AWS APIGatewayv2 Construct Library

Table of Contents

Introduction
HTTP API
WebSocket API
- Manage Connections Permission
- Managing access to WebSocket APIs

Introduction

Amazon API Gateway is an AWS service for creating, publishing, maintaining, monitoring, and securing REST, HTTP, and WebSocket APIs at any scale. API developers can create APIs that access AWS or other web services, as well as data stored in the AWS Cloud. As an API Gateway API developer, you can create APIs for use in your own client applications. Read the Amazon API Gateway Developer Guide.

This module supports features under API Gateway v2 that lets users set up Websocket and HTTP APIs. REST APIs can be created using the aws-cdk-lib/aws-apigateway module.

HTTP and Websocket APIs use the same CloudFormation resources under the hood. However, this module separates them into two separate constructs for a more efficient abstraction since there are a number of CloudFormation properties that specifically apply only to each type of API.

HTTP API

HTTP APIs enable creation of RESTful APIs that integrate with AWS Lambda functions, known as Lambda proxy integration, or to any routable HTTP endpoint, known as HTTP proxy integration.

Defining HTTP APIs

HTTP APIs have two fundamental concepts - Routes and Integrations.

Routes direct incoming API requests to backend resources. Routes consist of two parts: an HTTP method and a resource path, such as, GET /books. Learn more at Working with routes. Use the ANY method to match any methods for a route that are not explicitly defined.

Integrations define how the HTTP API responds when a client reaches a specific Route. HTTP APIs support Lambda proxy integration, HTTP proxy integration and, AWS service integrations, also known as private integrations. Learn more at Configuring integrations.

Integrations are available at the aws-apigatewayv2-integrations module and more information is available in that module. As an early example, we have a website for a bookstore where the following code snippet configures a route GET /books with an HTTP proxy integration. All other HTTP method calls to /books route to a default lambda proxy for the bookstore.

from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration, HttpLambdaIntegration

# book_store_default_fn: lambda.Function


get_books_integration = HttpUrlIntegration("GetBooksIntegration", "https://get-books-proxy.example.com")
book_store_default_integration = HttpLambdaIntegration("BooksIntegration", book_store_default_fn)

http_api = apigwv2.HttpApi(self, "HttpApi")

http_api.add_routes(
    path="/books",
    methods=[apigwv2.HttpMethod.GET],
    integration=get_books_integration
)
http_api.add_routes(
    path="/books",
    methods=[apigwv2.HttpMethod.ANY],
    integration=book_store_default_integration
)

The URL to the endpoint can be retrieved via the apiEndpoint attribute. By default this URL is enabled for clients. Use disableExecuteApiEndpoint to disable it.

http_api = apigwv2.HttpApi(self, "HttpApi",
    disable_execute_api_endpoint=True
)

The defaultIntegration option while defining HTTP APIs lets you create a default catch-all integration that is matched when a client reaches a route that is not explicitly defined.

from aws_cdk.aws_apigatewayv2_integrations import HttpUrlIntegration


apigwv2.HttpApi(self, "HttpProxyApi",
    default_integration=HttpUrlIntegration("DefaultIntegration", "https://example.com")
)

The routeSelectionExpression option allows configuring the HTTP API to accept only ${request.method} ${request.path}. Setting it to true automatically applies this value.

apigwv2.HttpApi(self, "HttpProxyApi",
    route_selection_expression=True
)

Publishing HTTP APIs

A Stage is a logical reference to a lifecycle state of your API (for example, dev, prod, beta, or v2). API stages are identified by their stage name. Each stage is a named reference to a deployment of the API made available for client applications to call.

Use HttpStage to create a Stage resource for HTTP APIs. The following code sets up a Stage, whose URL is available at https://{api_id}.execute-api.{region}.amazonaws.com/beta.

# api: apigwv2.HttpApi


apigwv2.HttpStage(self, "Stage",
    http_api=api,
    stage_name="beta",
    description="My Stage"
)

If you omit the stageName will create a $default stage. A $default stage is one that is served from the base of the API’s URL - https://{api_id}.execute-api.{region}.amazonaws.com/.

Note that, HttpApi will always creates a $default stage, unless the createDefaultStage property is unset.

Custom Domain

Custom domain names are simpler and more intuitive URLs that you can provide to your API users. Custom domain name are associated to API stages.

