ChannelDbConnectionPool replace connection#4429
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Pull request overview
Implements connection replacement support for the channel-based connection pool, including a new slot-level atomic replace operation and expanded unit test coverage around replacement behavior.
Changes:
- Implement
ChannelDbConnectionPool.ReplaceConnection(...)and introduce internal replacement acquisition logic (idle-preferred, otherwise create new). - Add
ConnectionPoolSlots.TryReplace(...)to atomically swap a connection within an existing reserved slot. - Update/extend unit tests, including a new dedicated
ChannelDbConnectionPoolReplaceConnectionTestsuite and an updated existing replacement test.
Reviewed changes
Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.
Show a summary per file
| File | Description |
|---|---|
| src/Microsoft.Data.SqlClient/tests/UnitTests/ConnectionPool/ConnectionPoolSlotsTest.cs | Adds new tests validating ConnectionPoolSlots.TryReplace behaviors. |
| src/Microsoft.Data.SqlClient/tests/UnitTests/ConnectionPool/ChannelDbConnectionPoolTest.cs | Updates the existing replace-connection test to exercise the new implementation. |
| src/Microsoft.Data.SqlClient/tests/UnitTests/ConnectionPool/ChannelDbConnectionPoolReplaceConnectionTest.cs | Adds a new test file covering replacement scenarios (idle preference, capacity behavior, failure propagation). |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/IDbConnectionPool.cs | Changes ReplaceConnection return type to nullable. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/ConnectionPoolSlots.cs | Adds TryReplace helper to atomically swap a connection in-place. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/ChannelDbConnectionPool.cs | Implements ReplaceConnection, adds replacement acquisition logic, and updates PrepareConnection to accept an optional transaction. |
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #4429 +/- ##
==========================================
- Coverage 65.83% 64.07% -1.77%
==========================================
Files 287 282 -5
Lines 43763 66706 +22943
==========================================
+ Hits 28812 42741 +13929
- Misses 14951 23965 +9014
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| if (!replaced) | ||
| { | ||
| // This should never happen because oldConnection is checked out and its slot is stable. | ||
| // Still, we need to check or we could vend a connection that is not tracked by the pool. | ||
| // TODO: error types and localization | ||
| throw new InvalidOperationException("Connection is no longer in the pool and cannot be replaced."); | ||
| } |
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| /// <summary> | ||
| /// Verifies that when activating the replacement connection fails, the newly created | ||
| /// connection is returned to the pool rather than leaked, keeping the pool count stable. | ||
| /// </summary> | ||
| [Fact] | ||
| public void ReplaceConnection_ActivationFails_NewConnectionReturnedToPool() |
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| // Assert — the new connection was returned to pool (not leaked). | ||
| // Pool count stays same because the new connection replaced the old one's slot | ||
| // and was then returned to idle. | ||
| Assert.Equal(countBefore, pool.Count); |
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| // NOTE: Preferring an idle connection over a new physical one is being added in a follow-up PR | ||
| // (branch dev/automation/replace-conn-idle-path), along with its ReplaceConnection_PrefersIdleOverNewConnection test. |
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| [Fact] | ||
| public void TestReplaceConnection() | ||
| { |
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