y-build-like-sync

#!/usr/bin/env bash
[ -z "$DEBUG" ] || set -x
set -eo pipefail

# Bash isn't a good tool for producing a tar from a build context
# but this script is an experiment on how to compose an image
# from a runtime and some static files using go-containerregistry's crane
# The user shouldn't need to write Dockerfile or .dockerignore,
# but we could probably use a generated Dockerfile + kaniko instead, or Buildpacks

# Settings
DEFAULT_REGISTRY=builds-registry.ystack.svc.cluster.local
[ -z "$BUILDS_REGISTRY" ] && BUILDS_REGISTRY=$DEFAULT_REGISTRY
[ -z "$PUSH_REGISTRY" ]   && PUSH_REGISTRY=$DEFAULT_REGISTRY

if [ "$(curl -s --connect-timeout 3 http://$BUILDS_REGISTRY/v2/)" != "{}" ]
then
  echo "ERROR Skaffold need local access to the builds registry for digest lookup"
  echo "Registry: $BUILDS_REGISTRY"
  echo "Look for y-stack's ingress or port-forward utilities"
  exit 1
fi

[ -z "$IMAGE" ] && echo "No IMAGE env (from for example Skaffold)" && exit 1

IMAGE=$IMAGE
case "$IMAGE" in
  $BUILDS_REGISTRY/* ) ;;
  $BUILDS_REGISTRY:80/* ) ;;
  $PUSH_REGISTRY/* ) echo "Unlike y-build this script won't push to non-build registries. Got: $IMAGE" && exit 1 ;;
  * ) echo "Output is restricted to PUSH_REGISTRY=$PUSH_REGISTRY. Got: $IMAGE" && exit 1 ;;
esac

RUNTIME_IMAGE=$1
[ -z "$RUNTIME_IMAGE" ] && echo "First argument must be a runtime image to append the layer to" \
  && echo "To improve build times use a runtime image in the target repo" && exit 1

# crane hangs for a long time if it doesn't know that the registry is plain http
RUNTIME_IMAGE=$(echo $RUNTIME_IMAGE | sed 's|.local/|.local:80/|')
IMAGE=$(echo $IMAGE | sed 's|.local/|.local:80/|')

# This is a PoC, let's make a lot of assumptions to simplify
context=.
src='**'
# assuming a single manual sync, which is the reasonable use case for a runtime
[ ! -f skaffold.yaml ] && echo "This composition example assumes a sync defined in a skaffold.yaml" && exit 1
dest=$(cat skaffold.yaml | grep 'dest:' | awk '{ print $2 }')
# this avoids "tar: Removing leading `/' from member names" and could come in handy if we can't use --transform
dest=$(echo $dest | sed 's|^/||')

list=$(mktemp)
# Wanted: a way to produce a build context like buildctl would
(cd $context; git ls-files -c -o --exclude-standard -- . || find . -type f) > $list
tar=$(mktemp)
tar --transform "s|^|$dest/|" --show-transformed-names -cvhf $tar -T $list --mode='ug+rw' --group=65534 --owner=65532
rm $list

set -x
y-crane append --insecure -b $RUNTIME_IMAGE -f $tar -t $IMAGE
set +x
rm $tar