單一輸入數據表會觸發死鎖

Question

我們有一個webapi，它可以處理很多請求，有時每秒處理一次，並且在每個請求開始時，我們使用Entity框架將日志條目發送到我們的logtable中。

但是，我們日志表中的此項通常會在另一個進程上陷入僵局，我不知道是什么原因造成的。

using (UnitOfWork unitofwork = new UnitOfWork())
{
    unitofwork.WebApiRequestLogRepository.Insert(new WebApiRequestLog
    {
        Created = DateTime.Now,
        Username = System.Threading.Thread.CurrentPrincipal.Identity.Name,
        Controller = actionContext.ActionDescriptor.ControllerDescriptor.ControllerName,
        Method = actionContext.ActionDescriptor.ActionName,
        MethodParameters = xml,
        ApplicationVersion = AppSettings.Instance.Version,
        Url = HttpContext.Current.Request.Url.ToString(),
    });
    unitofwork.Save();
}

工作單元是圍繞單個上下文的包裝，可以同時進行多個更改。 保存調用上下文.SaveChanges

實體框架生成的SQL代碼

INSERT [log].[WebApiRequestLog]([Created], [Username], [Controller], [Method], [ApplicationVersion], [Url], [MethodParameters])
VALUES (@0, @1, @2, @3, @4, @5, @6)
SELECT [Id]
FROM [log].[WebApiRequestLog]
WHERE @@ROWCOUNT > 0 AND [Id] = scope_identity()

誰能向我解釋為什么一次插入日志表會導致死鎖？

編輯

public virtual void Insert(TEntity entity)
{
    DbSet.Add(entity);
}

public void Save()
    {
        StringBuilder builder = new StringBuilder();
        try
        {
            _context.Database.Log = s => builder.AppendLine(s);
            _context.SaveChanges();
        }
        catch (DbEntityValidationException e)
        {
            HandleDbEntityValidationException(e);
        }
        catch (Exception e)
        {
            Exception ex = new Exception(builder.ToString(), e);
            throw ex;
        }
    }

Answer 1

我拋出了一些有用的查詢，您可以在死鎖期間運行這些查詢以顯示當前的等待時間。 它們可以幫助您確定出現僵局的情況。

另外，您可能想查詢死鎖圖在發生時如何保存到數據庫中。 如果您在Database Administrator Exchange上發布了死鎖圖，我相信您會找到有關鎖定內容的更多信息。

1. 確保您沒有破壞TransactionScope，或者確保其他開發人員坐在 TransactionScope代碼塊內的斷點上 。

2. 如果您的數據庫非常忙，並且您不擔心臟臟，那么可以通過以下提示減少讀取鎖定。

    CREATE PROCEDURE SaveWebApiRequestLog(...) AS BEGIN SET TRANSACTION ISOLATION LEVEL READ UNCOMMITTED INSERT log.WebApiRequestLog(Created,Username,Controller,Method,ApplicationVersion,Url,MethodParameters) VALUES(...) SELECT Id FROM log.WebApiRequestLog WHERE Id = @@IDENTITY END 

   要么

    INSERT [log].[WebApiRequestLog]([Created], [Username], [Controller], [Method], [ApplicationVersion], [Url], [MethodParameters]) VALUES (@0, @1, @2, @3, @4, @5, @6) SELECT [Id] FROM [log].[WebApiRequestLog] WITH NOLOCK WHERE @@ROWCOUNT > 0 AND [Id] = scope_identity() 

顯示等待

--kill 65
SELECT 
    S.Text, R.Session_id,R.Status,R.Command,R.CPU_Time,R.Total_Elapsed_Time
FROM    
    sys.dm_exec_requests R
    CROSS APPLY sys.dm_exec_sql_text(sql_handle) AS S 

--EXEC sp_who2
SELECT  W.session_id,ot.task_state,W.wait_type, W.wait_duration_ms, W.blocking_session_id, W.resource_description, S.host_name, S.program_name
FROM  
    sys.dm_os_waiting_tasks  W  
    INNER  JOIN sys.dm_os_tasks ot ON ot.task_address = W.waiting_task_address 
    INNER JOIN sys.dm_exec_sessions S ON S.session_id = W.session_id 
WHERE 
    S.is_user_process =  1

SELECT 
    SessionID = es.session_id,
    Login =es.original_login_name,
    Host = es.host_name,
    RequestStart=es.last_request_start_time,
    RequerstEnd=es.last_request_end_time,
    Status =es.status,
    BockedBy =er.blocking_session_id,
    WaitType =er.wait_type, 
    WaitTime = er.wait_time,
    LastWaitType = er.last_wait_type,
    WaitResource = er.wait_resource,
    DatabaseID = DB_NAME(er.database_id),
    Command = er.command,
    --,sql_text=st.text
    TransactionIsolation =
        CASE es.transaction_isolation_level
            WHEN 0 THEN 'Unspecified'
            WHEN 1 THEN 'Read Uncommitted'
            WHEN 2 THEN 'Read Committed'
            WHEN 3 THEN 'Repeatable'
            WHEN 4 THEN 'Serializable'
            WHEN 5 THEN 'Snapshot'
        END,
    CPUTime = COALESCE(es.cpu_time,0) + COALESCE(er.cpu_time,0),
    IOTime = COALESCE(es.reads,0) + COALESCE(es.writes,0) + COALESCE(er.reads,0) + COALESCE(er.writes,0),
    TransactioCount = COALESCE(er.open_transaction_count,-1),
    ProgramName = COALESCE(es.program_name,''),
    LoginTme = es.login_time
FROM 
    sys.dm_exec_sessions es
    LEFT OUTER JOIN sys.dm_exec_connections ec ON es.session_id = ec.session_id
    LEFT OUTER JOIN sys.dm_exec_requests er ON es.session_id = er.session_id
    LEFT OUTER JOIN sys.server_principals sp ON es.security_id = sp.sid
    LEFT OUTER JOIN sys.dm_os_tasks ota ON es.session_id = ota.session_id
    LEFT OUTER JOIN sys.dm_os_threads oth ON ota.worker_address = oth.worker_address
    CROSS APPLY sys.dm_exec_sql_text(er.sql_handle) AS st
WHERE 
    es.is_user_process = 1 
    and 
    es.session_id <> @@spid
ORDER BY
     es.session_id