analyze-docker-image-size

Docker Image Size Analysis

Analyze Docker images for PHP projects to identify bloat sources and provide size reduction strategies.

Expected Size Ranges

Common Bloat Sources

1. Build Dependencies Not Cleaned

# BLOATED: Dev packages remain in final image
RUN apk add --no-cache $PHPIZE_DEPS icu-dev libzip-dev \
    && docker-php-ext-install intl zip

# OPTIMIZED: Remove build deps after compilation
RUN apk add --no-cache --virtual .build-deps $PHPIZE_DEPS icu-dev libzip-dev \
    && docker-php-ext-install intl zip \
    && apk del .build-deps \
    && apk add --no-cache icu-libs libzip

2. Vendor with Dev Dependencies

# BLOATED: Includes dev dependencies (+30-80MB)
RUN composer install

# OPTIMIZED: No dev dependencies, optimized autoloader
RUN composer install --no-dev --no-scripts --prefer-dist --optimize-autoloader

3. Full Debian Instead of Alpine

# BLOATED: Full Debian base (~150MB base)
FROM php:8.4-fpm

# OPTIMIZED: Alpine base (~30MB base)
FROM php:8.4-fpm-alpine

4. Package Manager Cache

# BLOATED: apt cache retained (~30-50MB)
RUN apt-get update && apt-get install -y libicu-dev

# OPTIMIZED: Clean apt cache in same layer
RUN apt-get update && apt-get install -y --no-install-recommends libicu-dev \
    && rm -rf /var/lib/apt/lists/*

5. Missing .dockerignore

.git
node_modules
vendor
tests
docs
var/cache
var/log
docker-compose*.yml
.env.local
*.md
Makefile

Size Estimation by Component

Multi-Stage Build (Best Practice)

FROM php:8.4-fpm-alpine AS builder
RUN apk add --no-cache --virtual .build-deps $PHPIZE_DEPS icu-dev libzip-dev \
    && docker-php-ext-install intl zip opcache \
    && apk del .build-deps
COPY composer.json composer.lock ./
RUN composer install --no-dev --prefer-dist --optimize-autoloader

FROM php:8.4-fpm-alpine AS runtime
RUN apk add --no-cache icu-libs libzip
COPY --from=builder /usr/local/lib/php/extensions/ /usr/local/lib/php/extensions/
COPY --from=builder /usr/local/etc/php/conf.d/ /usr/local/etc/php/conf.d/
COPY --from=builder /var/www/vendor /var/www/vendor
COPY . /var/www/

Grep Patterns

# Find base images used
Grep: "^FROM " --glob "**/Dockerfile*"

# Find missing cache cleanup
Grep: "apt-get install" --glob "**/Dockerfile*"
Grep: "apk add(?!.*--no-cache)" --glob "**/Dockerfile*"

# Find composer install without --no-dev
Grep: "composer install(?!.*--no-dev)" --glob "**/Dockerfile*"

# Find COPY . (copies everything)
Grep: "^COPY \. " --glob "**/Dockerfile*"

# Check for .dockerignore
Glob: "**/.dockerignore"

# Find multi-stage builds
Grep: "^FROM.*AS " --glob "**/Dockerfile*"

Reduction Impact

Severity Classification

Output Format

### Image Size Issue: [Category]

**Severity:** Critical/Major/Minor
**Current Size:** X MB
**Estimated Savings:** Y MB
**Layer:** Dockerfile:line

**Issue:**
[Description of the bloat source]

**Current:**
```dockerfile
// Current Dockerfile instruction

Optimized:

// Optimized Dockerfile instruction

Expected Size After Fix: Before: X MB -> After: Z MB (saved Y MB)