feat: faster builds with registry cache

Automatically pull Docker build cache from remote registry. This
considerably improves build performances, as discovered here:
https://github.com/overhangio/test-docker-build/

changelog.d/20230427_165520_regis_build_mount.md

@@ -0,0 +1 @@
+- [Improvement] Automatically pull Docker image cache from the remote registry. Again, this will considerably improve image build-time, particularly in "cold-start" scenarios, where the images need to be built from scratch. The registry cache can be disabled with the `tutor images build --no-registry-cache` option. (by @regisb)

tutor/commands/images.py

@@ -6,7 +6,7 @@
 
 from tutor import config as tutor_config
 from tutor import env as tutor_env
-from tutor import exceptions, hooks, images
+from tutor import exceptions, hooks, images, utils
 from tutor.commands.context import Context
 from tutor.core.hooks import Filter
 from tutor.types import Config
@@ -68,14 +68,21 @@ def images_command() -> None:
     pass
 
 
-@click.command(
-    short_help="Build docker images",
-    help="Build the docker images necessary for an Open edX platform.",
-)
+@click.command()
 @click.argument("image_names", metavar="image", nargs=-1)
 @click.option(
     "--no-cache", is_flag=True, help="Do not use cache when building the image"
 )
+@click.option(
+    "--no-registry-cache",
+    is_flag=True,
+    help="Do not use registry cache when building the image",
+)
+@click.option(
+    "--cache-to-registry",
+    is_flag=True,
+    help="Push the build cache to the remote registry. You should only enable this option if you have push rights to the remote registry.",
+)
 @click.option(
     "-a",
     "--build-arg",
@@ -105,11 +112,19 @@ def build(
     context: Context,
     image_names: list[str],
     no_cache: bool,
+    no_registry_cache: bool,
+    cache_to_registry: bool,
     build_args: list[str],
     add_hosts: list[str],
     target: str,
     docker_args: list[str],
 ) -> None:
+    """
+    Build docker images
+
+    Build the docker images necessary for an Open edX platform. By default, the remote
+    registry cache will be used for better performance.
+    """
     config = tutor_config.load(context.root)
     command_args = []
     if no_cache:
@@ -120,15 +135,25 @@ def build(
         command_args += ["--add-host", add_host]
     if target:
         command_args += ["--target", target]
+    if utils.is_buildkit_enabled():
+        # Export image to docker.
+        command_args.append("--output=type=image")
     if docker_args:
         command_args += docker_args
     for image in image_names:
         for _name, path, tag, custom_args in find_images_to_build(config, image):
+            image_build_args = [*command_args, *custom_args]
+            if not no_registry_cache:
+                # Use registry cache
+                image_build_args.append(f"--cache-from=type=registry,ref={tag}-cache")
+            if cache_to_registry:
+                image_build_args.append(
+                    f"--cache-to=type=registry,mode=max,ref={tag}-cache"
+                )
             images.build(
                 tutor_env.pathjoin(context.root, *path),
                 tag,
-                *command_args,
-                *custom_args,
+                *image_build_args,
             )