Config Drift Scanner

Find configuration differences across your environments before they cause incidents. Compare config files, environment variables, feature flags, database settings, and runtime parameters between dev/staging/production — catching the "works on my machine" problems that slip past code review.

Use when: "compare configs between environments", "find config drift", "why does staging work but prod doesn't", "audit environment parity", "check env vars across deploys", or after an incident caused by config mismatch.

Commands

1. scan — Detect Drift Across Environments

Step 1: Discover Configuration Sources

# Find config files in the project
find . -maxdepth 4 \( \
  -name "*.env" -o -name "*.env.*" -o \
  -name "*.config.*" -o -name "config.yaml" -o -name "config.json" -o \
  -name "*.toml" -o -name "settings.*" -o \
  -name "docker-compose*.yml" -o -name "docker-compose*.yaml" -o \
  -name "values*.yaml" -o -name "*.tfvars" \
  \) -not -path "*/node_modules/*" -not -path "*/.git/*" 2>/dev/null

# Find environment variable references in code
rg "process\.env\.|os\.environ|os\.getenv|ENV\[|System\.getenv" \
  --type-not binary -g '!node_modules' -g '!vendor' --stats 2>&1 | tail -5

Step 2: Extract Config from Each Environment

For Kubernetes:

# ConfigMaps
for env in dev staging prod; do
  kubectl get configmaps -n "$env" -o json | python3 -c "
import json, sys
cms = json.load(sys.stdin)['items']
for cm in cms:
    name = cm['metadata']['name']
    for k, v in cm.get('data', {}).items():
        print(f'{name}.{k}={v}')
" > "/tmp/config-$env.txt"
done

For .env files:

# Compare .env files across environments
for f in .env.development .env.staging .env.production; do
  if [[ -f "$f" ]]; then
    echo "=== $f ==="
    grep -v '^#' "$f" | grep -v '^$' | sort
  fi
done

For Terraform:

# Compare tfvars across environments
for f in terraform/environments/*/terraform.tfvars; do
  echo "=== $f ==="
  cat "$f"
done

Step 3: Diff and Classify

Compare each key across environments and classify differences:

🔴 Dangerous Drift (same key, unexpected difference):

• Database connection strings pointing to wrong environment
• API keys that should be environment-specific but are shared
• Feature flags enabled in prod but disabled in staging (testing gap)
• Timeout values that differ without documented reason
• Memory/CPU limits that are lower in prod than staging

🟡 Expected Drift (different by design):

• Database URLs (each env has its own DB)
• API endpoints (staging.api.com vs api.com)
• Log levels (DEBUG in dev, INFO in prod)
• Replica counts (1 in dev, 3 in prod)

🟢 Missing in Environment (potential problem):

• Env var exists in prod but not staging → can't test that code path
• Config key exists in staging but not prod → forgot to add on deploy

Step 4: Generate Report

# Configuration Drift Report

## Environments Compared: dev ↔ staging ↔ production

## 🔴 Dangerous Drift (3 found)
1. `DATABASE_POOL_SIZE`: dev=5, staging=10, **prod=5**
   → Prod should be ≥ staging. Likely copy-paste from dev config.

2. `FEATURE_NEW_CHECKOUT`: dev=true, staging=true, **prod=false**
   → Feature tested in staging but not enabled in prod. Intentional? If so, document.

3. `REDIS_TIMEOUT_MS`: dev=5000, **staging=500**, prod=5000
   → Staging has 10× shorter timeout. Will mask timeout bugs in staging tests.

## 🟡 Expected Drift (8 found)
- DATABASE_URL: different per environment ✅
- LOG_LEVEL: debug/info/warn ✅
- API_BASE_URL: per-environment ✅

## 🟢 Missing Variables (2 found)
- `SENTRY_DSN`: exists in prod, missing in staging → errors not tracked in staging
- `RATE_LIMIT_RPS`: exists in prod (100), missing in dev/staging → no rate limit testing

## Recommendations
1. Add SENTRY_DSN to staging for error visibility
2. Fix DATABASE_POOL_SIZE in prod (should be ≥ staging value)
3. Document why FEATURE_NEW_CHECKOUT differs between staging and prod

2. watch — Continuous Drift Monitoring

Set up a CI check that runs on every config change:

# GitHub Actions
name: Config Drift Check
on:
  push:
    paths:
      - '**/*.env*'
      - '**/config.*'
      - '**/values*.yaml'
      - '**/*.tfvars'
jobs:
  drift:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - name: Check for drift
        run: |
          # Compare all env files and flag dangerous differences
          diff <(grep -v '^#' .env.staging | sort) <(grep -v '^#' .env.production | sort) || true

3. template — Generate Config Parity Checklist

For a new environment setup, generate a checklist of all config keys that need to be set, with:

• Required vs optional
• Expected value ranges
• Whether the value should differ or match other environments
• Where to get the value (secrets manager, team lead, auto-generated)

4. secrets-check — Verify Secret Rotation

Cross-reference config with secrets management:

• Which secrets are hardcoded vs pulled from vault/secrets manager?
• When were secrets last rotated?
• Are any secrets shared across environments (bad practice)?
• Are test/dev credentials accidentally in prod config?