Process data from a queue with a Map state in Step Functions - Amazon Step Functions
Step 1: Create the state machineStep 2: Subscribe to the Amazon SNS topicStep 3: Add messages to the Amazon SQS queueStep 4: Run the state machine
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Process data from a queue with a Map state in Step Functions

In this sample workflow, a Map workflow state state processes data from a queue, sending messages to subscribers and storing them in a database.

Step Functions uses an optimized integration to pull messages from an Amazon SQS queue. When messages are available, a Choice state passes an array of JSON messages to a Map state for processing. For each message, the state machine writes the message to DynamoDB, removes the message from the queue, and publishes the message to an Amazon SNS topic.

This sample project includes the following resources:

  • An Amazon Step Functions state machine

  • An Amazon SQS queue from which the Map state reads and removes messages iteratively.

  • A DynamoDB table to which the Map state writes messages iteratively.

  • An Amazon SNS topic to which Step Functions publishes the messages it reads from the Amazon SQS queue.

  • Related Amazon Identity and Access Management (IAM) roles

Step 1: Create the state machine

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

  2. Find and choose Dynamically process data with a Map state. Choose Next to continue.

  3. Choose Run a demo to create a read-only and ready-to-deploy workflow, or choose Build on it to create an editable state machine definition that you can build on and later deploy.

  4. Choose Use template to continue with your selection.

Next steps depend on your previous choice:

  1. Run a demo – You can review the state machine before you create a read-only project with resources deployed by Amazon CloudFormation to your Amazon Web Services account.

    You can view the state machine definition, and when you are ready, choose Deploy and run to deploy the project and create the resources.

    Deploying can take up to 10 minutes to create resources and permissions. You can use the Stack ID link to monitor progress in Amazon CloudFormation.

    After deploy completes, you should see your new state machine in the console.

  2. Build on it – You can review and edit the workflow definition. You might need to set values for placeholders in the sample project before attemping to run your custom workflow.

Note

Standard charges might apply for services deployed to your account.

Step 2: Subscribe to the Amazon SNS topic

Tip

Subscribe to the Amazon SNS topic and add items to the Amazon SQS queue before you run your state machine.

  1. Open the Amazon SNS console.

  2. Choose Topics and find the topic that was created by the sample project.

  3. Choose Create subscription, and for Protocol, choose Email.

  4. Under Endpoint, enter your email address to subscribe to the topic.

  5. Choose Create subscription.

  6. Confirm the subscription in your email to activate the subscription.

Step 3: Add messages to the Amazon SQS queue

  1. Open the Amazon SQS console.

  2. Choose the queue that was created by the sample project.

  3. Choose Send and receive messages, enter a message and choose Send message. Repeat this step to add several messages to the queue.

Step 4: Run the state machine

Tip

Queues in Amazon SNS are eventually consistent. You may need to wait a few minutes after sending messages to the queue before running your state machine.

  1. On the State machines page, choose your sample project.

  2. On the sample project page, choose Start execution.

  3. In the Start execution dialog box, do the following:

    1. (Optional) Enter a custom execution name to override the generated default.

      Non-ASCII names and logging

      Step Functions accepts names for state machines, executions, activities, and labels that contain non-ASCII characters. Because such characters will not work with Amazon CloudWatch, we recommend using only ASCII characters so you can track metrics in CloudWatch.

    2. (Optional) In the Input box, enter input values as JSON. You can skip this step if you are running a demo.

    3. Choose Start execution.

    The Step Functions console will direct you to an Execution Details page where you can choose states in the Graph view to explore related information in the Step details pane.

Congratulations!

You should now have either a running demo or a state machine definition that you can customize.