基于Service Broker的异步消息传递

核心提示：这里演示同一个SQL Server中不同数据库之间的基于Service Broker的异步消息传递，其中Stored Procedure充当Service Program，基于Service Broker的异步消息传递，HelloWorldDB为目标数据库，DotNetFun2则为消息发送发的数据库，可以通过如下SQL

这里演示同一个SQL Server中不同数据库之间的基于Service Broker的异步消息传递，其中Stored Procedure充当Service Program。HelloWorldDB为目标数据库，DotNetFun2则为消息发送发的数据库。

同时，假设Server Broker的基本对象类型已经创建，如MessageType(XMLMessage), Contract(XMLContract), Queue(SendingQueue and ReceivingQueue)等等，具体操作可以参考《A simple tutorial on SQL Server 2005 Beta 2 Service Broker》。另外，因为在不同的Databases之间进行消息传递，因此需要创建Route，具体操作可以参考《SQL Server 2005 Beta 2 Service Broker: Create Route》。

1.创建Stored Procedure作为Internal Service Program.

USE HelloWorldDB
GO
Alter Procedure HelloWorldResponder
As
Begin
Declare @conversationHandle UNIQUEIDENTIFIER
Declare @message_body nvarchar(MAX)
Declare @message_type_name SYSNAME
WHILE (1=1)
BEGIN
BEGIN TRANSACTION
-- Wait for 1 seconds for messages to arrive
WAITFOR (
-- For simplicity we process one message at a time
RECEIVE TOP(1)
@message_type_name=message_type_name,
@conversationHandle=conversation_handle,
@message_body=message_body
FROM [ReceivingQueue]), TIMEOUT 1000
-- If a message was received, process it, else skip
IF (@@rowcount <= 0)
BREAK;
-- If this is a XML message,
-- respond with an appropriate greeting
IF @message_type_name = 'XMLMessage'
BEGIN
SEND ON CONVERSATION @conversationHandle
MESSAGE TYPE XMLMessage
('<hello>Hello From Rickie</hello>')
END CONVERSATION @conversationHandle
END
COMMIT
END
COMMIT
END
GO

该Stored Procedure负责从ReceivingQueue中检索消息，并根据Queue的Retention设置，来确定从Queue中移除消息或更新Queue中消息的状态。

2.设置目标队列（Target Queue）的激活机制

Use HelloWorldDB
go
ALTER QUEUE [ReceivingQueue] WITH
ACTIVATION (
STATUS = ON, -- Turn on internal activation
PROCEDURE_NAME = [HelloWorldResponder], -- Our stored proc
MAX_QUEUE_READERS = 4, -- Up to 4 concurrent readers
EXECUTE AS SELF)　-- Execute as user of incoming dialog

设置上述创建的Stored Procedure，该Stored Procedure将被激活并处理Queue中的消息。

3.在Initiator端发送消息

Use DotNetFun2
go
DECLARE @conversationHandle uniqueidentifier
BEGIN TRANSACTION
-- Begin a dialog to the Hello World Service
BEGIN DIALOG　@conversationHandle
FROM SERVICE　　[SendingService]
TO SERVICE　　　'ReceivingService','a727462b-52e7-4405-9eee-d19923729790'
ON CONTRACT　　 [XMLContract]
WITH ENCRYPTION = OFF, LIFETIME = 600;
-- Send message
SEND ON CONVERSATION @conversationHandle
MESSAGE TYPE [XMLMessage]
('<hello>Welcome to Rickie Lee''s blog, www.cnblogs.com/rickie</hello>');
Select * From sys.conversation_endpoints
COMMIT

其中，TO SERVICE 'ReceivingService','a727462b-52e7-4405-9eee-d19923729790'，’ReceivingSerice’表示目标Service名称，'a727462b-52e7-4405-9eee-d19923729790'则指定目标Service所在的数据库，可以通过如下SQL Script获取：

-- Retrieve remote broker instance guid
SELECT service_broker_guid
FROM sys.databases
WHERE database_id = DB_ID('HelloWorldDB')

另外，可以通过如下的SQL script来检测Initiator端收到的Reply消息：

Select cast(message_body as XML) From SendingQueue
Receive message_type_name,
cast(message_body as XML)
From SendingQueue

4.查询对话端点状态（State of Conversation Endpoints）

最后，可以通过在Target/Initiator端查询sys.conversation_endpoints表，获取Dialog对话状态：

Select * From sys.conversation_endpoints