Step 1: Create the State Machine and Provision Resources Step 2: Run the state machine Example State Machine Code for the Parent (Standard Workflows)Example IAM Role for the Parent State Machine Example State Machine Code for the Nested State Machine (Express Workflows)Example IAM Role for Child State Machine

Perform selective checkpointing using Standard and Express workflows

This sample project demonstrates how to combine Standard and Express Workflows by running a mock e-commerce workflow that does selective checkpointing. Deploying this sample project creates a Standard workflows state machine, a nested Express Workflows state machine, an AWS Lambda function, an Amazon Simple Queue Service (Amazon SQS) queue, and an Amazon Simple Notification Service (Amazon SNS) topic.

For more information about Express Workflows, nested workflows, and Step Functions service integrations, see the following:

Step 1: Create the State Machine and Provision Resources

Open the Step Functions console and choose Create state machine.
Type Selective checkpointing example in the search box, and then choose Selective checkpointing example from the search results that are returned.
Choose Next to continue.
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.

This sample project deploys the following resources:
- An AWS Lambda function
- An Amazon SQS queue
- An Amazon SNS topic
- An AWS Step Functions state machine of type Standard
- A Step Functions state machine of type Express
- Related AWS Identity and Access Management (IAM) roles
The following image shows the workflow graph for the Selective checkpointing example sample project:
Choose Use template to continue with your selection.

Next steps depend on your previous choice:

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

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

After the resources of the sample project are deployed do the following.

Step 2: Run the state machine

On the State machines page, choose your sample project.
On the sample project page, choose Start execution.
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.
Go to your CloudWatch Logs log group and inspect the logs. The name of the log group will look like example-ExpressLogGroup-wJalrXUtnFEMI.

Example State Machine Code for the Parent (Standard Workflows)

The state machine in this sample project integrates with Amazon SQS , Amazon SNS, and Step Functions Express Workflows.

Browse through this example state machine to see how Step Functions processes input from Amazon SQS and Amazon SNS, and then uses a nested Express Workflows state machine to update backend systems.

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


{
    "Comment": "An example of combining standard and express workflows to run a mock e-commerce workflow that does selective checkpointing.",
    "StartAt": "Approve Order Request",
    "States": {
        "Approve Order Request": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sqs:sendMessage.waitForTaskToken",
            "Parameters": {
                "QueueUrl": "<SQS_QUEUE_URL>",
                "MessageBody": {
                    "MessageTitle": "Order Request received. Pausing workflow to wait for manual approval. ",
                    "TaskToken.$": "$$.Task.Token"
                }
            },
            "Next": "Notify Order Success",
            "Catch": [
                {
                    "ErrorEquals": [
                        "States.ALL"
                    ],
                    "Next": "Notify Order Failure"
                }
            ]
        },
        "Notify Order Success": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sns:publish",
            "Parameters": {
                "Message": "Order has been approved. Resuming workflow.",
                "TopicArn": "<SNS_ARN>"
            },
            "Next": "Process Payment"
        },
        "Notify Order Failure": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sns:publish",
            "Parameters": {
                "Message": "Order not approved. Order failed.",
                "TopicArn": "<SNS_ARN>"
            },
            "End": true
        },
        "Process Payment": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sqs:sendMessage.waitForTaskToken",
            "Parameters": {
                "QueueUrl": "<SQS_QUEUE_URL>",
                "MessageBody": {
                    "MessageTitle": "Payment sent to third-party for processing. Pausing workflow to wait for response.",
                    "TaskToken.$": "$$.Task.Token"
                }
            },
            "Next": "Notify Payment Success",
            "Catch": [
                {
                    "ErrorEquals": [
                        "States.ALL"
                    ],
                    "Next": "Notify Payment Failure"
                }
            ]
        },
        "Notify Payment Success": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sns:publish",
            "Parameters": {
                "Message": "Payment processing succeeded. Resuming workflow.",
                "TopicArn": "<SNS_ARN>"
            },
            "Next": "Workflow to Update Backend Systems"
        },
        "Notify Payment Failure": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sns:publish",
            "Parameters": {
                "Message": "Payment processing failed.",
                "TopicArn": "<SNS_ARN>"
            },
            "End": true
        },
        "Workflow to Update Backend Systems": {
            "Comment": "Starting an execution of an Express workflow to handle backend updates. Express workflows are fast and cost-effective for steps where checkpointing isn't required.",
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::states:startExecution.sync",
            "Parameters": {
                "StateMachineArn": "<UPDATE_DATABASE_EXPRESS_STATE_MACHINE_ARN>",
                "Input": {
                    "AWS_STEP_FUNCTIONS_STARTED_BY_EXECUTION_ID.$": "$$.Execution.Id"
                }
            },
            "Next": "Ship the Package"
        },
        "Ship the Package": {
            "Type": "Task",
            "Resource": "arn:<PARTITION>:states:::sns:publish",
            "Parameters": {
                "Message": "Order and payment received, database is updated and the package is ready to ship.",
                "TopicArn": "<SNS_ARN>"
            },
            "End": true
        }
    }
}

