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The CDK Construct Library for AWS::ApiGateway

Project description

Amazon API Gateway Construct Library

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Stability: Stable


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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 resource is api.root.

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

# Example may have issues. See https://github.com/aws/jsii/issues/826
api = apigateway.RestApi(self, "books-api")

api.root.add_method("ANY")

books = api.root.add_resource("books")
books.add_method("GET")
books.add_method("POST")

book = books.add_resource("{book_id}")
book.add_method("GET")
book.add_method("DELETE")

AWS Lambda-backed APIs

A very common practice is to use Amazon API Gateway with AWS Lambda as the backend integration. The LambdaRestApi construct makes it easy:

The following code defines a REST API that routes all requests to the specified AWS Lambda function:

# Example may have issues. See https://github.com/aws/jsii/issues/826
backend = lambda.Function(...)
apigateway.LambdaRestApi(self, "myapi",
    handler=backend
)

You can also supply proxy: false, in which case you will have to explicitly define the API model:

# Example may have issues. See https://github.com/aws/jsii/issues/826
backend = lambda.Function(...)
api = apigateway.LambdaRestApi(self, "myapi",
    handler=backend,
    proxy=False
)

items = api.root.add_resource("items")
items.add_method("GET")# GET /items
items.add_method("POST")# POST /items

item = items.add_resource("{item}")
item.add_method("GET")# GET /items/{item}

# the default integration for methods is "handler", but one can
# customize this behavior per method or even a sub path.
item.add_method("DELETE", apigateway.HttpIntegration("http://amazon.com"))

Integration Targets

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:

# Example may have issues. See https://github.com/aws/jsii/issues/826
get_book_handler = lambda.Function(...)
get_book_integration = apigateway.LambdaIntegration(get_book_handler)
book.add_method("GET", get_book_integration)

Integration options can be optionally be specified:

# Example may have issues. See https://github.com/aws/jsii/issues/826
get_book_integration = apigateway.LambdaIntegration(get_book_handler,
    content_handling=apigateway.ContentHandling.CONVERT_TO_TEXT, # convert to base64
    credentials_passthrough=True
)

Method options can optionally be specified when adding methods:

# Example may have issues. See https://github.com/aws/jsii/issues/826
book.add_method("GET", get_book_integration,
    authorization_type=apigateway.AuthorizationType.IAM,
    api_key_required=True
)

The following example shows how to use an API Key with a usage plan:

# Example may have issues. See https://github.com/aws/jsii/issues/826
hello = lambda.Function(self, "hello",
    runtime=lambda.Runtime.NODEJS_10_X,
    handler="hello.handler",
    code=lambda.Code.from_asset("lambda")
)

api = apigateway.RestApi(self, "hello-api")
integration = apigateway.LambdaIntegration(hello)

v1 = api.root.add_resource("v1")
echo = v1.add_resource("echo")
echo_method = echo.add_method("GET", integration, api_key_required=True)
key = api.add_api_key("ApiKey")

plan = api.add_usage_plan("UsagePlan",
    name="Easy",
    api_key=key
)

plan.add_api_stage(
    stage=api.deployment_stage,
    throttle=[{
        "method": echo_method,
        "throttle": {
            "rate_limit": 10,
            "burst_limit": 2
        }
    }
    ]
)

Working with models

When you work with Lambda integrations that are not Proxy integrations, you have to define your models and mappings for the request, response, and integration.

# Example may have issues. See https://github.com/aws/jsii/issues/826
hello = lambda.Function(self, "hello",
    runtime=lambda.Runtime.NODEJS_10_X,
    handler="hello.handler",
    code=lambda.Code.from_asset("lambda")
)

api = apigateway.RestApi(self, "hello-api")
resource = api.root.add_resource("v1")

You can define more parameters on the integration to tune the behavior of API Gateway

