CI/CD resources for working with Prefect.
Many organizations deploy Prefect workflows through their CI/CD process. Each organization has their own unique CI/CD setup, but a common pattern is to use CI/CD to manage Prefect deployments. Combining Prefect’s deployment features with CI/CD tools enables efficient management of flow code updates, scheduling changes, and container builds. This guide uses GitHub Actions to implement a CI/CD process, but these concepts are generally applicable across many CI/CD tools.
Note that Prefect’s primary ways for creating deployments, a .deploy
flow method or a prefect.yaml
configuration file, are both designed for building and pushing images to a Docker registry.
In this example, you’ll write a GitHub Actions workflow that runs each time you push to your repository’s
main
branch. This workflow builds and pushes a Docker image containing your flow code to Docker Hub, then deploys the flow to Prefect Cloud.
Your CI/CD process must be able to authenticate with Prefect to deploy flows.
Deploy flows securely and non-interactively in your CI/CD process by saving your PREFECT_API_URL
and
PREFECT_API_KEY
as secrets in your repository’s settings. This allows them to be accessed in your CI/CD runner’s environment without exposing them in any scripts or configuration files.
In this scenario, deploying flows involves building and pushing Docker images, so add DOCKER_USERNAME
and DOCKER_PASSWORD
as secrets to your repository as well.
Create secrets for GitHub Actions in your repository under Settings -> Secrets and variables -> Actions -> New repository secret:
To deploy your flow through GitHub Actions, you need a workflow YAML file. GitHub looks for workflow
YAML files in the .github/workflows/
directory in the root of your repository. In their simplest form,
GitHub workflow files are made up of triggers and jobs.
The on:
trigger is set to run the workflow each time a push occurs on the main
branch of the repository.
The deploy
job is comprised of four steps
:
Checkout
clones your repository into the GitHub Actions runner so you can reference files or
run scripts from your repository in later steps.Log in to Docker Hub
authenticates to DockerHub so your image can be pushed to the Docker
registry in your DockerHub account. docker/login-action is an
existing GitHub action maintained by Docker. with:
passes values into the Action, similar to passing
parameters to a function.Setup Python
installs your selected version of Python.Prefect Deploy
installs the dependencies used in your flow, then deploys your flow. env:
makes
the PREFECT_API_KEY
and PREFECT_API_URL
secrets from your repository available as environment variables during this step’s execution.For reference, the examples below live in their respective branches of this repository.
flow.py
.github/workflows/deploy-prefect-flow.yaml
flow.py
.github/workflows/deploy-prefect-flow.yaml
flow.py
prefect.yaml
.github/workflows/deploy-prefect-flow.yaml
After pushing commits to your repository, GitHub automatically triggers a run of your workflow. Monitor the status of running and completed workflows from the Actions tab of your repository.
View the logs from each workflow step as they run. The Prefect Deploy
step includes output about
your image build and push, and the creation/update of your deployment.
In more complex scenarios, CI/CD processes often need to accommodate several additional considerations to enable a smooth development workflow:
This example repository addresses each of these considerations with a combination of Prefect’s and GitHub’s capabilities.
The deployment processes to run are automatically selected when changes are pushed, depending on two conditions:
branches:
- which branch has changed. This ultimately selects which Prefect workspace a
deployment is created or updated in. In this example, changes on the stg
branch deploy flows to a
staging workspace, and changes on the main
branch deploy flows to a production workspace.paths:
- which project folders’ files have changed. Since each project folder contains its own flows,
dependencies, and prefect.yaml
, it represents a complete set of logic and configuration that can deploy
independently. Each project in this repository gets its own GitHub Actions workflow YAML file.The prefect.yaml
file in each project folder depends on environment variables dictated by the
selected job in each CI/CD workflow; enabling external code storage for Prefect deployments that is clearly
separated across projects and environments.
Deployments in this example use S3 for code storage. So it’s important that push steps place flow files in separate locations depending upon their respective environment and project—so no deployment overwrites another deployment’s files.
Since building Docker images and installing Python dependencies are essential parts of the deployment process, it’s useful to rely on caching to skip repeated build steps.
The setup-python
action offers caching options
so Python packages do not have to be downloaded on repeat workflow runs.
The build-push-action
for building Docker images also offers
caching options for GitHub Actions.
If you are not using GitHub, other remote cache backends
are available as well.
Prefect provides its own GitHub Actions for authentication
and deployment creation.
These actions simplify deploying with CI/CD when using prefect.yaml
,
especially in cases where a repository contains flows used in multiple deployments across multiple
Prefect Cloud workspaces.
Here’s an example of integrating these actions into the workflow above:
The docker/login-action
GitHub Action supports pushing images to a wide variety of image registries.
For example, if you are storing Docker images in AWS Elastic Container Registry, you can add your ECR
registry URL to the registry
key in the with:
part of the action and use an AWS_ACCESS_KEY_ID
and
AWS_SECRET_ACCESS_KEY
as your username
and password
.
You can manage resources with the Terraform provider for Prefect.