Create a task timer with Lambda and Amazon SNS

This sample project creates a task timer. It implements an AWS Step Functions state machine that implements a Wait state, and uses an AWS Lambda function that sends an Amazon Simple Notification Service (Amazon SNS) notification. A Wait workflow state state is a state type that waits for a trigger to perform a single unit of work.

Note

This sample project implements an AWS Lambda function to send an Amazon Simple Notification Service (Amazon SNS) notification. You can also send an Amazon SNS notification directly from the Amazon States Language. See Integrating other services with Step Functions.

This sample project creates the state machine, a Lambda function, and an Amazon SNS topic, and configures the related AWS Identity and Access Management (IAM) permissions. For more information about the resources that are created with the Task Timer sample project, see the following:

For more information about how AWS Step Functions can control other AWS services, see Integrating other services with Step Functions.

• AWS CloudFormation User Guide

• Amazon Simple Notification Service Developer Guide

• AWS Lambda Developer Guide

• IAM Getting Started Guide

Step 1: Create the state machine and provision resources

1. Open the Step Functions console and choose Create state machine.

2. Type Task Timer in the search box, and then choose Task Timer from the search results that are returned.

3. Choose Next to continue.

4. Step Functions lists the AWS services used in the sample project you selected. It also shows a workflow graph for the sample project. Deploy this project to your AWS account or use it as a starting point for building your own projects. Based on how you want to proceed, choose Run a demo or Build on it.

   This sample project deploys the following resources:

   • a Lambda function that sends an Amazon SNS notification.

   • An AWS Step Functions state machine

   • Related AWS Identity and Access Management (IAM) roles

   The following image shows the workflow graph for the Task Timer sample project:

   

5. Choose Use template to continue with your selection.

6. Do one of the following:

   • If you selected Build on it, Step Functions creates the workflow prototype for the sample project you selected. Step Functions doesn't deploy the resources listed in the workflow definition.

     In Workflow Studio's Design mode, drag and drop states from the States browser to continue building your workflow protoype. Or switch to the Code mode that provides an integrated code editor similar to VS Code for updating the Using Amazon States Language to define Step Functions workflows (ASL) definition of your state machine within the Step Functions console. For more information about using Workflow Studio to build your state machines, see Creating a workflow with Workflow Studio in Step Functions.

     Important

     Remember to update the placeholder Amazon Resource Name (ARN) for the resources used in the sample project before you run your workflow.

   • If you selected Run a demo, Step Functions creates a read-only sample project which uses an AWS CloudFormation template to deploy the AWS resources listed in that template to your AWS account.

     Tip

     To view the state machine definition of the sample project, choose Code.

     When you're ready, choose Deploy and run to deploy the sample project and create the resources.

     It can take up to 10 minutes for these resources and related IAM permissions to be created. While your resources are being deployed, you can open the CloudFormation Stack ID link to see which resources are being provisioned.

     After all the resources in the sample project are created, you can see the new sample project listed on the State machines page.

     Important

     Standard charges may apply for each service used in the CloudFormation template.

Step 2: Run the state machine

After all the resources are provisioned and deployed, the Start execution dialog box is displayed with example input similar to the following.

{
    "jobName": "my-job",{
  "topic": "arn:aws:sns:us-east-2:123456789012:StepFunctionsSample-TaskTimercc68840e-c3d3-42a8-911e-821b7ce248e5-SNSTopic-44UjcFxzhACT",
  "message": "HelloWorld",
  "timer_seconds": 10
}

• In the Start execution dialog box, do the following:

  1. (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.

     Note

     Step Functions allows you to create names for state machines, executions, and activities, and labels that contain non-ASCII characters. These non-ASCII names don't work with Amazon CloudWatch. To ensure that you can track CloudWatch metrics, choose a name that uses only ASCII characters.

  2. (Optional) In the Input box, enter input values in JSON format to run your workflow.

     If you chose to Run a demo, you need not provide any execution input.

     Note

     If the demo project you deployed contains prepopulated execution input data, use that input to run the state machine.

  3. Choose Start execution.

  4. The Step Functions console directs you to a page that's titled with your execution ID. This page is known as the Execution Details page. On this page, you can review the execution results as the execution progresses or after it's complete.

     To review the execution results, choose individual states on the Graph view, and then choose the individual tabs on the Step details pane to view each state's details including input, output, and definition respectively. For details about the execution information you can view on the Execution Details page, see Execution Details page – Interface overview.

  For example, the following image shows the output of the selected step Wait for Timestamp. The output of this step is passed as input to the Send SNS Message step.