docker-compose-buildkite-plugin.sh

## SAVING

if [[ $BUILDKITE_BRANCH == "master" ]]; then
    echo "+++ :docker: Saving image $COMPOSE_SERVICE_DOCKER_IMAGE_NAME"
    local name="${BUILDKITE_PIPELINE_SLUG}_${BUILDKITE_BRANCH}_${COMPOSE_SERVICE_NAME}"
    local slug=/tmp/docker-cache/$name.tar.gz
    local BUILDKITE_IMAGE_CACHE_BUCKET="xxx-docker-cache"
    local images_file=s3://$BUILDKITE_IMAGE_CACHE_BUCKET/$name.images
    local images=$(echo $(docker images -a | grep $(echo $BUILDKITE_JOB_ID | sed 's/-//g') | awk '{print $1}' | xargs -n 1 docker history -q | grep -v '<missing>'))

    if [[ -n $images ]] && ( ! aws s3 ls $images_file || [[ "$images" != $(aws s3 cp $images_file -) ]]) ; then
        rm -rf /tmp/docker-cache
        mkdir -p /tmp/docker-cache

        docker save $images | gzip -c > $slug

        aws s3 cp $slug s3://$BUILDKITE_IMAGE_CACHE_BUCKET/$name.tar.gz
        echo "$images" | aws s3 cp - s3://$BUILDKITE_IMAGE_CACHE_BUCKET/$name.images
    fi
  fi
  
#   ...

## LOADING

echo "+++ :docker: Fetching cached docker images"

# see if we are missing any of the images locally, and load them if we are
(
  BUILDKITE_IMAGE_CACHE_BUCKET="xxx-docker-cache"
  name="${BUILDKITE_PIPELINE_SLUG}_${BUILDKITE_BRANCH}_${COMPOSE_SERVICE_NAME}"
  backup_name="${BUILDKITE_PIPELINE_SLUG}_master_${COMPOSE_SERVICE_NAME}"
  images_file=s3://$BUILDKITE_IMAGE_CACHE_BUCKET/$name.images
  backup_images_file=s3://$BUILDKITE_IMAGE_CACHE_BUCKET/${backup_name}.images
  has_images=$(docker inspect $(aws s3 cp $images_file -) > /dev/null; echo $?)
  has_backup_images=$(docker inspect $(aws s3 cp $backup_images_file -) > /dev/null; echo $?)
  if aws s3 ls $images_file && [[ $has_images -eq 1 ]]; then
      echo "Downloading cache"
      aws s3 cp s3://$BUILDKITE_IMAGE_CACHE_BUCKET/$name.tar.gz - | gunzip -c | docker load
  elif aws s3 ls $backup_images_file &&  [[ $has_backup_images -eq 1 ]]; then
    echo "Downloading backup cache (master)"
    aws s3 cp s3://$BUILDKITE_IMAGE_CACHE_BUCKET/${backup_name}.tar.gz - | gunzip -c | docker load
  else
    echo "No cache found"
  fi
)