記一次公司倉庫數據庫服務器死鎖過程及解決辦法

死鎖的四個必要條件：

互斥條件(Mutual exclusion)：資源不能被共享，只能由一個進程使用。

請求與保持條件(Hold and wait)：已經得到資源的進程可以再次申請新的資源。

非剝奪條件(No pre-emption)：已經分配的資源不能從相應的進程中被強制地剝奪。

循環等待條件(Circular wait)：系統中若干進程組成環路，該環路中每個進程都在等待相鄰進程正占用的資源。

倉庫揀貨卡死，排查了數據庫的很多地方，都沒有頭緒，最後到SQL Server 錯誤日志裡查看，終於發現了蛛絲馬跡

EXEC xp_readerrorlog 0,1,NULL,NULL,'2015-09-21','2015-10-10','DESC'
   waiter id=process5c30e08 mode=U requestType=wait
  waiter-list
   owner id=process5c26988 mode=X
  owner-list
  keylock hobtid=72057597785604096 dbid=33 objectname=stoxxx.dbo.Orderxxx indexname=IX_PricingExpressProductCode_State id=lock17fa96980 mode=X associatedObjectId=72057597785604096
   waiter id=process5c26988 mode=U requestType=wait
  waiter-list
   owner id=process5c30e08 mode=X
  owner-list
  keylock hobtid=72057597785604096 dbid=33 objectname=stoxxx.dbo.Orderxxx indexname=IX_PricingExpressProductCode_State id=lock87d69e780 mode=X associatedObjectId=72057597785604096
 resource-list
(@OperateState money,@HandledByNewWms bit,@State int,@OrderOut int)
UPDATE [Orderxx] SET [OperateState] = @OperateState,[HandledByNewWms] = @HandledByNewWms WHERE (([Orderxxx].[State] = @State) And ([Orderxxx].[OrderOut] = @OrderOut) And ([Orderxxx].[PricingExpressProductCode] IN ('UKNIR')))  
  inputbuf
unknown   
   frame procname=unknown line=1 sqlhandle=0x000000000000000000000000000000000000000000000000
UPDATE [Orderxxx] SET [OperateState] = @OperateState,[HandledByNewWms] = @HandledByNewWms WHERE (([Orderxxx].[State] = @State) And ([Orderxxx].[OrderOut] = @OrderOut) And ([Orderxxx].[PricingExpressProductCode] IN ('UKNIR')))   
   frame procname=adhoc line=1 stmtstart=134 sqlhandle=0x020000009d376d18a17e7ea51289d8caa2fb4de65c976389
  executionStack
  process id=process5c30e08 taskpriority=0 logused=10320 waitresource=KEY: 33:72057597785604096 (112399c2054a) waittime=4813 ownerId=31578743038 transactionname=user_transaction lasttranstarted=2015-09-24T10:22:58.410 XDES=0x372e95950 lockMode=U schedulerid=17 kpid=8496 status=suspended spid=153 sbid=0 ecid=0 priority=0 trancount=2 lastbatchstarted=2015-09-24T10:22:58.540 lastbatchcompleted=2015-09-24T10:22:58.540 clientapp=.Net SqlClient Data Provider hostname=CK1-WIN-WEB02 hostpid=37992 loginname=ck1.biz isolationlevel=read committed (2) xactid=31578743038 currentdb=33 lockTimeout=4294967295 clientoption1=671088672 clientoption2=128056
(@OperateState money,@HandledByNewWms bit,@State int,@OrderOut int)UPDATE [Orderxxx] SET [OperateState] = @OperateState,[HandledByNewWms] = @HandledByNewWms WHERE (([Orderxxx].[State] = @State) And ([Orderxxx].[OrderOut] = @OrderOut) And ([Orderxxx].[PricingExpressProductCode] IN ('UKNIR')))  
  inputbuf
unknown   
   frame procname=unknown line=1 sqlhandle=0x000000000000000000000000000000000000000000000000
UPDATE [Orderxxx] SET [OperateState] = @OperateState,[HandledByNewWms] = @HandledByNewWms WHERE (([Orderxxx].[State] = @State) And ([Orderxxx].[OrderOut] = @OrderOut) And ([Orderxxx].[PricingExpressProductCode] IN ('UKNIR')))   
   frame procname=adhoc line=1 stmtstart=134 sqlhandle=0x020000009d376d18a17e7ea51289d8caa2fb4de65c976389
  executionStack
  process id=process5c26988 taskpriority=0 logused=9892 waitresource=KEY: 33:72057597785604096 (70f5b089bb2b) waittime=4813 ownerId=31579268946 transactionname=user_transaction lasttranstarted=2015-09-24T10:27:01.357 XDES=0x98312f950 lockMode=U schedulerid=16 kpid=9184 status=suspended spid=454 sbid=0 ecid=0 priority=0 trancount=2 lastbatchstarted=2015-09-24T10:27:01.490 lastbatchcompleted=2015-09-24T10:27:01.487 clientapp=.Net SqlClient Data Provider hostname=CK1-WIN-WEB02 hostpid=37992 loginname=ck1.biz isolationlevel=read committed (2) xactid=31579268946 currentdb=33 lockTimeout=4294967295 clientoption1=671088672 clientoption2=128056
 process-list
 deadlock victim=process5c26988
deadlock-list

咋一看上面的錯誤信息，可以發現兩條相同的語句造成的死鎖，但是這麼短的語句不可能持有排他鎖太久

再仔細分析一下錯誤日志，發現都死鎖在同一個非聚集索引上，再問了一下開發，開發那邊說，這條語句是在一個大事務裡面，這個事務會做7、8件事

索引屬性

還有索引裡面的數據，發現很多重復值

SQL語句是這樣的

(@OperateState money,@HandledByNewWms bit,@State int,@OrderOut int)
@HandledByNewWms=(1) @OperateState=($1.0000) @OrderOut=(4055484) @State=(3) 
UPDATE [Orderxxx] SET [OperateState] = $1.0000,[HandledByNewWms] = 1
WHERE (([Orderxxx].[State] = 3) And ([Orderxxx].[OrderOut] = 4055484) And ([Orderxxx].[PricingExpressProductCode] IN ('UKRRM','UKRLE')))

下圖為語句生成的執行計劃

當時的情況是大量SQL語句被阻塞，而阻塞的語句正是下面這條語句

UPDATE [Orderxxx] SET [OperateState] = $1.0000,[HandledByNewWms] = 1
WHERE (([Orderxxx].[State] = 3) And ([Orderxxx].[OrderOut] = 4055484) And ([Orderxxx].[PricingExpressProductCode] IN ('UKRRM','UKRLE')))

解決方法

上面得出幾個症狀

1、update語句是在一個大事務裡面，事務太大導致其他session等待排他鎖的時間變長

2、大家都在使用同一個非聚集索引，並掃描PricingExpressProductCode字段

3、索引裡的重復值很多

從上面的症狀基本可以判斷，這個非聚集索引無啥用，可以禁用之

ALTER INDEX [IX_PricingExpressProductCode_State] ON [dbo].[Orderxxx] DISABLE

禁用之後，死鎖消失，問題解決，倉庫的怨氣也隨之消失

這一次排查過程時間有點長，但是很好定位，SQL Server錯誤日志給出了足夠的信息定位死鎖問題，所以遇到問題的時候一定要分析清楚日志