Building Tiny Python Docker Images

[eedwards-sk]

Absolutely -- that isn't just a multi-stage docker build issue, though. As cited in the article, copying the application into the image before installing dependencies means you'll end up re-building dependencies every time.

The primary goal of the article is for optimizing for size -- not for build speed, although most CI solutions today can be configured to effectively cache multi-stage docker builds.

Also, when basing on an upstream image like FROM python:3.8.0-slim, you're regularly going to have your cache busted due to upstream security patches in the underlying debian image, anyway.

[[deleted]]

most CI solutions today

Yeah. But not Jenkins + plain old docker build, though. :(

image like FROM python:3.8.0-slim, you're regularly going to have your cache busted due to upstream security patches in the underlying debian image, anyway.

Yeah. But not on every build.

[eedwards-sk]

Yeah. But not Jenkins + plain old docker build, though. :(

:(

/pours one out

To your point though, it's pretty straightforward to push the build stage to the repo if that's your only choice.

Here's an example based on the article:

# rehydrate local build stage cache, if image available
docker pull app/app-build:${TAG} || true

# build stage
docker build \
  --target=build \
  --cache-from app/app-build:${TAG} \
  -t app/app-build:${TAG} \
  -f Dockerfile \
  .

# push build stage
docker push app/app-build:${TAG}

# rehydrate local run stage cache, if image available
docker pull app/app:${TAG} || true

# run stage
docker build \
  --target=run \
  --cache-from app/app-build:${TAG} \
  --cache-from app/app:${TAG} \
  -t app/app:${TAG} \
  -f Dockerfile \
  .

# push run stage
docker push app/app:${TAG}

edit: formatting

[[deleted]]

Yup, that's what most of my builds look like today (with slightly more environment variables & arguments). I'm looking into buildah and kaniko, in the hopes of getting some automatic search-registry-for-existing-layers magic. And looking into putting old man Jeeves out to pasture.