AWS Lambda Rust docker builder 🐑 🐳 🦀

🤔 about

This docker image extends lambda ci provided builder docker image, a faithful reproduction of the actual AWS "provided" Lambda runtime environment, and installs rustup and the stable rust toolchain.

📦 install

Tags for this docker image follow the naming convention softprops/lambda-rust:{version}-rust-{rust-stable-version} where {rust-stable-version} is a stable version of rust.

You can find a list of available docker tags here

💡 If you don't find the version you're looking for, please open a new github issue to publish one

You can also depend directly on softprops/lambda-rust:latest for the most recently published version.

🤸 usage

The default docker entrypoint will build a packaged release optimized version your Rust artifact under target/lambda/release to isolate the lambda specific build artifacts from your host-local build artifacts.

⚠️ Note: you can switch from the release profile to a custom profile like dev by providing a PROFILE environment variable set to the name of the desired profile. i.e. -e PROFILE=dev in your docker run

⚠️ Note: you can include debug symbols in optimized release build binaries by setting DEBUGINFO. By default, debug symbols will be stripped from the release binary and set aside in a separate .debug file.

You will want to volume mount /code to the directory containing your cargo project.

You can pass additional flags to cargo, the Rust build tool, by setting the CARGO_FLAGS docker env variable

A typical docker run might look like the following.

$ docker run --rm \
    -v ${PWD}:/code \
    -v ${HOME}/.cargo/registry:/root/.cargo/registry \
    -v ${HOME}/.cargo/git:/root/.cargo/git \
    softprops/lambda-rust

💡 The -v (volume mount) flags for /root/.cargo/{registry,git} are optional but when supplied, provides a much faster turn around when doing iterative development

If you are using Windows, the command above may need to be modified to include a BIN environment variable set to the name of the binary to be build and packaged

$ docker run --rm \
    -e BIN={your-binary-name} \
    -v ${PWD}:/code \
    -v ${HOME}/.cargo/registry:/root/.cargo/registry \
    -v ${HOME}/.cargo/git:/root/.cargo/git \
    softprops/lambda-rust

🤸🤸 usage via cargo aws-lambda subcommand

If you want to set up ad hoc lambda functions or have another reason to not to go with full blown devops orchestration tools, there's a cargo subcommand to compile your code into a zip file and deploy it to an existing function. This comes with only rust and docker as dependencies.

Setup

$ cargo install cargo-aws-lambda

To compile and deploy in your project directory

$ cargo aws-lambda {your aws function's full ARN} {your-binary-name}

To list all options

$ cargo aws-lambda --help

More instructions can be found here.

🔬 local testing

Once you've built a Rust lambda function artifact, the provided runtime expects deployments of that artifact to be named "bootstrap". The lambda-rust docker image builds a zip file, named after the binary, containing your binary files renamed to "bootstrap"

You can invoke this bootstap executable with the lambda-ci docker image for the provided AWS lambda runtime.

# start a docker container replicating the "provided" lambda runtime
# awaiting an event to be provided via stdin
$ unzip -o \
    target/lambda/release/{your-binary-name}.zip \
    -d /tmp/lambda && \
  docker run \
    -i -e DOCKER_LAMBDA_USE_STDIN=1 \
    --rm \
    -v /tmp/lambda:/var/task \
    lambci/lambda:provided

# provide an event payload via stdin (typically a json blob)

# Ctrl-D to yield control back to your function