How to Clean Up Expired SqlDependency Objects in SQL Server to Prevent Memory Leaks?

Addressing Expired SqlDependency Objects in SQL Server to Avoid Memory Leaks

The Issue:

SQL Server's SqlDependency objects persist in memory even after expiration, leading to escalating memory usage and potential server crashes. This article outlines how to proactively remove these lingering queries.

Resolution:

Even after employing SqlDependency.Stop(), remnants—conversation groups and endpoints—remain within the database. To rectify this, execute the following SQL script:

<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 Shortcomings:

A key limitation of SqlDependency is its incomplete notification coverage for all table modifications during resubscription.

A Superior Alternative: SqlDependencyEx

The open-source SqlDependencyEx library leverages database triggers and Service Broker notifications to overcome SqlDependency's shortcomings. Here's an illustrative usage 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 modifications.
    MakeTableInsertDeleteChanges(changesCount);

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

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

Employing SqlDependencyEx offers a more robust solution for tracking table changes while preventing the memory-related problems inherent in the standard SqlDependency class.

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