deploy: CHANGE Dockerfile to multilayer and distroless OS

Dockerfile

@@ -1,28 +1,65 @@
-FROM python:3.11-slim
+# syntax=docker/dockerfile:1.7
 
-# Create non-root user
+# ============================================================================
-RUN useradd -m -u 1000 appuser
+# Build stage: Debian 12's Python (paths/libs match the distroless runtime)
+# ============================================================================
+# Don't use python:3.11-slim-bookworm — that image installs Python to /usr/local
+# with an RPATH that breaks under distroless. Debian's apt python3 lives at the
+# same paths as distroless's, so symlinks and libpython resolve correctly.
+FROM debian:12-slim AS builder
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1 \
+    PIP_NO_CACHE_DIR=1 \
+    PIP_DISABLE_PIP_VERSION_CHECK=1
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends \
+         python3 python3-pip python3-venv \
+    && rm -rf /var/lib/apt/lists/*
+
+# Default (symlink) venv. /opt/venv/bin/python ends up as a symlink to
+# /usr/bin/python3, which distroless also provides.
+RUN python3 -m venv /opt/venv
+ENV PATH=/opt/venv/bin:$PATH
+
+# Install runtime deps (cached layer — only rebuilt when requirements.txt changes)
+COPY requirements.txt /tmp/requirements.txt
+RUN pip install -r /tmp/requirements.txt
+
+# Pre-compile bytecode for faster cold start on a read-only rootfs
+RUN python3 -m compileall -q /opt/venv
+
+# Pre-create writable mount points so the runtime rootfs can stay read-only.
+# `uploads/` always needs to be writable; `logs/` only if LOGGING_ENABLED=true.
+RUN mkdir -p /app/uploads /app/logs
+
+# ============================================================================
+# Runtime stage: distroless Python 3.11, non-root (uid 65532), no shell
+# ============================================================================
+# gcr.io/distroless/python3-debian12 ships Python 3.11 with NO shell, NO
+# package manager, and NO setuid binaries. The :nonroot tag pins USER to
+# uid 65532 / gid 65532.
+FROM gcr.io/distroless/python3-debian12:nonroot
+
+ENV PYTHONDONTWRITEBYTECODE=1 \
+    PYTHONUNBUFFERED=1
 
-# Set working directory
 WORKDIR /app
 
-# Copy requirements first for better caching
+# Venv ships its site-packages; bin/python is a symlink resolved by distroless's
-COPY requirements.txt .
+# /usr/bin/python3 and Debian's libpython under /usr/lib.
+COPY --from=builder --chown=nonroot:nonroot /opt/venv /opt/venv
 
-# Install dependencies
+# Pre-created data dirs owned by the runtime user (mount writable volumes here)
-RUN pip install --no-cache-dir -r requirements.txt
+COPY --from=builder --chown=nonroot:nonroot /app/uploads /app/uploads
+COPY --from=builder --chown=nonroot:nonroot /app/logs /app/logs
 
-# Copy only necessary files
+# Application source — its own layer so app-only changes don't bust the dep cache
-COPY main.py .
+COPY --chown=nonroot:nonroot main.py /app/
 
-# Create uploads directory
+USER nonroot
-RUN mkdir -p uploads && chown appuser:appuser uploads
-
-# Switch to non-root user
-USER appuser
-
-# Expose port
 EXPOSE 8000
 
-# Run the application
+ENTRYPOINT ["/opt/venv/bin/python", "-m", "uvicorn"]
-CMD ["python", "main.py"]
+CMD ["main:app", "--host", "0.0.0.0", "--port", "8000"]