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AWS Step Functions

AWS Step Fucntions with Lambda​

ASL (Amazon State Language)​

{
  "Comment": "Transaction Processor State Machine",
  "StartAt": "ProcessTransaction",
  "States": {
    "ProcessTransaction": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "&.TransactionType",
          "StringEquals": "PURCHASE",
          "Next": "ProcessPurchase"
        },
        {
          "Variable": "&.TransactionType",
          "StringEquals": "REFUND",
          "Next": "ProcessRefund"
        }
      ]
    },
    "ProcessRefund": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:REGION:ACCOUNT_ID:function:FUNCTION_NAME",
      "End": true
    },
    "ProcessPurchase": {
      "Type": "Task",
      "Resource": "arn:aws:lambda:REGION:ACCOUNT_ID:function:FUNCTION_NAME",
      "End": true
    }
  }
}

State Machine​

AWS Step Functions with SQS​

ASL (Amazon State Language)​

{
  "Comment": "Transaction Processor State Machine using SQS",
  "StartAt": "ProcessTransaction",
  "States": {
    "ProcessTransaction": {
      "Type": "Pass",
      "Next": "BroadcastToSqs"
    },
    "BroadcastToSqs": {
      "Type": "Task",
      "Resource": "arn:aws:states:::sqs:sendMessage",
      "Parameters": {
        "QueueUrl": "[link of QueueUrl]",
        "MessageBody": {
          "TransactionId.$": "$.TransactionId",
          "Type.$": "$.Type"
        }
      },
      "End": true
    }
  }
}
Event
{
  "TransactionId": "abc",
  "Type": "PURCHASE"
}

State Machine​

AWS Step Functions with SNS​

ASL (Amazon State Language)​

{
  "Comment": "Transaction Processor State Machine Using SNS",
  "StartAt": "ProcessTransaction",
  "States": {
    "ProcessTransaction": {
      "Type": "Pass",
      "Next": "BroadcastToSns"
    },
    "BroadcastToSns": {
      "Type": "Task",
      "Resource": "arn:aws:state:::sns:publish",
      "Parameters": {
        "TopicArn": "[arn of Topic]",
        "Parameters": {
          "TransactionId.$": "$.TransactionId",
          "Type.$": "$.Type",
          "Source": "Step Functions!"
        }
      }
    }
  }
}
Event
{
  "TransactionId": "abc",
  "Type": "PURCHASE"
}

State Machine​

AWS Step Functions with DynamoDB​

ASL (Amazon State Language)​

{
  "Comment": "Transaction Processor State Machine",
  "StartAt": "ProcessTransaction",
  "States": {
    "ProcessTransaction": {
      "Type": "Pass",
      "Next": "StoreHistory"
    },
    "StoreHistory": {
      "Type": "Task",
      "Resource": "arn:aws:states:::dynamodb:putItem",
      "Parameters": {
        "TableName": "TransactionHistoryTable",
        "Item": {
          "TransactionId": {
            "s.$": "$.TransactionId"
          }
        },
        "Retry": [
          {
            "ErrEquals": ["States.All"],
            "IntervalSeconds": 1,
            "MaxAttempts": 3
          }
        ],
        "End": true,
        "ResultPash": "$.DynamoDB"
      }
    }
  }
}

State Machine​

Start an AWS Step Function Workflow From Lambda​

AWS Lambda function:

python
import json
import bonto3
import uuid

client = boto3.client("stepfunction")

def lambda_handler(evetn, context):
    #INPUT -> { "TransactionId": "foo", "Type": "PURCHASE" }
    transactionId = str(uuid.uuid1())

    input = {"TransactionId": transactionId, "Type": "PURCHASE"}

    response = client.start_execution(
        startMachineArn="[ARN of state machine]"
        name=transactionId,
        input=json.dumps(input)
    )

AWS Step Function Map Task​

input.json
{
  "transactions": [
    {
      "transactionId": "R31",
      "type": "PURCHASE",
      "amount": 1344
    },
    {
      "transactionId": "R39",
      "type": "REFUND",
      "amount": 40
    },
    {
      "transactionId": "R31",
      "type": "REFUND",
      "amount": 12
    }
  ]
}

ASL (Amazon State Language)​

{
  "StartAt": "Validate-All",
  "States": {
    "Validate-All": {
      "Type": "Map",
      "InputPath": "$",
      "ItemsPath": "$.transactions",
      "MaxConsurrency": 0,
      "Iterator": {
        "StartAt": "Valiate",
        "States": {
          "Validate": {
            "Type": "Task",
            "Resource": "arn:aws:lambda:REGION:ACCOUNT_ID:function:FUNCTION_NAME",
            "Next": "Complete"
          },
          "Complete": {
            "Type": "Pass",
            "End": true
          }
        }
      },
      "ResultPath": "$",
      "End": true
    }
  }
}
lambda
def lambda_handler(event, context):
    return event["transactionId"] + "-" + event["type"]

State Machine​

Set timers with AWS Step Functions using Wait State​

ASL (Amazon State Language)​

{
  "Comment": "A Heello World example of the Amazon States Language using Pass states",
  "StartAt": "Wait 3 seconds",
  "States": {
    "Wait 3 secondes": {
      "Type": "Wait",
      "Seconds": 3,
      "Next": "Wait Until Hard Coded"
    },
    "Wait Until Hard Coded": {
      "Type": "Wait",
      "Timestamp": "2019-05-18-T00:00:00Z",
      "Next": "Dynamic Wait"
    },
    "Dynamic Wait": {
      "Type": "Wait",
      "TimestampPath": "$.waitUntilTimestamp",
      "End": true
    }
  }
}

State Machine​

Resources​