LambdaBootstrap no longer throws if initialization fails when not using SnapStart

[martincostello]

Describe the bug

In my MartinCostello.Testing.AwsLambdaTestServer library I have a test that verifies that an exception is thrown if a function fails to startup.

With the changes to enable SnapStart in #1876 this appears to no longer occur an instead RunAsync() just runs to completion with no obvious sign of failure.

Is this an intentional behaviour change? It seems like an oversight to me as with SnapStart enabled the code will terminate the process:

aws-lambda-dotnet/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs

Lines 216 to 221 in 7ca5c8c

	#if NET8_0_OR_GREATER
	if (_configuration.IsInitTypeSnapstart)
	{
	System.Environment.Exit(1); // This needs to be non-zero for Lambda Sandbox to know that Runtime client encountered an exception
	}
	#endif

But without, it will return false and then just return:

aws-lambda-dotnet/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs

Line 223 in 7ca5c8c

return false;

aws-lambda-dotnet/Libraries/src/Amazon.Lambda.RuntimeSupport/Bootstrap/LambdaBootstrap.cs

Lines 156 to 159 in 7ca5c8c

	if (_initializer != null && !(await InitializeAsync()))
	{
	return;
	}

As an aside, Environment.Exit(1) isn't great from a testability perspective (IMHO) as if IsInitTypeSnapstart was true in my test, it would terminate the test process.

Regression Issue

• Select this option if this issue appears to be a regression.

Expected Behavior

An exception is thrown.

Current Behavior

LambdaBootstrap.RunAsync() returns with no error without invoking the lambda function.

Reproduction Steps

1. Clone martincostello/lambda-test-server@b71e148
2. Run build.ps1 from the root of the cloned repository.

Possible Solution

Preserve the original behaviour by throwing in the catch block if IsInitTypeSnapstart is false.

Additional Information/Context

No response

AWS .NET SDK and/or Package version used

Amazon.Lambda.RuntimeSupport 1.12.0

Targeted .NET Platform

.NET 9

Operating System and version

Any

[normj]

This was intentional change for when this was running in SnapStart. Due to an upstream issue we needed to force an exit quickly otherwise we weren't getting the logs correctly sent to the Lambda service. We are hoping for an upstream change so we can get rid of the Environment.Exit call. I don't like calling Environment.Exit either.

The non SnapStart behavior change was a side effect of diagnosing the log issue. I'll revert the behavior so that in non SnapStart case if there was an error to let the exception bubble up.

[normj]

Version 1.12.1 of Amazon.Lambda.RuntimeSupport was released that reverts back the behavior for non SnapStart situation.

[martincostello]

Thanks Norm - that went straight through with no issues: martincostello/lambda-test-server#823

[normj]

Great! Thanks for letting us know the change was successful.

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