arazzo: 1.0.1
info:
  title: AWS Lambda Find a Compatible Layer Version to Attach
  summary: Filter the account's layers by runtime and architecture, list the versions of a chosen layer, and resolve one to the exact ARN a function needs.
  description: >-
    The lookup that has to happen before a layer can be attached to a function.
    Functions reference a layer by a fully qualified version ARN, not by layer
    name, so a caller who knows only "we have a shared logging layer" cannot act
    on that. This read-only flow narrows the account's layers to those compatible
    with a given runtime and architecture, lists the versions of the chosen
    layer, and reads one back to yield the LayerVersionArn plus the licence and
    size details worth checking before taking a dependency. Lambda caps a
    function at five layers and 250 MB unzipped across all of them, which is why
    the size is worth knowing up front. 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: layer-discovery
  summary: Resolve a compatible layer to a specific version ARN a function can reference.
  description: >-
    Lists layers compatible with a runtime and architecture, enumerates the
    versions of a named layer, and resolves a specific version to its ARN and
    content metadata.
  inputs:
    type: object
    required:
    - layerName
    - versionNumber
    properties:
      layerName:
        type: string
        description: The name or ARN of the layer to resolve to a version ARN.
      versionNumber:
        type: integer
        description: The version number of the layer to resolve.
      compatibleRuntime:
        type: string
        description: >-
          Only list layers and versions compatible with this runtime (e.g.
          nodejs20.x, python3.12). Lambda rejects attaching an incompatible
          layer.
      compatibleArchitecture:
        type: string
        description: Only list layers and versions compatible with this architecture (x86_64 or arm64).
      maxItems:
        type: integer
        description: Maximum number of items returned per list call (1-10000).
  steps:
  - stepId: findCompatibleLayers
    description: >-
      List the account's layers narrowed to those compatible with the target
      runtime and architecture, showing the latest version of each. Filtering
      here rather than after the fact avoids surfacing layers the function could
      never load.
    operationId: listLayers
    parameters:
    - name: CompatibleRuntime
      in: query
      value: $inputs.compatibleRuntime
    - name: CompatibleArchitecture
      in: query
      value: $inputs.compatibleArchitecture
    - name: MaxItems
      in: query
      value: $inputs.maxItems
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      layers: $response.body#/Layers
      nextMarker: $response.body#/NextMarker
  - stepId: listVersionsOfLayer
    description: >-
      List the versions of the chosen layer. Deleted versions are not returned,
      so anything listed here can still be attached to a function.
    operationId: listLayerVersions
    parameters:
    - name: LayerName
      in: path
      value: $inputs.layerName
    - name: CompatibleRuntime
      in: query
      value: $inputs.compatibleRuntime
    - name: CompatibleArchitecture
      in: query
      value: $inputs.compatibleArchitecture
    - name: MaxItems
      in: query
      value: $inputs.maxItems
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      layerVersions: $response.body#/LayerVersions
      nextMarker: $response.body#/NextMarker
  - stepId: resolveVersionArn
    description: >-
      Read the specific layer version to obtain the LayerVersionArn a function's
      configuration must reference, along with the code size and licence terms
      worth reviewing before depending on it.
    operationId: getLayerVersion
    parameters:
    - name: LayerName
      in: path
      value: $inputs.layerName
    - name: VersionNumber
      in: path
      value: $inputs.versionNumber
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      layerVersionArn: $response.body#/LayerVersionArn
      layerArn: $response.body#/LayerArn
      version: $response.body#/Version
      compatibleRuntimes: $response.body#/CompatibleRuntimes
      compatibleArchitectures: $response.body#/CompatibleArchitectures
      licenseInfo: $response.body#/LicenseInfo
      codeSize: $response.body#/Content/CodeSize
      codeSha256: $response.body#/Content/CodeSha256
  outputs:
    compatibleLayers: $steps.findCompatibleLayers.outputs.layers
    layerVersions: $steps.listVersionsOfLayer.outputs.layerVersions
    layerVersionArn: $steps.resolveVersionArn.outputs.layerVersionArn
    codeSize: $steps.resolveVersionArn.outputs.codeSize