Struct AdapterOptions 

pub struct AdapterOptions {

    pub host: String,
    pub port: String,
    pub readiness_check_port: String,
    pub readiness_check_path: String,
    pub readiness_check_protocol: Protocol,
    pub readiness_check_min_unhealthy_status: u16,
    pub readiness_check_healthy_status: Vec<u16>,
    pub base_path: Option<String>,
    pub pass_through_path: String,
    pub async_init: bool,
    pub compression: bool,
    pub invoke_mode: LambdaInvokeMode,
    pub authorization_source: Option<String>,
    pub error_status_codes: Option<Vec<u16>>,
}

Configuration options for the Lambda Web Adapter.

This struct holds all configuration parameters for the adapter. It can be constructed manually or using Default::default() which reads values from environment variables.

Environment Variables

When using Default::default(), the following environment variables are read:

Field	Environment Variable	Fallback	Default
host	AWS_LWA_HOST	HOST	127.0.0.1
port	AWS_LWA_PORT	PORT	8080
readiness_check_port	AWS_LWA_READINESS_CHECK_PORT	READINESS_CHECK_PORT	Same as port
readiness_check_path	AWS_LWA_READINESS_CHECK_PATH	READINESS_CHECK_PATH	/
readiness_check_protocol	AWS_LWA_READINESS_CHECK_PROTOCOL	READINESS_CHECK_PROTOCOL	HTTP
readiness_check_healthy_status	AWS_LWA_READINESS_CHECK_HEALTHY_STATUS	-	100-499
base_path	AWS_LWA_REMOVE_BASE_PATH	REMOVE_BASE_PATH	None
async_init	AWS_LWA_ASYNC_INIT	ASYNC_INIT	false
compression	AWS_LWA_ENABLE_COMPRESSION	-	false
invoke_mode	AWS_LWA_INVOKE_MODE	-	buffered

Deprecated Environment Variables

The non-prefixed environment variables (e.g., HOST, READINESS_CHECK_PORT) are deprecated and will be removed in version 2.0. Please use the AWS_LWA_ prefixed versions. Note: PORT is not deprecated and remains a supported fallback for AWS_LWA_PORT.

Examples

use lambda_web_adapter::{AdapterOptions, Protocol, LambdaInvokeMode};

// Use defaults from environment variables
let options = AdapterOptions::default();

// Or configure manually
let options = AdapterOptions {
    host: "127.0.0.1".to_string(),
    port: "3000".to_string(),
    readiness_check_path: "/health".to_string(),
    readiness_check_protocol: Protocol::Http,
    invoke_mode: LambdaInvokeMode::ResponseStream,
    ..Default::default()
};

Fields

host: String

Host address where the web application is listening. Default: 127.0.0.1

port: String

Port where the web application is listening. Falls back to PORT env var, then default 8080.

readiness_check_port: String

Port to use for readiness checks. Defaults to the same as port. Useful when your application exposes health checks on a different port.

readiness_check_path: String

HTTP path for readiness checks. Default: /

readiness_check_protocol: Protocol

Protocol to use for readiness checks. Default: Protocol::Http

readiness_check_min_unhealthy_status: u16

👎Deprecated since 1.0.0: Use readiness_check_healthy_status instead

Deprecated: Use readiness_check_healthy_status instead.

Minimum HTTP status code considered unhealthy.

readiness_check_healthy_status: Vec<u16>

List of HTTP status codes considered healthy for readiness checks.

Can be configured via AWS_LWA_READINESS_CHECK_HEALTHY_STATUS using:

• Single codes: 200,201,204
• Ranges: 200-399
• Mixed: 200-299,301,302,400-499

Default: 100-499 (all 1xx, 2xx, 3xx, and 4xx status codes)

base_path: Option<String>

Base path to strip from incoming requests.

Useful when your Lambda is behind an API Gateway with a stage name or custom path that your application doesn’t expect.

Example: If set to /prod, a request to /prod/api/users becomes /api/users.

pass_through_path: String

Path to forward pass-through events to. Default: /events

async_init: bool

Enable async initialization mode.

When true, the adapter will cancel readiness checks after ~9.8 seconds to avoid Lambda’s 10-second init timeout. The application can continue booting in the background and will be checked again on the first request.

Default: false

compression: bool

Enable response compression.

When true, responses will be compressed using gzip, deflate, or brotli based on the Accept-Encoding header.

Note: Compression is not supported with response streaming (LambdaInvokeMode::ResponseStream). If both are enabled, compression will be automatically disabled with a warning.

Default: false

invoke_mode: LambdaInvokeMode

Lambda invoke mode for response handling. Default: LambdaInvokeMode::Buffered

authorization_source: Option<String>

Header name to copy to the Authorization header.

Useful when your authorization token comes in a custom header (e.g., from API Gateway authorizers) and your application expects it in the standard Authorization header.

error_status_codes: Option<Vec<u16>>

HTTP status codes that should trigger a Lambda error response.

When the web application returns one of these status codes, the adapter will return an error to Lambda instead of the response. This can be useful for triggering Lambda retry behavior.

Trait Implementations

impl Default for AdapterOptions

fn default() -> Self

Returns the “default value” for a type.