Creating AWS Lambdas in Rust

Getting started with AWS Lambda Rust Runtime

Quick tutorial to create a sample "hello world" lambda using AWS Lambda Rust Runtime

Pre-requisite

1. Install rust/cargo/etc
2. Code editor
3. AWS Account

Create a new rust binary

cargo new lambda_test

Add the code

To start with something easy lets copy the code from the AWS Lambda Rust Runtime README example. (Note: make sure you've selected the tag for version, v0.5 at the time I'm writing this)

main.rs

use lambda_runtime::{service_fn, LambdaEvent, Error};
use serde_json::{json, Value};

#[tokio::main]
async fn main() -> Result<(), Error> {
    let func = service_fn(func);
    lambda_runtime::run(func).await?;
    Ok(())
}

async fn func(event: LambdaEvent<Value>) -> Result<Value, Error> {
    let (event, _context) = event.into_parts();
    let first_name = event["firstName"].as_str().unwrap_or("world");

    Ok(json!({ "message": format!("Hello, {}!", first_name) }))
}

Fix the copy pasta errors

Currently the lambda will not build, your IDE may show some crate not found errors.

Lets update the Cargo.toml with the required libraries.

I use Cargo Edit which extends Cargo with commands to manage dependencies without having to manually edit your Cargo.toml

cargo add lambda_runtime

cargo add serde_json

cargo add tokio

Finally, the project should be ready to build.

How to build

Check that normal local builds are working, and fix any dependency issues if needed.

cargo build

Build for AWS Lambda install x86 target

• First install Zig

brew install zig

• Install cargo zigbuild

cargo install cargo-zigbuild

• Add the target for x86

rustup target add x86_64-unknown-linux-gnu

• Finally, we build the release

cargo zigbuild --release --target x86_64-unknown-linux-gnu

Create a zip archive

cp ./target/x86_64-unknown-linux-gnu/release/lambda_test ./bootstrap && zip lambda.zip bootstrap && rm bootstrap

Create new function

TODO: how to create the role, then in IAM can copy ARN

aws lambda create-function --function-name rustTest \
  --handler doesnt.matter \
  --zip-file fileb://./lambda.zip \
  --runtime provided.al2 \
  --role arn:aws:iam::{PUT_AWS_ACCT}:role/lambda_basic_execution \
  --environment Variables={RUST_BACKTRACE=1} \
  --tracing-config Mode=Active

Test invoke

aws lambda invoke \
  --cli-binary-format raw-in-base64-out \
  --function-name rustTest \
  --payload '{"firstName": "James"}' \
  output.json

Check output

> cat output.json
{"message":"Hello, James!"}%

Check logs

TODO: how to check cloudwatch logs from cli?

START RequestId: 2b0a5ad0
Version: $LATEST
END RequestId: 2b0a5ad0
REPORT RequestId: 2b0a5ad0	Duration: 0.85 ms	Billed Duration: 1 ms	Memory Size: 128 MB	Max Memory Used: 15 MB	
XRAY TraceId: 1-6213be54	SegmentId: 282cd	Sampled: true