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WIP: Fix connection pool concurrency issue #3632

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1c671db
Fix connection pool concurrency issue caused due to waiting on multip…
cheenamalhotra Sep 23, 2025
4e9ffea
Address feedback, manage semaphore with a semaphoreHolder
cheenamalhotra Oct 1, 2025
48f797f
Add tests
cheenamalhotra Oct 2, 2025
baf7d3d
Update sln
cheenamalhotra Oct 2, 2025
e2cc20f
Test formatting
cheenamalhotra Oct 2, 2025
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78 changes: 78 additions & 0 deletions src/Microsoft.Data.SqlClient.sln
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -303,6 +303,18 @@ Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Microsoft.Data.SqlClient.Un
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "Common", "Microsoft.Data.SqlClient\tests\Common\Common.csproj", "{67128EC0-30F5-6A98-448B-55F88A1DE707}"
EndProject
Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "Stress", "Stress", "{02EA681E-C7D8-13C7-8484-4AC65E1B71E8}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "IMonitorLoader", "Microsoft.Data.SqlClient\tests\StressTests\IMonitorLoader\IMonitorLoader.csproj", "{1A29B520-D16A-35F2-5CAC-64573C86E63D}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SqlClient.Stress.Common", "Microsoft.Data.SqlClient\tests\StressTests\SqlClient.Stress.Common\SqlClient.Stress.Common.csproj", "{2AA12D54-540B-E515-CB82-80D691C9DCF1}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SqlClient.Stress.Framework", "Microsoft.Data.SqlClient\tests\StressTests\SqlClient.Stress.Framework\SqlClient.Stress.Framework.csproj", "{92D9C6D6-6925-1AD1-69FA-485F83943BD2}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SqlClient.Stress.Runner", "Microsoft.Data.SqlClient\tests\StressTests\SqlClient.Stress.Runner\SqlClient.Stress.Runner.csproj", "{4A9C11F4-9577-ABEC-C070-83A194746D9B}"
EndProject
Project("{FAE04EC0-301F-11D3-BF4B-00C04F79EFBC}") = "SqlClient.Stress.Tests", "Microsoft.Data.SqlClient\tests\StressTests\SqlClient.Stress.Tests\SqlClient.Stress.Tests.csproj", "{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}"
EndProject
Global
GlobalSection(SolutionConfigurationPlatforms) = preSolution
Debug|Any CPU = Debug|Any CPU
Expand Down Expand Up @@ -571,6 +583,66 @@ Global
{67128EC0-30F5-6A98-448B-55F88A1DE707}.Release|x64.Build.0 = Release|x64
{67128EC0-30F5-6A98-448B-55F88A1DE707}.Release|x86.ActiveCfg = Release|x86
{67128EC0-30F5-6A98-448B-55F88A1DE707}.Release|x86.Build.0 = Release|x86
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|Any CPU.Build.0 = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|x64.ActiveCfg = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|x64.Build.0 = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|x86.ActiveCfg = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Debug|x86.Build.0 = Debug|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|Any CPU.ActiveCfg = Release|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|Any CPU.Build.0 = Release|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|x64.ActiveCfg = Release|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|x64.Build.0 = Release|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|x86.ActiveCfg = Release|Any CPU
{1A29B520-D16A-35F2-5CAC-64573C86E63D}.Release|x86.Build.0 = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|Any CPU.Build.0 = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|x64.ActiveCfg = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|x64.Build.0 = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|x86.ActiveCfg = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Debug|x86.Build.0 = Debug|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|Any CPU.ActiveCfg = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|Any CPU.Build.0 = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|x64.ActiveCfg = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|x64.Build.0 = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|x86.ActiveCfg = Release|Any CPU
{2AA12D54-540B-E515-CB82-80D691C9DCF1}.Release|x86.Build.0 = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|Any CPU.Build.0 = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|x64.ActiveCfg = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|x64.Build.0 = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|x86.ActiveCfg = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Debug|x86.Build.0 = Debug|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|Any CPU.ActiveCfg = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|Any CPU.Build.0 = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|x64.ActiveCfg = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|x64.Build.0 = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|x86.ActiveCfg = Release|Any CPU
{92D9C6D6-6925-1AD1-69FA-485F83943BD2}.Release|x86.Build.0 = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|Any CPU.Build.0 = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|x64.ActiveCfg = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|x64.Build.0 = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|x86.ActiveCfg = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Debug|x86.Build.0 = Debug|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|Any CPU.ActiveCfg = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|Any CPU.Build.0 = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|x64.ActiveCfg = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|x64.Build.0 = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|x86.ActiveCfg = Release|Any CPU
{4A9C11F4-9577-ABEC-C070-83A194746D9B}.Release|x86.Build.0 = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|Any CPU.Build.0 = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|x64.ActiveCfg = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|x64.Build.0 = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|x86.ActiveCfg = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Debug|x86.Build.0 = Debug|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|Any CPU.ActiveCfg = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|Any CPU.Build.0 = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|x64.ActiveCfg = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|x64.Build.0 = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|x86.ActiveCfg = Release|Any CPU
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C}.Release|x86.Build.0 = Release|Any CPU
EndGlobalSection
GlobalSection(SolutionProperties) = preSolution
HideSolutionNode = FALSE
Expand Down Expand Up @@ -621,6 +693,12 @@ Global
{AD738BD4-6A02-4B88-8F93-FBBBA49A74C8} = {4CAE9195-4F1A-4D48-854C-1C9FBC512C66}
{4461063D-2F2B-274C-7E6F-F235119D258E} = {0CC4817A-12F3-4357-912C-09315FAAD008}
{67128EC0-30F5-6A98-448B-55F88A1DE707} = {0CC4817A-12F3-4357-912C-09315FAAD008}
{02EA681E-C7D8-13C7-8484-4AC65E1B71E8} = {0CC4817A-12F3-4357-912C-09315FAAD008}
{1A29B520-D16A-35F2-5CAC-64573C86E63D} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
{2AA12D54-540B-E515-CB82-80D691C9DCF1} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
{92D9C6D6-6925-1AD1-69FA-485F83943BD2} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
{4A9C11F4-9577-ABEC-C070-83A194746D9B} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
{FAA1E517-581A-D3DC-BAC9-FAD1D5A5142C} = {02EA681E-C7D8-13C7-8484-4AC65E1B71E8}
EndGlobalSection
GlobalSection(ExtensibilityGlobals) = postSolution
SolutionGuid = {01D48116-37A2-4D33-B9EC-94793C702431}
Expand Down
73 changes: 44 additions & 29 deletions ....Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/WaitHandleDbConnectionPool.cs
View file
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Original file line number Diff line number Diff line change
Expand Up @@ -383,6 +383,41 @@ internal WaitHandle[] GetHandles(bool withCreate)
}
}

