Creating a Step Functions State Machine That Uses Lambda

Open the Lambda console and choose Create function.

On the Create function page, choose Author from scratch.

In the Basic information section, configure your Lambda function:

1. For Function name, enter HelloFunction.

2. For Runtime, choose Node.js 14.x.

3. In Change default execution role, choose Create a new role with basic Lambda permissions.

4. Choose Create function.

5. After your Lambda function is created, copy the function's Amazon Resource Name (ARN) displayed in the upper-right corner of the page. To copy the ARN, click . The following is an example ARN:

   arn:aws-cn:lambda:us-east-1:123456789012:function:HelloFunction

Copy the following code for the Lambda function into the Code source section of the HelloFunction page.

exports.handler = (event, context, callback) => {
    callback(null, "Hello from " + event.who + "!");
};

This code assembles a greeting using the who field of the input data, which is provided by the event object passed into your function. You add input data for this function later, when you start a new execution. The callback method returns the assembled greeting from your function.

Choose Deploy.

Choose Test.

In the Configure test event dialog box, enter HelloEvent in the Event name box.

Replace the example data with the following.

{
    "who": "Amazon Step Functions"
}

The "who" entry corresponds to the event.who field in your Lambda function, completing the greeting. You will input the same input data when you run your state machine.

Choose Create.

On the HelloFunction page, choose Test to test your Lambda function using the new data.

The results of the test are displayed in the Execution results tab.

Choose the Execution results tab to see the output.

Open the Step Functions console and choose Create state machine.

On the Choose authoring method page, choose Design your workflow visually.

For Type, retain the default selection, that is, Standard.

Choose Next. This will open Workflow Studio.

From the States browser on the left, choose the Actions panel.

1. Drag and drop the Amazon Lambda Invoke API into the empty state labelled Drag first state here.

   

In the Inspector panel on the right, configure the Lambda function and its name:

1. Choose Configuration, and then edit the State name, if required.

2. In the API Parameters section, choose the Lambda function that you created earlier in the Function name dropdown list.

3. Retain the default selection in the Payload dropdown list.

Choose Next.

On the Review generated code page, review the state machine's Amazon States Language (ASL) definition, which is automatically generated based on your selections in the Actions and Inspector panel.

Choose Next.

Enter a Name for your state machine, for example, LambdaStateMachine.

In Execution role, under the Permissions section, choose Create new role.

Choose Create state machine.

On the LambdaStateMachine page, choose Start execution.

The Start execution dialog box is displayed.

(Optional) To identify your execution, you can specify a name for it in the Name box. By default, Step Functions generates a unique execution name automatically.

In the execution input area, replace the example data with the following.

{
    "who" : "Amazon Step Functions"
}

"who" is the key name that your Lambda function uses to get the name of the person to greet.

Choose Start Execution.

A new execution of your state machine starts, and a new page showing your running execution is displayed.

To view the results of your execution, choose the Execution output tab.