now relies on a bullet-proof mutex. Also added the option 'debug=1' to output the call stack in case an exception occurs (not always because of passwords being shown in the call stack)

git-svn-id: http://svn.code.sf.net/p/itop/code/trunk@2834 a333f486-631f-4898-b8df-5754b55c2be0

core/mutex.class.inc.php

@@ -0,0 +1,138 @@
+<?php
+// Copyright (C) 2013 Combodo SARL
+//
+//   This file is part of iTop.
+//
+//   iTop is free software; you can redistribute it and/or modify	
+//   it under the terms of the GNU Affero General Public License as published by
+//   the Free Software Foundation, either version 3 of the License, or
+//   (at your option) any later version.
+//
+//   iTop is distributed in the hope that it will be useful,
+//   but WITHOUT ANY WARRANTY; without even the implied warranty of
+//   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+//   GNU Affero General Public License for more details.
+//
+//   You should have received a copy of the GNU Affero General Public License
+//   along with iTop. If not, see <http://www.gnu.org/licenses/>
+
+
+/**
+ * Class iTopMutex
+ * A class to serialize the execution of some code sections
+ * Emulates the API of PECL Mutex class
+ * Relies on MySQL locks because the API sem_get is not always present in the
+ * installed PHP.    
+ *
+ * @copyright   Copyright (C) 2013 Combodo SARL
+ * @license     http://opensource.org/licenses/AGPL-3.0
+ */
+class iTopMutex
+{
+	protected $sName;
+	protected $hDBLink;
+
+	public function __construct($sName)
+	{
+		// Compute the name of a lock for mysql
+		// Note: the name is server-wide!!!
+		$this->sName = 'itop.'.$sName;
+
+		// It is a MUST to create a dedicated session each time a lock is required, because
+		// using GET_LOCK anytime on the same session will RELEASE the current and unique session lock (known issue)
+		$oConfig = utils::GetConfig();
+		$this->InitMySQLSession($oConfig->GetDBHost(), $oConfig->GetDBUser(), $oConfig->GetDBPwd());
+	}
+
+	public function __destruct()
+	{
+		$this->Unlock();
+		mysqli_close($this->hDBLink);
+	}
+
+	/**
+	 *	Acquire the mutex
+	 */	
+	public function Lock()
+	{
+		do
+		{
+			$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 3600)");
+			if (is_null($res))
+			{
+				throw new Exception("Failed to acquire the lock '".$this->sName."'");
+			}
+			// $res === '1' means I hold the lock
+			// $res === '0' means it timed out
+		}
+		while ($res !== '1');
+	}
+
+	/**
+	 *	Attempt to acquire the mutex
+	 *	@returns bool True if the mutex is acquired, false if already locked elsewhere	 
+	 */	
+	public function TryLock()
+	{
+		$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 0)");
+		if (is_null($res))
+		{
+			throw new Exception("Failed to acquire the lock '".$this->sName."'");
+		}
+		// $res === '1' means I hold the lock
+		// $res === '0' means it timed out
+		return ($res === '1');
+	}
+
+	/**
+	 *	Release the mutex
+	 */	
+	public function Unlock()
+	{
+		$res = $this->QueryToScalar("SELECT RELEASE_LOCK('".$this->sName."')");
+	}
+
+
+
+	public function InitMySQLSession($sHost, $sUser, $sPwd)
+	{
+		$aConnectInfo = explode(':', $sHost);
+		if (count($aConnectInfo) > 1)
+		{
+			// Override the default port
+			$sServer = $aConnectInfo[0];
+			$iPort = $aConnectInfo[1];
+			$this->hDBLink = @mysqli_connect($sServer, $sUser, $sPwd, '', $iPort);
+		}
+		else
+		{
+			$this->hDBLink = @mysqli_connect($sHost, $sUser, $sPwd);
+		}
+
+		if (!$this->hDBLink)
+		{
+			throw new Exception("Could not connect to the DB server (host=$sHost, user=$sUser): ".mysqli_connect_error().' (mysql errno: '.mysqli_connect_errno().')');
+		}
+	}
+
+
+	protected function QueryToScalar($sSql)
+	{
+		$result = mysqli_query($this->hDBLink, $sSql);
+		if (!$result)
+		{
+			throw new Exception("Failed to issue MySQL query '".$sSql."': ".mysqli_error($this->hDBLink).' (mysql errno: '.mysqli_errno($this->hDBLink).')');
+		}
+		if ($aRow = mysqli_fetch_array($result, MYSQLI_BOTH))
+		{
+			$res = $aRow[0];
+		}
+		else
+		{
+			mysqli_free_result($result);
+			throw new Exception("No result for query '".$sSql."'");
+		}
+		mysqli_free_result($result);
+		return $res;
+	}
+}

