How Can I Efficiently Purge Stale SqlDependency Connections in SQL Server?

Managing SqlDependency Connections for Optimal SQL Server Performance

Inefficient management of SqlDependency objects in SQL Server can lead to memory leaks and performance bottlenecks. This article details strategies for effectively cleaning up these resources after event processing.

The Problem: Accumulating Resources

Using SqlDependency creates conversation groups and endpoints within the database. These resources accumulate over time, potentially exhausting memory, especially in SQL Server Express editions.

Database Cleanup Solution

The following SQL script identifies and removes inactive conversation endpoints, freeing up 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>

SqlDependency Limitations

The standard SqlDependency class has limitations:

• Inconsistent change detection: It doesn't reliably capture all table modifications.
• Persistent resources: Conversation groups and endpoints remain indefinitely, contributing to resource buildup.

A Superior Alternative: SqlDependencyEx

SqlDependencyEx, an open-source library, provides enhanced capabilities:

• Reliable change tracking: Uses database triggers and Service Broker for more accurate change detection.
• Example usage:

<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 changes.
    MakeTableInsertDeleteChanges(changesCount);

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

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

By employing the database cleanup procedure or migrating to SqlDependencyEx, you can effectively manage SqlDependency resources, preventing memory issues and optimizing SQL Server performance.

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