# Example may have issues. See https://github.com/aws/jsii/issues/826
integration = LambdaIntegration(hello,
    proxy=False,
    request_parameters={
        # You can define mapping parameters from your method to your integration
        # - Destination parameters (the key) are the integration parameters (used in mappings)
        # - Source parameters (the value) are the source request parameters or expressions
        # @see: https://docs.aws.amazon.com/apigateway/latest/developerguide/request-response-data-mappings.html
        "integration.request.querystring.who": "method.request.querystring.who"
    },
    allow_test_invoke=True,
    request_templates={
        # You can define a mapping that will build a payload for your integration, based
        #  on the integration parameters that you have specified
        # Check: https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
        "application/json": JSON.stringify(action="sayHello", poll_id="$util.escapeJavaScript($input.params('who'))")
    },
    # This parameter defines the behavior of the engine is no suitable response template is found
    passthrough_behavior=PassthroughBehavior.NEVER,
    integration_responses=[{
        # Successful response from the Lambda function, no filter defined
        #  - the selectionPattern filter only tests the error message
        # We will set the response status code to 200
        "status_code": "200",
        "response_templates": {
            # This template takes the "message" result from the Lambda function, adn embeds it in a JSON response
            # Check https://docs.aws.amazon.com/apigateway/latest/developerguide/api-gateway-mapping-template-reference.html
            "application/json": JSON.stringify(state="ok", greeting="$util.escapeJavaScript($input.body)")
        },
        "response_parameters": {
            # We can map response parameters
            # - Destination parameters (the key) are the response parameters (used in mappings)
            # - Source parameters (the value) are the integration response parameters or expressions
            "method.response.header._content-_type": "'application/json'",
            "method.response.header._access-_control-_allow-_origin": "'*'",
            "method.response.header._access-_control-_allow-_credentials": "'true'"
        }
    }, {
        # For errors, we check if the error message is not empty, get the error data
        "selection_pattern": "(\n|.)+",
        # We will set the response status code to 200
        "status_code": "400",
        "response_templates": {
            "application/json": JSON.stringify(state="error", message="$util.escapeJavaScript($input.path('$.errorMessage'))")
        },
        "response_parameters": {
            "method.response.header._content-_type": "'application/json'",
            "method.response.header._access-_control-_allow-_origin": "'*'",
            "method.response.header._access-_control-_allow-_credentials": "'true'"
        }
    }
    ]
)

You can define models for your responses (and requests)

# Example may have issues. See https://github.com/aws/jsii/issues/826
# We define the JSON Schema for the transformed valid response
response_model = api.add_model("ResponseModel",
    content_type="application/json",
    model_name="ResponseModel",
    schema={"$schema": "http://json-schema.org/draft-04/schema#", "title": "pollResponse", "type": "object", "properties": {"state": {"type": "string"}, "greeting": {"type": "string"}}}
)

# We define the JSON Schema for the transformed error response
error_response_model = api.add_model("ErrorResponseModel",
    content_type="application/json",
    model_name="ErrorResponseModel",
    schema={"$schema": "http://json-schema.org/draft-04/schema#", "title": "errorResponse", "type": "object", "properties": {"state": {"type": "string"}, "message": {"type": "string"}}}
)

And reference all on your method definition.

# Example may have issues. See https://github.com/aws/jsii/issues/826
# If you want to define parameter mappings for the request, you need a validator
validator = api.add_request_validator("DefaultValidator",
    validate_request_body=False,
    validate_request_parameters=True
)
resource.add_method("GET", integration,
    # We can mark the parameters as required
    request_parameters={
        "method.request.querystring.who": True
    },
    # We need to set the validator for ensuring they are passed
    request_validator=validator,
    method_responses=[{
        # Successful response from the integration
        "status_code": "200",
        # Define what parameters are allowed or not
        "response_parameters": {
            "method.response.header._content-_type": True,
            "method.response.header._access-_control-_allow-_origin": True,
            "method.response.header._access-_control-_allow-_credentials": True
        },
        # Validate the schema on the response
        "response_models": {
            "application/json": response_model
        }
    }, {
        # Same thing for the error responses
        "status_code": "400",
        "response_parameters": {
            "method.response.header._content-_type": True,
            "method.response.header._access-_control-_allow-_origin": True,
            "method.response.header._access-_control-_allow-_credentials": True
        },
        "response_models": {
            "application/json": error_response_model
        }
    }
    ]
)

Default Integration and Method Options

The defaultIntegration and defaultMethodOptions properties can be used to configure a default integration at any resource level. These options will be used when defining method under this resource (recursively) with undefined integration or options.

If not defined, the default integration is MockIntegration. See reference documentation for default method options.

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.

# Example may have issues. See https://github.com/aws/jsii/issues/826
books_backend = apigateway.LambdaIntegration(...)
api = apigateway.RestApi(self, "books",
    default_integration=books_backend
)

books = api.root.add_resource("books")
books.add_method("GET")# integrated with `booksBackend`
books.add_method("POST")# integrated with `booksBackend`

book = books.add_resource("{book_id}")
book.add_method("GET")

Proxy Routes

The addProxy method can be used to install a greedy {proxy+} resource on a path. By default, this also installs an "ANY" method:

# Example may have issues. See https://github.com/aws/jsii/issues/826
proxy = resource.add_proxy(
    default_integration=LambdaIntegration(handler),

    # "false" will require explicitly adding methods on the `proxy` resource
    any_method=True
)

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 will be have open access from the 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 unless cloudWatchRole is set to false.

