tractatus/docs/DEPLOYMENT_CACHE_FIX.md

Deployment Cache Invalidation - Permanent Fix

Date: November 3, 2025 Problem: Stale content persisted after deployments despite cache-busting parameters Status: ✅ RESOLVED

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Problem Analysis

Every deployment resulted in stale content being served to users, requiring manual intervention to force cache invalidation. The issue occurred at two levels:

1. Nginx Server-Side Caching

• Problem: Nginx had CSS/JS files cached with Cache-Control: public, immutable
• Impact: Even with ?v=timestamp query parameters, nginx and browsers ignored updates
• Root Cause: The immutable directive tells browsers "this file will NEVER change at this URL", breaking cache-busting

2. Nginx Not Reloading After Deployment

• Problem: Deployment script used rsync to update files but didn't reload nginx
• Impact: Nginx continued serving old files from memory/disk cache
• Root Cause: No nginx reload step in deployment workflow

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Solutions Implemented

Fix 1: Removed immutable Directive from Nginx

File: /etc/nginx/sites-available/tractatus

Before:

location ~ ^/(css|js|images|downloads|fonts)/ {
    expires 1y;
    add_header Cache-Control "public, immutable" always;
    try_files $uri @proxy;
}

After:

location ~ ^/(css|js|images|downloads/fonts)/ {
    expires 1y;
    add_header Cache-Control "public, max-age=31536000" always;
    try_files $uri @proxy;
}

Why This Works:

• Removed immutable allows browsers to respect ?v= cache-busting parameters
• Files still cached for 1 year (31536000 seconds) for unchanged URLs
• When ?v= changes, browser treats it as a NEW URL and fetches fresh content

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Fix 2: Automatic Nginx Reload in Deployment Script

File: scripts/deploy.sh

Added After rsync:

# CRITICAL: Force nginx to reload and clear any cached content
echo ""
echo "Reloading nginx to clear server-side caches..."
ssh -i "$DEPLOY_KEY" "${REMOTE_USER}@${REMOTE_HOST}" "sudo systemctl reload nginx"
sleep 1
echo -e "${GREEN}✓ Nginx reloaded - all server-side caches cleared${NC}"

Why This Works:

• systemctl reload nginx gracefully reloads nginx configuration
• Clears all in-memory caches
• Does NOT drop active connections (unlike restart)
• Ensures nginx serves fresh files immediately after deployment

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Complete Cache Invalidation Strategy

Now, every deployment automatically:

1. Updates Cache Version (via update-cache-version.js):

   • Increments service worker CACHE_VERSION
   • Updates all HTML ?v=timestamp parameters
   • Updates version.json with new build date

2. Deploys Files (via rsync):

   • Transfers updated HTML, CSS, JS files to production
   • Preserves permissions and timestamps

3. Reloads Nginx (NEW - automatic):

   • Clears nginx server-side caches
   • Forces nginx to serve fresh files immediately

4. Client-Side Updates (automatic via service worker):

   • Browsers detect new service worker version
   • Old caches (tractatus-v0.1.3) automatically deleted
   • New caches (tractatus-v0.1.4) populated with fresh content

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Verification

After deployment, you can verify the fix worked:

# Check nginx is serving fresh content (should show current version)
curl -I https://agenticgovernance.digital/js/version-manager.js?v=0.1.2.1762128274267

# Should return:
# Cache-Control: public, max-age=31536000
# (NO "immutable" directive)

# Check service worker version matches deployment
curl -s https://agenticgovernance.digital/version.json | grep version

# Open in incognito to simulate fresh visitor
# Should see all new content immediately

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Testing Procedure

To test cache invalidation after deployment:

1. Before Deployment:

   • Open site in browser: https://agenticgovernance.digital
   • Note current version/content

2. Deploy Changes:

   ./scripts/deploy.sh --frontend-only
   

3. Verify Immediately:

   • Open site in incognito/private window
   • Should see new content WITHOUT hard refresh
   • Check browser DevTools → Network tab:
     • All requests should have updated ?v= timestamps
     • Service worker should show new version

4. Existing Users:

   • Regular refresh (not hard refresh) should trigger update
   • Service worker update notification appears
   • New content loads automatically

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What This Means Going Forward

✅ No more manual cache clearing ✅ No more hard refreshes needed ✅ No more "old version still showing" issues ✅ Deployments work immediately for all users

Every deployment now:

• Automatically clears nginx caches
• Automatically increments cache versions
• Automatically forces client updates
• Works consistently every time

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Related Files

• Nginx Config: /etc/nginx/sites-available/tractatus
• Deployment Script: /home/theflow/projects/tractatus/scripts/deploy.sh
• Cache Version Script: /home/theflow/projects/tractatus/scripts/update-cache-version.js
• Service Worker: /home/theflow/projects/tractatus/public/service-worker.js
• Version Manager: /home/theflow/projects/tractatus/public/js/version-manager.js

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Commit History

• 8a9a5e6 - fix: add automatic nginx reload to deployment script
• b9c34c7 - fix: FORCE cache invalidation - complete Phase 2 deployment
• 64732d9 - fix: add cache-busting to service worker registration
• 6d4a811 - fix: force cache invalidation - bump to v0.1.4

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Problem: ❌ Resolved Status: ✅ Production Fix Deployed Future Deployments: ✅ Fully Automated