webservices/cron.php

@@ -19,7 +19,7 @@
 /**
  * Heart beat of the application (process asynchron tasks such as broadcasting email)
  *
- * @copyright   Copyright (C) 2010-2012 Combodo SARL
+ * @copyright   Copyright (C) 2010-2013 Combodo SARL
  * @license     http://opensource.org/licenses/AGPL-3.0
  */
 
@@ -59,7 +59,7 @@ function UsageAndExit($oP)
 	if ($bModeCLI)
 	{
 		$oP->p("USAGE:\n");
-		$oP->p("php cron.php --auth_user=<login> --auth_pwd=<password> [--param_file=<file>] [--verbose=1] [--status_only=1]\n");		
+		$oP->p("php cron.php --auth_user=<login> --auth_pwd=<password> [--param_file=<file>] [--verbose=1] [--debug=1] [--status_only=1]\n");		
 	}
 	else
 	{
@@ -337,6 +337,7 @@ foreach(get_declared_classes() as $sPHPClass)
 
 
 $bVerbose = utils::ReadParam('verbose', false, true /* Allow CLI */);
+$bDebug = utils::ReadParam('debug', false, true /* Allow CLI */);
 
 if ($bVerbose)
 {
@@ -355,42 +356,35 @@ if (utils::ReadParam('status_only', false, true /* Allow CLI */))
 	exit(0);
 }
 
-// Compute the name of a lock for mysql
-// The name is server-wide
-$oConfig = utils::GetConfig();
-$sLockName = 'itop.cron.'.$oConfig->GetDBName().'_'.$oConfig->GetDBSubname();
-
+require_once(APPROOT.'core/mutex.class.inc.php');
 $oP->p("Starting: ".time().' ('.date('Y-m-d H:i:s').')');
 
-// CAUTION: using GET_LOCK anytime on the same connexion will RELEASE the lock
-// Todo: invoke GET_LOCK from a dedicated session (encapsulate that into a mutex class)
-$res = CMDBSource::QueryToScalar("SELECT GET_LOCK('$sLockName', 1)");// timeout = 1 second (see also IS_FREE_LOCK)
-if (is_null($res))
-{
-	// TODO - Log ?
-	$oP->p("ERROR: Failed to acquire the lock '$sLockName'");
-}
-elseif ($res === '1')
+try
 {
-	// The current session holds the lock
-	try
+	$oConfig = utils::GetConfig();
+	$oMutex = new iTopMutex('cron.'.$oConfig->GetDBName().'_'.$oConfig->GetDBSubname());
+	if ($oMutex->TryLock())
 	{
 		CronExec($oP, $aProcesses, $bVerbose);
+
+		$oMutex->Unlock();
 	}
-	catch(Exception $e)
+	else
 	{
-		// TODO - Log ?
-	   $oP->p("ERROR:".$e->getMessage());
-	   $oP->p($e->getTraceAsString());
+		// Exit silently
+		$oP->p("Already running...");
 	}
-	$res = CMDBSource::QueryToScalar("SELECT RELEASE_LOCK('$sLockName')");
 }
-else
+catch (Exception $e)
 {
-	// Lock already held by another session
-	// Exit silently
-	$oP->p("Already running...");
+	$oP->p("ERROR: '".$e->getMessage()."'");
+	if ($bDebug)
+	{
+		// Might contain verb parameters such a password...
+		$oP->p($e->getTraceAsString());
+	}
 }
+
 $oP->p("Exiting: ".time().' ('.date('Y-m-d H:i:s').')');
 
 $oP->Output();