Select Actions

select_actions allows users to choose from a list of predefined actions for their build, push, and pull steps. When select_actions is invoked, any combination of --build, --push, and --pull may be provided. These steps must be defined under the actions portion of a prefect.yaml file. Each action selected will override the default step definition at the root level of your prefect.yaml.

Examples

This repository supposes the following, for the sake of example:

• You have two Prefect workspaces, one used for staging and one used for production.
• You have one or more deployments which should be mirrored across workspaces.
• Your deployments are configured to use git code storage, and the branch a deployment uses should differ per workspace.
• Flows run in containers, so images need to be rebuilt when Python dependencies or docker build steps change. Since dependencies can differ per branch/workspace, each branch/workspace pairing should have its own image.
• Images are stored on Dockerhub.
• The following values are stored as secrets in the repository's settings:
  • PREFECT_API_KEY
  • PREFECT_API_URL (API url for produciton workspace)
  • PREFECT_API_URL_STG (API url for staging workspace)
  • DOCKERHUB_USERNAME
  • DOCKERHUB_TOKEN

When the Github Actions workflow is run, select_actions will modify the prefect.yaml that has been cloned into the Github Actions runner. prefect deploy --all will be run against the modified yaml, which only persists for the duration of the Actions workflow.

select_actions is used as part of a Github Actions workflow to modify prefect.yaml according to a set of triggers and conditions. Since these deployments are using git code storage, there are a limited set of conditions under which running prefect deploy is required.

See .github/workflows for more complete examples.

Starting prefect.yaml (actions section only)

actions:
  build:
    build_image_stg:
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-stg
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
    build_image_prod:
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-prod
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
  push:
    push_image:
      - prefect_docker.deployments.steps.push_docker_image:
          requires: prefect-docker
          image_name: "{{ build-image.image_name }}"
          tag: "{{ build-image.tag }}"
  pull:
    staging:
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: staging
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"
    production:
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: main
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"

build: null

push: null

pull: null

Build and push an image

When the Dockerfile or requirements.txt changes, the image must be built and pushed. Let's say this has happened on the main branch. The Github Actions workflow will detect these changes and run the following:

python select_actions.py --build build_image --push push_image --pull production

actions:
  build:
    build_image_stg: &id001
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-stg
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
    build_image_prod:
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-prod
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
  push:
    push_image: &id002
      - prefect_docker.deployments.steps.push_docker_image:
          requires: prefect-docker
          image_name: "{{ build-image.image_name }}"
          tag: "{{ build-image.tag }}"
  pull:
    staging:
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: staging
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"
    production: &id003
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: main
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"

build: *id001

push: *id002

pull: *id003

Update or create a deployment in prefect.yaml

When a deployment definition is changed or added, we need to persist those changes to Prefect Cloud/Server, but no image building or pushing is required. This time, the changes were pushed to the staging branch:

python select_actions.py --pull staging

actions:
  build:
    build_image_stg:
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-stg
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
    build_image_prod:
      - prefect.deployments.steps.run_shell_script:
          id: get-commit-hash
          script: git rev-parse --short HEAD
          stream_output: false
      - prefect_docker.deployments.steps.build_docker_image:
          id: build-image
          requires: prefect-docker
          image_name: kevingrismoreprefect/github-actions-demo-prod
          tag: "{{ get-commit-hash.stdout }}"
          dockerfile: Dockerfile
  push:
    push_image:
      - prefect_docker.deployments.steps.push_docker_image:
          requires: prefect-docker
          image_name: "{{ build-image.image_name }}"
          tag: "{{ build-image.tag }}"
  pull:
    staging: &id001
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: staging
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"
    production:
      - prefect.deployments.steps.git_clone:
        repository: git@github.com:kevingrismore/prefect-select-actions.git
        branch: main
        credentials: "{{ prefect.blocks.github-credentials.my-block-name }}"

build:

push:

pull: *id001