网上看到的一篇文章来追踪阻塞的，非常简便而且性能很好，跟大家分享。原文地址：AnXEventa Day (21 of 31) – The Future – Tracking Blocking in Denali
在2005新增的Blocked Process Report trace事件是我最喜欢的功能之一，当进程被阻塞超过用户允许的阻塞时间后会自动产生XML的报表。我曾经2年前针对这个功能在SQLServer Center写过一篇文章Using the Blocked Process Reportin SQL Server 2005/2008。使用这个事件需要使用SQL Server trace或者配置Event Notifications在Service Broker Queue中捕获事件信息。这两种配置都比较复杂。在SQL Server2012中引入了一个新的扩展事件sqlserver.blocked_process_report，非常方便使用。我们现在可以通过创建一个活动会话来捕获被阻塞的进程信息。我们仍然需要配置‘blocked process threshold’选项。
CREATE EVENT SESSIONMonitorBlocking
ON SERVER
ADD EVENT sqlserver.blocked_process_report
ADD TARGET package0.ring_buffer(SETMAX_MEMORY=2048)
WITH (MAX_DISPATCH_LATENCY= 5SECONDS)
GO
ALTER EVENT SESSIONMonitorBlocking
ON SERVER
STATE=START
GO
EXECUTE sp_configure 'show advanced options',1
GO
RECONFIGURE
GO
EXECUTE sp_configure 'blocked process threshold',15
GO
RECONFIGURE
GO
EXECUTE sp_configure 'show advanced options',0
GO
RECONFIGURE
GO
为了测试这个会话事件，我们在SSMS中开启两个查询窗口然后连接到数据库执行下面的代码：
USE [tempdb]
GO
CREATETABLE t1(RowIDintidentityprimarykey)
GO
BEGINTRANSACTION
INSERTINTO t1DEFAULTVALUES
WAITFOR DELAY'00:00:30'
COMMIT
第二个窗口代码：
USE [tempdb]
GO
SELECT*FROM t1
第一个查询将会阻塞第二个查询知道执行完成，在目标ring_buffer将会为我们的事件会话产生blocked processreport。查询ring_buffer目标的阻塞信息，我们可以快速的使用XQuery解析XML数据，代码如下：
-- Query the XML to get the Target Data
SELECT
n.value('(event/@name)[1]','varchar(50)')AS event_name,
n.value('(event/@package)[1]','varchar(50)')AS package_name,
DATEADD(hh,
DATEDIFF(hh,GETUTCDATE(),CURRENT_TIMESTAMP),
n.value('(event/@timestamp)[1]','datetime2'))AS [timestamp],
ISNULL(n.value('(event/data[@name="database_id"]/value)[1]','int'),
n.value('(event/action[@name="database_id"]/value)[1]','int'))as[database_id],
n.value('(event/data[@name="database_name"]/value)[1]','nvarchar(128)')as [database_name],
n.value('(event/data[@name="object_id"]/value)[1]','int')as[object_id],
n.value('(event/data[@name="index_id"]/value)[1]','int')as[index_id],
CAST(n.value('(event/data[@name="duration"]/value)[1]','bigint')/1000000.0AS decimal(6,2))as[duration_seconds],
n.value('(event/data[@name="lock_mode"]/text)[1]','nvarchar(10)')as [file_handle],
n.value('(event/data[@name="transaction_id"]/value)[1]','bigint')as[transaction_id],
n.value('(event/data[@name="resource_owner_type"]/text)[1]','nvarchar(10)')as [resource_owner_type],
CAST(n.value('(event/data[@name="blocked_process"]/value)[1]','nvarchar(max)')as XML) as[blocked_process_report]
FROM
( SELECTtd.query('.')asn
FROM
(
SELECTCAST(target_dataAS XML)astarget_data
FROM sys.dm_xe_sessionsASs
JOIN sys.dm_xe_session_targetsASt
ON s.address=t.event_session_address
WHERE s.name='MonitorBlocking'
ANDt.target_name= 'ring_buffer'
) ASsub
CROSS APPLY target_data.nodes('RingBufferTarget/event')ASq(td)
) as tab
GO
blocked process report的扩展事件输出中包含了很多额外的信息比如database_id, object_id, index_id, duration, lock_mode,transaction_id, and resource_owner_type 。XML输出可以在SSMS中打开：
<blocked-process-report>
<blocked-process>
<processid="process2eb8bda8"taskpriority="0"logused="0"waitresource="KEY: 2:2666130980878942208 (61a06abd401c)"
waittime="25480"ownerId="12748"transactionname="SELECT"lasttranstarted="2010-12-21T18:19:03.263"
XDES="0x2dfb9c10"lockMode="S"schedulerid="1"kpid="2484"status="suspended"spid="60"sbid="0"ecid="0"
priority="0"trancount="0"lastbatchstarted="2010-12-21T18:19:03.263"
lastbatchcompleted="2010-12-21T18:19:03.263"clientapp="Microsoft SQL Server Management Studio - Query"
hostname="WIN-5B9V8JPLP3H"hostpid="2708"loginname="WIN-5B9V8JPLP3H\Administrator"
isolationlevel="read committed (2)"xactid="12748"currentdb="2"lockTimeout="4294967295"
clientoption1="671090784"clientoption2="390200">
<executionStack>
<frameline="1"sqlhandle="0x02000000d9de7b2f4f3a78e40f100bc02a84efbb9f01a84d"/>
</executionStack>
<inputbuf>
SELECT * FROM t1 </inputbuf>
</process>
</blocked-process>
<blocking-process>
<processstatus="suspended"waittime="27430"spid="57"sbid="0"ecid="0"priority="0"trancount="1"
lastbatchstarted="2010-12-21T18:19:01.437"lastbatchcompleted="2010-12-21T18:13:25.637"
clientapp="Microsoft SQL Server Management Studio - Query"hostname="WIN-5B9V8JPLP3H"
hostpid="2708"loginname="WIN-5B9V8JPLP3H\Administrator"isolationlevel="read committed (2)"
xactid="12733"currentdb="2"lockTimeout="4294967295"clientoption1="671090784"clientoption2="390200">
<executionStack>
<frameline="3"stmtstart="100"stmtend="150"sqlhandle="0x020000005a74b3030117e049389a93b2ce5bfb48e272f938"/>
</executionStack>
<inputbuf>
BEGIN TRANSACTION
INSERT INTO t1 DEFAULT VALUES
WAITFOR DELAY '00:00:30'
COMMIT </inputbuf>
</process>
</blocking-process>
</blocked-process-report>
blocked process report在Extended Events中的输出跟SQL Server trace或者Event Notifications是相同的。这种方法只是一个新的手机信息的机制。
注意：当你不想获得阻塞信息的时候，记得关闭‘blocked process threshold选项，默认值为0.
本文转自 lzf328 51CTO博客，原文链接:
http://blog.51cto.com/lzf328/1363321
