Add Docker support with multi-stage build and startup script

Author: wasswarichard

.dockerignore

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+# Exclude unnecessary files from Docker build context
+
+# VCS and IDE
+.git/
+.gitignore
+.idea/
+*.iml
+.vscode/
+
+# OS junk
+.DS_Store
+Thumbs.db
+
+# Build outputs
+/target/
+/build/
+/out/
+/dist/
+/dist-newstyle/
+/.stack-work/
+
+# Java/Maven/Gradle
+.mvn/
+.gradle/
+.settings/
+.classpath
+.project
+
+# Logs and temp
+*.log
+*.tmp
+/tmp/
+
+# Coverage and test caches
+/coverage/
+/.pytest_cache/
+
+# Avoid copying CI configs if not needed in image
+.github/
+qodana.yaml

Dockerfile

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+# Multi-stage Dockerfile for the polyglot scheduling stack
+# Stage 1: builder and test runner
+FROM ubuntu:22.04 AS builder
+
+ENV DEBIAN_FRONTEND=noninteractive
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    ca-certificates curl git \
+    ghc cabal-install \
+    swi-prolog \
+    build-essential \
+  && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+COPY . /app
+
+# Install Haskell dependencies required by GeneticSchedule.hs
+RUN cabal update && cabal install aeson --lib
+
+# Build the Haskell scheduler as a native binary for faster startup
+RUN ghc -O2 -threaded haskell/GeneticSchedule.hs -o /app/genetic-schedule
+
+# Run smoke tests during the build to ensure the image is healthy
+# If tests are not desired, pass --target runtime when building.
+RUN bash tests/run_all.sh || (echo "Tests failed during Docker build" && exit 1)
+
+# Stage 2: runtime image with just what we need
+FROM ubuntu:22.04 AS runtime
+
+ENV DEBIAN_FRONTEND=noninteractive
+# libgmp is required by GHC-built binaries; include swipl runtime as optional tool and a minimal JRE
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    libgmp10 \
+    swi-prolog-nox \
+    ca-certificates \
+    openjdk-17-jre-headless \
+  && rm -rf /var/lib/apt/lists/*
+
+WORKDIR /app
+# Copy compiled binary and necessary assets
+COPY --from=builder /app/genetic-schedule /app/genetic-schedule
+COPY --from=builder /app/prolog /app/prolog
+COPY --from=builder /app/sample-request.json /app/sample-request.json
+
+# Copy startup script that decides whether to run Java or the Haskell scheduler
+COPY start.sh /app/start.sh
+RUN chmod +x /app/start.sh
+
+# Document ENV that Java service would use if run in this container later
+ENV SCHEDULER_HS_CMD=/app/genetic-schedule \
+    SCHEDULER_HS_SCRIPT=""
+
+# Expose Spring Boot default port (used when running the Java app)
+EXPOSE 8080
+
+# Default entrypoint delegates to the start script
+ENTRYPOINT ["/app/start.sh"]

start.sh

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+#!/usr/bin/env bash
+set -euo pipefail
+
+# If a Spring Boot fat JAR is present at /app/app.jar, start the Java API.
+# Otherwise, run the Haskell scheduler (default behavior of this image).
+
+if [[ -f "/app/app.jar" ]]; then
+  echo "[start.sh] Detected /app/app.jar. Launching Java Spring Boot API..."
+  export SCHEDULER_HS_CMD="/app/genetic-schedule"
+  export SCHEDULER_HS_SCRIPT=""
+  exec java -jar /app/app.jar
+else
+  echo "[start.sh] No /app/app.jar found. Launching Haskell scheduler binary..."
+  echo "[start.sh] Tip: To run the Java API, copy or mount your Spring Boot fat JAR to /app/app.jar"
+  exec /app/genetic-schedule
+fi