Скачать или смотреть Properly Utilize Docker Multi-Stage Builds with BuildKit

Learn how to effectively manage multi-stage builds in Docker, ensuring efficient runs with the `BuildKit` feature to skip unnecessary stages.
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Understanding Docker Multi-Stage Builds: The Problem with Targets

When working with Docker and multi-stage builds, you may find yourself perplexed by the way stages are handled, especially when using the --target option during the build process. As you build your Docker image, you might work with a Dockerfile that includes multiple stages, like the one you've encountered. The challenge arises when you intend to run a specific stage but notice that all preceding stages are executed as well. This can lead to unnecessary build times and resource usage.

The Dockerfile Scenario

In your case, you have a Dockerfile structured to build two distinct environments: one for testing (tst) and one for a different purpose (hlg). You’ve set it up like so:

[[See Video to Reveal this Text or Code Snippet]]

!-- Dockerfile code added as a code block for clarity --

After constructing your Dockerfile, you attempted to build the tst target with the command:

[[See Video to Reveal this Text or Code Snippet]]

However, your expectation that only the tst stage would run proved incorrect, as all stages executed during the build.

The Solution: Leveraging Docker BuildKit

Understanding the Typical Build Behavior

By default, Docker processes a multi-stage build sequentially. This means that even when you specify a target, it still builds all prior stages. To address this issue and gain more control over the build process, you can utilize Docker's BuildKit, which changes the standard build behavior by treating the Dockerfile as a dependency graph, skipping stages that are not necessary for the final image.

Enabling BuildKit

To start using BuildKit, you can enable it in your current shell session by running:

[[See Video to Reveal this Text or Code Snippet]]

For a more permanent solution that applies across all Docker builds, you need to modify your daemon.json file. Here’s how:

Open or create the Docker daemon configuration file, typically located at /etc/docker/daemon.json.

Add the following configuration to enable the BuildKit feature:

[[See Video to Reveal this Text or Code Snippet]]

Once you've made your changes, you need to reload the Docker engine to apply the changes. You can do this with the command:

[[See Video to Reveal this Text or Code Snippet]]

Benefits of Using BuildKit

By utilizing BuildKit, you can expect improvements in:

Performance: Only build the stages that are required, reducing build time.

Efficiency: Eliminate the waste of resources by skipping unnecessary stages in the build process.

Advanced features: Benefit from parallel builds and more sophisticated caching strategies.

Conclusion: Building Efficiently with Docker

Managing multi-stage builds in Docker doesn't have to be a hassle. With the right tools and techniques—especially enabling BuildKit—you can ensure that your builds are efficient, skipping unused stages and saving time and resources. By following the steps outlined above, you can successfully run targeted builds without unwanted execution of other stages.

In summary, leveraging Docker's new build strategies allows for a smoother, more efficient workflow. It's time to enhance your build processes with these powerful updates!