A 502 Bad Gateway error in the DDM web interface indicates that the front-end web server is operational but is unable to obtain a valid response from the upstream DDM application service. This typically occurs when the backend service is unavailable, has crashed, or is still in the process of starting.
Additionally, the error can be triggered by performance-related conditions, where the backend service is running but is too slow or overloaded to respond within the expected time. Network-related factors such as firewall rules, port blockages, connectivity issues, or SSL/TLS mismatches between components can also disrupt communication and lead to a 502 error.
For more information on how DDM works, see How does DDM work and what ports does it require?
Note that when accessing DDM in High Availability, it is expected to see this when accessing both the Auxiliary and Arbiter nodes.
| Restart | Restart the DDM through the administrator menu > Shutdown/Reboot | Restarting the operating system may restart any disabled services |
| Check firewall rules | Review host-based and network firewalls to ensure required ports are open between components | Blocked ports will prevent communication and trigger a 502 error |
| Validate port configuration | Confirm the backend service is listening on the expected IP and port | Even with open firewalls, incorrect ports will cause connection failures |