iTop使用MGR集群 | 知行近思

MySQL Group Replication 能比较方便的实现高可用，但是 iTop 文档里明确说不支持多主的 MySQL 集群：

Galera clusters with multiple masters are NOT supported by iTop, because such clusters do not properly implement the GET_LOCK MySQL function (for more information: Galera cluster known limitations).

MGR 文档里也明确说不支持 GET_LOCK：

Table Locks and Named Locks. The certification process does not take into account table locks (see Section 13.3.6, “LOCK TABLES and UNLOCK TABLES Statements”) or named locks (see GET_LOCK()).

那么到底是哪些功能会受到影响呢？

Contents

1 架构
2 代码分析
3 测试用例
4 结论
5 参考资料

架构

计划分别测试 iTop 使用单主（Single Primary）和多主（Multi Primary）模式的 MGR 集群，以及单节点，对比结果。以下是 MGR 单主和多主的架构图。

代码分析

搜索代码，可知 GET_LOCK 主要在 iTopMutex 类的 Lock() 方法里用到。

/**
* Acquire the mutex. Uses a MySQL lock. <b>Warn</b> : can have an abnormal behavior on MySQL clusters (see R-016204)
*
* @see https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock
*/	
public function Lock()
{
if ($this->bLocked)
	{
	// Lock already acquired
	return;
	}
	if (self::$aAcquiredLocks[$this->sName] == 0)
	{
	do
	{
	$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 3600)");

/**

* Acquire the mutex. Uses a MySQL lock. <b>Warn</b> : can have an abnormal behavior on MySQL clusters (see R-016204)

* @see https://dev.mysql.com/doc/refman/5.7/en/miscellaneous-functions.html#function_get-lock

public function Lock()

{

if ($this->bLocked)

{

// Lock already acquired

return;

}

if (self::$aAcquiredLocks[$this->sName] == 0)

{

$res = $this->QueryToScalar("SELECT GET_LOCK('".$this->sName."', 3600)");

继续搜索 ->Lock(，找到以下文件：

./core/counter.class.inc.php:		$oiTopMutex->Lock();
./core/log.class.inc.php:			$oLock->Lock();
./core/ormlinkset.class.inc.php:		$oMtx->Lock();
./core/ownershiplock.class.inc.php:		$oMutex->Lock();
./core/ownershiplock.class.inc.php:		$oMutex->Lock();
./core/ownershiplock.class.inc.php:		$oMutex->Lock();
./core/ownershiplock.class.inc.php:		$oMutex->Lock();
./core/ownershiplock.class.inc.php:		$oMutex->Lock();
./datamodels/2.x/itop-backup/ajax.backup.php:				$oRestoreMutex->Lock();
./datamodels/2.x/itop-backup/main.itop-backup.php:		$oMutex->Lock();
./datamodels/2.x/itop-core-update/src/Service/CoreUpdater.php:		$oMutex->Lock();
./datamodels/2.x/itop-hub-connector/ajax.php:	$oMutex->Lock();
./synchro/synchro_import.php:		$oMutex->Lock();
./synchro/synchrodatasource.class.inc.php:			$oMutex->Lock();

./core/counter.class.inc.php: $oiTopMutex->Lock();

./core/log.class.inc.php: $oLock->Lock();

./core/ormlinkset.class.inc.php: $oMtx->Lock();

./core/ownershiplock.class.inc.php: $oMutex->Lock();

./datamodels/2.x/itop-backup/ajax.backup.php: $oRestoreMutex->Lock();

./datamodels/2.x/itop-backup/main.itop-backup.php: $oMutex->Lock();

./datamodels/2.x/itop-core-update/src/Service/CoreUpdater.php: $oMutex->Lock();

./datamodels/2.x/itop-hub-connector/ajax.php: $oMutex->Lock();

./synchro/synchro_import.php: $oMutex->Lock();

./synchro/synchrodatasource.class.inc.php: $oMutex->Lock();

下面基于 core/counter.class.inc.php，core/ormlinkset.class.inc.php以及 core/ownershiplock.class.inc.php 来测试 MGR 的影响。其他文件基本是关于日志和备份的。暂时没有想到测试用例。

测试用例

core/counter

此文件定义了 iTopCounter 类，IncClass() 方法用到了 iTopMutex，此方法最终用在了 Ticket 的 MakeTicketRef() 里，被用户生成工单编号，即 R-000001 这种编号。

    public function MakeTicketRef()
    {
          $iNextId = ItopCounter::IncClass(get_class($this));
          $sRef = $this->MakeTicketRef($iNextId);
          $this->SetIfNull('ref', $sRef);
          $iKey = parent::DBInsertNoReload();
          return $iKey;
    }

public function MakeTicketRef()

