Support for Rust Lambda function with Cargo

[sapessi]

Description of changes: Added a new rust_cargo workflow. Uses cargo build --release by default to compile the function and automatically renames the executable to bootstrap. If the processing is running on a non-linux system the build process automatically attempts to target x86_64-unknown-linux-musl. The copy source steps looks for both the bootstrap executable and a runtime_release metadata file if it is available.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[sapessi]

I'll work on unit tests over the next few days

[jesskfullwood]

Has this PR stalled? If so I would be interested in taking it on

[sanathkr]

@jesskfullwood Yes, it would be great if you can pick up this PR. It just some work to become compatible with latest interface of the Workflow/Builder classes. You can follow the other workflows as an example for the pattern. It should be straightforward.

[sanathkr]

@jesskfullwood To make this work with SAM CLI, you need to make a code change to automatically pick up the Rust builder based on the presence of Cargo manifest as I explained here - aws/aws-sam-cli#1099 (comment)

Let me know how we can help you with this

[jackric]

@jesskfullwood @sanathkr is this stalled? I want it in SAM; I may take it on

[ramosbugs]

I've been wondering the same thing! Started working on reviving this PR last night, and hoping to have a new PR out early next week. But if someone beats me to it, great :-)

It sounds like the main missing piece is test coverage? Hopefully the Workflow/Builder interface changes alluded to above will become obvious as I continue trying to get this to work.

And then once this change gets merged we need a separate PR for aws-sam-cli to make it usable? That part seems to require primarily changing https://github.com/awslabs/aws-sam-cli/blob/98be672418f76bf1cc54db7528988b8a1c6a6b52/samcli/lib/build/workflow_config.py#L213 to

"provided": ManifestWorkflowSelector([PROVIDED_MAKE_CONFIG, RUST_CARGO_CONFIG])

@sanathkr Does that seem to match what you had in mind above?

[sriram-mv]

there is now a makefile builder workflow that can be directly https://docs.aws.amazon.com/serverless-application-model/latest/developerguide/building-custom-runtimes.html

[ramosbugs]

great, that seems like a more flexible solution than special-casing Rust. I'll just use that, thanks!