Automate container image builds and maintenance with ACR Tasks
Containers provide new levels of virtualization, isolating application and developer dependencies from infrastructure and operational requirements. What remains, however, is the need to address how this application virtualization is managed and patched over the container lifecycle.
What is ACR Tasks?
ACR Tasks is a suite of features within Azure Container Registry. It provides cloud-based container image building for platforms including Linux, Windows, and ARM, and can automate OS and framework patching for your Docker containers. ACR Tasks not only extends your "inner-loop" development cycle to the cloud with on-demand container image builds, but also enables automated builds triggered by source code updates, updates to a container's base image, or timers. For example, with base image update triggers, you can automate your OS and application framework patching workflow, maintaining secure environments while adhering to the principles of immutable containers.
ACR Tasks supports several scenarios to build and maintain container images and other artifacts. See the following sections in this article for details.
- Quick task - Build and push a single container image to a container registry on-demand, in Azure, without needing a local Docker Engine installation. Think
docker pushin the cloud.
- Automatically triggered tasks - Enable one or more triggers to build an image:
- Multi-step task - Extend the single image build-and-push capability of ACR Tasks with multi-step, multi-container-based workflows.
Each ACR Task has an associated source code context - the location of a set of source files used to build a container image or other artifact. Example contexts include a Git repository or a local filesystem.
Tasks can also take advantage of run variables, so you can reuse task definitions and standardize tags for images and artifacts.
The inner-loop development cycle, the iterative process of writing code, building, and testing your application before committing to source control, is really the beginning of container lifecycle management.
Before you commit your first line of code, ACR Tasks's quick task feature can provide an integrated development experience by offloading your container image builds to Azure. With quick tasks, you can verify your automated build definitions and catch potential problems prior to committing your code.
Using the familiar
docker build format, the az acr build command in the Azure CLI takes a context (the set of files to build), sends it ACR Tasks and, by default, pushes the built image to its registry upon completion.
For an introduction, see the quickstart to build and run a container image in Azure Container Registry.
ACR Tasks is designed as a container lifecycle primitive. For example, integrate ACR Tasks into your CI/CD solution. By executing az login with a service principal, your CI/CD solution could then issue az acr build commands to kick off image builds.
Learn how to use quick tasks in the first ACR Tasks tutorial, Build container images in the cloud with Azure Container Registry Tasks.
If you want to build and push an image directly from source code, without a Dockerfile, Azure Container Registry provides the az acr pack build command (preview). This tool builds and pushes an image from application source code using Cloud Native Buildpacks.
Trigger task on source code update
Trigger a container image build or multi-step task when code is committed, or a pull request is made or updated, to a public or private Git repository in GitHub or Azure DevOps. For example, configure a build task with the Azure CLI command az acr task create by specifying a Git repository and optionally a branch and Dockerfile. When your team updates code in the repository, an ACR Tasks-created webhook triggers a build of the container image defined in the repo.
ACR Tasks supports the following triggers when you set a Git repo as the task's context:
|Trigger||Enabled by default|
To configure a source code update trigger, you need to provide the task a personal access token (PAT) to set the webhook in the public or private GitHub or Azure DevOps repo.
Currently, ACR Tasks doesn't support commit or pull request triggers in GitHub Enterprise repos.
Learn how to trigger builds on source code commit in the second ACR Tasks tutorial, Automate container image builds with Azure Container Registry Tasks.
Automate OS and framework patching
The power of ACR Tasks to truly enhance your container build workflow comes from its ability to detect an update to a base image. A feature of most container images, a base image is a parent image on which one or more application images are based. Base images typically contain the operating system, and sometimes application frameworks.
You can set up an ACR task to track a dependency on a base image when it builds an application image. When the updated base image is pushed to your registry, or a base image is updated in a public repo such as in Docker Hub, ACR Tasks can automatically build any application images based on it. With this automatic detection and rebuilding, ACR Tasks saves you the time and effort normally required to manually track and update each and every application image referencing your updated base image.
Learn more about base image update triggers for ACR Tasks. And learn how to trigger an image build when a base image is pushed to a container registry in the tutorial Automate container image builds when a base image is updated in a Azure container registry
Schedule a task
Optionally schedule a task by setting up one or more timer triggers when you create or update the task. Scheduling a task is useful for running container workloads on a defined schedule, or running maintenance operations or tests on images pushed regularly to your registry. For details, see Run an ACR task on a defined schedule.
Multi-step tasks provide step-based task definition and execution for building, testing, and patching container images in the cloud. Task steps defined in a YAML file specify individual build and push operations for container images or other artifacts. They can also define the execution of one or more containers, with each step using the container as its execution environment.
For example, you can create a multi-step task that automates the following:
- Build a web application image
- Run the web application container
- Build a web application test image
- Run the web application test container, which performs tests against the running application container
- If the tests pass, build a Helm chart archive package
- Perform a
helm upgradeusing the new Helm chart archive package
Multi-step tasks enable you to split the building, running, and testing of an image into more composable steps, with inter-step dependency support. With multi-step tasks in ACR Tasks, you have more granular control over image building, testing, and OS and framework patching workflows.
Learn about multi-step tasks in Run multi-step build, test, and patch tasks in ACR Tasks.
The following table shows examples of supported context locations for ACR Tasks:
|Local filesystem||Files within a directory on the local filesystem.||
|GitHub master branch||Files within the master (or other default) branch of a public or private GitHub repository.||
|GitHub branch||Specific branch of a public or private GitHub repo.||
|GitHub subfolder||Files within a subfolder in a public or private GitHub repo. Example shows combination of a branch and subfolder specification.||
|GitHub commit||Specific commit in a public or private GitHub repo. Example shows combination of a commit hash (SHA) and subfolder specification.||
|Azure DevOps subfolder||Files within a subfolder in a public or private Azure repo. Example shows combination of branch and subfolder specification.||
|Remote tarball||Files in a compressed archive on a remote webserver.||
|Artifact in container registry||OCI artifact files in a container registry repository.||
When using a private Git repo as a context for a task, you need to provide a personal access token (PAT).
By default, ACR Tasks builds images for the Linux OS and the amd64 architecture. Specify the
--platform tag to build Windows images or Linux images for other architectures. Specify the OS and optionally a supported architecture in OS/architecture format (for example,
--platform Linux/arm). For ARM architectures, optionally specify a variant in OS/architecture/variant format (for example,
View task output
Each task run generates log output that you can inspect to determine whether the task steps ran successfully. When you trigger a task manually, log output for the task run is streamed to the console and also stored for later retrieval. When a task is automatically triggered, for example by a source code commit or a base image update, task logs are only stored. View the run logs in the Azure portal, or use the az acr task logs command.
See more about viewing and managing task logs.
When you're ready to automate container image builds and maintenance in the cloud, check out the ACR Tasks tutorial series.
Optionally install the Docker Extension for Visual Studio Code and the Azure Account extension to work with your Azure container registries. Pull and push images to an Azure container registry, or run ACR Tasks, all within Visual Studio Code.