Troubleshooting CyberPanel 503 Service Unavailable and 502 Bad Gateway

Unlike Apache which displays white screens on PHP crashes, OpenLiteSpeed serves a crisp **"503 Service Unavailable"** or **"502 Bad Gateway"** page whenever its external PHP process (LSPHP) terminates or fails to respond in time.

Here is how to identify and resolve the failure.

1. Restart OpenLiteSpeed and PHP Workers Often a crashed worker is held in memory: Run in terminal: ```bash systemctl restart lsws killall -9 lsphp ``` Or in CyberPanel dashboard: **Server → Server Status → Reboot LiteSpeed**.

2. Check the OpenLiteSpeed Error Log Inspect the server log to see why the worker crashed: ```bash tail -n 50 /usr/local/lsws/logs/error.log ``` Common entries: - `[STDERR] PHP Fatal error: Out of memory` → Increase memory in CyberPanel PHP configuration - `Connection to [uds://tmp/lshttpd/...] failed` → Socket permission mismatch

3. Increase LSPHP Memory & Process Limits 1. Log in to the OpenLiteSpeed WebAdmin console at `https://YOUR_IP:7080` 2. Navigate to **Server Configuration → External App → your PHP version (e.g. lsphp82)** 3. Adjust: - **Memory Soft Limit (bytes)**: Increase to `2047M` - **Memory Hard Limit (bytes)**: Increase to `2047M` - **Max Connections**: Increase from `35` to `100` 4. Perform a Graceful Restart of LiteSpeed.

4. Check for Corrupt Plugins or Memory Leaks If 503 occurs only on specific pages (like WooCommerce checkout or Elementor editor), a rogue script is exceeding execution time. Temporarily rename `wp-content/plugins` to isolate the offending module.