Serverless workflows

AWS SWF - Simple Workflow Service

• Coordinate work amongst applications
• Code runs on EC2 (not serverless)
• 1 year max runtime
• Requires you to write application code
• One time only completion is key feature that ensures that a task is assigned only once and is never duplicated.
• 💡❗ Step functions is recommended to be used for new applications, except if you need:
  • external signals to intervene in the processes
  • child processes that return values to parent processes
  • long running up to 1 year
• Actors
  • Workflow starters: Any application that initiates workflow
  • Deciders: control flow activity tasks
  • Activity workers: carry out the activity tasks
• Steps: Activity, Decision, Human intervention
• Tasks
  • Activity task: Tell activity worker to execute its task.
  • Decision task: It tells the decider the state of the workflow execution.
  • Lambda task: Executes lambda
• 💡 Use case e.g. order fulfilment from web to warehouse to delivery.
• 🤗 AWS uses SWF to run their warehouses.

Step Functions

• Build serverless visual workflow to orchestrate your Lambda functions
  • E.g. Start => Submit Job => Wait X seconds => Get Job Status => Job Compete ? next : Go back to Wait X seconds -> End
• Represent flow as a JSON 📝state machine
• Features: sequence, parallel, conditions, timeouts, error handling …
• The steps of your workflow can exist anywhere, including in AWS Lambda functions, on Amazon EC2, or on-premises.
• Integrated with & can coordinate many AWS services: Amazon ECS, AWS Fargate, Amazon DynamoDB, Amazon SNS, Amazon SQS, AWS Batch, AWS Glue, and Amazon SageMaker.
• ❗ Maximum execution time of 1 year
• Possibility to implement human approval feature
  • E.g. API gateway to send human approval accepted or not query.
• 💡 Use cases: any 📝workflow
• Monitoring
  • Each executed branch can be monitored and have different steps.
  • Each step has Success, Failed, Cancelled, In Progress states.
• Can use Callback patterns
  • Pauses execution of the workflow until your application returns a token.
  • Supports callback patterns with Amazon ECS, Amazon SNS, Amazon SQS, AWS Fargate, and AWS Lambda.
  • Can also integrate with on-premises

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