{

$iNextId = ItopCounter::IncClass(get_class($this));

$sRef = $this->MakeTicketRef($iNextId);

$this->SetIfNull('ref', $sRef);

$iKey = parent::DBInsertNoReload();

return $iKey;

}

测试思路，并发创建工单，查看是否有重复的工单编号。编写以下 Shell 脚本：

#!/bin/bash

[ $# -lt 2 ] && echo "$0 password url" && exit 1
user=admin
password=$1
url=$2
json_data='{"operation":"core/create","comment":"test mgr","class":"UserRequest","output_fields":"id,friendlyname","fields":{"org_id":"SELECT Organization WHERE name = \"Demo\"","caller_id":{"name":"Christie", "first_name":"Agatha"},"title":"Test MGR From API", "description":"Test"}}'

curl -s "$url/webservices/rest.php?version=1.3" -d "auth_user=$user&auth_pwd=$password&json_data=$json_data"

#!/bin/bash

[ $# -lt 2 ] && echo "$0 password url" && exit 1

user=admin

password=$1

url=$2

json_data='{"operation":"core/create","comment":"test mgr","class":"UserRequest","output_fields":"id,friendlyname","fields":{"org_id":"SELECT Organization WHERE name = \"Demo\"","caller_id":{"name":"Christie", "first_name":"Agatha"},"title":"Test MGR From API", "description":"Test"}}'

curl -s "$url/webservices/rest.php?version=1.3" -d "auth_user=$user&auth_pwd=$password&json_data=$json_data"

使用 parallel 同时在 3 个 iTop 实例上并发调用：

#!/bin/bash

for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.101 &
for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.102 &
for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.103 &

#!/bin/bash

for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.101 &

for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.102 &

for id in `seq 1 100`;do echo $id;done |parallel -j 3 ./ticket-api.sh admin http://192.168.10.103 &

结果出现较多重复编号：

2 R-000686

3 R-000596

3 R-000685

4 R-000593

4 R-000598

5 R-000597

MGR单主和单节点未出现重复工单编号。

core/ormlinkset

OrmLinkSet 类的 DBWrite() 方法使用了 iTopMutex，DBWrite 被 DBObject 的 DBWriteLinks 调用。DBWriteLinks 又被 DBOject 的 DBInsertNoReload 和 DBUpdate 调用。

/**
 * used both by insert/update
 *
 * @internal
 *
 * @throws \CoreException
 */
private function DBWriteLinks()
{
    foreach(MetaModel::ListAttributeDefs(get_class($this)) as $sAttCode => $oAttDef)
    {
        if (!$oAttDef->IsLinkSet()) continue;
        if (!array_key_exists($sAttCode, $this->m_aTouchedAtt)) continue;
        if (array_key_exists($sAttCode, $this->m_aModifiedAtt) && ($this->m_aModifiedAtt[$sAttCode] == false)) continue;

        /** @var \ormLinkSet $oLinkSet */
        $oLinkSet = $this->m_aCurrValues[$sAttCode];
        $oLinkSet->DBWrite($this);
    }
}

/**

* used both by insert/update

* @internal

* @throws \CoreException

private function DBWriteLinks()

{

foreach(MetaModel::ListAttributeDefs(get_class($this)) as $sAttCode => $oAttDef)

{

if (!$oAttDef->IsLinkSet()) continue;

if (!array_key_exists($sAttCode, $this->m_aTouchedAtt)) continue;

if (array_key_exists($sAttCode, $this->m_aModifiedAtt) && ($this->m_aModifiedAtt[$sAttCode] == false)) continue;

/** @var \ormLinkSet $oLinkSet */

$oLinkSet = $this->m_aCurrValues[$sAttCode];

$oLinkSet->DBWrite($this);

}

测试思路，并发更新 Person 的 team_list，观察是否创建重复的 lnkPersonToTeam。编写以下 Shell 脚本：

#!/bin/bash

[ $# -lt 2 ] && echo "$0 password url" && exit 1
user=admin
password=$1
url=$2
json_data='{"operation":"core/update","comment":"test mgr","class":"Person","key":"SELECT Person WHERE name=\"Xing\" AND first_name=\"Ming\"","output_fields":"id,team_list,friendlyname","fields":{"team_list":[{"team_id":{"name":"Helpdesk"}}]}}'

curl -s "$url/webservices/rest.php?version=1.3" -d "auth_user=$user&auth_pwd=$password&json_data=$json_data" |jq .

