Question

我们正在构建自己的自定义消息传递系统，并且存在并发问题。以下是规则：

进程（EXE）控制台应用程序锁定3条记录并将其返回
没有其他进程正在运行（我们有5个EXE正在运行）可以选择其他进程已经采取的任何记录。

那很简单，但是，我很困惑。

SQL SPROC执行＆＃34; Lock And Peek＆＃34;：

这背后的想法是我们保留三个＆＃34; NEW＆＃34;记录并将其状态更改为＆＃34; IN PROGRESS＆＃34;在SELECT和UPDATE语句中使用ROWLOCK。因此理论上，这些记录应该锁定一个过程，以便其他过程不能更新甚至选择它们。有人可以告诉我，我做错了吗？

ALTER PROCEDURE [dbo].[LockAndPeek] 
    @Count INT,
    @QueueTypeId INT
AS
BEGIN
    SET NOCOUNT ON;

    DECLARE @ListofIDs TABLE(ID INT);
    DECLARE @StatusIDInProgress INT

    SELECT @StatusIDInProgress = ID FROM QueueStatuses (NOLOCK)
    WHERE Name = 'In Progress'

    INSERT INTO @ListofIDs
    (ID)
    SELECT TOP (@Count) Q.ID 
    FROM
        Queues Q (ROWLOCK) INNER JOIN
        QueueStatuses QS (ROWLOCK) ON Q.StatusID = QS.ID
    WHERE
        QS.Name IN ('New', 'Errored') AND
        Q.TypeID = @QueueTypeID AND
        Q.AvailableTime IS NOT NULL AND
        Q.AvailableTime <= GETUTCDATE()
    ORDER BY Q.ID

    UPDATE Q WITH (ROWLOCK)
    SET 
        STATUSID = @StatusIDInProgress,
        PROCESSED = GETUTCDATE()
    FROM
        Queues Q (ROWLOCK) INNER JOIN
        QueueStatuses QS (ROWLOCK) ON Q.StatusID = QS.ID INNER JOIN
        @ListofIDs LI ON Q.ID = LI.ID
    WHERE
        QS.Name IN ('New', 'Errored')

    SELECT  Q.ID, 
            Q.AvailableTime,
            Q.NumberOfTries,
            Q.Created,
            Q.Processed,
            Q.ErrorData,
            QT.ID QueueTypeID,
            QT.Name QueueTypeName,
            QS.ID QueueStatusID,
            QS.Name QueueStatusName,
            Q.Message
    FROM 
        Queues Q (NOLOCK) INNER JOIN
        QueueStatuses QS (NOLOCK) ON Q.StatusID = QS.ID INNER JOIN
        QueueTypes QT (NOLOCK) ON Q.TypeId = QT.ID INNER JOIN
        @ListofIDs LI ON Q.ID = LI.ID

END

Answer 1

发现它！ @MaxVernon的大热门！

http://rusanu.com/2010/03/26/using-tables-as-queues/基本上是@MaxVernon作为评论发布的变体。我的查询看起来像这样，比以前简单得多：

ALTER PROCEDURE [dbo].[LockAndPeek] 
    @Count INT,
    @QueueTypeId INT
AS
BEGIN

SET XACT_ABORT ON; -- blow up the whole tran on any errors
SET TRANSACTION ISOLATION LEVEL READ COMMITTED;
BEGIN TRAN

UPDATE Q
SET 
    StatusID = 2, -- In Progress
    Processed = GETUTCDATE()
OUTPUT Inserted.*
FROM (
    SELECT TOP (@Count) * 
    FROM
        Queues WITH (READPAST, ROWLOCK)
    WHERE
        StatusID = 1 AND -- New 
        TypeID = @QueueTypeID AND
        AvailableTime IS NOT NULL AND
        AvailableTime <= GETUTCDATE()
   ORDER BY ID
) Q;

COMMIT TRAN;

END

尝试锁定自定义消息传递系统（队列）中的记录时遇到并发问题

1 个答案: