如何创建在镜像状态更改时运行作业/过程的事件通知

Question

我按照这个问题的顺序问这个问题我可以使用 T-SQL 通过 TCP 发送一个字符串吗？

Remus Rusanu 揭示了它似乎是我问题的最佳解决方案，但是......我太不成熟了，无法理解和理解他所说的一切。

到目前为止，我认为我需要为 DATABASE_MIRRORING_STATE_CHANGE 创建通知事件，我说得对吗？

我如何创建此事件通知，以使其触发时在表中插入一行，该行存储来自通知的时间戳和 ID。

到目前为止，我正在为每个 ID 设置一个警报，每个警报都运行这样的作业（此示例适用于 ID = 1）：

    DECLARE @state AS varchar(50);
    SELECT @state = mirroring_state_desc FROM SYS.database_mirroring WHERE mirroring_guid IS NOT NULL;
    IF (@state IS null) SET @state = ' ';
    INSERT INTO MirroringAlerts (DateTime, alertID, alertDesc, Sync, alertCreator) values (SYSDATETIME(), 1, 'Principal synchronized with W ', @state, @@SERVERNAME)

基本上我在这个数据库中创建一个内部日志：

CREATE TABLE [dbo].[MirroringAlerts](
    [DateTime] [datetime] NOT NULL,
    [alertID] [smallint] NOT NULL,
    [alertDesc] [nchar](50) NOT NULL,
    [Sync] [nchar](12) NOT NULL,
    [alertCreator] [nchar](128) NULL
) ON [PRIMARY]

但是这样……警报的触发速度不够快……所以我正在丢失信息……

你能告诉我如何通过为数据库镜像状态改变事件创建事件通知来编程这种行为吗？

此致

Answer 1

第 1 步：创建一个服务来接收通知和一个队列：

use msdb;
go

create queue dbm_notifications_queue;
create service dbm_notification_service
    on queue dbm_notifications_queue
    ([http://schemas.microsoft.com/SQL/Notifications/PostEventNotification]);
go

create event notification dbm_notifications
    on server   
    for database_mirroring_state_change
    to service N'dbm_notification_service', N'current database';
go

请注意，我正在使用msdb，这并非偶然。因为msdb如果您msdb也在msdb.

第二步：创建事件通知处理流程：

use msdb;
go

create table dbm_notifications_errors (
    incident_time datetime not null,
    session_id int not null,
    has_rolled_back bit not null,
    [error_number] int not null,
    [error_message] nvarchar(4000) not null,
    [message_body] varbinary(max));
create clustered index cdx_dbm_notifications_errors 
    on dbm_notifications_errors  (incident_time);
go

create table mirroring_alerts (
    alert_time datetime not null,
    start_time datetime not null,
    processing_time datetime not null,
    database_id smallint not null,
    database_name sysname not null,
    [state] tinyint not null,
    [text_data] nvarchar(max),
    event_data xml not null);
create clustered index cdx_mirroring_alerts
    on mirroring_alerts (alert_time);   
go      

create procedure dbm_notifications_procedure
as
begin
    declare @dh uniqueidentifier, @mt sysname, @raw_body varbinary(max), @xml_body xml; 
    
    begin transaction;
    begin try;
        receive top(1)
            @dh = conversation_handle,
            @mt = message_type_name,
            @raw_body = message_body
        from dbm_notifications_queue;
        if N'http://schemas.microsoft.com/SQL/Notifications/EventNotification' = @mt
        begin
            set @xml_body = cast(@raw_body as xml);
             -- shred the XML and process it accordingly
             -- IMPORTANT! IMPORTANT!
             -- DO NOT LOOK AT sys.database_mirroring
             -- The view represents the **CURRENT** state
             -- This message reffers to an **EVENT** that had occured
             -- the current state may or may no be relevant for this **PAST** event
            declare @alert_time datetime
                , @start_time datetime
                , @processing_time datetime = getutcdate()
                , @database_id smallint 
                , @database_name sysname
                , @state tinyint
                , @text_data nvarchar(max);
                
            set @alert_time = @xml_body.value (N'(//EVENT_INSTANCE/PostTime)[1]', 'DATETIME');
            set @start_time = @xml_body.value (N'(//EVENT_INSTANCE/StartTime)[1]', 'DATETIME');
            set @database_id = @xml_body.value (N'(//EVENT_INSTANCE/DatabaseID)[1]', 'SMALLINT');
            set @database_name = @xml_body.value (N'(//EVENT_INSTANCE/DatabaseName)[1]', 'SYSNAME');
            set @state = @xml_body.value (N'(//EVENT_INSTANCE/State)[1]', 'TINYINT');
            set @text_data = @xml_body.value (N'(//EVENT_INSTANCE/TextData)[1]', 'NVARCHAR(MAX)');
            
            insert into mirroring_alerts (
                alert_time, 
                start_time,
                processing_time,
                database_id,
                database_name,
                [state],
                text_data,
                event_data)
            values (
                @alert_time, 
                @start_time,
                @processing_time,
                @database_id,
                @database_name,
                @state,
                @text_data,
                @xml_body);
        end
        else if N'http://schemas.microsoft.com/SQL/ServiceBroker/Error' = @mt
        begin
        set @xml_body = cast(@raw_body as xml);
        DECLARE @error INT
                , @description NVARCHAR(4000);
        WITH XMLNAMESPACES ('http://schemas.microsoft.com/SQL/ServiceBroker/Error' AS ssb)
        SELECT @error = CAST(@xml_body AS XML).value('(//ssb:Error/ssb:Code)[1]', 'INT'),
            @description = CAST(@xml_body AS XML).value('(//ssb:Error/ssb:Description)[1]', 'NVARCHAR(4000)');          
        
        insert into dbm_notifications_errors(
            incident_time,
            session_id, 
            has_rolled_back,
            [error_number],
            [error_message],
            [message_body])
        values (
            getutcdate(),
            @@spid,
            0,
            @error,
            @description,
            @raw_body);
            end conversation @dh;
        end
        else if N'http://schemas.microsoft.com/SQL/ServiceBroker/EndDialog' = @mt
        begin
            end conversation @dh;
        end
        commit;
    end try
    begin catch
        declare @xact_state int = xact_state(), 
            @error_number int = error_number(), 
            @error_message nvarchar(4000) = error_message(),
            @has_rolled_back bit = 0;
        if @xact_state = -1
        begin
            -- Doomed transaction, it must rollback
            rollback;
            set @has_rolled_back = 1;
        end
        else if @xact_state = 0
        begin
            -- transaction was already rolled back (deadlock?)
            set @has_rolled_back = 1;
        end
        insert into dbm_notifications_errors(
            incident_time,
            session_id, 
            has_rolled_back,
            [error_number],
            [error_message],
            [message_body])
        values (
            getutcdate(),
            @@spid,
            @has_rolled_back,
            @error_number,
            @error_message,
            @raw_body);
        if (@has_rolled_back = 0)
        begin
            commit;
        end
    end catch
end
go

编写服务代理程序不是您的普通代码。一个人必须遵循一定的标准，很容易误入流沙领域。这段代码展示了一些好的做法：

• 将消息出队和处理包装在一个事务中。没脑子，一目了然。
• 始终检查收到的消息类型。一个好的服务代理程序必须通过结束对话来适当地处理Error和EndDialog消息。不这样做会导致句柄泄漏（sys.conversation_endpoints增长）
• 始终检查消息是否由 RECEIVE 出列。一些示例在 之后检查@@rowcount RECEIVE，这完全没问题。此示例代码依赖于消息名称检查（没有消息意味着 NULL 消息类型名称）并隐式处理这种情况。
• 创建处理错误表。SSB 激活过程的背景特性使得如果消息只是在没有跟踪的情况下消失，则很难对错误进行故障排除。

此外，这段代码还做了一些关于手头任务（监控 DBM）的良好实践代码：

• 区分post_time（通知何时发送？），start_time（触发通知的操作何时开始？）和processing_time（通知何时处理？）。post_time并且start_time可能完全相同或非常接近，但processing_time可能相差几秒、几小时、几天post_time。有趣的审计通常是post_time.
• 由于 thepost_time和 theprocessing_time不同，很明显，一个通知激活过程中的 DBM 监控任务没有sys.database_mirroring查看视图的业务。该视图将显示处理时的当前状态，这可能与事件有关，也可能无关。如果在事件发布后很长时间进行处理（认为维护停机时间），那么问题就很明显了，但是如果 DBM 非常快速地更改状态并在一个事件中发布两个（或更多）事件，它也可以在“健康”处理中进行处理行（经常发生）：在这种情况下，处理过程，就像您发布的代码一样，在事件发生时审核事件，但会记录当前的最终状态。以后阅读这样的审计可能会非常混乱。
• 始终审核原始 XML 事件。通过这种方式，您可以稍后在此 XML 中查询未“分解”到审计表中的列中的任何信息。

第 3 步：将过程附加到队列中：

alter queue dbm_notifications_queue
with activation (
    status=on,
    procedure_name = [dbm_notifications_procedure],
    max_queue_readers = 1,
    execute as  owner);

