Runtime Extensions for AWS Lambda in Rust

lambda-extension is a library that makes it easy to write AWS Lambda Runtime Extensions in Rust. It also helps with using Lambda Logs API.

Example extensions

Simple extension

The code below creates a simple extension that's registered to every INVOKE and SHUTDOWN events, and logs them in CloudWatch.

use lambda_extension::{service_fn, Error, LambdaEvent, NextEvent};

async fn my_extension(event: LambdaEvent) -> Result<(), Error> {
    match event.next {
        NextEvent::Shutdown(_e) => {
            // do something with the shutdown event
        }
        NextEvent::Invoke(_e) => {
            // do something with the invoke event
        }
    }
    Ok(())
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    tracing_subscriber::fmt()
        .with_max_level(tracing::Level::INFO)
        .with_ansi(false)
        .without_time()
        .init();

    let func = service_fn(my_extension);
    lambda_extension::run(func).await
}

Log processor extension

use lambda_extension::{service_fn, Error, Extension, LambdaLog, LambdaLogRecord, SharedService};
use tracing::info;

async fn handler(logs: Vec<LambdaLog>) -> Result<(), Error> {
    for log in logs {
        match log.record {
            LambdaLogRecord::Function(_record) => {
                // do something with the function log record
            },
            LambdaLogRecord::Extension(_record) => {
                // do something with the extension log record
            },
            },
            _ => (),
        }
    }

    Ok(())
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    let logs_processor = SharedService::new(service_fn(handler));

    Extension::new().with_logs_processor(logs_processor).run().await?;

    Ok(())
}

Deployment

Lambda extensions can be added to your functions either using Lambda layers, or adding them to containers images.

Regardless of how you deploy them, the extensions MUST be compiled against the same architecture that your lambda functions runs on.

Building extensions

• Install cargo-lambda

• Build the extension with:

cargo lambda build --release --extension

If you want to run the extension in ARM processors, add the --arm64 flag to the previous command:

cargo lambda build --release --extension --arm64

This previous command will generate a binary file in target/lambda/extensions called basic. When the extension is registered with the Runtime Extensions API, that's the name that the extension will be registered with. If you want to register the extension with a different name, you only have to rename this binary file and deploy it with the new name.

Deploying extensions

• Make sure you have the right credentials in your terminal by running the AWS CLI configure command:

aws configure

• Deploy the extension as a layer with:

cargo lambda deploy --extension