# Example may have issues. See https://github.com/aws/jsii/issues/826
api = apigateway.RestApi(self, "books",
    deploy_options={
        "logging_level": apigateway.MethodLoggingLevel.INFO,
        "data_trace_enabled": 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 deleted. You can set retainDeployments: true to allow users revert the stage to an old deployment manually.

Custom Domains

To associate an API with a custom domain, use the domainName configuration when you define your API:

# Example may have issues. See https://github.com/aws/jsii/issues/826
api = apigw.RestApi(self, "MyDomain",
    domain_name={
        "domain_name": "example.com",
        "certificate": acm_certificate_for_example_com
    }
)

This will define a DomainName resource for you, along with a BasePathMapping from the root of the domain to the deployment stage of the API. This is a common set up.

To route domain traffic to an API Gateway API, use Amazon Route 53 to create an alias record. An alias record is a Route 53 extension to DNS. It's similar to a CNAME record, but you can create an alias record both for the root domain, such as example.com, and for subdomains, such as www.example.com. (You can create CNAME records only for subdomains.)

# Example may have issues. See https://github.com/aws/jsii/issues/826
route53.ARecord(self, "CustomDomainAliasRecord",
    zone=hosted_zone_for_example_com,
    target=route53.AddressRecordTarget.from_alias(route53_targets.ApiGateway(api))
)

You can also define a DomainName resource directly in order to customize the default behavior:

# Example may have issues. See https://github.com/aws/jsii/issues/826
apigw.DomainName(self, "custom-domain",
    domain_name="example.com",
    certificate=acm_certificate_for_example_com,
    endpoint_type=apigw.EndpointType.EDGE
)

Once you have a domain, you can map base paths of the domain to APIs. The following example will map the URL https://example.com/go-to-api1 to the api1 API and https://example.com/boom to the api2 API.

# Example may have issues. See https://github.com/aws/jsii/issues/826
domain.add_base_path_mapping(api1, base_path="go-to-api1")
domain.add_base_path_mapping(api2, base_path="boom")

NOTE: currently, the mapping will always be assigned to the APIs deploymentStage, which will automatically assigned to the latest API deployment. Raise a GitHub issue if you require more granular control over mapping base paths to stages.

If you don't specify basePath, all URLs under this domain will be mapped to the API, and you won't be able to map another API to the same domain:

# Example may have issues. See https://github.com/aws/jsii/issues/826
domain.add_base_path_mapping(api)

This can also be achieved through the mapping configuration when defining the domain as demonstrated above.

If you wish to setup this domain with an Amazon Route53 alias, use the route53_targets.ApiGatewayDomain:

# Example may have issues. See https://github.com/aws/jsii/issues/826
route53.ARecord(self, "CustomDomainAliasRecord",
    zone=hosted_zone_for_example_com,
    target=route53.AddressRecordTarget.from_alias(route53_targets.ApiGatewayDomain(domain_name))
)

Cross Origin Resource Sharing (CORS)

Cross-Origin Resource Sharing (CORS) is a mechanism that uses additional HTTP headers to tell browsers to give a web application running at one origin, access to selected resources from a different origin. A web application executes a cross-origin HTTP request when it requests a resource that has a different origin (domain, protocol, or port) from its own.

You can add the CORS preflight OPTIONS HTTP method to any API resource via the defaultCorsPreflightOptions option or by calling the addCorsPreflight on a specific resource.

The following example will enable CORS for all methods and all origins on all resources of the API:

# Example may have issues. See https://github.com/aws/jsii/issues/826
apigateway.RestApi(self, "api",
    default_cors_preflight_options={
        "allow_origins": apigateway.Cors.ALL_ORIGINS,
        "allow_methods": apigateway.Cors.ALL_METHODS
    }
)

The following example will add an OPTIONS method to the myResource API resource, which only allows GET and PUT HTTP requests from the origin https://amazon.com.

# Example may have issues. See https://github.com/aws/jsii/issues/826
my_resource.add_cors_preflight(
    allow_origins=["https://amazon.com"],
    allow_methods=["GET", "PUT"]
)

See the CorsOptions API reference for a detailed list of supported configuration options.

You can specify defaults this at the resource level, in which case they will be applied to the entire resource sub-tree:

# Example may have issues. See https://github.com/aws/jsii/issues/826
subtree = resource.add_resource("subtree",
    default_cors_preflight_options={
        "allow_origins": ["https://amazon.com"]
    }
)

This means that all resources under subtree (inclusive) will have a preflight OPTIONS added to them.

See #906 for a list of CORS features which are not yet supported.


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

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