The code snippet below creates a custom domain and configures a default domain mapping for your API that maps the custom domain to the $default stage of the API.

import aws_cdk.aws_certificatemanager as acm
from aws_cdk.aws_apigatewayv2_integrations import HttpLambdaIntegration

# handler: lambda.Function


cert_arn = "arn:aws:acm:us-east-1:111111111111:certificate"
domain_name = "example.com"

dn = apigwv2.DomainName(self, "DN",
    domain_name=domain_name,
    certificate=acm.Certificate.from_certificate_arn(self, "cert", cert_arn)
)
api = apigwv2.HttpApi(self, "HttpProxyProdApi",
    default_integration=HttpLambdaIntegration("DefaultIntegration", handler),
    # https://${dn.domainName}/foo goes to prodApi $default stage
    default_domain_mapping=apigwv2.DomainMappingOptions(
        domain_name=dn,
        mapping_key="foo"
    )
)

To migrate a domain endpoint from one type to another, you can add a new endpoint configuration via addEndpoint() and then configure DNS records to route traffic to the new endpoint. After that, you can remove the previous endpoint configuration. Learn more at Migrating a custom domain name

To associate a specific Stage to a custom domain mapping -

# api: apigwv2.HttpApi
# dn: apigwv2.DomainName


api.add_stage("beta",
    stage_name="beta",
    auto_deploy=True,
    # https://${dn.domainName}/bar goes to the beta stage
    domain_mapping=apigwv2.DomainMappingOptions(
        domain_name=dn,
        mapping_key="bar"
    )
)

The same domain name can be associated with stages across different HttpApi as so -

from aws_cdk.aws_apigatewayv2_integrations import HttpLambdaIntegration

# handler: lambda.Function
# dn: apigwv2.DomainName


api_demo = apigwv2.HttpApi(self, "DemoApi",
    default_integration=HttpLambdaIntegration("DefaultIntegration", handler),
    # https://${dn.domainName}/demo goes to apiDemo $default stage
    default_domain_mapping=apigwv2.DomainMappingOptions(
        domain_name=dn,
        mapping_key="demo"
    )
)

The mappingKey determines the base path of the URL with the custom domain. Each custom domain is only allowed to have one API mapping with undefined mappingKey. If more than one API mappings are specified, mappingKey will be required for all of them. In the sample above, the custom domain is associated with 3 API mapping resources across different APIs and Stages.

API	Stage	URL
api	$default	`https://${domainName}/foo`
api	beta	`https://${domainName}/bar`
apiDemo	$default	`https://${domainName}/demo`

You can retrieve the full domain URL with mapping key using the domainUrl property as so -

# api_demo: apigwv2.HttpApi

demo_domain_url = api_demo.default_stage.domain_url

Mutual TLS (mTLS)

Mutual TLS can be configured to limit access to your API based by using client certificates instead of (or as an extension of) using authorization headers.

import aws_cdk.aws_s3 as s3
import aws_cdk.aws_certificatemanager as acm
# bucket: s3.Bucket


cert_arn = "arn:aws:acm:us-east-1:111111111111:certificate"
domain_name = "example.com"

apigwv2.DomainName(self, "DomainName",
    domain_name=domain_name,
    certificate=acm.Certificate.from_certificate_arn(self, "cert", cert_arn),
    mtls=apigwv2.MTLSConfig(
        bucket=bucket,
        key="someca.pem",
        version="version"
    )
)

Instructions for configuring your trust store can be found here

Managing access to HTTP APIs

API Gateway supports multiple mechanisms for controlling and managing access to your HTTP API through authorizers.

These authorizers can be found in the APIGatewayV2-Authorizers constructs library.

Metrics

The API Gateway v2 service sends metrics around the performance of HTTP APIs to Amazon CloudWatch. These metrics can be referred to using the metric APIs available on the HttpApi construct. The APIs with the metric prefix can be used to get reference to specific metrics for this API. For example, the method below refers to the client side errors metric for this API.

api = apigwv2.HttpApi(self, "my-api")
client_error_metric = api.metric_client_error()

Please note that this will return a metric for all the stages defined in the api. It is also possible to refer to metrics for a specific Stage using the metric methods from the Stage construct.

api = apigwv2.HttpApi(self, "my-api")
stage = apigwv2.HttpStage(self, "Stage",
    http_api=api
)
client_error_metric = stage.metric_client_error()

VPC Link

Private integrations let HTTP APIs connect with AWS resources that are placed behind a VPC. These are usually Application Load Balancers, Network Load Balancers or a Cloud Map service. The VpcLink construct enables this integration. The following code creates a VpcLink to a private VPC.

import aws_cdk.aws_ec2 as ec2
import aws_cdk.aws_elasticloadbalancingv2 as elb
from aws_cdk.aws_apigatewayv2_integrations import HttpAlbIntegration


vpc = ec2.Vpc(self, "VPC")
alb = elb.ApplicationLoadBalancer(self, "AppLoadBalancer", vpc=vpc)

vpc_link = apigwv2.VpcLink(self, "VpcLink", vpc=vpc)

# Creating an HTTP ALB Integration:
alb_integration = HttpAlbIntegration("ALBIntegration", alb.listeners[0])

Any existing VpcLink resource can be imported into the CDK app via the VpcLink.fromVpcLinkAttributes().

import aws_cdk.aws_ec2 as ec2

# vpc: ec2.Vpc

awesome_link = apigwv2.VpcLink.from_vpc_link_attributes(self, "awesome-vpc-link",
    vpc_link_id="us-east-1_oiuR12Abd",
    vpc=vpc
)

Private Integration

Private integrations enable integrating an HTTP API route with private resources in a VPC, such as Application Load Balancers or Amazon ECS container-based applications. Using private integrations, resources in a VPC can be exposed for access by clients outside of the VPC.

