Monthly Archives: May 2012

SQL Server 2012 – What’s new in Service Broker?

Service Broker has come a long way since its’  introduction in Microsoft SQL Server 2005. SQL Server 2008 brought a host of Service Broker enhancements like conversation priorities, the ssbdiagnose utility, alternate poison message handling and new performance objects & counters. SQL Server 2012 is a major release that comes with an astonishing  array of enhancements and new features, including  new bells & whistles for Service Broker.

A significant new feature for Service Broker is the ability to Multicast messages. This enables a single initiator service to send messages to multiple target services, akin to SQL Server Replication, where multiple subscribers can subscribe to the same publication. The syntax of the send command has been extended to enable multicasting , by allowing multiple conversation handles.

DECLARE @cvh1 UNIQUEIDENTIFIER,
 @cvh2 UNIQUEIDENTIFIER,
 @cvh3 UNIQUEIDENTIFIER,
 @TestMsgBody XML ;

SET @TestMsgBody = '<test>Test Message</test>' ;

BEGIN DIALOG @cvh1
FROM SERVICE [//InitiatorService]
TO SERVICE '//TargetService1'
ON CONTRACT [//TestProcessing] ;

BEGIN DIALOG @cvh2
FROM SERVICE [//InitiatorService]
TO SERVICE '//TargetService2'
ON CONTRACT [//TestProcessing] ;

BEGIN DIALOG @cvh3
FROM SERVICE [//InitiatorService]
TO SERVICE '//TargetService3'
ON CONTRACT [//TestProcessing] ;

SEND ON CONVERSATION (@cvh1, @cvh2, @cvh3)
 MESSAGE TYPE [//TestMgsType]
 (@TestMsgBody) ;

Another new feature is the addition of a new column - message_enqueue_time – to the Queues. This column helps us determine the time spent by a message on the queue.  The message_enqueue_time column is of datetimeoffset data type and stores the date and time (with time zone awareness) when the message arrives on the queue. Its’ exposed to the application via a direct query on the Queue itself, as well as a column in the Receive statement. Let’s look at an example;

-- Begin dialog & send message
DECLARE @ch UNIQUEIDENTIFIER;

BEGIN DIALOG CONVERSATION @ch
 FROM SERVICE [manual_activation_initiator_service]
 TO SERVICE 'manual_activation_target_service'
 ON CONTRACT [manual_activation_contract]
 WITH ENCRYPTION = OFF ;

SEND ON CONVERSATION @ch
 MESSAGE TYPE [manual_activation_demo_request]
 ('<test>test_message_body</test>');
GO

-- A Direct Select statament from the Queue
SELECT
 conversation_handle
 ,CAST ( message_body AS XML) AS [msg_body]
 ,DATEDIFF(second,message_enqueue_time,getutcdate()) AS [time_in_queue(Seconds)]
FROM [manual_activation_target_queue];

-- Results
conversation_handle                  msg_body                        time_in_queue(Seconds)
------------------------------------ ------------------------------- ----------------------
C0CB3200-809F-E111-8B29-005056BE0088 <test>test_message_body</test>  21

(1 row(s) affected)

-- Retrieve the message off of the Queue with a Receive
WAITFOR (
 RECEIVE TOP(1)
 conversation_handle
 ,CAST(message_body AS XML) AS [msg_body]
 ,DATEDIFF(second,message_enqueue_time,getutcdate()) AS [time_in_queue(Seconds)]
FROM manual_activation_target_queue),
TIMEOUT 5;

-- Results
conversation_handle                  msg_body                        time_in_queue(Seconds)
------------------------------------ ------------------------------- ----------------------
C0CB3200-809F-E111-8B29-005056BE0088 <test>test_message_body</test>  21

(1 row(s) affected)

Please note that this column is not well documented yet and to derive the time spent by a message on the queue  in seconds, one must use a few date & time functions.   

 Service Broker Remote Messaging needs some additional configuration in order to get along with the Always On Availability Groups, due to the complexity added by the Listener for an Availability group. The Always On Availability Groups feature  introduced in SQL Server 2012,  is a high availability and disaster recovery solution that provides an enterprise level alternative to database mirroring.

For a Service in an Availability Group to be able to Receive remote messages;

  • The Availability Group must have a listener configured
  • Service Broker Endpoint must be created and configured with the Listener, for every instance of SQL Server in the Availability Group
  • Connect permissions must be granted on the endpoints to the the appropriate login(s)
  • msdb must contain a route

For a Service in an Availability Group to be able to Send messages to a remote service;

  • Configure a route to the target service using the listener
  • msdb must contain a route

And last but not the least, its always worth mentioning that since SQL Server 2008 R2, Poison message handling can be disabled at the time of queue creation or at a later time by using the alter queue statement. You can also check the status of poison message handling for each queue, by querying the sys.service_queues catalog view, which has the column, is_poison_message_handling_enabled to indicate whether poison message is enabled or disabled.

Advanced T-SQL with Itzik Ben-Gan

I recently had the privilege of learning Advanced T-SQL  with Itzik Ben-Gan (Blog|Twitter), a mentor and one of the founders of SolidQ. This 2 day Advanced T-SQL course spanned across a range of interesting topics that a Database Developer would find extremely valuable on a day to day basis ! Not only does Itzik deliver a remarkable lecture, but also encourages questions and discussions, which adds a great deal of value to the learning experience. Some of the topics we covered in detail are;

  • SQL Server Internals & Index Tuning – This was my very first deep dive into SQL Server Internals pertinent to Indexes. The multitude of Index access methods that the Optimizer can choose from, and their impact on Query performance has opened a whole new world of indexing strategies for me. Filtered Indexes and Columnstore Indexes some of the newer features I am looking forward to try out.
  • Temporary Tables – Never before has the distinction between Temporary tables, Table variables and Common Table Expressions (CTEs) been presented with so much clarity  and lucidity. I now have a solid understanding of which to use in any given scenario.
  • Sets vs Cursors – Again, a classic topic. Never hurts to reinforce the advantages of a Set based solution versus cursors.
  • Query Tuning has never been so interesting with a real life example of dramatic performance gains between various revisions of the same query.
  • Apply – I cannot believe I had used the apply operator only for XML Queries so for. I have now learned its uses for unpivoting, aggregating and reusing column aliases.
  • Grouping Sets – I had learned this one while studying for my MCTS certification, but had never got around to making much use of it. This gave me the chance to understand its full potential and applicability.
  • Sequences – I had done some research on this topic before to my blog post about the same, but I found out soon that  there is still so much more to it, especially when comparing it with Identity.
  • The enhancements to Window Functions and the world of Partitioning, Ordering and Framing offers a whole new paradigm for OLAP Queries used in Reporting.

Over the next few weeks, I intend to take the time to absorb all the new concepts and ideas I learned in this 2 day course, and find areas to implement these ideas.

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