Fix thread pool starvation under multi-concurrency

.autover/changes/45c6fa93-45cc-402a-869c-41dbcec2c799.json

@@ -0,0 +1,11 @@
+{
+  "Projects": [
+    {
+      "Name": "Amazon.Lambda.RuntimeSupport",
+      "Type": "Patch",
+      "ChangelogMessages": [
+        "Fix thread pool starvation under multi-concurrency"
+      ]
+    }
+  ]
+}

CHANGELOG.md

@@ -1,3 +1,18 @@
+## Release 2026-05-18
+
+### Amazon.Lambda.Core (3.1.0)
+* [Preview] Add LambdaLogger.ConfigureStructuredLogging to customize the JsonSerializerOptions used for serializing logging parameters.
+* Add preview ILambdaSerializer Serializer property to ILambdaContext (default-implemented to null on net8.0+) so user code can access the serializer registered with the runtime. Marked [Experimental("AWSLAMBDA001")]; class-library mode requires an updated managed Lambda runtime to populate this property. The Experimental flag will be removed in a follow-up release once the managed runtime is deployed.
+### Amazon.Lambda.RuntimeSupport (2.1.0)
+* Add support for handling the structured logging customization from Amazon.Lambda.Core.
+* Propagate the registered ILambdaSerializer to the per-invocation ILambdaContext.Serializer. Surfaces the new preview ILambdaContext.Serializer (AWSLAMBDA001); the Experimental flag will be removed in a follow-up release once the managed runtime is deployed.
+### Amazon.Lambda.Annotations (2.0.1)
+* Fix CS0121 ambiguity error in generated Program.g.cs when a Lambda handler has no input parameters and returns Task. The source generator now uses the unambiguous LambdaBootstrapBuilder.Create(Func<Stream, Task>) overload for this case.
+### Amazon.Lambda.TestUtilities (4.1.0)
+* Add Serializer setter to TestLambdaContext to mirror the new preview ILambdaContext.Serializer property. Marked [Experimental("AWSLAMBDA001")]; the Experimental flag will be removed in a follow-up release once the managed runtime is deployed.
+### Amazon.Lambda.AspNetCoreServer (10.1.1)
+* Fix InvokeFeatures.Set<TFeature> to bump the feature collection revision so middleware that wraps the response body (e.g. OutputCache, ResponseCompression) is properly visible to ASP.NET Core's FeatureReferences cache. Resolves https://github.com/aws/aws-lambda-dotnet/issues/1702 where IOutputCache stored empty response bodies.
+
 ## Release 2026-05-15
 
 ### Amazon.Lambda.AspNetCoreServer (10.1.0)

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Amazon.Lambda.Annotations.SourceGenerator.csproj

@@ -21,7 +21,7 @@
     <CopyLocalLockFileAssemblies>true</CopyLocalLockFileAssemblies>
     <IncludeBuildOutput>false</IncludeBuildOutput>
 
-    <Version>2.0.0</Version>
+    <Version>2.0.1</Version>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Templates/ExecutableAssembly.cs

@@ -142,6 +142,64 @@ public static async Task Main(string[] args)
 
             #line 45 "C:\codebase\V3\HLL\aws-lambda-dotnet\Libraries\src\Amazon.Lambda.Annotations.SourceGenerator\Templates\ExecutableAssembly.tt"
 
+            }
+            else if (!model.GeneratedMethod.Parameters.Any() && model.LambdaMethod.ReturnsVoidTask)
+            {
+
+
+            #line default
+            #line hidden
+            this.Write("                Func<Stream, System.Threading.Tasks.Task> ");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.ExecutableAssemblyHandlerName));
+
+            #line default
+            #line hidden
+            this.Write(" = new ");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.ContainingNamespace));
+
+            #line default
+            #line hidden
+            this.Write(".");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.ContainingType.Name));
+
+            #line default
+            #line hidden
+            this.Write("_");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.Name));
+
+            #line default
+            #line hidden
+            this.Write("_Generated().");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.Name));
+
+            #line default
+            #line hidden
+            this.Write(";\r\n                await Amazon.Lambda.RuntimeSupport.LambdaBootstrapBuilder.Crea" +
+                    "te(");
+
+            #line default
+            #line hidden
+            this.Write(this.ToStringHelper.ToStringWithCulture(model.LambdaMethod.ExecutableAssemblyHandlerName));
+
+            #line default
+            #line hidden
+            this.Write(").Build().RunAsync();\r\n                break;\r\n");
+
             }
             else
             {

Libraries/src/Amazon.Lambda.Annotations.SourceGenerator/Templates/ExecutableAssembly.tt