These integrations can be found in the aws-apigatewayv2-integrations constructs library.

Generating ARN for Execute API

The arnForExecuteApi function in AWS CDK is designed to generate Amazon Resource Names (ARNs) for Execute API operations. This is particularly useful when you need to create ARNs dynamically based on different parameters like HTTP method, API path, and stage.

api = apigwv2.HttpApi(self, "my-api")
arn = api.arn_for_execute_api("GET", "/myApiPath", "dev")

Ensure that the path parameter, if provided, starts with ‘/’.
The ‘ANY’ method can be used for matching any HTTP methods not explicitly defined.
The function gracefully handles undefined parameters by using wildcards, making it flexible for various API configurations.

WebSocket API

A WebSocket API in API Gateway is a collection of WebSocket routes that are integrated with backend HTTP endpoints, Lambda functions, or other AWS services. You can use API Gateway features to help you with all aspects of the API lifecycle, from creation through monitoring your production APIs. Read more

WebSocket APIs have two fundamental concepts - Routes and Integrations.

WebSocket APIs direct JSON messages to backend integrations based on configured routes. (Non-JSON messages are directed to the configured $default route.)

Integrations define how the WebSocket API behaves when a client reaches a specific Route. Learn more at Configuring integrations.

Integrations are available in the aws-apigatewayv2-integrations module and more information is available in that module.

To add the default WebSocket routes supported by API Gateway ($connect, $disconnect and $default), configure them as part of api props:

from aws_cdk.aws_apigatewayv2_integrations import WebSocketLambdaIntegration

# connect_handler: lambda.Function
# disconnect_handler: lambda.Function
# default_handler: lambda.Function


web_socket_api = apigwv2.WebSocketApi(self, "mywsapi",
    connect_route_options=apigwv2.WebSocketRouteOptions(integration=WebSocketLambdaIntegration("ConnectIntegration", connect_handler)),
    disconnect_route_options=apigwv2.WebSocketRouteOptions(integration=WebSocketLambdaIntegration("DisconnectIntegration", disconnect_handler)),
    default_route_options=apigwv2.WebSocketRouteOptions(integration=WebSocketLambdaIntegration("DefaultIntegration", default_handler))
)

apigwv2.WebSocketStage(self, "mystage",
    web_socket_api=web_socket_api,
    stage_name="dev",
    description="My Stage",
    auto_deploy=True
)

To retrieve a websocket URL and a callback URL:

# web_socket_stage: apigwv2.WebSocketStage


web_socket_uRL = web_socket_stage.url
# wss://${this.api.apiId}.execute-api.${s.region}.${s.urlSuffix}/${urlPath}
callback_uRL = web_socket_stage.callback_url

To add any other route:

from aws_cdk.aws_apigatewayv2_integrations import WebSocketLambdaIntegration

# message_handler: lambda.Function

web_socket_api = apigwv2.WebSocketApi(self, "mywsapi")
web_socket_api.add_route("sendmessage",
    integration=WebSocketLambdaIntegration("SendMessageIntegration", message_handler)
)

To add a route that can return a result:

from aws_cdk.aws_apigatewayv2_integrations import WebSocketLambdaIntegration

# message_handler: lambda.Function

web_socket_api = apigwv2.WebSocketApi(self, "mywsapi")
web_socket_api.add_route("sendmessage",
    integration=WebSocketLambdaIntegration("SendMessageIntegration", message_handler),
    return_response=True
)

To import an existing WebSocketApi:

web_socket_api = apigwv2.WebSocketApi.from_web_socket_api_attributes(self, "mywsapi", web_socket_id="api-1234")

To generate an ARN for Execute API:

api = apigwv2.WebSocketApi(self, "mywsapi")
arn = api.arn_for_execute_api("GET", "/myApiPath", "dev")

For a detailed explanation of this function, including usage and examples, please refer to the Generating ARN for Execute API section under HTTP API.

Manage Connections Permission

Grant permission to use API Gateway Management API of a WebSocket API by calling the grantManageConnections API. You can use Management API to send a callback message to a connected client, get connection information, or disconnect the client. Learn more at Use @connections commands in your backend service.

# fn: lambda.Function


web_socket_api = apigwv2.WebSocketApi(self, "mywsapi")
stage = apigwv2.WebSocketStage(self, "mystage",
    web_socket_api=web_socket_api,
    stage_name="dev"
)
# per stage permission
stage.grant_management_api_access(fn)
# for all the stages permission
web_socket_api.grant_manage_connections(fn)

Managing access to WebSocket APIs

API Gateway supports multiple mechanisms for controlling and managing access to a WebSocket API through authorizers.