Automate container image builds and maintenance with Azure Container Registry tasks

Containers provide new levels of virtualization by isolating application and developer dependencies from infrastructure and operational requirements. What remains is the need to address how this application virtualization is managed and patched over the container lifecycle.

Azure Container Registry tasks are a suite of features that:

• Provide cloud-based container image building for platforms like Linux, Windows, and ARM.
• Extend the early parts of an application development cycle to the cloud with on-demand container image builds.
• Enable automated builds triggered by source code updates, updates to a container's base image, or timers.

For example, with triggers for updates to a base image, you can automate OS and framework patching for your Docker containers. These triggers can help you maintain secure environments while adhering to the principles of immutable containers.

Task scenarios

Azure Container Registry tasks support several scenarios to build and maintain container images and other artifacts. This article describes quick tasks, automatically triggered tasks, and multi-step tasks.

Each task has an associated source code context, which is the location of source files that are used to build a container image or other artifact. Example contexts include a Git repository and a local file system.

Tasks can also take advantage of run variables, so you can reuse task definitions and standardize tags for images and artifacts.

Quick tasks

The inner-loop development cycle is the iterative process of writing code, building, and testing your application before committing to source control. It's really the beginning of container lifecycle management.

The quick task feature in Azure Container Registry tasks can provide an integrated development experience by offloading your container image builds to Azure. You can build and push a single container image to a container registry on demand, in Azure, without needing a local Docker Engine installation. Think docker build, docker push in the cloud. With quick tasks, you can verify your automated build definitions and catch potential problems before committing your code.

By using the familiar docker build format, the az acr build command in the Azure CLI takes a context. The command then sends the context to Azure Container Registry and (by default) pushes the built image to its registry upon completion.

Azure Container Registry tasks are designed as a container lifecycle primitive. For example, you can integrate Azure Container Registry tasks into your continuous integration and continuous delivery (CI/CD) solution. If you run az login with a service principal, your CI/CD solution can then issue az acr build commands to start image builds.

To learn how to use quick tasks, see the quickstart and tutorial for building and deploying container images by using Azure Container Registry tasks.

Automatically triggered tasks

Enable one or more triggers to build an image.

Trigger a task on a source code update

You can 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, a webhook created in Azure Container Registry tasks triggers a build of the container image defined in the repo.

Azure Container Registry tasks support the following triggers when you set a Git repo as a task's context:

To learn how to trigger builds on source code commits, see Automate container image builds with Azure Container Registry tasks.

Personal access token

To configure a trigger for source code updates, you need to provide the task a personal access token to set the webhook in the public or private GitHub or Azure DevOps repo. Required scopes for the personal access token are as follows:

To create a personal access token, see the GitHub or Azure DevOps documentation.

Automate OS and framework patching

The power of Azure Container Registry tasks to enhance your container build workflow comes from their ability to detect an update to a base image. A base image is a feature of most container images. It's 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 Azure Container Registry 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, Azure Container Registry tasks can automatically build any application images based on it. With this automatic detection and rebuilding, Azure Container Registry tasks save you the time and effort that's normally required to manually track and update every application image that references your updated base image.

For more information, see About base image updates for Azure Container Registry tasks and Tutorial: Automate container image builds when a base image is updated in an Azure container registry.

Schedule a task

You can 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 more information, see Run an Azure Container Registry task on a defined schedule.

Multi-step tasks

Extend the single-image build-and-push capability of Azure Container Registry tasks with multi-step workflows that are based on multiple containers.

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 steps:

1. Build a web application image.
2. Run the web application container.
3. Build a web application test image.
4. Run the web application test container, which performs tests against the running application container.
5. If the tests pass, build a Helm chart archive package.
6. Perform a helm upgrade task by using 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 dependency support between steps. With multi-step tasks in Azure Container Registry tasks, you have more granular control over workflows for image building, testing, and OS and framework patching.

Learn more about running multi-step build, test, and patch tasks in Azure Container Registry tasks.

Context locations

The following table shows examples of supported context locations for Azure Container Registry tasks:

Image platforms

By default, Azure Container Registry tasks build 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, --platform Linux/arm64/v8).

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 stored for later retrieval. When a task is triggered automatically (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.

Learn more about viewing and managing task logs.

Related content

• When you're ready to automate container image builds and maintenance in the cloud, see Tutorial: Build and deploy container images in the cloud with Azure Container Registry tasks.

• Optionally, learn about the Docker extension and the Azure Account extension for Visual Studio Code. You can use these extensions to pull images from a container registry, push images to a container registry, or run Azure Container Registry tasks, all within Visual Studio Code.