Step Function (serverless)

• https://aws.amazon.com/step-functions/

0. intro

• function orchestrator that makes it easy to sequence AWS Lambda functions and multiple AWS services into business-critical applications
• can create and run a series of checkpointed and event-driven workflows
• output of one step acts as an input to the next
• visual workflows
• Improve resiliency
• manages state, checkpoints and restarts for you to make sure that your application executes in order and as expected.
• Built-in try/catch, retry and rollback capabilities deal with errors and exceptions automatically

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1. State machine

• model workflow as state-machine
• from workflow studio / console UI
• create ASL (Amazon State lamguage), json.
• has states to do some work, like
• 

• 

• type:

• standard
• express

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2. state

• type
• pass
• choice
• wait
• parallel
• fail
• Activity task
  • have poll mechanism.
  • activity worker (lambda, ec2, ecs) polls for task (taskToken-1)
  • API : getActivityTask
  • send back :
  • API : sendTaskSuccess / SendTaskfailure
    • output/error
    • taskToken-1
  • waits for worker, options:
  • option-1: worker-1, periodically send heardbeat, API: SendtaskHeartBeat
    • upto 1 year
  • option-2 : configure TimeOutSecond
  • 

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3. wait for task Token

• similar to activity task
• task --> depend on 3rd app response

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4. Error handing

• can handle in Application code
• can handle in state machine using retry and catch
• udemy Video ref

Retry

Catch

• error/exception
• note: CustomError in screenshot : coming from Application/lambda code

  • States.ALL        : matches any error name
  • States.Timeout    : Task ran longer than TimeoutSeconds or no heartbeat received
  • States.TaskFailed : execution failure
  • States.Permissions: insufficient privileges to execute code
  

• 

• resultpath : input to next state

• 

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5. security