From b950178733ca02c8d4434c7b6fb18333dacdec1d Mon Sep 17 00:00:00 2001
From: Ian Wienand <iwienand@redhat.com>
Date: Wed, 25 Aug 2021 08:29:22 +1000
Subject: [PATCH] build-docker-image: Add flag to use BuildKit

It seems like BuildKit is the next generation, but not likely to be
enabled by default soon (https://github.com/moby/moby/issues/40379).
Add a flag so people who want to use its features can easily opt-in.

Change-Id: I862819959c77a557199f64b4d42109bc7915959c
---
 roles/build-docker-image/common.rst         | 8 ++++++++
 roles/build-docker-image/defaults/main.yaml | 1 +
 roles/build-docker-image/tasks/build.yaml   | 2 ++
 3 files changed, 11 insertions(+)

diff --git a/roles/build-docker-image/common.rst b/roles/build-docker-image/common.rst
index 5b899a8d6..09fc08421 100644
--- a/roles/build-docker-image/common.rst
+++ b/roles/build-docker-image/common.rst
@@ -80,6 +80,14 @@ using this role.
 
         repository: "^myorgname/{{ zuul.project.short_name }}.*"
 
+  .. zuul:rolevar:: docker_use_buildkit
+     :type: bool
+     :default: false
+
+     Use `BuildKit
+     <https://docs.docker.com/develop/develop-images/build_enhancements/>`__
+     when creating images.
+
 .. zuul:rolevar:: docker_images
    :type: list
 
diff --git a/roles/build-docker-image/defaults/main.yaml b/roles/build-docker-image/defaults/main.yaml
index 24a195ad1..6d402ceb0 100644
--- a/roles/build-docker-image/defaults/main.yaml
+++ b/roles/build-docker-image/defaults/main.yaml
@@ -1,3 +1,4 @@
 zuul_work_dir: "{{ zuul.project.src_dir }}"
 docker_dockerfile: "Dockerfile"
 docker_registry: ''
+docker_use_buildkit: false
diff --git a/roles/build-docker-image/tasks/build.yaml b/roles/build-docker-image/tasks/build.yaml
index 301268041..e726be9b0 100644
--- a/roles/build-docker-image/tasks/build.yaml
+++ b/roles/build-docker-image/tasks/build.yaml
@@ -28,6 +28,8 @@
     --label "org.zuul-ci.change_url={{ zuul.change_url }}"
   args:
     chdir: "{{ zuul_work_dir }}/{{ zj_image.context }}"
+  environment:
+    DOCKER_BUILDKIT: '{{ "1" if docker_use_buildkit else "0" }}'
 
 - name: Cleanup sibling source directory
   include_tasks: clean-siblings.yaml