Dockerfile

# --- First stage: Get our app, work out its dependencies, create a JRE
FROM gradle:9.3.0-jdk25-noble AS builder
# See https://hub.docker.com/_/gradle for available images

WORKDIR /app

# Copy our gradle build environment over
RUN mkdir app
COPY app ./app/

RUN mkdir gradle
COPY gradle ./gradle/

COPY settings.gradle ./

# And the run scripts we'll need in stage 2
COPY run.sh ./
COPY setup_auth.sh ./

# Start by building the app as a fat (uber) JAR
# This gives us a smaller executable in stage 2
RUN gradle clean AnomalyDetectorAppUberJar --no-daemon

RUN cp app/build/libs/AnomalyDetectorApp-uber.jar ./

# Unpack the contents of our fat JAR
RUN mkdir temp && cd temp && jar xf ../AnomalyDetectorApp-uber.jar
# And find out what depedencies it lacks - this tells us what we need from
# the external Java environment
RUN jdeps --print-module-deps \
    --ignore-missing-deps \
    --recursive \
    --multi-release 17 \
    --class-path="./temp/BOOT-INF/lib/*" \
    --module-path="./temp/BOOT-INF/lib/*" \
    ./AnomalyDetectorApp-uber.jar > modules.txt

# Now assemble our own custom JRE with only those things in it
RUN $JAVA_HOME/bin/jlink \
    --verbose \
    --add-modules $(cat modules.txt) \
    --strip-debug \
    --no-man-pages \
    --no-header-files \
    --compress=zip-6 \
    --output ./custom-jre

# ----------------------------------------------------------------------------
# --- Second stage: Run the actual image
# Use the smallest base image possible (alpine)
FROM debian:bookworm-slim

WORKDIR /app

# Install RocksDB library for Kafka Streams
RUN apt-get update \
    && apt-get install -y librocksdb7.8

RUN apt-get autoremove -y \
    && apt-get clean -y \
    && apt-get autoclean -y \
    && rm -rf /var/lib/apt/lists/*

# Copy the custom JRE and application artifacts from the builder stage
COPY --from=builder /app/custom-jre /usr/lib/jvm/custom-jre
COPY --from=builder /app/AnomalyDetectorApp-uber.jar ./
COPY --from=builder /app/setup_auth.sh ./
COPY --from=builder /app/run.sh ./

RUN chmod +x ./run.sh
RUN chmod +x ./setup_auth.sh

# Set the custom entrypoint
CMD [ "./run.sh" ]