CSHARP-6089: Gate baseBackoffMS integration test on a server feature and adapt tests to the new OperationContext API

- Add Feature.ClientBackpressureBaseBackoffMs (wire version Server90) and
  gate the integration test on it instead of a server-version string, so it
  runs on 9.0 pre-release servers rather than skipping until GA.
- Adopt the updated spec test 5 shape (absolute backoff bounds + assert the
  driver parsed baseBackoffMS) for the mocked unit test.
- Fix GetOperationRetryBackoffDelay test bounds for the 2^attempt exponent.
- Adapt tests to the CSHARP-6011 change (Session moved onto OperationContext;
  OperationContext(TimeSpan, CancellationToken) and NoTimeout removed).

Author: papafe

src/MongoDB.Driver/Core/Misc/Feature.cs

@@ -112,6 +112,11 @@ public class Feature
     /// </summary>
     public static Feature ChangeStreamSplitEventStage { get; } = new("ChangeStreamSplitEventStage", WireVersion.Server70);
 
+    /// <summary>
+    /// Gets the client backpressure baseBackoffMS feature.
+    /// </summary>
+    public static Feature ClientBackpressureBaseBackoffMs { get; } = new("ClientBackpressureBaseBackoffMs", WireVersion.Server90);
+
     /// <summary>
     /// Gets the client bulk write feature.
     /// </summary>

tests/MongoDB.Driver.Tests/Core/Operations/RetryabilityHelperTests.cs

@@ -317,10 +317,10 @@ public void GetBaseBackoffMs_should_return_expected_result(string resultJson, in
         }
 
         [Theory]
-        [InlineData(1, null, 0, 100)]
-        [InlineData(2, null, 0, 200)]
-        [InlineData(1, 50, 0, 50)]
-        [InlineData(2, 50, 0, 100)]
+        [InlineData(1, null, 0, 200)]
+        [InlineData(2, null, 0, 400)]
+        [InlineData(1, 50, 0, 100)]
+        [InlineData(2, 50, 0, 200)]
         [InlineData(1, 10000, 0, 10000)]
         [InlineData(2, 20000, 0, 10000)]
         public void GetOperationRetryBackoffDelay_should_apply_baseBackoffMs_override(int attempt, int? baseBackoffMs, int expectedRangeMin, int expectedRangeMax)

tests/MongoDB.Driver.Tests/Core/Operations/RetryableReadOperationExecutorTests.cs

@@ -147,10 +147,10 @@ public void ShouldRetry_with_baseBackoffMs_should_use_it_as_backoff_base(
             int expectedRangeMinMs,
             int expectedRangeMaxMs)
         {
-            var context = CreateContext(retryRequested: true, isInTransaction: false);
+            var context = CreateContext(retryRequested: true);
             var result = BsonDocument.Parse($"{{ ok : 0, code : 2, baseBackoffMS : {baseBackoffMs} }}");
             var exception = CoreExceptionHelper.CreateMongoCommandExceptionWithLabels(result, "SystemOverloadedError", "RetryableError");
-            var operationContext = new OperationContext(null, CancellationToken.None);
+            using var operationContext = new OperationContext(NoCoreSession.NewHandle());
             var randomMock = new Mock<IRandom>();
             randomMock.Setup(r => r.NextDouble()).Returns(1.0);
 

tests/MongoDB.Driver.Tests/Core/Operations/RetryableWriteOperationExecutorTests.cs

@@ -104,7 +104,7 @@ public void ShouldRetry_with_baseBackoffMs_should_use_it_as_backoff_base(
             var context = CreateContext(retryRequested: true, areRetryableWritesSupported: true, hasSessionId: true, isInTransaction: false);
             var result = BsonDocument.Parse($"{{ ok : 0, code : 2, baseBackoffMS : {baseBackoffMs} }}");
             var exception = CoreExceptionHelper.CreateMongoCommandExceptionWithLabels(result, "SystemOverloadedError", "RetryableError");
-            var operationContext = new OperationContext(null, CancellationToken.None);
+            using var operationContext = new OperationContext(NoCoreSession.NewHandle());
             var randomMock = new Mock<IRandom>();
             randomMock.Setup(r => r.NextDouble()).Returns(1.0);
 

tests/MongoDB.Driver.Tests/Core/WireProtocol/CommandWriteProtocolTests.cs

@@ -516,9 +516,10 @@ public async Task Execute_should_preserve_server_supplied_baseBackoffMS_in_the_c
                 null, // serverApi
                 TimeSpan.FromMilliseconds(42));
 
