---
name: cdn-simulation-bridge
description: Build a two-way integration between Cloudflare CDN and an autonomous system. Read analytics, push redirects, monitor cache performance, detect Vary header fragmentation.
allowed-tools: Bash(curl *), Bash(node *)
---

# CDN-Simulation Bridge

## Prerequisites
- Cloudflare account with API token (Zone Analytics Read + Cache Purge permissions)
- Node.js 18+
- Environment variables: CF_API_TOKEN, CF_ZONE_ID

## Step 1: Read cache hit rate from Cloudflare
```bash
CF_TOKEN="${CF_API_TOKEN:-your_token_here}"
CF_ZONE="${CF_ZONE_ID:-your_zone_id_here}"
YESTERDAY=$(date -u -d 'yesterday' '+%Y-%m-%d' 2>/dev/null || date -u -v-1d '+%Y-%m-%d')

curl -s -X POST "https://api.cloudflare.com/client/v4/graphql" \
  -H "Authorization: Bearer $CF_TOKEN" \
  -H "Content-Type: application/json" \
  -d "{"query":"{ viewer { zones(filter: {zoneTag: \\"$CF_ZONE\\"}) { httpRequests1dGroups(filter: {date: \\"$YESTERDAY\\"} limit: 1) { sum { requests cachedRequests bytes cachedBytes } } } } }"}" | python3 -c "
import sys, json
d = json.load(sys.stdin)
groups = d.get('data',{}).get('viewer',{}).get('zones',[{}])[0].get('httpRequests1dGroups',[])
if groups:
  s = groups[0]['sum']
  total, cached = s['requests'], s['cachedRequests']
  pct = round(cached/max(total,1)*100, 1)
  print(f'Cache hit rate: {pct}% ({cached:,}/{total:,} requests)')
  if pct < 50: print('WARNING: Cache rate below 50% — check Vary headers and rule coverage')
"
```
Expected output: Cache hit rate percentage. Alert if below 50%.

## Step 2: Detect Vary header fragmentation (the silent cache killer)
```bash
echo "=== Vary Header Check ==="
for path in "/" "/about" "/contact" "/blog"; do
  VARY=$(curl -sI "https://your-domain.com${path}" 2>/dev/null | grep -i "^vary:" | tr -d '\r')
  echo "${path}: ${VARY:-no Vary header}"
done
echo ""
echo "If Vary contains 'rsc' or 'next-router-state-tree', apply CF Transform Rule:"
echo "  Set Vary: Accept-Encoding (strips RSC fragmentation)"
```
Expected output: Vary headers per page. Next.js App Router adds rsc/next-router-state-tree which fragments CF cache per browser request.

## Step 3: Fix Vary fragmentation via CF Transform Rule
```bash
CF_TOKEN="${CF_API_TOKEN}"
CF_ZONE="${CF_ZONE_ID}"

curl -s -X POST "https://api.cloudflare.com/client/v4/zones/${CF_ZONE}/rulesets" \
  -H "Authorization: Bearer $CF_TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Response Header Fix",
    "kind": "zone",
    "phase": "http_response_headers_transform",
    "rules": [{
      "expression": "true",
      "description": "Strip Next.js Vary headers",
      "action": "rewrite",
      "action_parameters": {"headers": {"Vary": {"operation": "set", "value": "Accept-Encoding"}}}
    }]
  }' | python3 -c "import sys,json; d=json.load(sys.stdin); print('OK' if d.get('success') else 'FAILED: '+str(d.get('errors')))"
```
Expected output: OK

## Step 4: Ping search engines after new content published
```bash
SITEMAP_URL="https://your-domain.com/sitemap.xml"
curl -s "https://www.google.com/ping?sitemap=${SITEMAP_URL}" -o /dev/null -w "Google: HTTP %{http_code}\n"
curl -s "https://www.bing.com/ping?sitemap=${SITEMAP_URL}" -o /dev/null -w "Bing: HTTP %{http_code}\n"
curl -s -X POST "https://api.cloudflare.com/client/v4/zones/${CF_ZONE_ID}/purge_cache" \
  -H "Authorization: Bearer ${CF_API_TOKEN}" -H "Content-Type: application/json" \
  -d "{"files":["${SITEMAP_URL}"]}" | python3 -c "import sys,json; d=json.load(sys.stdin); print('CF purge: OK' if d.get('success') else 'FAILED')"
```
Expected output: Google HTTP 200, Bing HTTP 200, CF purge OK