How to Clean Up Expired SqlDependency Objects from SQL Server Memory?

Addressing Memory Leaks Caused by SqlDependency Objects in SQL Server

SqlDependency objects, crucial for monitoring SQL Server data changes, can accumulate in memory, negatively impacting server performance. This article details how to effectively remove these expired objects.

Understanding the Issue

When a SqlDependency object triggers an event, a new object is needed for continued monitoring. The old object, however, remains in memory, potentially leading to resource exhaustion.

Memory Cleanup Procedure

The following SQL script identifies and terminates inactive conversation endpoints, freeing up the consumed memory:

<code class="language-sql">DECLARE @ConvHandle uniqueidentifier
DECLARE Conv CURSOR FOR
SELECT CEP.conversation_handle FROM sys.conversation_endpoints CEP
WHERE CEP.state = 'DI' or CEP.state = 'CD'
OPEN Conv;
FETCH NEXT FROM Conv INTO @ConvHandle;
WHILE (@@FETCH_STATUS = 0) BEGIN
    END CONVERSATION @ConvHandle WITH CLEANUP;
    FETCH NEXT FROM Conv INTO @ConvHandle;
END
CLOSE Conv;
DEALLOCATE Conv;</code>

This script targets conversation endpoints in a disconnected or cancelled state.

An Alternative Approach: SqlDependencyEx

For improved functionality and to avoid potential problems inherent in the standard SqlDependency class, consider using SqlDependencyEx, an open-source alternative. This solution leverages database triggers and native Service Broker notifications.

Illustrative Example using SqlDependencyEx

Here's a code example demonstrating SqlDependencyEx:

<code class="language-csharp">int changesReceived = 0;
using (SqlDependencyEx sqlDependency = new SqlDependencyEx(
          TEST_CONNECTION_STRING, TEST_DATABASE_NAME, TEST_TABLE_NAME)) 
{
    sqlDependency.TableChanged += (o, e) => changesReceived++;
    sqlDependency.Start();

    // Simulate table modifications.
    MakeTableInsertDeleteChanges(changesCount);

    // Allow time for change detection.
    Thread.Sleep(1000);
}

Assert.AreEqual(changesCount, changesReceived);</code>

This showcases real-time change notification using SqlDependencyEx.

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