At $job, we’ve started using AWS CodePipeline and AWS CodeBuild to build and
deploy our Docker images to ECS. Once we got the pipeline working, we could
git push and a few minutes later a container build would kickoff. This was
mostly great, but the problem was that our builds took too long. Developers
would push their changes and expect to see them live, but it took about half an
hour for the build to complete and go live.
Speeding up our Docker builds on CodeBuild
Docker layer caching leads to way faster container builds, and CodeBuild supports caching, so we should be good, right?
Wrong. CodeBuild doesn’t support Docker layer caching at all (as of this writing). You have to roll your own here.
Docker pull and –cache-from
Specifically, before we run a
docker build, we have our CodeBuild buildspec.yml
pull in the Docker image of our last build, so we can use it as a source to
docker pull $ECR_URL:latest || true
Then when we build a container, we use
docker build --cache-from $ECR_URL:latest.
This, along with reorganizing our Dockerfile to make it more cache-friendly,
has cut our builds time by two-thirds. Pretty cool.