Dev/mdaigle/pool rate limit#4376
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Pull request overview
This PR adds infrastructure for connection-pool rate limiting and aligns both pool implementations on a shared “blocking period” error-state mechanism (fast-fail after connection-creation failures with exponential backoff), with accompanying unit tests and a draft spec.
Changes:
- Introduces
BlockingPeriodErrorStateand integrates it into bothChannelDbConnectionPoolandWaitHandleDbConnectionPool. - Adds initial plumbing for connection-creation rate limiting in
ChannelDbConnectionPool(plusNoOpAcquiredLease). - Adds unit tests and a feature spec/diagram documenting intended behavior.
Reviewed changes
Copilot reviewed 10 out of 10 changed files in this pull request and generated 7 comments.
Show a summary per file
| File | Description |
|---|---|
| src/Microsoft.Data.SqlClient/tests/UnitTests/ConnectionPool/ChannelDbConnectionPoolTest.cs | Adds unit tests for blocking period behavior and rate-limit lease disposal scenarios. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/WaitHandleDbConnectionPool.cs | Refactors blocking-period logic to use the shared BlockingPeriodErrorState and pool-group policy helper. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/NoOpAcquiredLease.cs | Adds a singleton no-op RateLimitLease used when no limiter is configured. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/DbConnectionPoolGroup.cs | Centralizes blocking-period enablement policy in IsBlockingPeriodEnabled(). |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/ChannelDbConnectionPool.cs | Adds blocking-period error state support and rate-limit acquisition logic on connection creation. |
| src/Microsoft.Data.SqlClient/src/Microsoft/Data/SqlClient/ConnectionPool/BlockingPeriodErrorState.cs | New shared implementation for cached error + exponential backoff + timer-based recovery. |
| src/Microsoft.Data.SqlClient/src/Microsoft.Data.SqlClient.csproj | Adds System.Threading.RateLimiting package reference. |
| specs/006-pool-rate-limiting/spec.md | Draft feature specification for rate limiting + blocking period semantics. |
| specs/006-pool-rate-limiting/diagrams.md | Mermaid diagrams comparing old vs new pool throttling approach. |
| Directory.Packages.props | Adds central package version entry for System.Threading.RateLimiting. |
Contributor
Author
|
@copilot add a System.Threading.RateLimiting dependency in the manual tests project |
Co-authored-by: mdaigle <4722049+mdaigle@users.noreply.github.com>
Contributor
Added |
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| /// <summary> | ||
| { | ||
| /// <summary> | ||
| /// Gets the number of times the pool asked the factory to create a physical connection. | ||
| /// </summary> | ||
| internal int CreateCount { get; private set; } | ||
|
|
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| /// <summary> | ||
| /// Creates a successful stub internal connection and increments the creation counter. | ||
| /// </summary> | ||
| protected override DbConnectionInternal CreateConnection( | ||
| SqlConnectionOptions options, | ||
| ConnectionPoolKey poolKey, | ||
| DbConnectionPoolGroupProviderInfo poolGroupProviderInfo, | ||
| IDbConnectionPool pool, | ||
| DbConnection owningConnection, | ||
| TimeoutTimer timeout) | ||
| { | ||
| CreateCount++; | ||
| return new StubDbConnectionInternal(); | ||
| } | ||
| } |
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| // Create the exit timer disarmed (infinite due time); it is armed below outside | ||
| // the lock. ADP.UnsafeCreateTimer suppresses execution-context flow so the timer | ||
| // doesn't capture and pin the current ExecutionContext and its AsyncLocals for its | ||
| // lifetime, while still honoring the injected TimeProvider for testability. | ||
| newTimer = ADP.UnsafeCreateTimer( | ||
| _timeProvider, | ||
| ExitCallback, | ||
| null, | ||
| Timeout.InfiniteTimeSpan, | ||
| Timeout.InfiniteTimeSpan); | ||
| oldTimer = _exitTimer; | ||
| _exitTimer = newTimer; | ||
|
|
BlockingPeriodErrorState calls a 5-arg UnsafeCreateTimer(TimeProvider, ...) returning ITimer that was missing from AdapterUtil, breaking the build. Re-add the overload, which suppresses ExecutionContext flow while honoring the injected TimeProvider for testability.
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| /// <summary> | ||
| { | ||
| /// <summary> | ||
| /// Gets the number of times the pool asked the factory to create a physical connection. | ||
| /// </summary> | ||
| internal int CreateCount { get; private set; } | ||
|
|
||
| /// <summary> | ||
| /// Creates a successful stub internal connection and increments the creation counter. | ||
| /// </summary> | ||
| protected override DbConnectionInternal CreateConnection( | ||
| SqlConnectionOptions options, | ||
| ConnectionPoolKey poolKey, | ||
| DbConnectionPoolGroupProviderInfo poolGroupProviderInfo, | ||
| IDbConnectionPool pool, | ||
| DbConnection owningConnection, | ||
| TimeoutTimer timeout) | ||
| { | ||
| CreateCount++; | ||
| return new StubDbConnectionInternal(); | ||
| } | ||
| } |
| // waiting on the idle channel, where it can be satisfied either by a | ||
| // returning connection or by a null poke from another caller releasing | ||
| // its rate-limit lease (see finally below). We prefer to recycle existing | ||
| // connections rather then queue on the rate limit. When no limiter is |
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| While in the error state the pool waits using exponential backoff (5s → 10s → 20s → 30s → 60s | ||
| cap) before allowing the next attempt. Once an attempt after the backoff succeeds, the error |
This was referenced Jun 23, 2026
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