Get/Return pooled connections (#3404)

* Add get flow and basic tests.

* Add tests. Clean up diff.

* Add additional tests. Refactor to test error behavior.

* Implement return flow and add return/reuse tests.

* Clean up comments and todos.

* Add test cases.

* Enable init property accessor in netfx.

* Switch to auto properties.

* Reorder class members.

* Address review comments.

* Fix channels package resolution.

* Review changes.

* Set CreateTime in constructor. This makes sense becuase CreateTime cannot be modified and should be set regardless of pooling status.

* Naming

* Fix potential connection leak when setting TaskCompletionSource result.

* Fix package reference for central package management.

* Fix formatting. Refactor get connection loop.

* Move concurrent data structures out to dedicated class.

* Refactor data structure to remove generics, revert to previous logic.

* Cleanup

* Fix timeout exception handling for async path.

* Review comments. Fix merge conflict.

* Change object reference to full type. Fix tab.

* cleanup

* Add link to github issue for async pathways.

* Remove side effects from IsLiveConnection. Fix exception handling and connection disposal when opening new connection.

* Minor review feedback. Make tests more reliable.

* Fix compilation

* Make reservation disposable.

* Fix tests

* Make async request order test more reliable.

* Avoid confusing double reservation release. Use params in callbacks to avoid closures.

* Doc comment cleanup. Add unit tests for ConnectionPoolSlots.

* Fix up tests

* Clean up unit test proj file.

* Make disposal safer. Clean up exception documentation.

* Improve tests.

* Clean up wrapped exceptions. Fix param nullability.

* Clean up tests based on new editorconfig settings.

* Review changes.

* Fix tests to expect unwrapped exception.

Author: mdaigle

src/Directory.Packages.props

@@ -100,6 +100,7 @@
     <PackageVersion Include="System.Memory" Version="4.6.3" />
     <PackageVersion Include="System.Text.Encodings.Web" Version="8.0.0" />
     <PackageVersion Include="System.ValueTuple" Version="4.6.1" />
+    <PackageVersion Include="System.Threading.Channels" Version="8.0.0" />
   </ItemGroup>
 
   <!-- =================================================================== -->

src/Microsoft.Data.SqlClient/netcore/ref/Microsoft.Data.SqlClient.csproj

@@ -46,6 +46,11 @@
     <!-- Transitive dependencies that would otherwise bring in older, vulnerable versions. -->
     <PackageReference Include="System.Text.Json" />
   </ItemGroup>
+
+  <!-- netstandard dependencies -->
+  <ItemGroup Condition="'$(TargetGroup)' != 'netcoreapp'">
+    <PackageReference Include="System.Threading.Channels" />
+  </ItemGroup>
 
   <Import Project="$(ToolsDir)targets\ResolveContract.targets" Condition="'$(OSGroup)' == 'AnyOS' AND '$(TargetGroup)' != 'netcoreapp'" />
   <Import Project="$(ToolsDir)targets\NotSupported.targets" Condition="'$(OSGroup)' == 'AnyOS' AND '$(TargetGroup)' != 'netcoreapp'" />

src/Microsoft.Data.SqlClient/netcore/src/Microsoft.Data.SqlClient.csproj

@@ -108,6 +108,9 @@
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\ChannelDbConnectionPool.cs">
       <Link>Microsoft\Data\SqlClient\ConnectionPool\ChannelDbConnectionPool.cs</Link>
     </Compile>
+    <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\ConnectionPoolSlots.cs">
+      <Link>Microsoft\Data\SqlClient\ConnectionPool\ConnectionPoolSlots.cs</Link>
+    </Compile>
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\DbConnectionPoolAuthenticationContext.cs">
       <Link>Microsoft\Data\SqlClient\ConnectionPool\DbConnectionPoolAuthenticationContext.cs</Link>
     </Compile>

src/Microsoft.Data.SqlClient/netfx/ref/Microsoft.Data.SqlClient.csproj

@@ -48,6 +48,7 @@
     <PackageReference Include="System.Security.Cryptography.Pkcs" />
     <PackageReference Include="System.Text.Encodings.Web" />
     <PackageReference Include="System.Text.Json" />
+    <PackageReference Include="System.Threading.Channels" />
   </ItemGroup>
   <Import Project="$(ToolsDir)targets\TrimDocsForIntelliSense.targets" />
 </Project>

