Using docker images from s3 for caching

create_docker_cache.sh

#!/bin/bash -e

# There's an assumption we're two directories into the repo (scripts/buildkite)
basedir=$(dirname $0)
pushd ${basedir}/../../

image_tag=$1
cache_sha_sum=$2

if [[ -z $image_tag || -z $cache_sha_sum ]]; then
  echo "Usage: $0 <image tag> <image id>"
  exit 1
fi

mkdir -p tmp
tar_file_name="tmp/${image_tag/\//-}-${cache_sha_sum}.tar"
docker save $image_tag > $tar_file_name
gzip $tar_file_name

popd

download_docker_cache.sh

#!/bin/bash

# I set this bucket up with a lifecycle policy to delete files after 30 days
# This is actually set at a pipeline level, since I use it in many scripts
BUILDKITE_CACHE_BUCKET="my-s3-bucket-used-for-caching"

# There's an assumption we're two directories into the repo (scripts/buildkite)
basedir=$(dirname $0)
pushd ${basedir}/../../

# We sha the docker image based on it's dependencies.
# This is for an NPM app, change out for your relevant dependancy files
cache_sha_sum=$(shasum <(shasum package.json yarn.lock) |cut -f1 -d' ')

image_tag=$1

if [[ -z $image_tag ]]; then
  echo "Usage: $0 <image tag>"
  exit 1
fi

s3_location="s3://${BUILDKITE_CACHE_BUCKET}/${BUILDKITE_PIPELINE_SLUG}"
cache_file="${image_tag/\//-}-${cache_sha_sum}.tar.gz"

if [[ $(docker images -q $image_tag |wc -l) -gt 0 ]]; then
  echo "A cached image already exists, not updating"
elif [[ $(aws s3 ls "${s3_location}/${cache_file}") ]]; then
  aws s3 cp "${s3_location}/${cache_file}" tmp/
  docker load < tmp/${cache_file}
  rm -f tmp/${cache_file}
else
  echo "No cache exists, the container will be built from scratch"
fi

popd

update_docker_cache.sh

#!/bin/bash -e

# I set this bucket up with a lifecycle policy to delete files after 30 days
# This is actually set at a pipeline level, since I use it in many scripts
BUILDKITE_CACHE_BUCKET="my-s3-bucket-used-for-caching"

# There's an assumption we're two directories into the repo (scripts/buildkite)
basedir=$(dirname $0)
pushd ${basedir}/../../

# We sha the docker image based on it's dependencies.
# This is for an NPM app, change out for your relevant dependancy files
cache_sha_sum=$(shasum <(shasum package.json yarn.lock) |cut -f1 -d' ')

image_tag=$1

if [[ -z $image_tag ]]; then
  echo "Usage: $0 <image tag>"
  exit 1
fi

cache_file="${image_tag/\//-}-${cache_sha_sum}.tar.gz"
s3_location="s3://${BUILDKITE_CACHE_BUCKET}/${BUILDKITE_PIPELINE_SLUG}"

mkdir -p tmp

if aws s3 ls "${s3_location}/${cache_file}"; then
  echo "Up to date docker cache already exists"
else
  echo "Updating cache"
  ./scripts/buildkite/create_docker_cache.sh $image_tag $cache_sha_sum
  aws s3 cp tmp/${cache_file} "${s3_location}/${cache_file}"
fi

popd