AWS Lambda Tear a Function Down in Dependency Order

arazzo: 1.0.1
info:
  title: AWS Lambda Tear a Function Down in Dependency Order
  summary: Detach the event sources and the public URL that outlive a function, then delete the function and all its versions and aliases.
  description: >-
    Deleting a Lambda function does not clean up after itself in the way most
    people assume. Deleting the function removes all of its versions and aliases,
    but event source mappings are separate resources that survive it: an orphaned
    mapping keeps polling the queue or stream and reports failures against a
    function that no longer exists. This workflow finds the mappings attached to
    the function, deletes one, removes the function URL so nothing on the public
    internet outlives the function either, and then deletes the function itself.
    Every step spells out its request inline so the flow can be read and executed
    without opening the underlying OpenAPI description.
  version: 1.0.0
sourceDescriptions:
- name: lambdaApi
  url: ../openapi/aws-lambda-api-openapi.yml
  type: openapi
workflows:
- workflowId: function-teardown
  summary: Remove a function's event source mapping and URL, then delete the function.
  description: >-
    Confirms the function, enumerates the event source mappings that would
    otherwise be orphaned, deletes the first of them and the function URL, and
    finally deletes the function together with its versions and aliases. Run once
    per attached mapping when a function consumes from more than one source.
  inputs:
    type: object
    required:
    - functionName
    properties:
      functionName:
        type: string
        description: The name or ARN of the function to tear down.
  steps:
  - stepId: confirmFunction
    description: >-
      Confirm the function exists and capture its ARN before anything is deleted,
      so a mistyped name fails before it can detach resources belonging to some
      other function.
    operationId: getFunction
    parameters:
    - name: FunctionName
      in: path
      value: $inputs.functionName
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      functionArn: $response.body#/Configuration/FunctionArn
      state: $response.body#/Configuration/State
  - stepId: findEventSourceMappings
    description: >-
      List the event source mappings pointed at this function. These are
      independent resources that survive the function's deletion, so they must be
      enumerated before it disappears and their UUIDs become hard to recover.
    operationId: listEventSourceMappings
    parameters:
    - name: FunctionName
      in: query
      value: $inputs.functionName
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      mappings: $response.body#/EventSourceMappings
      firstMappingUuid: $response.body#/EventSourceMappings/0/UUID
    onSuccess:
    - name: hasMappings
      type: goto
      stepId: deleteFirstMapping
      criteria:
      - context: $response.body
        condition: $.EventSourceMappings.length > 0
        type: jsonpath
    - name: noMappings
      type: goto
      stepId: deleteFunctionUrl
      criteria:
      - context: $response.body
        condition: $.EventSourceMappings.length == 0
        type: jsonpath
  - stepId: deleteFirstMapping
    description: >-
      Delete the mapping so Lambda stops polling the event source. Deletion is
      asynchronous and returns 202 while the mapping drains in-flight records.
    operationId: deleteEventSourceMapping
    parameters:
    - name: UUID
      in: path
      value: $steps.findEventSourceMappings.outputs.firstMappingUuid
    successCriteria:
    - condition: $statusCode == 202
    outputs:
      deletedMappingUuid: $response.body#/UUID
      deletionState: $response.body#/State
  - stepId: deleteFunctionUrl
    description: >-
      Remove the public HTTPS endpoint. A function with no URL configured returns
      404 here, which is a successful outcome for a teardown, so the flow
      continues to the deletion either way.
    operationId: deleteFunctionUrlConfig
    parameters:
    - name: FunctionName
      in: path
      value: $inputs.functionName
    successCriteria:
    - condition: $statusCode == 204
    onFailure:
    - name: noUrlConfigured
      type: goto
      stepId: deleteTheFunction
      criteria:
      - condition: $statusCode == 404
  - stepId: deleteTheFunction
    description: >-
      Delete the function itself. Qualifier is deliberately omitted so that every
      version and alias is removed rather than a single version, leaving nothing
      behind.
    operationId: deleteFunction
    parameters:
    - name: FunctionName
      in: path
      value: $inputs.functionName
    successCriteria:
    - condition: $statusCode == 204
  outputs:
    functionArn: $steps.confirmFunction.outputs.functionArn
    detachedMappings: $steps.findEventSourceMappings.outputs.mappings
    deletedMappingUuid: $steps.deleteFirstMapping.outputs.deletedMappingUuid