From 383dc385e5c38a13f5c9345387f1c4122b80cb79 Mon Sep 17 00:00:00 2001
From: Zanie Blue <contact@zanie.dev>
Date: Wed, 4 Sep 2024 11:41:40 -0500
Subject: [PATCH] Add multistage Docker example (#14)

---
 .github/workflows/ci.yaml | 27 ++++++++++++++++++++++++++-
 Dockerfile.multistage     | 29 +++++++++++++++++++++++++++++
 README.md                 |  9 +++++++++
 3 files changed, 64 insertions(+), 1 deletion(-)
 create mode 100644 Dockerfile.multistage

diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 480672e..24b6a64 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -30,12 +30,27 @@ jobs:
           cache-to: type=gha,mode=min,scope=uv-docker-example
           outputs: type=docker,dest=/tmp/uv-docker-example.tar
 
+      - name: Build and export (multistage)
+        uses: docker/build-push-action@v6
+        with:
+          file: Dockerfile.multistage
+          tags: uv-docker-example-multistage:latest
+          cache-from: type=gha,scope=uv-docker-example-multistage
+          cache-to: type=gha,mode=min,scope=uv-docker-example-multistage
+          outputs: type=docker,dest=/tmp/uv-docker-example-multistage.tar
+
       - name: Upload artifact
         uses: actions/upload-artifact@v4
         with:
           name: uv-docker-example
           path: /tmp/uv-docker-example.tar
 
+      - name: Upload artifact (multistage)
+        uses: actions/upload-artifact@v4
+        with:
+          name: uv-docker-example-multistage
+          path: /tmp/uv-docker-example-multistage.tar
+
   test:
     name: "test image"
     runs-on: ubuntu-latest
@@ -49,9 +64,16 @@ jobs:
           name: uv-docker-example
           path: /tmp
 
-      - name: Load image
+      - name: Download artifact (multistage)
+        uses: actions/download-artifact@v4
+        with:
+          name: uv-docker-example-multistage
+          path: /tmp
+
+      - name: Load images
         run: |
           docker load --input /tmp/uv-docker-example.tar
+          docker load --input /tmp/uv-docker-example-multistage.tar
           docker image ls -a
 
       - name: Test command line
@@ -61,3 +83,6 @@ jobs:
         run: |
           docker compose up --watch -d
           docker compose down
+
+      - name: Test command line (multistage)
+        run: docker run uv-docker-example-multistage:latest hello
diff --git a/Dockerfile.multistage b/Dockerfile.multistage
new file mode 100644
index 0000000..e6d31b3
--- /dev/null
+++ b/Dockerfile.multistage
@@ -0,0 +1,29 @@
+# An example using multi-stage image builds to create a final image without uv.
+
+# First, build the application in the `/app` directory.
+# See `Dockerfile` for details.
+FROM ghcr.io/astral-sh/uv:python3.12-bookworm-slim AS builder
+WORKDIR /app
+RUN --mount=type=cache,target=/root/.cache/uv \
+    --mount=type=bind,source=uv.lock,target=uv.lock \
+    --mount=type=bind,source=pyproject.toml,target=pyproject.toml \
+    uv sync --frozen --no-install-project
+ADD . /app
+RUN --mount=type=cache,target=/root/.cache/uv \
+    uv sync --frozen
+
+
+# Then, use a final image without uv
+FROM python:3.12-slim-bookworm
+# It is important to use the image that matches the builder, as the path to the
+# Python executable must be the same, e.g., using `python:3.11-slim-bookworm`
+# will fail.
+
+# Copy the application from the builder
+COPY --from=builder --chown=app:app /app /app
+
+# Place executables in the environment at the front of the path
+ENV PATH="/app/.venv/bin:$PATH"
+
+# Run the FastAPI application by default
+CMD ["fastapi", "dev", "--host", "0.0.0.0", "/app/src/uv_docker_example"]
diff --git a/README.md b/README.md
index fe8619b..3e5acec 100644
--- a/README.md
+++ b/README.md
@@ -50,6 +50,9 @@ The [`Dockerfile`](./Dockerfile) defines the image and includes:
 - Placing environment executables on the `PATH`
 - Running the web application
 
+The [`Dockerfile.multistage`](./Dockerfile.multistage) example extends the `Dockerfile` example to
+use multistage builds to reduce the final size of the image.
+
 ### Dockerignore file
 
 The [`.dockerignore`](./.dockerignore) file includes an entry for the `.venv` directory to ensure the
@@ -99,3 +102,9 @@ To build the image without running anything:
 ```console
 $ docker build .
 ```
+
+To build the multistage image:
+
+```console
+$ docker build . --file Dockerfile.multistage
+```