arazzo: 1.0.1
info:
  title: AWS Lambda Publish a Layer Version and Attach It to a Function
  summary: Publish a shared dependency layer from S3, verify the version, attach it to a function, and wait for the configuration update to settle.
  description: >-
    How shared dependencies reach a Lambda function. Layers package libraries or
    a custom runtime once and are attached to many functions, and every call to
    publish creates a brand new immutable version rather than mutating the last
    one. This workflow publishes the layer version, reads it back to confirm the
    runtime compatibility Lambda actually recorded, attaches the resulting
    version ARN to the target function, and polls until LastUpdateStatus reports
    the configuration change is live. 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: publish-layer-and-attach
  summary: Publish a new layer version and wire it into a function's configuration.
  description: >-
    Creates a new immutable version of a layer from an S3 archive, verifies it,
    then updates the function to reference that exact layer version ARN and
    waits for the update to complete.
  inputs:
    type: object
    required:
    - layerName
    - functionName
    - s3Bucket
    - s3Key
    - compatibleRuntimes
    properties:
      layerName:
        type: string
        description: The name of the layer to publish a new version of.
      functionName:
        type: string
        description: The name or ARN of the function the layer is attached to.
      s3Bucket:
        type: string
        description: The S3 bucket holding the layer archive ZIP.
      s3Key:
        type: string
        description: The S3 key of the layer archive ZIP.
      compatibleRuntimes:
        type: array
        description: Runtimes this layer supports (e.g. ["nodejs20.x"]). Lambda rejects attaching a layer to an incompatible runtime.
        items:
          type: string
      compatibleArchitectures:
        type: array
        description: Instruction set architectures this layer supports (x86_64 and/or arm64).
        items:
          type: string
      layerDescription:
        type: string
        description: Description recorded against the published layer version.
      licenseInfo:
        type: string
        description: The layer's software license (an SPDX identifier, a URL, or the full text).
  steps:
  - stepId: publishTheLayerVersion
    description: >-
      Publish a new immutable version of the layer from the staged S3 archive.
      The version number increments on every call; existing versions are never
      overwritten, so functions pinned to an older version are unaffected.
    operationId: publishLayerVersion
    parameters:
    - name: LayerName
      in: path
      value: $inputs.layerName
    requestBody:
      contentType: application/json
      payload:
        Description: $inputs.layerDescription
        Content:
          S3Bucket: $inputs.s3Bucket
          S3Key: $inputs.s3Key
        CompatibleRuntimes: $inputs.compatibleRuntimes
        CompatibleArchitectures: $inputs.compatibleArchitectures
        LicenseInfo: $inputs.licenseInfo
    successCriteria:
    - condition: $statusCode == 201
    outputs:
      layerVersionArn: $response.body#/LayerVersionArn
      layerArn: $response.body#/LayerArn
      version: $response.body#/Version
      codeSha256: $response.body#/Content/CodeSha256
  - stepId: verifyLayerVersion
    description: >-
      Read the published version back to confirm the archive landed and to see
      the runtime compatibility Lambda recorded, before any function is pointed
      at it.
    operationId: getLayerVersion
    parameters:
    - name: LayerName
      in: path
      value: $inputs.layerName
    - name: VersionNumber
      in: path
      value: $steps.publishTheLayerVersion.outputs.version
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      verifiedArn: $response.body#/LayerVersionArn
      compatibleRuntimes: $response.body#/CompatibleRuntimes
      codeSize: $response.body#/Content/CodeSize
  - stepId: attachLayerToFunction
    description: >-
      Update the function to reference the new layer version ARN. The Layers
      list is replaced wholesale rather than appended to, so the caller supplies
      the full intended set through this single new ARN.
    operationId: updateFunctionConfiguration
    parameters:
    - name: FunctionName
      in: path
      value: $inputs.functionName
    requestBody:
      contentType: application/json
      payload:
        Layers:
        - $steps.publishTheLayerVersion.outputs.layerVersionArn
    successCriteria:
    - condition: $statusCode == 200
    outputs:
      lastUpdateStatus: $response.body#/LastUpdateStatus
      revisionId: $response.body#/RevisionId
  - stepId: waitForConfigUpdate
    description: >-
      Poll until LastUpdateStatus reports "Successful". Until then the function
      is still being provisioned with the new layer and invocations continue to
      use the previous configuration.
    operationId: getFunctionConfiguration
    parameters:
    - name: FunctionName
      in: path
      value: $inputs.functionName
    successCriteria:
    - condition: $statusCode == 200
    - context: $response.body
      condition: $.LastUpdateStatus == "Successful"
      type: jsonpath
    onFailure:
    - name: keepWaitingForUpdate
      type: retry
      retryAfter: 5
      retryLimit: 60
      criteria:
      - condition: $statusCode == 200
    outputs:
      lastUpdateStatus: $response.body#/LastUpdateStatus
      lastUpdateStatusReason: $response.body#/LastUpdateStatusReason
      attachedLayers: $response.body#/Layers
  outputs:
    layerVersionArn: $steps.publishTheLayerVersion.outputs.layerVersionArn
    layerVersion: $steps.publishTheLayerVersion.outputs.version
    attachedLayers: $steps.waitForConfigUpdate.outputs.attachedLayers