These example AWS Identity and Access Management (IAM) policies generated by the sample project include the least privilege necessary to execute the state machine and related resources. We recommend that you include only those permissions that are necessary in your IAM policies.

Amazon SNS policy:


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "sns:Publish"
            ],
            "Resource": "arn:aws:sns:us-east-1:123456789012:Checkpoint-SNSTopic-wJalrXUtnFEMI",
            "Effect": "Allow"
        }
    ]
}

Amazon SQS policy:


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "sqs:SendMessage"
            ],
            "Resource": "arn:aws:sqs:us-east-1:123456789012:Checkpoint-SQSQueue-je7MtGbClwBF",
            "Effect": "Allow"
        }
    ]
}

States execution policy:


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "states:StartExecution",
                "states:DescribeExecution",
                "states:StopExecution"
            ],
            "Resource": "*",
            "Effect": "Allow"
        },
        {
            "Action": [
                "events:PutTargets",
                "events:PutRule",
                "events:DescribeRule"
            ],
            "Resource": "arn:aws:events:us-east-1:123456789012:rule/StepFunctionsGetEventsForStepFunctionsExecutionRule",
            "Effect": "Allow"
        }
    ]
}

Example State Machine Code for the Nested State Machine (Express Workflows)

The state machine in this sample project updates backend information when called by the parent state machine.

Browse through this example state machine to see how Step Functions updates the different components of the mock e-commerce backend systems.

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


{
  "StartAt": "Update Order History",
  "States": {
    "Update Order History": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "Checkpoint-UpdateDatabaseLambdaFunction-wJalrXUtnFEMI",
        "Payload": {
          "Message": "Update order history."
        }
      },
      "Next": "Update Data Warehouse"
    },
    "Update Data Warehouse": {
      "Type" : "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "Checkpoint-UpdateDatabaseLambdaFunction-wJalrXUtnFEMI",
        "Payload": {
          "Message": "Update data warehouse."
        }
      },
      "Next": "Update Customer Profile"
    },
    "Update Customer Profile": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "Checkpoint-UpdateDatabaseLambdaFunction-wJalrXUtnFEMI",
        "Payload": {
          "Message": "Update customer profile."
        }
      },
      "Next": "Update Inventory"
    },
    "Update Inventory": {
      "Type": "Task",
      "Resource": "arn:aws:states:::lambda:invoke",
      "Parameters": {
        "FunctionName": "Checkpoint-UpdateDatabaseLambdaFunction-wJalrXUtnFEMI",
        "Payload": {
          "Message": "Update inventory."
        }
      },
      "End": true
    }
  }
}

Example IAM Role for Child State Machine

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. We recommend that you include only those permissions that are necessary in your IAM policies.


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "lambda:InvokeFunction"
            ],
            "Resource": [
                "arn:aws:lambda:us-east-1:123456789012:function:Example-UpdateDatabaseLambdaFunction-wJalrXUtnFEMI"
            ],
            "Effect": "Allow"
        }
    ]
}

The following policy ensures that there are sufficient permissions for CloudWatch Logs.


{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Action": [
                "logs:CreateLogDelivery",
                "logs:GetLogDelivery",
                "logs:UpdateLogDelivery",
                "logs:DeleteLogDelivery",
                "logs:ListLogDeliveries",
                "logs:PutResourcePolicy",
                "logs:DescribeResourcePolicies",
                "logs:DescribeLogGroups"
            ],
            "Resource": [
                "*"
            ],
            "Effect": "Allow"
        }
    ]
}

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

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