Add example using GHA cache backend

.github/workflows/pants.yaml

@@ -27,6 +27,26 @@ jobs:
     - uses: actions/setup-python@v4
       with:
         python-version: ${{ matrix.python-version }}
+    - uses: crazy-max/ghaction-setup-docker@v3
+      with:
+        daemon-config: |
+            {
+              "features": {
+                "containerd-snapshotter": true
+              }
+            }       
+    - uses: docker/setup-buildx-action@v3
+      with:
+        install: true
+        driver: docker
+    # Required for multi-platform builds
+    - name: Setup QEMU
+      uses: docker/setup-qemu-action@v3
+      with:
+        platforms: linux/amd64,linux/arm64
+    # Exposes Github env vars needed for docker caching - see https://github.com/orgs/community/discussions/42856
+    - name: Expose GitHub Runtime
+      uses: crazy-max/ghaction-github-runtime@v3
     - uses: pantsbuild/actions/init-pants@v5-scie-pants
       # This action bootstraps pants and manages 2-3 GHA caches.
       # See: github.com/pantsbuild/actions/tree/main/init-pants/
@@ -58,7 +78,7 @@ jobs:
       env:
         DYNAMIC_TAG: workflow
       run: |
-        pants package ::
+        pants --docker-build-verbose package ::
     - name: Upload Pants log
       uses: actions/upload-artifact@v3
       with:

pants.toml

@@ -28,3 +28,11 @@ interpreter_constraints = ["==3.8.*"]
 
 [python-infer]
 use_rust_parser = true
+
+[docker]
+env_vars = [
+  "ACTIONS_CACHE_URL",
+  "ACTIONS_RUNTIME_TOKEN",
+  "DYNAMIC_TAG",
+]
+use_buildx=true

src/docker/caching/BUILD

@@ -0,0 +1,8 @@
+# Copyright 2022 Pants project contributors.
+# Licensed under the Apache License, Version 2.0 (see LICENSE).
+
+docker_image(
+    name="with-gha-cache-backend",
+    cache_to={"type": "gha", "mode": "max"},
+    cache_from={"type": "gha"},
+)

src/docker/caching/Dockerfile

@@ -0,0 +1,4 @@
+FROM alpine@sha256:21a3deaa0d32a8057914f36584b5288d2e5ecc984380bc0118285c70fa8c9300
+
+RUN echo "hello" > msg.txt && \
+  sleep 60

src/docker/multiplatform/BUILD

@@ -0,0 +1,15 @@
+# Note that multistage buildx builds requires using the containerd image store, due to
+# limitations with the docker-container driver (https://github.com/moby/buildkit/issues/2343)
+
+docker_image(
+    name="multiplatform-base",
+    source="Dockerfile.base",
+    skip_push=True,
+    build_platform=["linux/amd64", "linux/arm64"],
+)
+
+docker_image(
+    name="multiplatform-final",
+    source="Dockerfile.final",
+    build_platform=["linux/amd64", "linux/arm64"],
+)

src/docker/multiplatform/Dockerfile.base

@@ -0,0 +1,3 @@
+FROM python:3.8
+
+RUN echo "base image" >> base.txt

src/docker/multiplatform/Dockerfile.final

@@ -0,0 +1,6 @@
+ARG PARENT=:multiplatform-base
+# hadolint ignore=DL3006
+FROM ${PARENT}
+
+RUN cat base.txt && \
+  echo "final image" >> final.txt