Creating a Step Functions API using API Gateway

Sign in to the IAM console and choose Roles, Create role.

On the Select trusted entity page, do the following:

1. For Trusted entity type, keep the default selection of AWS service.

2. For Use case, choose API Gateway from the dropdown list.

Select API Gateway, and then choose Next.

On the Add permissions page, choose Next.

(Optional) On the Name, review, and create page, enter details, such as the role name. For example, enter APIGatewayToStepFunctions.

Choose Create role.

The IAM role appears in the list of roles.

Choose the name of your role and note the Role ARN, as shown in the following example.

arn:aws:iam::123456789012:role/APIGatewayToStepFunctions

On the Roles page, search for your role (APIGatewayToStepFunctions), and then choose the role.

On the Permissions tab, choose Add permissions, and then choose Attach policies.

On the Attach Policy page, search for AWSStepFunctionsFullAccess, choose the policy, and then choose Add permissions.

Open the Amazon API Gateway console, and then choose Create API.

On the Choose an API type page, in the REST API pane, choose Build.

On the Create REST API page, select New API, and then enter StartExecutionAPI for the API name.

Keep API endpoint type as Regional, and then choose Create API.

On the Resources page of StartExecutionAPI, choose Create resource.

On the Create resource page, enter execution for Resource name, and then choose Create resource.

Choose the /execution resource, and then choose Create method.

For Method type, choose POST.

For Integration type, choose AWS service.

For AWS Region, choose a Region from the list.

For AWS service, choose Step Functions from the list.

Keep AWS subdomain blank.

For HTTP method, choose POST from the list.

For Action type, select Use action name.

For Action name, enter StartExecution.

For Execution role, enter the role ARN of the IAM role that you created earlier, as shown in the following example.

arn:aws:iam::123456789012:role/APIGatewayToStepFunctions

Keep the default options for Credential cache and Default timeout, and then choose Save.

On the /execution - POST - Method Execution page, choose the Test tab. You might need to choose the right arrow button to show the tab.

On the /execution - POST - Method Test tab, copy the following request parameters into the Request body section using the ARN of an existing state machine (or create a new state machine that uses a Lambda function), and then choose Test.

{
   "input": "{}",
   "name": "MyExecution",
   "stateMachineArn": "arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld"
}

For more information, see the StartExecution Request Syntax in the AWS Step Functions API Reference.

{
    "input": "$util.escapeJavaScript($input.json('$'))",
    "stateMachineArn": "$util.escapeJavaScript($stageVariables.arn)"
}

The execution starts and the execution ARN and its epoch date are displayed under Response body.

{
   "executionArn": "arn:aws:states:us-east-1:123456789012:execution:HelloWorld:MyExecution",
   "startDate": 1486768956.878
}

On the Resources page of StartExecutionAPI, choose Deploy API.

For Stage, select New stage.

For Stage name, enter alpha.

(Optional) For Description, enter a description.

Choose Deploy.

On the Stages page of StartExecutionAPI, expand alpha, /, /execution, POST, and then choose the POST method.

Under Method overrides, choose the copy icon to copy your API's invoke URL. The full URL should look like the following example.

https://a1b2c3d4e5.execute-api.us-east-1.amazonaws.com/alpha/execution

From the command line, run the curl command using the ARN of your state machine, and then invoke the URL of your deployment, as shown in the following example.

curl -X POST -d '{"input": "{}","name": "MyExecution","stateMachineArn": "arn:aws:states:us-east-1:123456789012:stateMachine:HelloWorld"}' https://a1b2c3d4e5.execute-api.us-east-1.amazonaws.com/alpha/execution

The execution ARN and its epoch date are returned, as shown in the following example.

{"executionArn":"arn:aws:states:us-east-1:123456789012:execution:HelloWorld:MyExecution","startDate":1.486772644911E9}