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CDK Construct Library for Amazon API Gateway

Amazon API Gateway is a fully managed service that makes it easy for developers to publish, maintain, monitor, and secure APIs at any scale. Create an API to access data, business logic, or functionality from your back-end services, such as applications running on Amazon Elastic Compute Cloud (Amazon EC2), code running on AWS Lambda, or any web application.

Defining APIs

APIs are defined as a hierarchy of resources and methods. addResource and addMethod can be used to build this hierarchy. The root of this hierarchy is the RestApi object (which can also be treated as a resource).

For example, the following code defines an API that includes the following HTTP endpoints: GET /books, POST /books, GET /books/{book_id}, DELETE /books/{book_id}.

const api = new apigateway.RestApi(this, 'books-api');

api.addMethod('GET');

const books = api.addResource('books');
books.addMethod('GET');
books.addMethod('POST');

const book = api.addResource('{book_id}');
book.addMethod('GET');
book.addMethod('DELETE');

Backend Integrations

Methods are associated with backend integrations, which are invoked when this method is called. API Gateway supports the following integrations:

  • MockIntegration - can be used to test APIs. This is the default integration if one is not specified.
  • LambdaIntegration - can be used to invoke an AWS Lambda function.
  • AwsIntegration - can be used to invoke arbitrary AWS service APIs.
  • HttpIntegration - can be used to invoke HTTP endpoints.

The following example shows how to integrate the GET /book/{book_id} method to an AWS Lambda function:

const getBookHandler = new lambda.Function(...);
const getBookIntegration = new apigateway.LambdaIntegration(getBookHandler);
book.addMethod('GET', getBookIntegration);

Integration options can be optionally be specified:

const getBookIntegration = new apigateway.LambdaIntegration(getBookHandler, {
  contentHandling: apigateway.ContentHandling.ConvertToText, // convert to base64
  credentialsPassthrough: true, // use caller identity to invoke the function
});

Method options can optionally be specified when adding methods:

book.addMethod('GET', getBookIntegration, {
  authorizationType: apigateway.AuthorizationType.IAM,
  apiKeyRequired: true
});

Default Integration

The defaultIntegration can be used to configure a default integration at the API level. This integration will be used if an integration was not specified.

If not defined, the default integration is MockIntegration

The following example defines the booksBackend integration as a default integration. This means that all API methods that do not explicitly define an integration will be routed to this AWS Lambda function.

const booksBackend = new apigateway.LambdaIntegration(...);
const api = new apigateway.RestApi(this, 'books', {
  defaultIntegration: booksBackend
});

const books = new api.addResource('books');
books.addMethod('GET');  // integrated with `booksBackend`
books.addMethod('POST'); // integrated with `booksBackend`

const book = books.addResource('{book_id}');
book.addMethod('GET');   // integrated with `booksBackend`

Deployments

By default, the RestApi construct will automatically create an API Gateway Deployment and a "prod" Stage which represent the API configuration you defined in your CDK app. This means that when you deploy your app, your API can be accessed from the public internet via the stage URL.

The URL of your API can be obtained from the attribute restApi.url, and is also exported as an Output from your stack, so it's printed when you cdk deploy your app:

$ cdk deploy
...
books.booksapiEndpointE230E8D5 = https://6lyktd4lpk.execute-api.us-east-1.amazonaws.com/prod/

To disable this behavior, you can set { deploy: false } when creating your API. This means that the API will not be deployed and a stage will not be created for it. You will need to manually define a apigateway.Deployment and apigateway.Stage resources.

Use the deployOptions property to customize the deployment options of your API.

The following example will configure API Gateway to emit logs and data traces to AWS CloudWatch for all API calls:

By default, an IAM role will be created and associated with API Gateway to allow it to write logs and metrics to AWS CloudWatch cloudWatchRole is set to false.

const api = new apigateway.RestApi(this, 'books', {
  deployOptions: {
    loggingLevel: apigateway.MethodLoggingLevel.Info,
    dataTraceEnabled: true
  }
})

Deeper dive: invalidation of deployments

API Gateway deployments are an immutable snapshot of the API. This means that we want to automatically create a new deployment resource every time the API model defined in our CDK app changes.

In order to achieve that, the AWS CloudFormation logical ID of the AWS::ApiGateway::Deployment resource is dynamically calculated by hashing the API configuration (resources, methods). This means that when the configuration changes (i.e. a resource or method are added, configuration is changed), a new logical ID will be assigned to the deployment resource. This will cause CloudFormation to create a new deployment resource.

By default, old deployments are retained, which means users can use the AWS API Gateway Web Console to point the stage to an old deployment. To disable this behavior, set the retainDeployments property to false.

TODO

The following features are not supported yet by this library:

This module is part of the AWS Cloud Development Kit project.