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Prayag edited this page Mar 8, 2023 · 6 revisions

Optimizing builds with cache management

  • Once a layer changes, then all downstream layers need to be rebuilt as well. Even if they wouldn’t build anything differently, they still need to re-run. Ex,
FROM openjdk:latest

COPY . java_context/
WORKDIR java_context
RUN ./gradlew build

EXPOSE 8080
EXPOSE 9090

CMD ["java", "-jar", "/java_context/build/libs/retailstore.jar"]

  • Because a change causes a rebuild for steps that follow, try to make expensive steps appear near the beginning of the Dockerfile.

  • Keep layers small, Don’t include unnecessary files: Running a command like COPY . /src_context will COPY your entire build context into the image. If you’ve got logs, package manager artifacts, or even previous build results in your current directory, those will also be copied over.

  • create a .dockerignore file, and use that to specify which files and directories to exclude from the build context.

  • If you’re sick of re-downloading all external dependencies every time there’s a change to one of them, the cache mount can help you save time in the future.

Inside of your Dockerfile, add a mount flag, specifying which directories should be cached during the step.

https://github.com/moby/buildkit/blob/master/frontend/dockerfile/docs/reference.md#mount-types

Example:

FROM gradle:7.3-jdk11 as builder

RUN --mount=type=cache,target=/var/cache/apt \
    --mount=type=cache,target=/var/cache/apt \
    --mount=type=secret,id=aws,target=/root/.aws/credentials

Using the explicit cache with the --mount=? flag keeps the contents of the target=? directory preserved between builds. When this layer needs to be rebuilt, then it’ll use the apt cache in /var/cache/apt.

  • Minimize the number of layers, Use an appropriate base image
  • Use multi-stage builds
  • Combine commands together wherever possible.

See:

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