In SQL Server Service Broker, the BEGIN CONVERSATION TIMER statement is used to start a timer for a conversation. This timer can be valuable for scenarios where you want to manage message processing, including implementing timeouts for message processing or automatic cleanup of inactive conversations.
Syntax
The syntax for the BEGIN CONVERSATION TIMER statement is as follows:
BEGIN CONVERSATION TIMER
[ conversation_handle ]
[ FOR timeout_value ]
Parameters
- conversation_handle: This is a unique identifier for the conversation that you want to start the timer for. The conversation handle is usually produced when starting a new conversation using the BEGIN DIALOG statement.
- timeout_value: This specifies the duration for which the timer should run. It is specified in seconds.
Example Usage
Here is a simple example of how you can use the BEGIN CONVERSATION TIMER statement in a SQL Server Service Broker context:
1. Start a Conversation:
First, you start a conversation using the BEGIN DIALOG statement.
DECLARE @conversation_handle UNIQUEIDENTIFIER;
BEGIN DIALOG CONVERSATION @conversation_handle
FROM SERVICE [SenderService]
TO SERVICE 'ReceiverService'
ON CONTRACT [YourContract]
WITH ENCRYPTION = OFF;
2. Begin Conversation Timer:
After starting the conversation, you can begin a timer for that conversation with a specified timeout duration.
BEGIN CONVERSATION TIMER @conversation_handle FOR 300; -- 300 seconds or 5 minutes
Purpose of Using Timer
The primary purpose of using the BEGIN CONVERSATION TIMER is to specify a timeout period for the conversation. If the timer expires and there are no further messages sent or received on that conversation, the conversation will be automatically ended by SQL Server. This helps in cleaning up resources and managing idle or abandoned conversations effectively.
Managing the Timer
1. Ending the Timer: If you complete processing for that conversation before the timer expires, you can use END CONVERSATION to clean it up:
END CONVERSATION @conversation_handle;
2. Handling Timeout: If the timer expires, you may want to implement logic to handle what should happen next, such as logging the timeout or alerting an administrator.
Note: The timer will only start after the BEGIN CONVERSATION TIMER statement is executed, and it is specific to that conversation handle. Each handle can have its timer.
Conclusion
Using BEGIN CONVERSATION TIMER in Service Broker allows you to manage message flows effectively and ensure that your application can handle situations where messages are not processed in a timely manner.