cargo-lambda-cdk

Cargo Lambda CDK construct

This library provides constructs for Rust Lambda functions built with Cargo Lambda

To use this module you will either need to have Cargo Lambda installed (0.12.0 or later), or Docker installed. See Local Bundling/Docker Bundling for more information.

Rust Function

Define a RustFunction:

import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(stack, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
});

The layout for this Rust project could look like this:

lambda-project
├── Cargo.toml
└── src
    └── main.rs

Runtime

The RustFunction uses the provided.al2023 runtime. If you want to change it, you can use the property runtime. The only other valid option is provided.al2:

import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(stack, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  runtime: 'provided.al2',
});

Rust Extension

Define a RustExtension that get's deployed as a layer to use it with any other function later.

import { RustExtension, RustFunction } from 'cargo-lambda-cdk';

const extensionLayer = new RustExtension(this, 'Rust extension', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
});

new RustFunction(this, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  layers: [
    extensionLayer
  ],
});

Bundling

Bundling is the process by which cargo lambda gets called to build, package, and deliver the Rust binary for CDK. This construct provides two methods of bundling:

• Local bundling where the locally installed cargo lambda tool will run
• Docker bundling where a Dockerfile can be specified to build an image

Local Bundling

If Cargo Lambda is installed locally then it will be used to bundle your code in your environment. Otherwise, bundling will happen in a Lambda compatible Docker container with the Docker platform based on the target architecture of the Lambda function.

Environment

Use the environment prop to define additional environment variables when Cargo Lambda runs:

import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(this, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  bundling: {
    environment: {
      HELLO: 'WORLD',
    },
  },
});

Docker

To force bundling in a docker container even if Cargo Lambda is available in your environment, set the forcedDockerBundling prop to true. This is useful if you want to make sure that your function is built in a consistent Lambda compatible environment.

By default, these constructs use ghcr.io/cargo-lambda/cargo-lambda as the image to build with. Use the bundling.dockerImage prop to use a custom bundling image:

import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(this, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  bundling: {
    dockerImage: DockerImage.fromBuild('/path/to/Dockerfile'),
  },
});

Additional docker options such as the user, file access, working directory or volumes can be configured by using the bundling.dockerOptions prop:

import * as cdk from 'aws-cdk-lib';
import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(this, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  bundling: {
    dockerOptions: {
      bundlingFileAccess: cdk.BundlingFileAccess.VOLUME_COPY,
    },
  },
});

This property mirrors values from the cdk.BundlingOptions and is passed into Code.fromAsset.

Command hooks

It is possible to run additional commands by specifying the commandHooks prop:

import { RustFunction } from 'cargo-lambda-cdk';

new RustFunction(this, 'Rust function', {
  manifestPath: 'path/to/package/directory/with/Cargo.toml',
  bundling: {
    commandHooks: {
      // run tests
      beforeBundling(inputDir: string, _outputDir: string): string[] {
        return ['cargo test'];
      },
    },
  },
});

The following hooks are available:

• beforeBundling: runs before all bundling commands
• afterBundling: runs after all bundling commands

They all receive the directory containing the Cargo.toml file (inputDir) and the directory where the bundled asset will be output (outputDir). They must return an array of commands to run. Commands are chained with &&.

The commands will run in the environment in which bundling occurs: inside the container for Docker bundling or on the host OS for local bundling.

Additional considerations

Depending on how you structure your Rust application, you may want to change the assetHashType parameter. By default this parameter is set to AssetHashType.OUTPUT which means that the CDK will calculate the asset hash (and determine whether or not your code has changed) based on the Rust executable that is created.

If you specify AssetHashType.SOURCE, the CDK will calculate the asset hash by looking at the folder that contains your Cargo.toml file. If you are deploying a single Lambda function, or you want to redeploy all of your functions if anything changes, then AssetHashType.SOURCE will probaby work.

LICENSE

This software is released under MIT license.