Amazon Fargate Tear Down a Service

arazzo: 1.0.1
info:
  title: Amazon Fargate Tear Down a Service
  summary: Scale a service to zero, wait for it to drain, then delete it.
  description: >-
    Safely decommissions a Fargate service. ECS requires a service to have zero
    running tasks before it can be deleted cleanly, so the workflow first
    updates the service desired count to zero, polls DescribeServices until the
    running count reaches zero, and then deletes the service. Each step inlines
    its AWS JSON 1.1 request and the X-Amz-Target action header so the teardown
    can be read and executed directly.
  version: 1.0.0
sourceDescriptions:
- name: fargateApi
  url: ../openapi/amazon-fargate-openapi.yml
  type: openapi
workflows:
- workflowId: teardown-service
  summary: Drain a service to zero tasks and then delete it.
  description: >-
    Chains updateService (desiredCount 0), a describeServices drain poll, and
    deleteService.
  inputs:
    type: object
    required:
    - cluster
    - service
    properties:
      cluster:
        type: string
        description: Name or ARN of the cluster hosting the service.
      service:
        type: string
        description: Name or ARN of the service to tear down.
  steps:
  - stepId: scaleToZero
    description: Update the service desired count to zero so its tasks drain.
    operationId: updateService
    parameters:
    - name: X-Amz-Target
      in: header
      value: AmazonEC2ContainerServiceV20141113.UpdateService
    requestBody:
      contentType: application/x-amz-json-1.1
      payload:
        cluster: $inputs.cluster
        service: $inputs.service
        desiredCount: 0
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      serviceArn: $response.body#/service/serviceArn
      desiredCount: $response.body#/service/desiredCount
  - stepId: pollDrained
    description: >-
      Poll DescribeServices until the running count reaches zero, re-entering
      while tasks are still draining.
    operationId: describeServices
    parameters:
    - name: X-Amz-Target
      in: header
      value: AmazonEC2ContainerServiceV20141113.DescribeServices
    requestBody:
      contentType: application/x-amz-json-1.1
      payload:
        cluster: $inputs.cluster
        services:
        - $inputs.service
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      runningCount: $response.body#/services/0/runningCount
      status: $response.body#/services/0/status
    onSuccess:
    - name: stillDraining
      type: goto
      stepId: pollDrained
      criteria:
      - context: $response.body
        condition: $.services[0].runningCount > 0
        type: jsonpath
    - name: drained
      type: goto
      stepId: deleteService
      criteria:
      - context: $response.body
        condition: $.services[0].runningCount == 0
        type: jsonpath
  - stepId: deleteService
    description: Delete the now-drained service from the cluster.
    operationId: deleteService
    parameters:
    - name: X-Amz-Target
      in: header
      value: AmazonEC2ContainerServiceV20141113.DeleteService
    requestBody:
      contentType: application/x-amz-json-1.1
      payload:
        cluster: $inputs.cluster
        service: $inputs.service
        force: false
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      serviceArn: $response.body#/service/serviceArn
      finalStatus: $response.body#/service/status
  outputs:
    serviceArn: $steps.deleteService.outputs.serviceArn
    finalStatus: $steps.deleteService.outputs.finalStatus