src/Microsoft.Data.SqlClient/netfx/src/Microsoft.Data.SqlClient.csproj

@@ -300,6 +300,9 @@
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\ChannelDbConnectionPool.cs">
       <Link>Microsoft\Data\SqlClient\ConnectionPool\ChannelDbConnectionPool.cs</Link>
     </Compile>
+    <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\ConnectionPoolSlots.cs">
+      <Link>Microsoft\Data\SqlClient\ConnectionPool\ConnectionPoolSlots.cs</Link>
+    </Compile>
     <Compile Include="$(CommonSourceRoot)Microsoft\Data\SqlClient\ConnectionPool\DbConnectionPoolAuthenticationContext.cs">
       <Link>Microsoft\Data\SqlClient\ConnectionPool\DbConnectionPoolAuthenticationContext.cs</Link>
     </Compile>
@@ -1058,6 +1061,7 @@
     <PackageReference Include="System.Text.Encodings.Web" />
     <PackageReference Include="System.Text.Json" />
     <PackageReference Include="System.ValueTuple" />
+    <PackageReference Include="System.Threading.Channels" />
   </ItemGroup>
   <Import Project="$(CommonSourceRoot)tools\targets\GenerateResourceStringsSource.targets" />
   <Import Project="$(NetFxSource)tools\targets\GenerateThisAssemblyCs.targets" />

src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj

@@ -26,5 +26,6 @@
     <Reference Include="System.Transactions" />
     <PackageReference Include="System.Data.Common" />
     <PackageReference Include="System.ValueTuple" />
-	</ItemGroup>
+    <PackageReference Include="System.Threading.Channels" />
+  </ItemGroup>
 </Project>

src/Microsoft.Data.SqlClient/src/Microsoft/Data/ProviderBase/DbConnectionInternal.cs

@@ -46,11 +46,6 @@ internal abstract class DbConnectionInternal
         /// </summary>
         private bool _cannotBePooled;
 
-        /// <summary>
-        /// When the connection was created.
-        /// </summary>
-        private DateTime _createTime;
-
         /// <summary>
         /// [usage must be thread-safe] the transaction that we're enlisted in, either manually or automatically.
         /// </summary>
@@ -93,10 +88,16 @@ internal DbConnectionInternal(ConnectionState state, bool hidePassword, bool all
             AllowSetConnectionString = allowSetConnectionString;
             ShouldHidePassword = hidePassword;
             State = state;
+            CreateTime = DateTime.UtcNow;
         }
 
         #region Properties
 
+        /// <summary>
+        /// When the connection was created.
+        /// </summary>
+        internal DateTime CreateTime { get; }
+
         internal bool AllowSetConnectionString { get; }
 
         internal bool CanBePooled => !IsConnectionDoomed && !_cannotBePooled && !_owningObject.TryGetTarget(out _);
@@ -542,7 +543,7 @@ internal void DeactivateConnection()
                 // If we're not already doomed, check the connection's lifetime and
                 // doom it if it's lifetime has elapsed.
                 DateTime now = DateTime.UtcNow;
-                if (now.Ticks - _createTime.Ticks > Pool.LoadBalanceTimeout.Ticks)
+                if (now.Ticks - CreateTime.Ticks > Pool.LoadBalanceTimeout.Ticks)
                 {
                     DoNotPoolThisConnection();
                 }
@@ -712,7 +713,6 @@ internal void MakeNonPooledObject(DbConnection owningObject)
         /// <param name="connectionPool"></param>
         internal void MakePooledConnection(IDbConnectionPool connectionPool)
         {
-            _createTime = DateTime.UtcNow;
             Pool = connectionPool;
         }
 
@@ -767,7 +767,7 @@ internal virtual void PrepareForReplaceConnection()
             // By default, there is no preparation required
         }
 
-        internal void PrePush(object expectedOwner)
+        internal void PrePush(DbConnection expectedOwner)
         {
             // Called by IDbConnectionPool when we're about to be put into it's pool, we take this
             // opportunity to ensure ownership and pool counts are legit.