docker-2-multi-stage-builds

# 2. Multi-Stage Builds

## 2. Multi-Stage Builds


**Python Multi-Stage Build:**
```dockerfile
# Stage 1: Build dependencies
FROM python:3.12-slim AS builder

WORKDIR /app

# Install build dependencies
RUN apt-get update && apt-get install -y --no-install-recommends \
    gcc \
    libpq-dev \
    && rm -rf /var/lib/apt/lists/*

# Create virtual environment
RUN python -m venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"

# Install dependencies
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Stage 2: Production image
FROM python:3.12-slim AS production

WORKDIR /app

# Install runtime dependencies only
RUN apt-get update && apt-get install -y --no-install-recommends \
    libpq5 \
    curl \
    && rm -rf /var/lib/apt/lists/*

# Copy virtual environment from builder
COPY --from=builder /opt/venv /opt/venv
ENV PATH="/opt/venv/bin:$PATH"

# Copy application code
COPY . .

# Create non-root user
RUN useradd --create-home --shell /bin/bash appuser \
    && chown -R appuser:appuser /app
USER appuser

EXPOSE 8000

HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
    CMD curl -f http://localhost:8000/health || exit 1

CMD ["gunicorn", "--bind", "0.0.0.0:8000", "app:app"]
```

**Node.js Multi-Stage Build:**
```dockerfile
# Stage 1: Install dependencies
FROM node:20-alpine AS deps

WORKDIR /app

COPY package*.json ./
RUN npm ci

# Stage 2: Build application
FROM node:20-alpine AS builder

WORKDIR /app

COPY --from=deps /app/node_modules ./node_modules
COPY . .

RUN npm run build

# Stage 3: Production image
FROM node:20-alpine AS production

WORKDIR /app

ENV NODE_ENV=production

# Copy only production dependencies
COPY --from=deps /app/node_modules ./node_modules
COPY --from=builder /app/dist ./dist
COPY --from=builder /app/package*.json ./

USER node

EXPOSE 3000

CMD ["node", "dist/server.js"]
```

**Go Multi-Stage Build (minimal image):**
```dockerfile
# Stage 1: Build
FROM golang:1.22-alpine AS builder

WORKDIR /app

# Download dependencies
COPY go.mod go.sum ./
RUN go mod download

# Copy source and build
COPY . .
RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-w -s" -o /app/main .

# Stage 2: Minimal production image
FROM scratch

# Copy SSL certificates for HTTPS
COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/

# Copy binary
COPY --from=builder /app/main /main

EXPOSE 8080

ENTRYPOINT ["/main"]
```