Tutorial: Build an API Gateway REST API with AWS integration

Both the Tutorial: Build a Hello World REST API with Lambda proxy integration and Build an API Gateway REST API with Lambda integration topics describe how to create an API Gateway API to expose the integrated Lambda function. In addition, you can create an API Gateway API to expose other AWS services, such as Amazon SNS, Amazon S3, Amazon Kinesis, and even AWS Lambda. This is made possible by the AWS integration. The Lambda integration or the Lambda proxy integration is a special case, where the Lambda function invocation is exposed through the API Gateway API.

All AWS services support dedicated APIs to expose their features. However, the application protocols or programming interfaces are likely to differ from service to service. An API Gateway API with the AWS integration has the advantage of providing a consistent application protocol for your client to access different AWS services.

In this walkthrough, we create an API to expose Amazon SNS. For more examples of integrating an API with other AWS services, see Amazon API Gateway tutorials and workshops.

Unlike the Lambda proxy integration, there is no corresponding proxy integration for other AWS services. Hence, an API method is integrated with a single AWS action. For more flexibility, similar to the proxy integration, you can set up a Lambda proxy integration. The Lambda function then parses and processes requests for other AWS actions.

API Gateway does not retry when the endpoint times out. The API caller must implement retry logic to handle endpoint timeouts.

This walkthrough builds on the instructions and concepts in Build an API Gateway REST API with Lambda integration. If you have not yet completed that walkthrough, we suggest that you do it first.

Prerequisites

Before you begin this walkthrough, do the following:

1. Complete the steps in Prerequisites for getting started with API Gateway.

2. Create a new API named MyDemoAPI. For more information, see Tutorial: Build a REST API with HTTP non-proxy integration.

3. Deploy the API at least once to a stage named test. For more information, see Deploy the API in Build an API Gateway REST API with Lambda integration.

4. Complete the rest of the steps in Build an API Gateway REST API with Lambda integration.

5. Create at least one topic in Amazon Simple Notification Service (Amazon SNS). You will use the deployed API to get a list of topics in Amazon SNS that are associated with your AWS account. To learn how to create a topic in Amazon SNS, see Create a Topic. (You do not need to copy the topic ARN mentioned in step 5.)

Step 1: Create the AWS service proxy execution role

To allow the API to invoke Amazon SNS actions, you must have the appropriate IAM policies attached to an IAM role.

To create the AWS service proxy execution role

1. Sign in to the AWS Management Console and open the IAM console at https://console.aws.amazon.com/iam/.

2. Choose Roles.

3. Choose Create role.

4. Choose AWS service under Select type of trusted entity, and then select API Gateway and select Allows API Gateway to push logs to CloudWatch Logs.

5. Choose Next, and then choose Next.

6. For Role name, enter APIGatewaySNSProxyPolicy, and then choose Create role.

7. In the Roles list, choose the role you just created. You may need to scroll or use the search bar to find the role.

8. For the selected role, select the Add permissions tab.

9. Choose Attach policies from the dropdown list.

10. In the search bar, enter AmazonSNSReadOnlyAccess and choose Add permissions.

    Note

    This tutorial uses a managed policy for simplicity. As a best practice, you should create your own IAM policy to grant the minimum permissions required.

11. Note the newly created Role ARN, you will use it later.

Step 2: Create the resource

In this step, you create a resource that enables the AWS service proxy to interact with the AWS service.

To create the resource

1. Sign in to the API Gateway console at https://console.aws.amazon.com/apigateway.

2. Choose your API.

3. Select the root resource, /, represented by a single forward slash (/), and then choose Create resource.

4. Keep Proxy resource turned off.

5. Keep Resource path as /.

6. For Resource name, enter mydemoawsproxy.

7. Keep CORS (Cross Origin Resource Sharing) turned off.

8. Choose Create resource.

Step 3: Create the GET method

In this step, you create a GET method that enables the AWS service proxy to interact with the AWS service.

To create the GET method

1. Select the /mydemoawsproxy resource, and then choose Create method.

2. For method type, select GET.

3. For Integration type, select AWS service.

4. For AWS Region, select the AWS Region where you created your Amazon SNS topic.

5. For AWS service, select Amazon SNS.

6. Keep AWS subdomain blank.

7. For HTTP method, select GET.

8. For Action type, select Use action name.

9. For Action name, enter ListTopics.

10. For Execution role, enter the role ARN for APIGatewaySNSProxyPolicy.

11. Choose Create method.

Step 4: Specify method settings and test the method

You can now test your GET method to verify that it has been properly set up to list your Amazon SNS topics.

To test the GET method

1. Choose the Test tab. You might need to choose the right arrow button to show the tab.

2. Choose Test.

   The result displays response similar to the following:

   {
     "ListTopicsResponse": {
       "ListTopicsResult": {
         "NextToken": null,
         "Topics": [
           {
             "TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-1"
           },
           {
             "TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-2"
           },
           ...
           {
             "TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-N"
           }
         ]
       },
       "ResponseMetadata": {
         "RequestId": "abc1de23-45fa-6789-b0c1-d2e345fa6b78"
       }
     }
   }

Step 5: Deploy the API

In this step, you deploy the API so that you can call it from outside of the API Gateway console.

To deploy the API

1. Choose Deploy API.

2. For Stage, select New stage.

3. For Stage name, enter test.

4. (Optional) For Description, enter a description.

5. Choose Deploy.

Step 6: Test the API

In this step, you go outside of the API Gateway console and use your AWS service proxy to interact with the Amazon SNS service.

1. In the main navigation pane, choose Stage.

2. Under Stage details, choose the copy icon to copy your API's invoke URL.

   It should look like this:

   https://my-api-id.execute-api.region-id.amazonaws.com/test

3. Enter the URL into the address box of a new browser tab.

4. Append /mydemoawsproxy so that the URL looks like this:

   https://my-api-id.execute-api.region-id.amazonaws.com/test/mydemoawsproxy

   Browse to the URL. Information similar to the following should be displayed:

   {"ListTopicsResponse":{"ListTopicsResult":{"NextToken": null,"Topics":[{"TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-1"},{"TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-2"},...{"TopicArn": "arn:aws:sns:us-east-1:80398EXAMPLE:MySNSTopic-N}]},"ResponseMetadata":{"RequestId":"abc1de23-45fa-6789-b0c1-d2e345fa6b78}}}

Step 7: Clean up

You can delete the IAM resources the AWS service proxy needs to work.

Warning

If you delete an IAM resource an AWS service proxy relies on, that AWS service proxy and any APIs that rely on it will no longer work. Deleting an IAM resource cannot be undone. If you want to use the IAM resource again, you must re-create it.

To delete the associated IAM resources

1. Open the IAM console at https://console.aws.amazon.com/iam/.

2. In the Details area, choose Roles.

3. Select APIGatewayAWSProxyExecRole, and then choose Role Actions, Delete Role. When prompted, choose Yes, Delete.

4. In the Details area, choose Policies.

5. Select APIGatewayAWSProxyExecPolicy, and then choose Policy Actions, Delete. When prompted, choose Delete.

You have reached the end of this walkthrough. For more detailed discussions about creating API as an AWS service proxy, see Tutorial: Create a REST API as an Amazon S3 proxy in API Gateway, Tutorial: Create a Calc REST API with two AWS service integrations and one Lambda non-proxy integration, or Tutorial: Create a REST API as an Amazon Kinesis proxy in API Gateway.