n8n Reports 'Connection Lost' Error Despite Workflow Success on AWS

Below is a few tips to check and adjust your setup. The error message you’re seeing is usually related to the WebSocket connection used by the editor. In many cases, when running n8n behind a reverse proxy (like Nginx Proxy Manager), the proxy needs to be set up to correctly forward WebSocket connections.

Verify Your Reverse Proxy Configuration

Make sure that Nginx Proxy Manager is configured to pass the necessary headers for WebSocket connections. Under the advanced configuration settings for your proxy host, ensure that you have something similar to the following:

NGINXCopied
location / {
    proxy_pass http://your-docker-host-IP:5678;
    proxy_http_version 1.1;
    proxy_set_header Upgrade $http_upgrade;
    proxy_set_header Connection "upgrade";
    proxy_set_header Host $host;
    proxy_set_header X-Real-IP $remote_addr;
}

Key parts are the
 • proxy_set_header Upgrade $http_upgrade;
 • proxy_set_header Connection "upgrade";

If these aren’t set, the WebSocket connection may close, which causes the “Connection lost…” error in the n8n editor.

Check n8n Environment Variables

Your Docker Compose already sets these variables:

• N8N_HOST=mydomain
• N8N_PROTOCOL=https
• VUE_APP_URL_BASE_API=https://mydomain

Double-check that:

• The domain used here matches exactly what you have configured in Nginx Proxy Manager.
• In Nginx you aren’t accidentally modifying or stripping the expected host header.
• There is no mismatch between the URL accessed by the browser and the configuration used by n8n.

Additional Considerations

• Port Forwarding:
  Although your server has the inbound/outbound ports configured, ensure that the reverse proxy is correctly routing to port 5678 where n8n is listening (as in your Docker Compose).

• HTTPS Termination:
  If Nginx Proxy Manager is handling HTTPS termination, ensure that the connection between it and n8n (running on HTTP) is configured with the appropriate headers and that N8N_PROTOCOL is set to https so that the client (n8n editor) uses the proper endpoint.

• Logging and Testing:
  Look at the n8n logs (via Portainer or Docker logs) during startup and when the connection drops. They might provide additional clues if there’s a misconfiguration.

In Summary

Adjust the proxy configuration to ensure WebSocket support (using the “Upgrade” and “Connection” headers) and verify your domain and protocol settings in n8n’s environment. With these changes, the connection between your editor and server should become more stable, and you should no longer see the “Connection lost” error.

Let me know if you need further details or additional logs to troubleshoot further.