To troubleshoot GDN network problems effectively, it’s essential to have a clear picture of the traffic routing flow. The most common issues in GDN network setup are due to misconfiguration of DNS, the proxy, or the GDN domain and segment settings.
A more systematic approach to troubleshooting is to check each ‘hop’ of the route from web browser to origin server in order to locate where the failure is happening. The key actions that take place at each hop and sample problems are shown in the table below.
|
Action |
Potential Problems |
Troubleshooting Approach |
|
Receive and process HTTP request |
Request not received Request wrong in some way (e.g., wrong Host header or URI path) |
Check server access logs to confirm. |
|
DNS lookup for IP address of next server in route |
DNS lookup failure |
Check server access logs to confirm. Manually run DNS lookup on the server using host |
|
Establish TCP connection to next server |
Fail to open connection |
Check server access logs to confirm. Manually attempt connection from server using curl command. |
|
Establish TLS/SSL session (if HTTPS) |
Fail to establish TLS session |
Check server access logs to confirm. Manually check certificate presented by upstream server using openssl command. Likely causes: certificate doesn’t match hostname; certificate not trusted; SNI enabled/disabled. |
|
Send HTTP request; receive HTTP response |
Timeout awaiting response. 5xx gateway error. 403 forbidden. Looping request. Other error response. |
Check server access logs to confirm. Manually send request through server using curl command and examine response. If 5xx, run curl from server. Use __smartling/api/headers.htm to see headers sent upstream from GDN. |