/// <summary>
/// Helper class to obtain and release a semaphore.
/// </summary>
internal class SemaphoreHolder : IDisposable
{
private readonly Semaphore _semaphore;

/// <summary>
/// Whether the semaphore was successfully obtained within the timeout.
/// </summary>
internal bool Obtained { get; private set; }

/// <summary>
/// Obtains the semaphore, waiting up to the specified timeout.
/// </summary>
/// <param name="semaphore"></param>
/// <param name="timeout"></param>
internal SemaphoreHolder(Semaphore semaphore, int timeout)
{
_semaphore = semaphore;
Obtained = _semaphore.WaitOne(timeout);
}

/// <summary>
/// Releases the semaphore if it was successfully obtained.
/// </summary>
public void Dispose()
{
if (Obtained)
{
_semaphore.Release(1);
}
}
}

private const int MAX_Q_SIZE = 0x00100000;

// The order of these is important; we want the WaitAny call to be signaled
Expand Down Expand Up @@ -1271,17 +1306,11 @@ private bool TryGetConnection(DbConnection owningObject, uint waitForMultipleObj

if (onlyOneCheckConnection)
{
if (_waitHandles.CreationSemaphore.WaitOne(unchecked((int)waitForMultipleObjectsTimeout)))
using SemaphoreHolder semaphoreHolder = new(_waitHandles.CreationSemaphore, unchecked((int)waitForMultipleObjectsTimeout));
if (semaphoreHolder.Obtained)
{
try
{
SqlClientEventSource.Log.TryPoolerTraceEvent("<prov.DbConnectionPool.GetConnection|RES|CPOOL> {0}, Creating new connection.", Id);
obj = UserCreateRequest(owningObject, userOptions);
}
finally
{
_waitHandles.CreationSemaphore.Release(1);
}
SqlClientEventSource.Log.TryPoolerTraceEvent("<prov.DbConnectionPool.GetConnection|RES|CPOOL> {0}, Creating new connection.", Id);
obj = UserCreateRequest(owningObject, userOptions);
}
else
{
Expand Down Expand Up @@ -1500,14 +1529,13 @@ private void PoolCreateRequest(object state)
{
return;
}
int waitResult = BOGUS_HANDLE;


try
{
// Obtain creation mutex so we're the only one creating objects
// and we must have the wait result
waitResult = WaitHandle.WaitAny(_waitHandles.GetHandles(withCreate: true), CreationTimeout);
if (CREATION_HANDLE == waitResult)
using SemaphoreHolder semaphoreHolder = new(_waitHandles.CreationSemaphore, CreationTimeout);

if (semaphoreHolder.Obtained)
{
DbConnectionInternal newObj;

Expand Down Expand Up @@ -1542,17 +1570,12 @@ private void PoolCreateRequest(object state)
}
}
}
else if (WaitHandle.WaitTimeout == waitResult)
else
{
// do not wait forever and potential block this worker thread
// instead wait for a period of time and just requeue to try again
QueuePoolCreateRequest();
}
else
{
// trace waitResult and ignore the failure
SqlClientEventSource.Log.TryPoolerTraceEvent("<prov.DbConnectionPool.PoolCreateRequest|RES|CPOOL> {0}, PoolCreateRequest called WaitForSingleObject failed {1}", Id, waitResult);
}
}
catch (Exception e)
{
Expand All @@ -1566,14 +1589,6 @@ private void PoolCreateRequest(object state)
// thrown to the user the next time they request a connection.
SqlClientEventSource.Log.TryPoolerTraceEvent("<prov.DbConnectionPool.PoolCreateRequest|RES|CPOOL> {0}, PoolCreateRequest called CreateConnection which threw an exception: {1}", Id, e);
}
finally
{
if (CREATION_HANDLE == waitResult)
{
// reuse waitResult and ignore its value
_waitHandles.CreationSemaphore.Release(1);
}
}
}
}
}
Expand Down
1 change: 1 addition & 0 deletions ...soft.Data.SqlClient/tests/ManualTests/Microsoft.Data.SqlClient.ManualTesting.Tests.csproj
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Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,7 @@
<None Include="SQL\ParameterTest\SqlParameterTest_ReleaseMode_Azure.bsl" />
</ItemGroup>
<ItemGroup Condition="'$(TestSet)' == '' OR '$(TestSet)' == '3'">
<Compile Include="SQL\ConnectionPoolTest\ConnectionPoolStressTest.cs" />
<Compile Include="TracingTests\MetricsTest.cs" />
<Compile Include="TracingTests\DiagnosticTest.cs" />
<Compile Include="TracingTests\FakeDiagnosticListenerObserver.cs" />
Expand Down
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