@@ -43,6 +43,18 @@ public class GeneratedProgram
                 await Amazon.Lambda.RuntimeSupport.LambdaBootstrapBuilder.Create(<#= model.LambdaMethod.ExecutableAssemblyHandlerName #>, new <#= this._lambdaFunctions[0].SerializerInfo.SerializerName #>()).Build().RunAsync();
                 break;
 <#    
+            }
+            else if (!model.GeneratedMethod.Parameters.Any() && model.LambdaMethod.ReturnsVoidTask)
+            {
+                // No typed input and Task return: Func<Stream, Task> is ambiguous between
+                // Create<TInput>(Func<TInput, Task>, ILambdaSerializer) and
+                // Create<TOutput>(Func<Stream, TOutput>, ILambdaSerializer).
+                // Use the non-generic, non-serializer overload to resolve CS0121.
+#>
+                Func<Stream, System.Threading.Tasks.Task> <#= model.LambdaMethod.ExecutableAssemblyHandlerName #> = new <#= model.LambdaMethod.ContainingNamespace #>.<#= model.LambdaMethod.ContainingType.Name #>_<#= model.LambdaMethod.Name #>_Generated().<#= model.LambdaMethod.Name #>;
+                await Amazon.Lambda.RuntimeSupport.LambdaBootstrapBuilder.Create(<#= model.LambdaMethod.ExecutableAssemblyHandlerName #>).Build().RunAsync();
+                break;
+<#
             }
             else
             {

Libraries/src/Amazon.Lambda.Annotations/Amazon.Lambda.Annotations.csproj

@@ -17,7 +17,7 @@
     <AssemblyOriginatorKeyFile>..\..\..\buildtools\public.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>
 
-    <Version>2.0.0</Version>
+    <Version>2.0.1</Version>
     <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
   </PropertyGroup>
 

Libraries/src/Amazon.Lambda.AspNetCoreServer/Amazon.Lambda.AspNetCoreServer.csproj

@@ -6,7 +6,7 @@
     <Description>Amazon.Lambda.AspNetCoreServer makes it easy to run ASP.NET Core Web API applications as AWS Lambda functions.</Description>
     <TargetFrameworks>$(DefaultPackageTargets)</TargetFrameworks>
     <AssemblyTitle>Amazon.Lambda.AspNetCoreServer</AssemblyTitle>
-    <Version>10.1.0</Version>
+    <Version>10.1.1</Version>
     <AssemblyName>Amazon.Lambda.AspNetCoreServer</AssemblyName>
     <PackageId>Amazon.Lambda.AspNetCoreServer</PackageId>
     <PackageTags>AWS;Amazon;Lambda;aspnetcore</PackageTags>

Libraries/src/Amazon.Lambda.AspNetCoreServer/Internal/InvokeFeatures.cs

@@ -117,10 +117,11 @@ public IEnumerator<KeyValuePair<Type, object>> GetEnumerator()
 
         public void Set<TFeature>(TFeature instance)
         {
-            if (instance == null)
-                return;
-
-            _features[typeof(TFeature)] = instance;
+            // Delegate to the indexer so _containerRevision is bumped, otherwise
+            // ASP.NET Core's FeatureReferences cache will return stale feature
+            // references after middleware (e.g. OutputCache, ResponseCompression)
+            // wraps the response body via HttpContext.Response.Body = wrapper.
+            this[typeof(TFeature)] = instance;
         }
 
         IEnumerator IEnumerable.GetEnumerator()

Libraries/src/Amazon.Lambda.Core/Amazon.Lambda.Core.csproj

@@ -6,7 +6,7 @@
     <TargetFrameworks>netstandard2.0;$(DefaultPackageTargets)</TargetFrameworks>
     <Description>Amazon Lambda .NET Core support - Core package.</Description>
     <AssemblyTitle>Amazon.Lambda.Core</AssemblyTitle>
-    <Version>3.0.0</Version>
+    <Version>3.1.0</Version>
     <AssemblyName>Amazon.Lambda.Core</AssemblyName>
     <PackageId>Amazon.Lambda.Core</PackageId>
     <PackageTags>AWS;Amazon;Lambda</PackageTags>

Libraries/src/Amazon.Lambda.Core/ILambdaContext.cs

@@ -1,6 +1,7 @@
 namespace Amazon.Lambda.Core
 {
     using System;
+    using System.Diagnostics.CodeAnalysis;
 
