ci: add multi-arch Docker builds (amd64 + arm64) (#355)

## Summary

- Add `compile:linux-arm64` script and use `TARGETARCH` in the
Dockerfile to select the correct compile target at build time
- Add QEMU and Docker Buildx steps to the release workflow, enabling
`platforms: linux/amd64,linux/arm64` multi-arch image builds
- Remove hardcoded `platform: linux/amd64` from `docker-compose.yml` so
the platform is auto-detected

## Verification

Multi-arch build tested successfully via `workflow_dispatch`:  
https://github.com/harrisony/plexus/actions/runs/25427061173

---------

Co-authored-by: Matt Cowger <matt@cowger.us>

Author: harrisony

.github/workflows/release-build-docker.yml

@@ -19,11 +19,23 @@ jobs:
       - name: Checkout repository
         uses: actions/checkout@v6
 
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v4
+
       - name: Set up Bun
         uses: oven-sh/setup-bun@v2
         with:
           bun-version: latest
 
+      - name: Cache Bun dependencies
+        uses: actions/cache@v4
+        with:
+          path: ~/.bun/install/cache
+          key: ${{ runner.os }}-bun-${{ hashFiles('**/bun.lock') }}
+
       - name: Install dependencies
         run: bun install --frozen-lockfile
 
@@ -52,13 +64,16 @@ jobs:
         with:
           context: .
           push: true
+          platforms: linux/amd64,linux/arm64
           tags: ${{ steps.meta.outputs.tags }}
           labels: ${{ steps.meta.outputs.labels }}
           build-args: |
             APP_VERSION=${{ inputs.tag }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
 
       - name: Smoke test Docker image
-        timeout-minutes: 1
+        timeout-minutes: 2
         run: |
           echo "Starting smoke test for Docker image..."
           TEST_ADMIN_KEY="test-admin-key-$(openssl rand -hex 8)"

.gitignore

@@ -69,3 +69,7 @@ packages/backend/.test-db.sqlite-wal
 .test-db.sqlite-wal
 .pi-lens
 docs/openapi.yaml
+
+# Compiled binaries
+plexus-
+plexus

Dockerfile

@@ -4,6 +4,7 @@ FROM oven/bun:1 AS builder
 WORKDIR /app
 
 ARG APP_VERSION=dev
+ARG TARGETPLATFORM
 ENV APP_VERSION=${APP_VERSION}
 
 # Copy root package files
@@ -26,15 +27,23 @@ COPY . .
 # Build the frontend and compile everything into a single self-contained binary.
 # Frontend assets (HTML, JS, CSS, images) and migration SQL files are all embedded
 # inside the binary via `bun build --compile` — no runtime file copies needed.
-RUN bun run compile:linux
+# Use BuildKit's TARGETPLATFORM to select the correct build target (e.g., linux/amd64, linux/arm64)
+RUN case "${TARGETPLATFORM}" in \
+         linux/arm64) bun run compile:linux-arm64 ;; \
+         linux/amd64) bun run compile:linux-amd64 ;; \
+         *) echo "Unsupported platform: ${TARGETPLATFORM}" && exit 1 ;; \
+    esac
 
 # Stage 2: Minimal production image — just the binary
 FROM debian:bookworm-slim
 
+ARG APP_VERSION=dev
+ARG TARGETPLATFORM
+
 WORKDIR /app
 
-# Copy the compiled binary from the builder stage
-COPY --from=builder /app/plexus-linux ./plexus
+# Copy the compiled binary from the builder stage (uses BuildKit's TARGETPLATFORM)
+COPY --from=builder /app/plexus-linux-${TARGETPLATFORM#linux/} ./plexus
 
 EXPOSE 4000
 
@@ -44,6 +53,7 @@ ENV LOG_LEVEL=info
 ENV DATA_DIR=/app/data
 ENV DATABASE_URL=sqlite:///app/data/plexus.db
 ENV CONFIG_FILE=/app/config/plexus.yaml
+ENV APP_VERSION=${APP_VERSION}
 # ADMIN_KEY must be provided at runtime (no default for security)
 
 CMD ["./plexus"]

docker-compose.yml

@@ -3,7 +3,6 @@ services:
     build: .
     image: plexus:latest
     container_name: plexus
-    platform: linux/amd64
     restart: unless-stopped
     ports:
       - "4000:4000"

package.json

@@ -18,7 +18,8 @@
     "dev:frontend": "cd packages/frontend && bun run dev",
     "build:frontend": "cd packages/frontend && bun run build",
     "compile:macos": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --target=bun-darwin-arm64 --outfile plexus-macos",
-    "compile:linux": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --target=bun-linux-x64 --outfile plexus-linux",
+    "compile:linux-amd64": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --target=bun-linux-x64 --outfile plexus-linux-amd64",
+    "compile:linux-arm64": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --target=bun-linux-arm64 --outfile plexus-linux-arm64",
     "compile:windows": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --target=bun-windows-x64 --outfile plexus.exe",
     "build:bin": "bun run build:frontend && bun build packages/backend/src/index.ts packages/backend/drizzle/migrations/*.sql packages/backend/drizzle/migrations_pg/*.sql packages/frontend/dist/*.png packages/frontend/dist/*.ico packages/frontend/dist/*.svg packages/frontend/dist/*.webmanifest --compile --asset-naming=\"[name].[ext]\" --outfile plexus",
     "install:all": "bun install && (cd packages/backend && bun install) && (cd packages/frontend && bun install)",