Sometimes it’s not sufficient to just cache directories (
CACHE), it’d be best
to cache complex state such as running processes or mounted files.
Webapp.io provides this powerful but dangerous caching mechanism via
RUN REPEATABLE. It’s particularly useful for complicated declarative cluster
It’s recommended to combine RUN REPEATABLE with multi-stage builds for large performance improvements.
# install docker COPY . . RUN REPEATABLE docker build -t myimage RUN docker run -d -p 8080:8080 myimage
In this Layerfile, the docker cache from previous runs will be reused because RUN REPEATABLE uses the cache from after the last time this step ran.
If you had three pipelines at 9am, 10am, and 11am, the effective steps run would look like this:
In particular, docker would see that it had been used multiple times, and would be able to re-use the docker cache from previous invocations to greatly improve build speed.
FROM vm/ubuntu:18.04 RUN apt-get update && \ apt-get install apt-transport-https ca-certificates curl software-properties-common && \ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add - && \ add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable" && \ apt-get update && \ apt install docker-ce RUN curl -L "https://github.com/docker/compose/releases/download/1.27.4/docker-compose-$(uname -s)-$(uname -m)" -o /usr/local/bin/docker-compose && \ chmod +x /usr/local/bin/docker-compose COPY . . RUN REPEATABLE docker-compose up -d --build --force-recreate --remove-orphans && sleep 5 EXPOSE WEBSITE localhost:8000
In this Layerfile, all of these things are reused from the moment immediately after the previous invocation:
FROM vm/ubuntu:18.04 # install the latest version of Docker, as in the official Docker installation tutorial. RUN apt-get update && \\ apt-get install apt-transport-https ca-certificates curl software-properties-common && \\ curl -fsSL https://download.docker.com/linux/ubuntu/gpg | apt-key add - && \\ add-apt-repository "deb [arch=amd64] https://download.docker.com/linux/ubuntu bionic stable" && \\ apt-get update && \\ apt install docker-ce # install & start k3s RUN curl -sfL https://get.k3s.io | sh -s - --docker # this script might use helm, kompose, jsonnet, or any other manifest handling logic RUN REPEATABLE ./build-images-and-manifests.sh && k3s kubectl apply -f dist/manifests --prune EXPOSE WEBSITE localhost:8000
RUN REPEATABLE gives 50-95% speedups here.
In this Layerfile, we’d set up a kubernetes cluster for you and then snapshot it after you’d started all of your services.
The next time you push, kubernetes’ own declarative logic would figure out which pods to delete/restart given the manifests created. This means that if you had 20 microservices and only changed one, it’d be the only one that is re-deployed with this Layerfile.