     /// <summary>
     /// Object that allows you to access useful information available within
@@ -95,6 +96,25 @@ public interface ILambdaContext
         /// The trace id generated by Lambda for distributed tracing across AWS services.
         /// </summary>
         string TraceId { get { return string.Empty; } }
+
+        /// <summary>
+        /// The <see cref="ILambdaSerializer"/> the Lambda function registered with the
+        /// runtime — either the instance passed to
+        /// <c>LambdaBootstrapBuilder.Create(handler, serializer)</c> /
+        /// <c>HandlerWrapper.GetHandlerWrapper(handler, serializer)</c>, or the type set
+        /// via <c>[assembly: LambdaSerializer(typeof(...))]</c> in class-library mode.
+        /// User code can reuse it for ad-hoc (de)serialization without re-instantiating.
+        /// Can be null when the function did not register a serializer (e.g., raw-stream
+        /// handlers).
+        /// </summary>
+        /// <remarks>
+        /// <para><b>Preview API.</b> Class-library mode requires an updated managed
+        /// Lambda runtime to populate this property; until that ships, the value will
+        /// be null when running in class-library mode. The <see cref="ExperimentalAttribute"/>
+        /// is applied to surface this caveat at the call site.</para>
+        /// </remarks>
+        [Experimental("AWSLAMBDA001")]
+        ILambdaSerializer Serializer { get { return null; } }
 #endif
     }
 }

Libraries/src/Amazon.Lambda.Core/LambdaLogger.cs

@@ -126,6 +126,33 @@ public static void Log(string level, Exception exception, string message, params
         /// <param name="message">Message to log. The message may have format arguments.</param>
         /// <param name="args">Arguments to format the message with.</param>
         public static void Log(LogLevel level, Exception exception, string message, params object[] args) => Log(level.ToString(), exception, message, args);
+
+        // This field must not be readonly because SetConfigureStructuredLoggingAction replaces the value
+        // when Amazon.Lambda.RuntimeSupport registers its structured logging callback.
+        private static Action<StructuredLoggingOptions> _configureStructuredLoggingAction = (options) => _placeHolderStructuredLoggingOptions = options;
+
+        // Because a user might call ConfigureStructuredLogging before the Lambda runtime has a chance to replace the _configureStructuredLoggingAction with the
+        // real implementation, we need to hold onto the options they provided until the Lambda runtime can use them to configure structured logging.
+        private static StructuredLoggingOptions _placeHolderStructuredLoggingOptions;
+
+        /// <summary>
+        /// When structured logging is enabled this method will allow overriding the default configuration the Lambda runtime uses for structured logging.
+        /// </summary>
+        /// <param name="options">The options to use for configuring structured logging.</param>
+        [RequiresPreviewFeatures("This method is in preview until the latest changes of the .NET Lambda runtime client have been deployed to the Lambda managed runtimes")]
+        public static void ConfigureStructuredLogging(StructuredLoggingOptions options) => _configureStructuredLoggingAction(options);
+
+        internal static void SetConfigureStructuredLoggingAction(Action<StructuredLoggingOptions> configureStructuredLoggingAction)
+        {
+            _configureStructuredLoggingAction = configureStructuredLoggingAction;
+
+            // If a user set the structured logging options before the Lambda runtime set the real _configureStructuredLoggingAction,
+            // we need to call it now to make sure the user's options are applied.
+            if (_placeHolderStructuredLoggingOptions != null)
+            {
+                _configureStructuredLoggingAction(_placeHolderStructuredLoggingOptions);
+            }
+        }
 #endif
     }
 }

Libraries/src/Amazon.Lambda.Core/StructuredLoggingOptions.cs

@@ -0,0 +1,18 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+#if NET8_0_OR_GREATER
+using System.Text.Json;
+
+namespace Amazon.Lambda.Core;
+
+/// <summary>
+/// The options that can be overridden for structured logging.
+/// </summary>
+public class StructuredLoggingOptions
+{
+    /// <summary>
+    /// Override the default JsonSerializerOptions used by the Lambda runtime for serializing object parameters in structured logs.
+    /// </summary>
+    public JsonSerializerOptions OverrideSerializerOptions { get; set; }
+}
+#endif

Libraries/src/Amazon.Lambda.RuntimeSupport/Amazon.Lambda.RuntimeSupport.csproj

@@ -4,7 +4,7 @@
 
   <PropertyGroup>
     <TargetFrameworks>net8.0;net9.0;net10.0</TargetFrameworks>
-    <Version>2.0.0</Version>
+    <Version>2.1.0</Version>
     <Description>Provides a bootstrap and Lambda Runtime API Client to help you to develop custom .NET Core Lambda Runtimes.</Description>
     <AssemblyTitle>Amazon.Lambda.RuntimeSupport</AssemblyTitle>
     <PackageId>Amazon.Lambda.RuntimeSupport</PackageId>