+            using var operationContext = new OperationContext(NoCoreSession.NewHandle());
             var exception = async
-                ? await Record.ExceptionAsync(() => subject.ExecuteAsync(OperationContext.NoTimeout, connection))
-                : Record.Exception(() => subject.Execute(OperationContext.NoTimeout, connection));
+                ? await Record.ExceptionAsync(() => subject.ExecuteAsync(operationContext, connection))
+                : Record.Exception(() => subject.Execute(operationContext, connection));
 
             var commandException = exception.Should().BeOfType<MongoCommandException>().Subject;
             commandException.Result["baseBackoffMS"].ToInt32().Should().Be(50);

tests/MongoDB.Driver.Tests/Specifications/client-backpressure/prose-tests/ClientBackpressureProseTests.cs

@@ -183,7 +183,8 @@ private async Task AssertBaseBackoffMsOverridesBackoff<TOperation, TContext>(
         Action<OperationContext, TOperation, TContext> executeSync,
         Func<OperationContext, TOperation, TContext, Task> executeAsync)
     {
-        var operationContext = new OperationContext(TimeSpan.FromSeconds(30), CancellationToken.None);
+        using var session = NoCoreSession.NewHandle();
+        using var operationContext = new OperationContext(session, timeout: TimeSpan.FromSeconds(30));
 
         var fullJitterRandom = new Mock<IRandom>();
         fullJitterRandom.Setup(r => r.NextDouble()).Returns(1.0);
@@ -197,9 +198,20 @@ private async Task AssertBaseBackoffMsOverridesBackoff<TOperation, TContext>(
         var overrideException = CoreExceptionHelper.CreateMongoCommandExceptionWithLabels(overrideResult, "SystemOverloadedError", "RetryableError");
         var withBaseBackoffMs = await MeasureBackoff(async, executeSync, executeAsync, operationContext, createOperation(overrideException), createContext(fullJitterRandom.Object));
 
-        // Per the spec: assertTrue(abs(exponential_backoff_time - (with_base_backoff_ms_time + 0.3s)) < 0.3s)
-        Math.Abs(exponentialMs - (withBaseBackoffMs + 300)).Should().BeLessThan(300,
-            $"baseBackoffMS should shorten the backoff base (exponential: {exponentialMs}ms, withBaseBackoffMS: {withBaseBackoffMs}ms)");
+        // The driver must have parsed the server-supplied baseBackoffMS off the error.
+        RetryabilityHelper.GetBaseBackoffMs(overrideException).Should().Be(50);
+
+        // Per the spec (jitter pinned to 1): the default backoffs sum to 0.2 + 0.4 = 0.6s and the
+        // baseBackoffMS = 50 backoffs sum to 0.1 + 0.2 = 0.3s. A run can never be faster than the sum of its backoffs.
+        // The operations here are mocked, so there is no server-round-trip cushion above the raw sleeps; allow a small
+        // tolerance on the lower bounds for timer granularity while still asserting baseBackoffMS shortens the backoff.
+        const long timerToleranceMs = 50;
+        exponentialMs.Should().BeGreaterOrEqualTo(600 - timerToleranceMs,
+            $"the default exponential backoff should sum to ~600ms (got {exponentialMs}ms)");
+        withBaseBackoffMs.Should().BeGreaterOrEqualTo(300 - timerToleranceMs,
+            $"the baseBackoffMS=50 backoff should sum to ~300ms (got {withBaseBackoffMs}ms)");
+        withBaseBackoffMs.Should().BeLessThan(600,
+            $"baseBackoffMS should shorten the backoff base (withBaseBackoffMS: {withBaseBackoffMs}ms, exponential: {exponentialMs}ms)");
     }
 
     private static async Task<long> MeasureBackoff<TOperation, TContext>(
@@ -374,7 +386,7 @@ public void Overload_errors_with_baseBackoffMS_shorten_the_backoff_base()
     {
         RequireServer.Check()
             .ClusterTypes(ClusterType.ReplicaSet)
-            .VersionGreaterThanOrEqualTo("9.0.0");
+            .Supports(Feature.ClientBackpressureBaseBackoffMs);
 
         var failPointCommand = BsonDocument.Parse(
             @"{