rust-lambda-setup

AWS Lambda Rust — Project Setup

Help the user initialize a new AWS Lambda function project in Rust.

Context to gather

If not provided in $ARGUMENTS, ask:

• Project name: the name for the new Lambda function (used in cargo lambda new <name>)
• Invocation type: will it be invoked via API Gateway / Function URL (HTTP) or with a custom JSON event?
• Event type: if HTTP → no pre-defined event type needed; if custom JSON → ask if they want a pre-defined event type (e.g. ApiGatewayProxyRequest, SqsEvent, S3Event) or a custom struct

Steps to execute

1. Install Cargo Lambda (if not present)

Cargo Lambda is the official third-party open-source extension to the Cargo CLI that simplifies building and deploying Rust Lambda functions.

cargo install cargo-lambda

Verify it installed correctly:

cargo lambda --version

2. Create the project

cargo lambda new <project-name>

When prompted by the CLI:

• HTTP function: answer Yes only if the function will be invoked via API Gateway or a Function URL. Otherwise answer No.
• Event type: select the correct pre-defined event type if needed, or leave blank for a custom JSON event.

3. Enter the project directory

cd <project-name>

4. Explain generated files

After creation, explain the generated structure to the user:

<project-name>/
├── src/
│   ├── main.rs          # Main application logic and entry point
│   └── generic_handler.rs  # Generic event handler (can be customized)
└── Cargo.toml           # Package metadata and dependencies

Key points about main.rs:

• #[tokio::main] marks the entry point and sets up the Tokio async runtime
• async fn main() specifies function_handler as the Lambda handler
• The lambda_runtime crate provides run, service_fn, LambdaEvent, and Error

5. Show the standard Cargo.toml dependencies

[dependencies]
lambda_runtime = "0.13.0"
serde = { version = "1", features = ["derive"] }
serde_json = "1"
tokio = { version = "1", features = ["full"] }

For SDK interactions, add specific crates (e.g. aws-sdk-s3 = "1.78.0").

6. Next steps

Suggest the user run /rust-lambda:build to compile the project, or /rust-lambda:new-handler to scaffold a handler with business logic.

Important notes

• The AWS Lambda Runtime for Rust (lambda_runtime crate) is NOT a managed runtime like Python or Node.js runtimes in Lambda. It is a crate that interfaces with Lambda's execution environment.
• Rust Lambda functions compile into a single executable binary — no separate runtime layer is needed.
• Do NOT recommend using Lambda layers to manage Rust dependencies; include all dependencies directly in the deployment package.