How Can I Efficiently Manage SqlDependency Objects to Avoid Memory Leaks in SQL Server?

Optimizing SqlDependency Object Management in SQL Server to Prevent Memory Leaks

Question: How can I effectively manage SqlDependency objects to prevent memory exhaustion in SQL Server?

Answer:

Microsoft's SqlDependency implementation exhibits a behavior that can lead to significant memory consumption: even after calling SqlDependency.Stop(), releasing the SqlCommand and SqlConnection, the database retains conversation groups (sys.conversation_groups) and endpoints (sys.conversation_endpoints). SQL Server appears to load all endpoints, potentially causing memory issues.

To resolve this, execute the following SQL script on your database:

<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>

Additionally, SqlDependency has limitations in reliably capturing all table changes, especially during resubscription.

Recommended Alternative: SqlDependencyEx

A superior alternative is the open-source SqlDependencyEx class. It uses database triggers and Service Broker notifications for more robust change tracking. Here's an example:

<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 detection
    Thread.Sleep(1000);
}

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

SqlDependencyEx offers improved reliability, efficiency, and memory management compared to the standard SqlDependency, ensuring accurate change tracking and preventing memory problems.

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