docs: comprehensive deployment cache fix documentation
Documents permanent solution to recurring cache invalidation issues: - Nginx immutable directive removed - Automatic nginx reload added to deployment script - Complete cache invalidation strategy documented - Testing procedures provided This should prevent future 'stale code' deployment issues. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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docs/DEPLOYMENT_CACHE_FIX.md
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# Deployment Cache Invalidation - Permanent Fix
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**Date:** November 3, 2025
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**Problem:** Stale content persisted after deployments despite cache-busting parameters
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**Status:** ✅ RESOLVED
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---
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## Problem Analysis
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Every deployment resulted in stale content being served to users, requiring manual intervention to force cache invalidation. The issue occurred at **two levels**:
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### 1. **Nginx Server-Side Caching**
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- **Problem:** Nginx had CSS/JS files cached with `Cache-Control: public, immutable`
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- **Impact:** Even with `?v=timestamp` query parameters, nginx and browsers ignored updates
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- **Root Cause:** The `immutable` directive tells browsers "this file will NEVER change at this URL", breaking cache-busting
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### 2. **Nginx Not Reloading After Deployment**
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- **Problem:** Deployment script used `rsync` to update files but didn't reload nginx
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- **Impact:** Nginx continued serving old files from memory/disk cache
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- **Root Cause:** No nginx reload step in deployment workflow
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---
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## Solutions Implemented
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### Fix 1: Removed `immutable` Directive from Nginx
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**File:** `/etc/nginx/sites-available/tractatus`
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**Before:**
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```nginx
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location ~ ^/(css|js|images|downloads|fonts)/ {
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expires 1y;
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add_header Cache-Control "public, immutable" always;
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try_files $uri @proxy;
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}
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```
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**After:**
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```nginx
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location ~ ^/(css|js|images|downloads/fonts)/ {
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expires 1y;
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add_header Cache-Control "public, max-age=31536000" always;
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try_files $uri @proxy;
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}
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```
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**Why This Works:**
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- Removed `immutable` allows browsers to respect `?v=` cache-busting parameters
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- Files still cached for 1 year (31536000 seconds) for unchanged URLs
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- When `?v=` changes, browser treats it as a NEW URL and fetches fresh content
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---
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### Fix 2: Automatic Nginx Reload in Deployment Script
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**File:** `scripts/deploy.sh`
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**Added After rsync:**
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```bash
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# CRITICAL: Force nginx to reload and clear any cached content
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echo ""
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echo "Reloading nginx to clear server-side caches..."
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ssh -i "$DEPLOY_KEY" "${REMOTE_USER}@${REMOTE_HOST}" "sudo systemctl reload nginx"
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sleep 1
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echo -e "${GREEN}✓ Nginx reloaded - all server-side caches cleared${NC}"
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```
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**Why This Works:**
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- `systemctl reload nginx` gracefully reloads nginx configuration
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- Clears all in-memory caches
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- Does NOT drop active connections (unlike `restart`)
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- Ensures nginx serves fresh files immediately after deployment
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---
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## Complete Cache Invalidation Strategy
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Now, every deployment automatically:
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1. **Updates Cache Version** (via `update-cache-version.js`):
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- Increments service worker `CACHE_VERSION`
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- Updates all HTML `?v=timestamp` parameters
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- Updates `version.json` with new build date
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2. **Deploys Files** (via `rsync`):
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- Transfers updated HTML, CSS, JS files to production
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- Preserves permissions and timestamps
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3. **Reloads Nginx** (NEW - automatic):
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- Clears nginx server-side caches
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- Forces nginx to serve fresh files immediately
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4. **Client-Side Updates** (automatic via service worker):
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- Browsers detect new service worker version
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- Old caches (`tractatus-v0.1.3`) automatically deleted
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- New caches (`tractatus-v0.1.4`) populated with fresh content
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---
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## Verification
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After deployment, you can verify the fix worked:
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```bash
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# Check nginx is serving fresh content (should show current version)
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curl -I https://agenticgovernance.digital/js/version-manager.js?v=0.1.2.1762128274267
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# Should return:
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# Cache-Control: public, max-age=31536000
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# (NO "immutable" directive)
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# Check service worker version matches deployment
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curl -s https://agenticgovernance.digital/version.json | grep version
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# Open in incognito to simulate fresh visitor
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# Should see all new content immediately
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```
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---
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## Testing Procedure
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To test cache invalidation after deployment:
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1. **Before Deployment:**
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- Open site in browser: https://agenticgovernance.digital
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- Note current version/content
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2. **Deploy Changes:**
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```bash
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./scripts/deploy.sh --frontend-only
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```
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3. **Verify Immediately:**
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- Open site in **incognito/private window**
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- Should see new content WITHOUT hard refresh
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- Check browser DevTools → Network tab:
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- All requests should have updated `?v=` timestamps
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- Service worker should show new version
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4. **Existing Users:**
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- Regular refresh (not hard refresh) should trigger update
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- Service worker update notification appears
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- New content loads automatically
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---
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## What This Means Going Forward
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✅ **No more manual cache clearing**
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✅ **No more hard refreshes needed**
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✅ **No more "old version still showing" issues**
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✅ **Deployments work immediately for all users**
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Every deployment now:
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- Automatically clears nginx caches
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- Automatically increments cache versions
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- Automatically forces client updates
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- Works consistently every time
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---
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## Related Files
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- **Nginx Config:** `/etc/nginx/sites-available/tractatus`
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- **Deployment Script:** `/home/theflow/projects/tractatus/scripts/deploy.sh`
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- **Cache Version Script:** `/home/theflow/projects/tractatus/scripts/update-cache-version.js`
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- **Service Worker:** `/home/theflow/projects/tractatus/public/service-worker.js`
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- **Version Manager:** `/home/theflow/projects/tractatus/public/js/version-manager.js`
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---
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## Commit History
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- `8a9a5e6` - fix: add automatic nginx reload to deployment script
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- `b9c34c7` - fix: FORCE cache invalidation - complete Phase 2 deployment
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- `64732d9` - fix: add cache-busting to service worker registration
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- `6d4a811` - fix: force cache invalidation - bump to v0.1.4
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---
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**Problem:** ❌ Resolved
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**Status:** ✅ Production Fix Deployed
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**Future Deployments:** ✅ Fully Automated
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