Feature request: Support Native AOT

[hjgraca]

Use case

Historically, .NET Lambda functions have cold-start times which impact user experience, system latency, and usage costs of your serverless applications. With .NET 8, Microsoft adds support for Native AOT compilation, which speeds up performance by compiling .NET code directly to machine and operating system native code, eliminating Just-in-Time (JIT) compiling at runtime. With .NET 8 Native AOT compilation, you can improve cold-start times of your Lambda functions. To learn more about Native AOT for .NET 8, see Using Native AOT in the Dotnet GitHub repository.

Solution/User Experience

Currently Native AOT is supported in .NET 8 but only a limited number of libraries are fully compatible with native AOT in .NET 8.
Lambda Powertools is not fully compatible with native AOT because of some libraries it uses (for example System.Text.Json.Serializer) which is not supported in native AOT

Proposal

All the work for this release will happen in a separate branch aot-support, this will allow us to publish alpha releases to Nuget. This will allow customers to get early access to the new features and optionally start applying the required changes or simply give feedback on the new items.

Quick summary

The work for AOT support will be done in multiple phases beginning on supporting Logging and Metrics and continuing to the remaining utilities. We believe these two utilities will have the most work and that is the reason we are starting from there.

Item	Issue	Status	Code change required	Notes
.NET 8 support	#542	✅
Create automation for .NET 8 release multiple target frameworks	#542	✅
Logging AOT support	#628	✅	Yes
Logging tackle AOT warnings	#628	✅		100+ warnings
Metrics AOT support	#602	✅	Yes
Metrics tackle AOT warnings	#602	✅	Yes	10+ warnings
Tracing AOT support	#607	✅	Yes
Tracing tackle AOT warnings	#607	✅	Yes	10+ warnings
Idempotency AOT support	#653	✅	Yes
Idempotency tackle AOT warnings	#653	✅	Yes	10+ warnings
Batch AOT support	#877	✅	Yes
Batch tackle AOT warnings		✅	Yes	10+ warnings
Parameters AOT support	#878	✅	Yes
Parameters tackle AOT warnings		✅	Yes	10+ warnings

Legend for Status column:

• ✅ Completed
• 🚧 Work in Progress
• ❌ Canceled / rescheduled to future release
• 🗓Backlog

Potential challenges

Tackling AOT trim warnings will be the most time consuming tasks, for this reason if some unforeseen blocker comes up we might decide to reprioritize and exclude some issues from the milestone.

Acknowledgment

• This feature request meets Lambda Powertools Tenets
• Should this be considered in other Lambda Powertools languages? i.e. Java, TypeScript

[jeastham1993]

@hjgraca PR raised for the first pass on native AOT support. I expect this will need some discussion, especially around logging. We can't easily support Exceptions in their entirety, byte[], streams or any anoymous types. Some of the unit tests will fail based on this missing functionality but I thought I would leave it that way as a means of discussion

#341

The crux of the work is adding a new IPowerToolsSerializer, initially with 2 implementations. A default one that uses System.Text.Json, and then a source genereted one that allows users to add a custom serialization context.

This is the same way it works for the Lambda runtime itself.