Amazon API Gateway Lambda Sync

The difference is in the back end type you use for your API. If you have an existing API server and you want to proxy or secure via API Gateway, you should use Amazon API Gateway Integration. That integration creates or updates API Gateway APIs that work in the HTTP Proxy mode. Lambda Sync is for API Gateway APIs that use Lambda functions as the back end.Amazon API Gateway Integration

API Hub for Design matches and creates Lambda functions in Node.js or Python by using the operationId property of each API operation:

paths:
  /pet:
    post:
      operationId: addPet
      description: Add a new pet to the store

If an operation does not have the operationId property (it is optional), it will be created for you. If a Lambda function already exists with the same name as the operationId, the existing function will be used (no new function will be created).

You an also add API Gateway-specific information to your OpenAPI definition by using API Gateway extensions. For example:

paths:
  /pet:
    post:
      ...
      x-amazon-apigateway-integration:
        type: "aws"
        uri: "arn:aws:apigateway:us-west-2:lambda:path/2015-03-31/functions/arn:aws:lambda:us-west-2:123456789012:function:addPet/invocations"
        passthroughBehavior: "when_no_match"
        httpMethod: "GET"
        responses:
          default:
            statusCode: "200"
        parameters:
          body: "$input.body"
        requestTemplates:
          application/json: "{\n  \"body\" : \"$input.body\"\n}"

Notes:

To be able to deploy to API Gateway, API Hub for Design needs access to AWS and a secret key with the appropriate permissions:

Each Lambda function has an execution role that gives it permissions to access other AWS services, such as S3, VPC or DynamoDB. Roles are created and managed in the IAM section of the AWS console. If you do not have a role for Lambda functions yet, you need to create one.

To create a role:

API Hub for Design pushes your API to Amazon API Gateway (creating the necessary Lambda functions) every time you save the API in API Hub for Design. If there was a problem with pushing the API to API Gateway, you will see an error at the top of the API Hub for Design Editor.

To see your API in API Gateway:

Each API operation is backed by a Lambda function in AWS. API Hub for Design generates function stubs, which you can later edit in Amazon to implement the business logic. Note that API Hub for Design does not overwrite any functions once they are created – it uses the function names to uniquely identify them.

To view the generated Lambda functions:

The default Node.js function code looks like this:

exports.handler = function(event, context, callback) {
  // string: (required)  The name that needs to be fetched. Use user1 for testing. 
  var username = event.username;
  callback(null, {
    message: 'created by API Hub for Design'
  });
}

And, the default Python function code looks like this:

def lambda_handler(event, context):
  # string: (required)  The name that needs to be fetched. Use user1 for testing.
  username = event.get('username')

  return 'created by API Hub for Design'

The event object provides access to the operation parameters passed in the request. In our example, the operation GET /user/{username} has just one parameter, username, which can be accessed as event.username. The autogenerated variables at the top store individual parameter values.

The returned value is specified by using the callback in Node.js or the return statement in Python.

To learn more about writing Lambda functions, see AWS Lambda documentation:

AWS Lambda Function Handler in Node.js

AWS Lambda Function Handler in Python

Let’s modify the function to pass the received user name back to the caller. If you use Node.js, replace

  callback(null, {
    message: 'created by API Hub for Design'
  });

with

  callback(null, {
    message: 'created by API Hub for Design',
    username: event.username
  });

If you use Python, replace

    return 'created by API Hub for Design'

with

  response = {
      "username" : username
  }

  return response

Then click Save to save the new code.

To test the function:

API Hub for Design does not overwrite any Lambda functions once they are created. For example, new or changed parameters in your API definition will not be reflected automatically in the Lambda functions.

To recreate a specific function with the latest definition, do the following:

API Hub for Design will recreate the missing function.

If you no longer want to sync your API definition and Lambda functions with Amazon API Gateway, you can do any of the following:

Your API and Lambda functions will remain in Amazon API Gateway, but API Hub for Design will not update them anymore.

The following limitations apply when importing OpenAPI definitions to Amazon API Gateway. Please note that these are the specifics of the Amazon API Gateway platform, not of API Hub for Design.

API Hub for Design will try to disable some unsupported keywords in your API definition by wrapping them into the x-disabled-for-amazon-gateway extension property. However, we recommend that you review your API definition manually and modify it to make it compatible with AWS.