Step Functions：サーバーレスワークフローのオーケストレーション

AWS Step Functionsとは

Amazon States Language（ASL）

{
  'Comment': 'Order processing workflow',
  'StartAt': 'ValidateOrder',
  'States': {
    'ValidateOrder': {
      'Type': 'Task',
      'Resource': 'arn:aws:lambda:us-east-1:123456789012:function:ValidateOrder',
      'Next': 'ChargePayment',
      'Retry': [{'ErrorEquals': ['Lambda.ServiceException'], 'IntervalSeconds': 2, 'MaxAttempts': 3}]
    },
    'ChargePayment': {
      'Type': 'Task',
      'Resource': 'arn:aws:states:::dynamodb:putItem',
      'Parameters': {'TableName': 'Orders', 'Item': {'orderId': {'S.$': '$.orderId'}}},
      'End': true
    }
  }
}

StandardワークフローとExpressワークフロー

# Create a Standard workflow state machine
aws stepfunctions create-state-machine \
  --name OrderProcessing \
  --definition file://order-state-machine.json \
  --role-arn arn:aws:iam::123456789012:role/StepFunctionsRole \
  --type STANDARD

# Create an Express workflow for high-throughput
aws stepfunctions create-state-machine \
  --name ClickstreamProcess \
  --definition file://click-state-machine.json \
  --role-arn arn:aws:iam::123456789012:role/StepFunctionsRole \
  --type EXPRESS

Task状態とサービス統合

# Sync integration: start Glue job and wait for completion
'RunGlueETL': {
  'Type': 'Task',
  'Resource': 'arn:aws:states:::glue:startJobRun.sync:2',
  'Parameters': {
    'JobName': 'clean-sales'
  },
  'Next': 'RunAthenaQuery'
}

分岐ロジックのためのChoice状態

'RouteByOrderType': {
  'Type': 'Choice',
  'Choices': [
    {
      'Variable': '$.orderType',
      'StringEquals': 'DIGITAL',
      'Next': 'FulfillDigital'
    },
    {
      'Variable': '$.orderType',
      'StringEquals': 'PHYSICAL',
      'Next': 'FulfillPhysical'
    }
  ],
  'Default': 'HandleUnknownType'
}

Parallel状態とMap状態

'ProcessImages': {
  'Type': 'Map',
  'ItemsPath': '$.imageKeys',
  'MaxConcurrency': 10,
  'Iterator': {
    'StartAt': 'ResizeImage',
    'States': {
      'ResizeImage': {
        'Type': 'Task',
        'Resource': 'arn:aws:lambda:us-east-1:123:function:ResizeImage',
        'End': true
      }
    }
  },
  'Next': 'NotifyComplete'
}

エラー処理：CatchとRetry

'ChargeCard': {
  'Type': 'Task',
  'Resource': 'arn:aws:lambda:us-east-1:123:function:ChargeCard',
  'Retry': [{
    'ErrorEquals': ['Lambda.ServiceException', 'States.TaskFailed'],
    'IntervalSeconds': 2,
    'MaxAttempts': 3,
    'BackoffRate': 2.0
  }],
  'Catch': [{
    'ErrorEquals': ['PaymentDeclined'],
    'Next': 'NotifyPaymentFailed',
    'ResultPath': '$.error'
  }],
  'Next': 'FulfillOrder'
}

Wait状態とコールバック

# Callback pattern: wait for human approval
'RequestApproval': {
  'Type': 'Task',
  'Resource': 'arn:aws:states:::sqs:sendMessage.waitForTaskToken',
  'Parameters': {
    'QueueUrl': 'https://sqs.us-east-1.amazonaws.com/123/approvals',
    'MessageBody': {
      'taskToken.$': '$$.Task.Token',
      'orderId.$': '$.orderId'
    }
  },
  'Next': 'ProcessApproval'
}

Step FunctionsとEventBridgeの統合

Step Functions実行の監視

# List recent executions and check status
aws stepfunctions list-executions \
  --state-machine-arn arn:aws:states:us-east-1:123456789012:stateMachine:OrderProcessing \
  --status-filter FAILED

# Describe a specific failed execution for debugging
aws stepfunctions describe-execution \
  --execution-arn arn:aws:states:us-east-1:123456789012:execution:OrderProcessing:exec-001

Step Functions、SQS、EventBridgeの比較

理解度チェック

レッスンのまとめ