Crate lambda_web_adapter 

Lambda Web Adapter

Lambda Web Adapter allows you to run web applications on AWS Lambda without code changes. It acts as a bridge between the Lambda Runtime API and your web application, translating Lambda events into HTTP requests and forwarding them to your application.

Overview

The adapter works by:

1. Starting as a Lambda extension alongside your web application
2. Waiting for your application to become ready (via health checks)
3. Receiving Lambda events and converting them to HTTP requests
4. Forwarding requests to your application and returning responses to Lambda

Quick Start

use lambda_web_adapter::{Adapter, AdapterOptions, Error};

fn main() -> Result<(), Error> {
    // Apply proxy config before starting tokio runtime
    Adapter::apply_runtime_proxy_config();

    let runtime = tokio::runtime::Builder::new_multi_thread()
        .enable_all()
        .build()?;

    runtime.block_on(async {
        let options = AdapterOptions::default();
        let mut adapter = Adapter::new(&options)?;
         
        adapter.register_default_extension();
        adapter.check_init_health().await;
        adapter.run().await
    })
}

Configuration

The adapter is configured via environment variables. All variables use the AWS_LWA_ prefix:

Variable	Description	Default
AWS_LWA_PORT	Port your application listens on (falls back to PORT)	8080
AWS_LWA_HOST	Host your application binds to	127.0.0.1
AWS_LWA_READINESS_CHECK_PATH	Health check endpoint path	/
AWS_LWA_READINESS_CHECK_PORT	Health check port	Same as AWS_LWA_PORT
AWS_LWA_READINESS_CHECK_PROTOCOL	Protocol for health checks (HTTP or TCP)	HTTP
AWS_LWA_READINESS_CHECK_HEALTHY_STATUS	Status codes considered healthy (e.g., 200-399,404)	100-499
AWS_LWA_ASYNC_INIT	Enable async initialization	false
AWS_LWA_REMOVE_BASE_PATH	Base path to strip from requests	None
AWS_LWA_INVOKE_MODE	Lambda invoke mode (buffered or response_stream)	buffered
AWS_LWA_ENABLE_COMPRESSION	Enable response compression (buffered mode only)	false

Response Streaming

For applications that need to stream responses (e.g., Server-Sent Events, large file downloads), set AWS_LWA_INVOKE_MODE=response_stream. This requires configuring your Lambda function URL with InvokeMode: RESPONSE_STREAM.

Modules

tracing

This module provides primitives to work with tracing and tracing-subscriber in Lambda functions.

Structs

Adapter

The Lambda Web Adapter.

AdapterOptions

Configuration options for the Lambda Web Adapter.

Enums

LambdaInvokeMode

Lambda function invoke mode.

Protocol

Protocol used for readiness checks.

Type Aliases

Error

Error type that lambdas may result in