对涉及镜像的所有实例重复上述步骤可确保无论哪个实例是主体，您都会收到通知。

Answer 2

阅读第 6 章后，我不得不购买“Pro SQL Server 2008 Mirroring”，我发现这样做的步骤是：

检查是否启用了服务代理

SELECT CASE is_broker_enabled
WHEN 1 Then 'Enabled'
ELSE 'Disabled'
END
FROM sys.databases
WHERE name = 'DataBaseName'

如果没有，运行

ALTER DATABASE DataBaseName set ENABLE_BROKER;

创建我们希望在通知事件到达时触发的存储过程：

CREATE PROCEDURE dbo.dba_MirroringStateChanged
AS
DECLARE @Message XML,
        @DBName sysname,
        @MirrorStateChange INT,
        @ServerName sysname,
        @PostTime datetime,
        @SPID INT,
        @TextData NVARCHAR(500),
        @DatabaseID INT,
        @TransactionsID INT,
        @StartTime datetime;
SET NOCOUNT ON;
-- Receive first unread message in service broker queue
RECEIVE TOP (1)
@Message = CAST(message_body AS XML)
FROM DBMirrorQueue;

BEGIN TRY
    -- Parse state change and database affected
    -- 7 or 8 = database failing over,
    --11 = synchronizing,
    --1 or 2 = synchronized
    SET @MirrorStateChange =
    @Message.value('(/EVENT_INSTANCE/State)[1]', 'int');
    SET @DBName =
    @Message.value('(/EVENT_INSTANCE/DatabaseName)[1]', 'sysname');
    SET @ServerName =
    @Message.value('(/EVENT_INSTANCE/ServerName)[1]', 'sysname');
    SET @PostTime =
    @Message.value('(/EVENT_INSTANCE/PostTime)[1]', 'datetime');
    SET @SPID = @Message.value('(/EVENT_INSTANCE/SPID)[1]', 'int');
    SET @TextData =
    @Message.value('(/EVENT_INSTANCE/TextData)[1]', 'nvarchar(500)');
    SET @DatabaseID =
    @Message.value('(/EVENT_INSTANCE/DatabaseID)[1]', 'int');
    SET @TransactionsID =
    @Message.value('(/EVENT_INSTANCE/TransactionsID)[1]', 'int');
    SET @StartTime =
    @Message.value('(/EVENT_INSTANCE/StartTime)[1]', 'datetime');
END TRY
    BEGIN CATCH
        PRINT 'Parse of mirroring state change message failed.';
    END CATCH

IF (@MirrorStateChange IN (1,2,3,4,5,6,7,8,9,10,11,12,13))
BEGIN

    DECLARE @state AS varchar(50);
    SELECT @state = mirroring_state_desc FROM SYS.database_mirroring WHERE mirroring_guid IS NOT NULL;
    IF (@state IS null) SET @state = ' ';
    INSERT INTO MirroringAlerts (DateTime, alertID, alertDesc, Sync, alertCreator) values (SYSDATETIME(), @MirrorStateChange , @TextData , @state, @SERVERNAME);

END

创建一个队列，作为服务和我们要触发的存储过程之间的某种中间人

-- Create Queue if not exists
IF NOT EXISTS (SELECT 1
    FROM sys.service_queues
    WHERE name = 'DBMirrorQueue')
BEGIN
    CREATE QUEUE DBMirrorQueue
    WITH ACTIVATION (
    PROCEDURE_NAME = dbo.dba_MirroringStateChanged,
    MAX_QUEUE_READERS = 1,
    EXECUTE AS OWNER);
END

创建将与事件关联的服务

-- Create Service if not exists
IF NOT EXISTS (SELECT 1
    FROM sys.services
    WHERE name = 'DBMirrorService')
BEGIN
    CREATE SERVICE DBMirrorService
    ON QUEUE DBMirrorQueue ([http://schemas.microsoft.com/SQL/Notifications/PostEventNotification]);
END

创建路线

-- Create Route if not exists
IF NOT EXISTS (SELECT 1
    FROM sys.routes
    WHERE name = 'DBMirrorRoute')
BEGIN
    CREATE ROUTE DBMirrorRoute
    WITH SERVICE_NAME = 'DBMirrorService',
    ADDRESS = 'Local';
END

然后创建事件通知

-- Create Event Notification if not exists
IF NOT EXISTS (SELECT 1
    FROM sys.server_event_notifications
    WHERE name = 'DBMirrorStateChange')
BEGIN
    CREATE EVENT NOTIFICATION DBMirrorStateChange
    ON SERVER
    FOR DATABASE_MIRRORING_STATE_CHANGE
    TO SERVICE 'DBMirrorService', 'current database';
END