Transfer Data Records (Lambda, DynamoDB, Amazon SQS)

This sample project demonstrates how to read values from an Amazon DynamoDB table and send them to Amazon SQS using AWS Step Functions. Deploying this sample project will create a Step Functions state machine, a DynamoDB table, an AWS Lambda function, and an Amazon SQS topic.

In this project, Step Functions uses the Lambda function to populate the DynamoDB table, uses a for loop to read each of the entries, and then sends each entry to Amazon SQS.

Create the State Machine and Provision Resources

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

2. Choose Sample Projects, and then choose Transfer Data Records.

   The state machine Code and Visual Workflow are displayed.

   
   Note

   The Code section in this state machine references the AWS resources that will be created for this sample project.

3. Choose Next.

   The Deploy resources page is displayed, listing the resources that will be created. For this sample project the resources include:

   • A Lambda function for seeding the DynamoDB table

   • An Amazon SQS queue

   • A DynamoDB table

4. Choose Deploy Resources.

   Note

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

Start a New Execution

1. On the New execution page, enter an execution name (optional) and choose Start Execution.

2. (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 state machine, execution, and activity names 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.

3. Optionally, you can go to the newly created state machine on the Step Functions Dashboard, and then choose New execution.

4. When an execution is complete, you can select states on the Visual workflow and browse the Input and Output under Step details

Example State Machine Code

The state machine in this sample project integrates with DynamoDB and Amazon SQS by passing parameters directly to those resources.

Browse through this example state machine to see how Step Functions controls DynamoDB and Amazon SQS by connecting to the Amazon Resource Name (ARN) in the Resource field, and by passing Parameters to the service API.

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

{
  "Comment" : "An example of the Amazon States Language for reading messages from a DynamoDB table and sending them to SQS",
  "StartAt": "Seed the DynamoDB Table",
  "TimeoutSeconds": 3600,
  "States": {
    "Seed the DynamoDB Table": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:us-east-1:123456789012:function:sqsconnector-SeedingFunction-T3U43VYDU5OQ",
      "ResultPath": "$.List",
      "Next": "For Loop Condition"
    },
    "For Loop Condition": {
      "Type": "Choice",
      "Choices": [
        {
          "Not": {
            "Variable": "$.List[0]",
            "StringEquals": "DONE"
          },
          "Next": "Read Next Message from DynamoDB"
        }
      ],
      "Default": "Succeed"
    },
    "Read Next Message from DynamoDB": {
      "Type": "Task",
      "Resource": "arn:aws:states:::dynamodb:getItem",
      "Parameters": {
        "TableName": "sqsconnector-DDBTable-1CAFOJWP8QD6I",
        "Key": {
          "MessageId": {"S.$": "$.List[0]"}
        }
      },
      "ResultPath": "$.DynamoDB",
      "Next": "Send Message to SQS"
    },
    "Send Message to SQS": {
      "Type": "Task",
      "Resource": "arn:aws:states:::sqs:sendMessage",
      "Parameters": {
        "MessageBody.$": "$.DynamoDB.Item.Message.S",
        "QueueUrl": "https://sqs.us-east-1.amazonaws.com/123456789012/sqsconnector-SQSQueue-QVGQBW134PWK"
      },
      "ResultPath": "$.SQS",
      "Next": "Pop Element from List"
    },
    "Pop Element from List": {
      "Type": "Pass",
      "Parameters": {
        "List.$": "$.List[1:]"
      },
      "Next": "For Loop Condition"
    },
    "Succeed": {
      "Type": "Succeed"
    }
  }
}

For more information about passing parameters and managing results, see the following:

• Pass parameters to a service API

• ResultPath

IAM Example

This example AWS Identity and Access Management (IAM) policy generated by the sample project includes the least privilege necessary to execute the state machine and related resources. It's a best practice to include only those permissions that are necessary in your IAM policies.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "dynamodb:GetItem"
            ],
            "Resource": [
                "arn:aws:dynamodb:ap-northeast-1:123456789012:table/TransferDataRecords-DDBTable-3I41R5L5EAGT"
            ],
            "Effect": "Allow"
        },
        {
            "Action": [
                "sqs:SendMessage"
            ],
            "Resource": [
                "arn:aws:sqs:ap-northeast-1:123456789012:TransferDataRecords-SQSQueue-BKWXTS09LIW1"
            ],
            "Effect": "Allow"
        },
        {
            "Action": [
                "lambda:invokeFunction"
            ],
            "Resource": [
                "arn:aws:lambda:ap-northeast-1:123456789012:function:TransferDataRecords-SeedingFunction-VN4KY2TPAZSR"
            ],
            "Effect": "Allow"
        }
    ]
}

For information about how to configure IAM when using Step Functions with other AWS services, see IAM Policies for integrated services.