# MIM4U 502 Error Resolution Guide

**Last Updated:** 2026-01-31  
**Document Version:** 1.0  
**Status:** Active Documentation

---

**Date**: 2026-01-18  
**Issue**: `https://mim4u.org/` returns HTTP 502 Bad Gateway  
**Status**: ⚠️ **RESOLUTION IN PROGRESS**

---

## Root Cause Analysis

### Current Situation

1. **VMID 7810 (mim-web-1) @ 192.168.11.37**:
   - ✅ Container is running
   - ❌ **nginx is NOT installed**
   - ❌ **No web service on port 80**

2. **VMID 7811 (mim-api-1) @ 192.168.11.36**:
   - ✅ Container is running
   - ❌ **No web service on port 80**
   - ❌ **Port 80 not accessible**

3. **NPMplus Configuration**:
   - ⚠️ Likely routing to old IP (192.168.11.36) OR
   - ⚠️ Routing to 192.168.11.37 but no service responding

---

## 502 Error Explanation

**HTTP 502 Bad Gateway** means:
- NPMplus received the request
- NPMplus tried to proxy to backend (192.168.11.36 or 192.168.11.37)
- Backend service is not responding or not accessible

---

## Solution Steps

### Step 1: Install nginx on VMID 7810

The container needs nginx installed and running to serve the web application.

**Option A — run the fix script (recommended):** From a host that can SSH to the Proxmox node (r630-02):

```bash
./scripts/mim4u-install-nginx-and-fix-502.sh
# Or dry-run: ./scripts/mim4u-install-nginx-and-fix-502.sh --dry-run
```

The script installs nginx, writes the security-enabled config (including rate limits in `/etc/nginx/conf.d/mim4u-rate-limit.conf` and the default site), ensures `/var/www/html` exists, and reloads nginx.

**Option B — manual steps:**

```bash
# SSH to Proxmox host
ssh root@192.168.11.12

# Install nginx in container
pct exec 7810 -- bash -c 'export DEBIAN_FRONTEND=noninteractive && apt-get update && apt-get install -y nginx'

# Start nginx
pct exec 7810 -- systemctl enable nginx
pct exec 7810 -- systemctl start nginx

# Verify
curl -I http://192.168.11.37:80/
```

### Step 2: Verify NPMplus Routing

Check what IP NPMplus is routing to:

1. **Access NPMplus Web UI**:
   - URL: `https://192.168.0.166:81` or `https://192.168.11.166:81`
   - Navigate to: Proxy Hosts → `mim4u.org` (and `www.mim4u.org`)

2. **Verify Configuration**:
   - Forward Hostname/IP: Should be `192.168.11.37`
   - Forward Port: Should be `80`
   - Forward Scheme: Should be `http`
   - **www.mim4u.org**: Same backend so both apex and www work. Optional: create a Redirect host for `www.mim4u.org` → `https://mim4u.org` in NPMplus to canonicalize to apex.

3. **Security (HSTS / SSL)**:
   - Enable **SSL** and **Force SSL** for mim4u.org (and www, secure, training) so HTTPS is used.
   - Enable **HSTS** in the proxy host’s SSL tab so browsers get `Strict-Transport-Security`. NPMplus adds the header when terminating SSL.

### Step 3: Deploy MIM4U Web Application (When Ready)

Once nginx is running, deploy the actual MIM4U web application:

- Application files go in: `/opt/miracles-in-motion/dist` (or configured path)
- Nginx config: `/etc/nginx/sites-available/miracles-in-motion`
- nginx should serve static files and proxy `/api/*` to VMID 7811

---

## Quick Fix (Temporary)

If you need the site working immediately, you can:

1. **Install nginx** on VMID 7810 (see Step 1 above)
2. **Configure basic nginx** to serve a default page:

```bash
# Basic nginx config (temporary) — server_name includes www so www.mim4u.org works; security headers (HSTS when on HTTPS via NPMplus, CSP)
pct exec 7810 -- bash -c 'cat > /etc/nginx/sites-available/default << EOF
server {
    listen 80;
    server_name mim4u.org www.mim4u.org secure.mim4u.org training.mim4u.org _;
    root /var/www/html;
    index index.html;

    # Security headers (HSTS added by NPMplus when terminating SSL; CSP reduces XSS)
    add_header X-Content-Type-Options "nosniff" always;
    add_header X-Frame-Options "SAMEORIGIN" always;
    add_header X-XSS-Protection "1; mode=block" always;
    add_header Referrer-Policy "strict-origin-when-cross-origin" always;
    add_header Content-Security-Policy "default-src '\''self'\''; script-src '\''self'\'' '\''unsafe-inline'\'' '\''unsafe-eval'\''; style-src '\''self'\'' '\''unsafe-inline'\'' https://fonts.googleapis.com; font-src '\''self'\'' https://fonts.gstatic.com; img-src '\''self'\'' data: https:; connect-src '\''self'\'' https://mim4u.org; frame-ancestors '\''self'\'';" always;
    
    location / {
        try_files \$uri \$uri/ /index.html =404;
    }
    
    location /api/ {
        proxy_pass http://192.168.11.36:3001;
        proxy_set_header Host \$host;
        proxy_set_header X-Real-IP \$remote_addr;
        proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto \$scheme;
    }
}
EOF'

pct exec 7810 -- nginx -t && pct exec 7810 -- systemctl reload nginx
```

This will at least allow nginx to respond and stop the 502 error.

---

## Complete Deployment

For full MIM4U deployment, see:
- `scripts/deploy-miracles-in-motion-pve2.sh` - Full deployment script
- [MIM4U_FIRST_PARTY_ANALYTICS.md](./MIM4U_FIRST_PARTY_ANALYTICS.md) — related MIM4U ops context

---

## Verification

After fixes:

```bash
# Test direct IP access
curl -I http://192.168.11.37:80/

# Test public domain (after NPMplus update)
curl -I https://mim4u.org/
```

**Expected**: HTTP 200 (not 502)

---

## Optional: Rate limiting for /api/

To rate-limit `/api/` at nginx, the `limit_req_zone` directive must live in the **http** block (e.g. in `/etc/nginx/nginx.conf`), not in the server block. Example:

```nginx
# In http { ... } in nginx.conf
limit_req_zone $binary_remote_addr zone=api_limit:10m rate=30r/m;
```

Then in your server block (or in the snippet above), inside `location /api/` add:

```nginx
limit_req zone=api_limit burst=5 nodelay;
```

Alternatively, use Cloudflare WAF rate limiting in front of mim4u.org (see [CLOUDFLARE_SETUP](../../miracles_in_motion/docs/deployment/CLOUDFLARE_SETUP.md)).

---

**Last Updated**: 2026-01-18  
**Status**: ⚠️ nginx installation needed on VMID 7810