#!/bin/bash

[ $# -lt 2 ] && echo "$0 password url" && exit 1

user=admin

password=$1

url=$2

json_data='{"operation":"core/update","comment":"test mgr","class":"Person","key":"SELECT Person WHERE name=\"Xing\" AND first_name=\"Ming\"","output_fields":"id,team_list,friendlyname","fields":{"team_list":[{"team_id":{"name":"Helpdesk"}}]}}'

curl -s "$url/webservices/rest.php?version=1.3" -d "auth_user=$user&auth_pwd=$password&json_data=$json_data" |jq .

使用 parallel 同时在3 个节点上并发操作：

#!/bin/bash

for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.101 &
for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.102 &
for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.103 &

#!/bin/bash

for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.101 &

for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.102 &

for id in `seq 1 10`;do echo $id;done |parallel -j 3 ./ormlinkset.sh admin http://192.168.10.103 &

多主，单主及单节点均出现重复创建的 lnkPersonToTeam。

此项测试单节点也有问题，有可能是测试用例设计的有问题。

core/ownershiplock

/**
 * Mechanism to obtain an exclusive lock while editing an object
 *
 * @package     iTopORM
 */

/**
 * Persistent storage (in the database) for remembering that an object is locked 
 */
class iTopOwnershipToken extends DBObject
{
...
}

/**
 * Utility class to acquire/extend/release/kill an exclusive lock on a given persistent object,
 * for example to prevent concurrent edition of the same object.
 * Each lock has an expiration delay of 120 seconds (tunable via the configuration parameter 'concurrent_lock_expiration_delay')
 * A watchdog (called twice during this delay) is in charge of keeping the lock "alive" while an object is being edited.
 */
class iTopOwnershipLock
{

/**

* Mechanism to obtain an exclusive lock while editing an object

* @package iTopORM

/**

* Persistent storage (in the database) for remembering that an object is locked

class iTopOwnershipToken extends DBObject

{

...

}

/**

* Utility class to acquire/extend/release/kill an exclusive lock on a given persistent object,

* for example to prevent concurrent edition of the same object.

* Each lock has an expiration delay of 120 seconds (tunable via the configuration parameter 'concurrent_lock_expiration_delay')

* A watchdog (called twice during this delay) is in charge of keeping the lock "alive" while an object is being edited.

class iTopOwnershipLock

{

主要用在 CMDBAbstractObject 的 DisplayModifyForm 和 DisplayStimulusForm 中。用于阻止并发修改。

注意到代码中检查了配置项 concurrent_lock_enabled：

$LockEnabled = MetaModel::GetConfig()->Get('concurrent_lock_enabled');

1	$LockEnabled = MetaModel::GetConfig()->Get('concurrent_lock_enabled');

可知阻止并发修改是一个可选的功能，默认是关闭的，如需使用，要在配置文件中开启[3]。此功能效果是，当有人正在编辑一个对象时，其他人浏览该对象，会提示对象被锁住，正在被某人修改，并且不显示修改按钮。

测试结果显示

MGR多主模式下不同iTop实例编辑同一对象，此功能无效
MGR多主模式下在同一iTop实例操作，此功能正常
MGR单主模式及单节点，此功能正常

结论

测试结果对照表

测试项	MGR多主	MGR单主	单节点	备注
工单编号	出现重复项	未见异常	未见异常
Ormlinkset	出现多lnk情况	出现多lnk情况	出现多lnk情况	可能测试用例错误
阻止并发修改	不同实例下异常	未见异常	未见异常

iTop MGR测试结果

因此，iTop 使用 MGR 单主模式可以在实现高可用的前提下获得最好的兼容性。

参考资料

1. https://www.itophub.io/wiki/page?id=2_7_0%3Ainstall%3Ainstalling_itop#software_requirements
2. https://dev.mysql.com/doc/refman/8.0/en/group-replication-limitations.html
3. https://www.itophub.io/wiki/page?id=2_2_0%3Aadmin%3Alocking

1. https://www.itophub.io/wiki/page?id=2_7_0%3Ainstall%3Ainstalling_itop#software_requirements

2. https://dev.mysql.com/doc/refman/8.0/en/group-replication-limitations.html

3. https://www.itophub.io/wiki/page?id=2_2_0%3Aadmin%3Alocking

知行近思

知行合一，切问近思

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架构

代码分析

测试用例

core/counter

core/ormlinkset

core/ownershiplock

结论

参考资料

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